Two multidimensional chromatographic methods for enantiomeric analysis of o,p?-DDT and o,p?-DDD in contaminated soil and air in a malaria area of South Africa

Publication year: 2012
Source:Analytica Chimica Acta, Volume 730

Yvette Naudé, Egmont R. Rohwer

In rural parts of South Africa the organochlorine insecticide DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane) is still used for malaria vector control where traditional dwellings are sprayed on the inside with small quantities of technical DDT. Since o,p?-DDT may show enantioselective oestrogenicity and biodegradability, it is important to analyse enantiomers of o,p?-DDT and its chiral degradation product, o,p?-DDD, for both health and environmental-forensic considerations. Generally, chiral analysis is performed using heart-cut multidimensional gas chromatography (MDGC) and, more recently, comprehensive two-dimensional gas chromatography (GC×GC). We developed an off-line gas chromatographic fraction collection (heart-cut) procedure for the selective capturing of the appropriate isomers from a first apolar column, followed by reinjection and separation on a second chiral column. Only the o,p?-isomers of DDT and DDD fractions from the first dimension complex chromatogram (achiral apolar GC column separation) were selectively collected onto a polydimethylsiloxane (PDMS) multichannel open tubular silicone rubber trap by simply placing the latter device on the flame tip of an inactivated flame ionisation detector (FID). The multichannel trap containing the o,p?-heart-cuts was then thermally desorbed into a GC with time-of-flight mass spectrometry detection (GC–TOFMS) for second dimension enantioselective separation on a chiral column (?-cyclodextrin-based). By selectively capturing only the o,p?-isomers from the complex sample chromatogram, ¹D separation of ultra-trace level enantiomers could be achieved on the second chiral column without matrix interference. Here, we present solventless concentration techniques for extraction of DDT from contaminated soil and air, and report enantiomeric fraction (EF) values of o,p?-DDT and o,p?-DDD obtained by a new multidimensional approach for heart-cut gas chromatographic fraction collection for off-line second dimension enantiomeric separation by ¹D GC–TOFMS of selected isomers. This multidimensional method is compared to the complementary technique of comprehensive GC×GC–TOFMS using the same enantioselective column, this time as the first dimension of separation.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Small molecule analysis using laser desorption/ionization mass spectrometry on nano-coated silicon with self-assembled monolayers

Publication year: 2012
Source:Analytica Chimica Acta, Volume 729

Ömür Çelikb?çak, Gökhan Demirel, Erhan Pi?kin, Bekir Salih

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is an emerging technique for the determination of the molecular weight of biomolecules and their non-covalent complexes without fragmentation. One problem with this technique is the use of excess amounts of matrices, which may produce intense fragment ions and/or clusters at low mass ranges between 1 and 800Da. These fragments lead to interference, especially concerning the signals of small target molecules. Here, a simple, reusable, and quite inexpensive approach was demonstrated to improve the effectiveness of laser desorption/ionization mass spectrometry (LDI-MS) analysis, especially for small molecules, without using matrix molecules. In this study, substrates with controllable morphologies and thicknesses were developed based on the self-assembly of silane molecules on silicon surfaces using N-(3-trimethoxysilylpropyl)diethylenetriamine (TPDA) and octadecyltrichlorosilane (OTS) molecules. Prepared substrates with nano-overlayers were successfully used in the analysis of different types of small target molecules, namely acrivastine, l-histidine, l-valine, l-phenylalanine, l-arginine, l-methionine and angiotensin I. Our substrates exhibited clear peaks almost without fragmentation for all target molecules, suggesting that these surfaces provide a number of important advantages for LDI-MS analysis, such as ease of preparation, costs, reusability, robustness, easy handling and preventing fragmentation.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

The application of an in vitro gastrointestinal extraction to assess the oral bioaccessibility of polycyclic aromatic hydrocarbons in soils from a former industrial site

Publication year: 2012
Source:Analytica Chimica Acta

Damien Lorenzi, Jane Entwistle, Mark Cave, Joanna Wragg, John R. Dean

The total and bioaccessible concentration of 16 polycyclic aromatic hydrocarbons (PAHs) in soil from a former industrial site was investigated. Typical total concentrations across the sampling sites ranged from 1.5mgkg^?1 for acenaphthylene up to 243mgkg^?1 for fluoranthene. The oral bioaccessibility of PAHs in soil was assessed using an in vitro gastrointestinal extraction (Fed Organic Estimation human Simulation Test, FOREhST method). The oral bioaccessibility data indicated that fluorene, phenanthrene, chrysene, indeno(1,2,3-cd)pyrene and dibenzo(a,h)anthracene had the highest % bioaccessible fraction (based on their upper 75^th percentile values being>60%) while the other PAHs had lower % bioaccessible fractions (means ranging between 35-59%). Significantly lower bioaccessibilities were determined for naphthalene. With respect to method validation and inter-laboratory comparison, the total and bioaccessible concentrations of benzo(a)anthracene, benzo(b)anthracene, benzo(k)fluoranthene, benzo(a)pyrene, indeno(1,2,3-cd)pyrene and dibenzo(a,h)anthracene was compared to published data derived using the same samples. The total PAH concentrations at the site were compared with generic assessment criteria (GAC) using the residential land use scenario (with plant uptake at 6% soil organic matter). Concentrations of 7 of the PAHs investigated within the soils could lead to an unacceptable risk to human health at this site.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Direct rapid analysis of trace bioavailable soil macronutrients by chemometrics-assisted energy dispersive X-ray fluorescence and scattering spectrometry

Publication year: 2012
Source:Analytica Chimica Acta, Volume 729

M.I. Kaniu, K.H. Angeyo, A.K. Mwala, M.J. Mangala

Precision agriculture depends on the knowledge and management of soil quality (SQ), which calls for affordable, simple and rapid but accurate analysis of bioavailable soil nutrients. Conventional SQ analysis methods are tedious and expensive. We demonstrate the utility of a new chemometrics-assisted energy dispersive X-ray fluorescence and scattering (EDXRFS) spectroscopy method we have developed for direct rapid analysis of trace ‘bioavailable’ macronutrients (i.e. C, N, Na, Mg, P) in soils. The method exploits, in addition to X-ray fluorescence, the scatter peaks detected from soil pellets to develop a model for SQ analysis. Spectra were acquired from soil samples held in a Teflon holder analyzed using ¹⁰⁹Cd isotope source EDXRF spectrometer for 200s. Chemometric techniques namely principal component analysis (PCA), partial least squares (PLS) and artificial neural networks (ANNs) were utilized for pattern recognition based on fluorescence and Compton scatter peaks regions, and to develop multivariate quantitative calibration models based on Compton scatter peak respectively. SQ analyses were realized with high CMD (R ² >0.9) and low SEP (0.01% for N and Na, 0.05% for C, 0.08% for Mg and 1.98?gg^?1 for P). Comparison of predicted macronutrients with reference standards using a one-way ANOVA test showed no statistical difference at 95% confidence level. To the best of the authors’ knowledge, this is the first time that an XRF method has demonstrated utility in trace analysis of macronutrients in soil or related matrices.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Analytical chemistry no longer neglected but gaps remain

Publication year: 2012
Source:Analytica Chimica Acta, Volume 730

Olivier Heudi, Nelson Torto

Posted on 28 May 2012 | 12:44 pm

Construction and performance characteristics of new ion selective electrodes based on carbon nanotubes for determination of meclofenoxate hydrochloride

Publication year: 2012
Source:Analytica Chimica Acta, Volume 730

Rasha M. El-Nashar, Nour T. Abdel Ghani, Sherif M. Hassan

This work offers construction and comparative evaluation the performance characteristics of conventional polymer (I), carbon paste (II) and carbon nanotubes chemically modified carbon paste ion selective electrodes (III) for meclofenoxate hydrochloride are described. These electrodes depend mainly on the incorporation of the ion pair of meclofenoxate hydrochloride with phosphomolybdic acid (PMA) or phosphotungestic acid (PTA). They showed near Nernestian responses over usable concentration range 1.0×10^?5 to 1.0×10^?2 M with slopes in the range 55.15–59.74mV(concentrationdecade)^?1. These developed electrodes were fully characterized in terms of their composition, response time, working concentration range, life span, usable pH and temperature range. The electrodes showed a very good selectivity for Meclo with respect to a large number of inorganic cations, sugars and in the presence of the degradation product of the drug (p-chloro phenoxy acetic acid). The standard additions method was applied to the determination of MecloCl in pure solution, pharmaceutical preparations and biological samples. Dissolution testing was also applied using the proposed sensors.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Comparative study of different alcohol sensors based on Screen-Printed Carbon Electrodes

Publication year: 2012
Source:Analytica Chimica Acta, Volume 728

Estefanía Costa Rama, Julien Biscay, María Begoña González García, A. Julio Reviejo, José Manuel Pingarrón Carrazón, Agustín Costa García

Different very simple single-use alcohol enzyme sensors were developed using alcohol oxidase (AOX) from three different yeast, Hansenula sp., Pichia pastoris and Candida boidinii, and employing three different commercial mediator-based Screen-Printed Carbon Electrodes as transducers. The mediators tested, Prussian Blue, Ferrocyanide and Co-phthalocyanine were included into the ink of the working electrode. The procedure to obtain these sensors consists of the immobilization of the enzyme on the electrode surface by adsorption. For the immobilization, an AOX solution is deposited on the working electrode and left until dried (1h) at room temperature. The best results were obtained with the biosensor using Screen-Printed Co-phthalocyanine/Carbon Electrode and AOX from Hansenula sp. The reduced cobalt–phthalocyanine form is amperometrically detected at +0.4V (vs. Ag pseudo reference electrode). This sensor shows good sensitivity (1211nAmM^?1), high precision (2.1% RSD value for the slope value of the calibration plot) and wide linear response (0.05–1.00mM) for ethanol determination. The sensor provides also accurate results for ethanol quantification in alcoholic drinks.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Using a photochemical method and chitosan to prepare surface-enhanced Raman scattering–active silver nanoparticles

Publication year: 2012
Source:Analytica Chimica Acta, Volume 729

Kuang-Hsuan Yang, Chia-Ming Chang

In this paper, we report a new strategy for the preparation of surface-enhanced Raman scattering (SERS)-active silver nanoparticles (Ag NPs), using a photochemical method and the presence of chitosan (Ch). First, Ag substrates were subjected to electrochemical oxidation/reduction cycles (ORCs) in deoxygenated aqueous solutions containing 0.1M HNO3 and 1gL^?1 Ch (pH 6.9, adjusted by adding 1M NaOH), resulting in Ag⁺–Ch complexes. These substrates were then irradiated with UV light at various wavelengths to yield the SERS-active Ag NPs. A stronger SERS effect was observed on the SERS-active Ag NPs prepared by using UV irradiation at 310nm. The pH of the solution and the presence of Ch during the preparation process both affected the resulting SERS activities.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Analytical techniques for wine analysis: An African perspective; a review

Publication year: 2012
Source:Analytica Chimica Acta, Volume 730

André de Villiers, Phillipus Alberts, Andreas G.J. Tredoux, Hélène H. Nieuwoudt

Analytical chemistry is playing an ever-increasingly important role in the global wine industry. Chemical analysis of wine is essential in ensuring product safety and conformity to regulatory laws governing the international market, as well as understanding the fundamental aspects of grape and wine production to improve manufacturing processes. Within this field, advanced instrumental analysis methods have been exploited more extensively in recent years. Important advances in instrumental analytical techniques have also found application in the wine industry. This review aims to highlight the most important developments in the field of instrumental wine and grape analysis in the African context. The focus of this overview is specifically on the application of advanced instrumental techniques, including spectroscopic and chromatographic methods. Recent developments in wine and grape analysis and their application in the African context are highlighted, and future trends are discussed in terms of their potential contribution to the industry.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Selective trace analysis of chloroacetamide herbicides in food samples using dummy molecularly imprinted solid phase extraction based on chemometrics and quantum chemistry

Publication year: 2012
Source:Analytica Chimica Acta, Volume 729

Lei Zhang, Fang Han, Yanyun Hu, Ping Zheng, Xuan Sheng, Hao Sun, Wei Song, Yaning Lv

A methodology based on chemometrics and quantum chemistry was proposed to design and synthesize dummy molecularly imprinted polymers (DMIPs) capable of extracting chloroacetamide herbicides from food samples. Molecular modeling approach in conjunction with clustering analysis was used to predict the most suitable dummy template. Metolachlor deschloro was selected as the template to synthesize DMIPs, which were used as the solid phase extraction (SPE) materials. The selective adsorption of DMIPs was evaluated by high performance liquid chromatography (HPLC). The retention property of six chloroacetamide herbicides on DMIPs was also predicted using clustering analysis. The optimum loading, washing and eluting conditions for dummy molecularly imprinted solid phase extraction (DMISPE) were established to obtain high selectivity and sensitivity. Water, dichloromethane and methanol were chosen as loading, washing and elution solvent, respectively. Under optimized DMISPE conditions, recoveries of analytes were in the range of 83.4–106.7% with satisfactory precision (RSD% lower than 13%). Compared with other commercial SPE columns, DMISPE exhibited selective binding properties for chloroacetamide herbicides and the matrix effect was significantly decreased.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

A new cleanup method of dioxins in sediment using large volume injection gas chromatography online coupled with liquid chromatography

Publication year: 2012
Source:Analytica Chimica Acta, Volume 729

Fengmei Tang, Yuwen Ni, Haijun Zhang, Yun Li, Jing Jin, Longxing Wang, Jiping Chen

A new cleanup method was developed and validated for the determination of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) in sediment. The sample extract was first treated with sulfuric acid and then cleaned up by a large volume injection gas chromatography online coupled with liquid chromatography (LVI-GC-LC) system. PCDD/Fs in the extract were separated by a GC column (DB-5), selected cut, cool trapped and transferred to a LC column (alumina). The fraction of PCDD/Fs eluted from the alumina column was collected and concentrated for the instrumental analysis. Under the optimized conditions, LVI-GC-LC method achieved the recoveries of 57–102% for 2,3,7,8-substituted PCDD/Fs, which met the requirements of US Environmental Protection Agency (EPA) Method 1613 and were better than those obtained using the conventional multistep column cleanup method. Meanwhile, compared with the conventional method, the limit of detection (LOD) values of 2,3,7,8-substituted PCDD/Fs cleaned up by LVI-GC-LC method were decreased due to the high-efficiency removal of interferents. These results suggested that the LVI-GC-LC cleanup method was a promising alternative to the multistep cleanup procedure for the determination of dioxins in environmental samples.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

A binderless, covalently bulk modified electrochemical sensor: Application to simultaneous determination of lead and cadmium at trace level

Publication year: 2012
Source:Analytica Chimica Acta, Volume 728

Raghu Gunigollahalli Kempegowda, Pandurangappa Malingappa

A new type of covalent binderless bulk modified electrode has been fabricated and used in the simultaneous determination of lead and cadmium ions at nanomolar level. The modification of graphitic carbon with 4-amino salicylic acid was carried out under microwave irradiation through the amide bond formation. The electrochemical behavior of the fabricated electrode has been carried out to decipher the interacting ability of the functional moieties present on the modifier molecules toward the simultaneous determination of Pb²⁺ and Cd²⁺ ions using cyclic and differential pulse anodic stripping voltammetry. The possible mode of interaction of functional groups with metal ions is proposed based on the pKa values of the modifier functionalities present on the surface of graphitic carbon particles. The analytical utility of the proposed sensor has been validated by measuring the lead and cadmium content from pretreated waste water samples of lead acid batteries.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

The role of analytical chemistry in Niger Delta petroleum exploration: A review

Publication year: 2012
Source:Analytica Chimica Acta, Volume 730

Akinsehinwa Akinlua

Petroleum and organic matter from which the petroleum is derived are composed of organic compounds with some trace elements. These compounds give an insight into the origin, thermal maturity and paleoenvironmental history of petroleum, which are essential elements in petroleum exploration. The main tool to acquire the geochemical data is analytical techniques. Due to progress in the development of new analytical techniques, many hitherto petroleum exploration problems have been resolved. Analytical chemistry has played a significant role in the development of petroleum resources of Niger Delta. Various analytical techniques that have aided the success of petroleum exploration in the Niger Delta are discussed. The analytical techniques that have helped to understand the petroleum system of the basin are also described. Recent and emerging analytical methodologies including green analytical methods as applicable to petroleum exploration particularly Niger Delta petroleum province are discussed in this paper. Analytical chemistry is an invaluable tool in finding the Niger Delta oils.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Novel method for determining DDT in vapour and particulate phases within contaminated indoor air in a malaria area of South Africa

Publication year: 2012
Source:Analytica Chimica Acta, Volume 730

Yvette Naudé, Egmont R. Rohwer

The organochlorine insecticide DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane) is still used for malaria vector control in certain areas of South Africa. The strict Stockholm Convention on Persistent Organic Pollutants (POPs) allows spraying on the inside of traditional dwellings with DDT. In rural villages contaminated dust presents an additional pathway for exposure to DDT. We present a new method for the determination of DDT in indoor air where separate vapour and particulate samples are collected in a single step with a denuder configuration of a multi-channel open tubular silicone rubber (polydimethylsiloxane (PDMS)) trap combined with a micro quartz fibre filter. The multi-channel PDMS trap section of the denuder concentrates vapour phase insecticide whereas particle associated insecticide is transferred downstream where it is collected on a micro-fibre filter followed by a second multi-channel PDMS trap to capture the blow-off from the filter. The multi-channel PDMS trap and filter combination are designed to fit a commercial thermal desorber for direct introduction of samples into a GC–MS. The technique is solvent-free. Analyte extraction and sample clean-up is not required. Two fractions, vapour phase and particulate phase p,p?-DDT, o,p?-DDT; p,p?-DDD, o,p?-DDD; p,p?-DDE and o,p?-DDE in 4L contaminated indoor air, were each quantitatively analysed by GC–MS using isotopically labelled ring substituted ¹³C12 – p,p?-DDT as an internal standard. Limits of detection were 0.07–0.35ngm^?3 for p,p?-DDT, o,p?-DDT, p,p?-DDD, o,p?-DDD, p,p?-DDE and o,p?-DDE. Ratios of airborne p,p?-DDD/p,p?-DDT and of o,p?-DDT/p,p?-DDT are unusual and do not match the ideal certified ingredient composition required of commercial DDT. Results suggest that the DDT products used for indoor residual spraying (IRS) prior to, and during 2007, may have been compromised with regards to insecticidal efficacy, demonstrating the power of this new environmental forensics tool.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Development of a dedicated peptide tandem mass spectral library for conservation science

Publication year: 2012
Source:Analytica Chimica Acta, Volume 728

Wim Fremout, Maarten Dhaenens, Steven Saverwyns, Jana Sanyova, Peter Vandenabeele, Dieter Deforce, Luc Moens

In recent years, the use of liquid chromatography tandem mass spectrometry (LC–MS/MS) on tryptic digests of cultural heritage objects has attracted much attention. It allows for unambiguous identification of peptides and proteins, and even in complex mixtures species-specific identification becomes feasible with minimal sample consumption. Determination of the peptides is commonly based on theoretical cleavage of known protein sequences and on comparison of the expected peptide fragments with those found in the MS/MS spectra. In this approach, complex computer programs, such as Mascot, perform well identifying known proteins, but fail when protein sequences are unknown or incomplete. Often, when trying to distinguish evolutionarily well preserved collagens of different species, Mascot lacks the required specificity. Complementary and often more accurate information on the proteins can be obtained using a reference library of MS/MS spectra of species-specific peptides. Therefore, a library dedicated to various sources of proteins in works of art was set up, with an initial focus on collagen rich materials. This paper discusses the construction and the advantages of this spectral library for conservation science, and its application on a number of samples from historical works of art.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Editorial Board

Publication year: 2012
Source:Analytica Chimica Acta, Volume 729

Posted on 28 May 2012 | 12:44 pm

Elemental composition and fatty acid profile of the edible fruits of Amatungula (Carissa macrocarpa) and impact of soil quality on chemical characteristics

Publication year: 2012
Source:Analytica Chimica Acta, Volume 730

Roshila Moodley, Neil Koorbanally, Sreekanth B. Jonnalagadda

The Amatungula fruit, from Carissa macrocarpa, is commonly consumed by the local people of KwaZulu-Natal (KZN), South Africa. Levels of elements in the fruit were determined to assess if they conform to recommended dietary allowances (RDAs) and to assess for potential toxicities. Soils and fruit samples from nine sites in eastern KZN were investigated. Concentrations of elements in the fruit were found to be in the order of Ca>Mg>Fe>Mn?Cu?Pb>Se>Cr>Ni>Zn. For the elements in focus, except for Pb, all of the elements found in the fruit contribute significantly towards the RDAs. Lipid profiling was also done to determine the fruits potential as a source of essential fatty acids. The fruit was rich in monounsaturated and essential fatty acids with the linoleic acid to ?-linolenic acid ratio conforming to the recommended range for cardiac health. Concentrations of elements in soil had no significant effect on plant concentrations, but competition between elements in soil influenced their availability. Total soil concentrations of most metals studied have significantly correlated Pb availability, indicating the impact of these metals on Pb availability. The Amatungula fruit showed tendency to accumulate Pb, with Pb levels in fruit at all sites being toxic to human health. Site location had a major effect on plant concentrations however uptake and distribution was primarily dependent on the plants inherent controls, as evidenced by the accumulation and exclusion of elements, to meet its physiological requirements.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Determination of inorganic phosphate by electroanalytical methods: A review

Publication year: 2012
Source:Analytica Chimica Acta, Volume 729

Sheela Berchmans, Touma B. Issa, Pritam Singh

Determination of inorganic phosphate is of very high importance in environmental and health care applications. Hence knowledge of suitable analytical techniques available for phosphate sensing for different applications becomes essential. Electrochemical methods for determining inorganic phosphate have several advantages over other common techniques, including detection selectivity, stability and relative environmental insensitivity of electroactive labels. The different electrochemical sensing strategies adopted for the determination of phosphate using selective ionophores are discussed in this review. The various sensing strategies are classified based on the electrochemical detection techniques used viz., potentiometry, voltammetry, amperometry, unconventional electrochemical methods etc., The enzymatic sensing of phosphate coupled with electrochemical detection is also included. Various electroanalytical methods available in the literature are assessed for their merits in terms of selectivity, simplicity, miniaturisation, adaptability and suitability for field measurements.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Determination of organphosphorus pesticides in ecological textiles by solid-phase microextraction with a siloxane-modified polyurethane acrylic resin fiber

Publication year: 2012
Source:Analytica Chimica Acta

Xianlei Hu, Mingqiu Zhang, Wenhong Ruan, Fang Zhu, Gangfeng Ouyang

A novel solid-phase microextraction (SPME) fiber coating was prepared with siloxane-modified polyurethane acrylic resin by photo-cured technology. The ratio of two monomers was investigated to obtain good microphase separation structure and better extraction performance. The self-made fiber was then applied to organophosphorus pesticides (OPPs) analysis and several factors, such as extraction/desorption time, extraction temperature, salinity and pH, were studied. The optimized conditions were: 15min extraction at 25°C, 5% Na2SO4 content, pH 7.0 and 4min desorption in GC inlet. The self-made fiber coating exhibited better extraction efficiency for OPPs, compared with three commercial fiber coatings. Under the optimized conditions, the detection limits of 11 OPPs were from 0.03?gL^?1 to 0.5?gL^?1. Good recoveries and repeatabilities were obtained when the method was used to determine OPPs in ecological textile.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Mesoporous TiO2 aerogel for selective enrichment of phosphopeptides in rat liver mitochondria

Publication year: 2012
Source:Analytica Chimica Acta, Volume 729

Liyuan Zhang, Zhen Liang, Kaiguang Yang, Simin Xia, Qi Wu, Lihua Zhang, Yukui Zhang

The enrichment of low abundance phosphopeptides before MS analysis is a critical step for in-depth phosphoproteome research. In this study, mesoporous titanium dioxide (TiO2) aerogel was prepared by precipitation and supercritical drying. The specific surface area up to 490.7m² g^?1 is achieved by TiO2 aerogel, much higher than those obtained by commercial TiO2 nanoparticles and by the latest reported mesoporous TiO2 spheres. Due to the large specific surface area and the mesoporous structure of the aerogel, the binding capacity for phosphopeptides is six times higher than that of conventional TiO2 microparticles (173 vs 28?molg^?1). Because of the good compatibility of enrichment procedure with MALDI-TOF-MS and the large binding capacity of TiO2 aerogel, a detection limit as low as 30amol for analyzing phosphopeptides in ?-casein digest was achieved. TiO2 aerogel was further applied to enrich phosphopeptides from rat liver mitochondria, and 266 unique phosphopeptides with 340 phosphorylation sites, corresponding to 216 phosphoprotein groups, were identified by triplicate nanoRPLC-ESI-MS/MS runs, with false-positive rate less than 1% at the peptide level. These results demonstrate that TiO2 aerogel is a kind of promising material for sample pretreatment in the large-scale phosphoproteome study.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Determination of potentially toxic heavy metals in traditionally used medicinal plants for HIV/AIDS opportunistic infections in Ngamiland District in Northern Botswana

Publication year: 2012
Source:Analytica Chimica Acta, Volume 730

Harriet Okatch, Barbara Ngwenya, Keleabetswe M. Raletamo, Kerstin Andrae-Marobela

The determination of four potentially toxic heavy metals, arsenic, chromium, lead and nickel in twelve plant species used for the treatment of perceived HIV and AIDS-associated opportunistic infections by traditional healers in Ngamiland District in Northern Botswana, a metal mining area, was carried out using atomic absorption spectrometry. The medicinal plants; Dichrostachys cinerea, Maerua angolensis, Mimusops zeyheri, Albizia anthelmintica, Plumbago zeylanica, Combretum imberbe, Indigofera flavicans, Clerodendrum ternatum, Solanum panduriforme, Capparis tomentosa, Terminalia sericea and Maytenus senegalensis contained heavy metals in varying quantities: arsenic 0.19–0.54?gg^?1, chromium 0.15–1.27?gg^?1, lead 0.12–0.23?gg^?1 and nickel 0.09–0.21?gg^?1 of dry weight. Chromium was found to be the most abundant followed by arsenic and lead. Nickel was undetectable in nine plant species. M. senegalensis contained the largest amounts of arsenic, chromium and lead. All metals determined were below the WHO permissive maximum levels. The possible maximum weekly intakes of the heavy metals following treatment regimes were insignificant compared to the provisional tolerable weekly intake levels recommended by WHO and the Joint FAO/WHO Expert Committee on Food Additives. This suggests that heavy metal exposure to patients originating from consumption of traditional medicinal plant preparations is within non health-compromising limits.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Measurement of laser activated electron tunneling from semiconductor zinc oxide to adsorbed organic molecules by a matrix assisted laser desorption ionization mass spectrometer

Publication year: 2012
Source:Analytica Chimica Acta, Volume 729

Hongying Zhong, Jieying Fu, Xiaoli Wang, Shi Zheng

Measurement of light induced heterogeneous electron transfer is important for understanding of fundamental processes involved in chemistry, physics and biology, which is still challenging by current techniques. Laser activated electron tunneling (LAET) from semiconductor metal oxides was observed and characterized by a MALDI (matrix assisted laser desorption ionization) mass spectrometer in this work. Nanoparticles of ZnO were placed on a MALDI sample plate. Free fatty acids and derivatives were used as models of organic compounds and directly deposited on the surface of ZnO nanoparticles. Irradiation of UV laser (? =355nm) with energy more than the band gap of ZnO produces ions that can be detected in negative mode. When TiO2 nanoparticles with similar band gap but much lower electron mobility were used, these ions were not observed unless the voltage on the sample plate was increased. The experimental results indicate that laser induced electron tunneling is dependent on the electron mobility and the strength of the electric field. Capture of low energy electrons by charge-deficient atoms of adsorbed organic molecules causes unpaired electron-directed cleavages of chemical bonds in a nonergodic pathway. In positive detection mode, electron tunneling cannot be observed due to the reverse moving direction of electrons. It should be able to expect that laser desorption ionization mass spectrometry is a new technique capable of probing the dynamics of electron tunneling. LAET offers advantages as a new ionization dissociation method for mass spectrometry.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Editorial Board

Publication year: 2012
Source:Analytica Chimica Acta, Volume 730

Posted on 28 May 2012 | 12:44 pm

Dual lifetime referenced fluorometry for the determination of doxorubicin in urine

Publication year: 2012
Source:Analytica Chimica Acta, Volume 729

Fernando Martínez Ferreras, Otto S. Wolfbeis, Hans H. Gorris

Dual lifetime referencing (DLR) is introduced as a rapid and self-referenced method for measuring the concentration of a fluorescent analyte in solution. The fluorescent cancer chemotherapeutic doxorubicin was chosen as a medically relevant analyte and blended with a reference dye (Ru(dpp)3) that displays overlapping excitation and emission spectra. The relative contributions of the short-lived (nanoseconds) fluorescent analyte and the long-lived (microseconds) reference dye define the observed lifetime. Measuring this lifetime by both frequency-domain DLR and time-domain DLR yields similar analytical ranges and limits of detection (0.4?M). To assess the matrix effect of medical samples, the standard addition method was employed to both modes of DLR. Urine was spiked with doxorubicin and recovery rates of ?97% were obtained.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Cytochrome c biosensor for determination of trace levels of cyanide and arsenic compounds

Publication year: 2012
Source:Analytica Chimica Acta, Volume 730

Xolile Fuku, Faiza Iftikar, Euodia Hess, Emmanuel Iwuoha, Priscilla Baker

An electrochemical method based on a cytochrome c biosensor was developed, for the detection of selected arsenic and cyanide compounds. Boron doped diamond (BDD) electrode was used as a transducer, onto which cytochrome c was immobilised and used for direct determination of Prussian blue, potassium cyanide and arsenic trioxide. The sensitivity as calculated from cyclic voltammetry (CV) and square wave voltammetry (SWV), for each analyte in phosphate buffer (pH=7) was found to be in the range of (1.1–4.5)×10^?8 A?M^?1 and the detection limits ranged from 4.3 to 9.1?M. The biosensor is therefore able to measure significantly lower than current Environmental Protection Agency (EPA) and World Health Organisation (WHO) guidelines, for these types of analytes. The protein binding was monitored as a decrease in biosensor peak currents by SWV and as an increase in biosensor charge transfer resistance by electrochemical impedance spectroscopy (EIS). EIS provided evidence that the electrocatalytic advantage of BDD electrode was not lost upon immobilisation of cytochrome c. The interfacial kinetics of the biosensor was modelled as equivalent electrical circuit based on electrochemical impedance spectroscopy data. UV–vis spectroscopy was used to confirm the binding of the protein in solution by monitoring the intensity of the soret bands and the Q bands. FTIR was used to characterise the protein in the immobilised state and to confirm that the protein was not denatured upon binding to the pre-treated bare BDD electrode. SNFTIR of cyt c immobilised at platinum electrode, was used to study the effect of oxidation state on the surface bond vibrations. The spherical morphology of the immobilised protein, which is typical of native cytochrome c, was observed using scanning electron microscopy (SEM) and confirmed the immobilisation of the cytochrome c without denaturisation.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Sequence-specific detection of nucleic acids utilizing isothermal enrichment of G-quadruplex DNAzymes

Publication year: 2012
Source:Analytica Chimica Acta, Volume 729

Hao-Jie Xiao, Ho Chol Hak, De-Ming Kong, Han-Xi Shen

G-quadruplex DNAzymes are peroxidase-like complexes formed by nucleic acid G-quadruplexes and hemin. Various chemical sensors and biosensors have been developed, based on such DNAzymes. Here we report a novel, specific nucleic acid detection method utilizing the isothermal amplification strategy of G-quadruplex DNAzymes. In this method, an unlabeled oligonucleotide probe was used. The probing sequence of the oligonucleotide was in the form of a stem-loop structure. A G-rich sequence, containing three GGG repeats, was linked to the 5?-end of the stem-loop structure. In the presence of target, the probing sequence hybridized to the target, and a G n (n ?2) repeat was extended from its 3?-end. This G n repeat, together with the three GGG repeats at the 5?-end, folded into a G-quadruplex, and displayed enhanced peroxidase acitivity upon hemin binding. Utilizing the dynamic binding interaction between the probe and its target, the enrichment of G-quadruplex DNAzymes was achieved. Using this method, simple, rapid and cost-effective nucleic acid detection could be achieved. This method displayed high target-length tolerance and good detection specificity; one-base mismatch could be judged easily, even by visual inspection. This method may be used as an auxiliary tool for amplified detection of specific DNA targets in some situations, in which isothermal detection is desirable.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Editorial Board

Publication year: 2012
Source:Analytica Chimica Acta, Volume 728

Posted on 28 May 2012 | 12:44 pm

Separation and determination of trace uranium using a double-receptor sandwich supramolecule method based on immobilized salophen and fluorescence labeled oligonucleotide

Publication year: 2012
Source:Analytica Chimica Acta, Volume 729

Minlong Wu, Lifu Liao, Minmin Zhao, Yingwu Lin, Xilin Xiao, Changming Nie

A double-receptor sandwich supramolecule method for the separation and determination of trace uranium was proposed in this paper. One receptor is a salophen which can react with uranyl to form a uranyl-salophen complex, and another receptor is an oligonucleotide which can bind uranyl to form oligonucleotide-uranyl-salophen supramolecule. The salophen was immobilized on the surface of silica gel particles and used as the solid phase receptor for separating uranium from solution. The oligonucleotide was labeled with a fluorescent group and used as the labeled receptor for quantitatively analyzing uranium. In the procedure of separation and determination, uranyl ion was first combined with the solid phase receptor and then conjugated with the labeled receptor to form the sandwich-type supramolecule. The labeled receptor in the sandwich supramolecule was then eluted and determined by fluorescence analysis. The experimental results demonstrate that this method has a number of advantages such as high selectivity, excellent pre-concentration capability, high sensitivity, good stability and low cost. Under optimal conditions, the linear range for the detection of uranium is 0.5–30.0ngmL^?1 with a detection limit of 0.2ngmL^?1. The proposed method was successfully applied for the separation and determination of uranium in real samples with the recoveries of 95.0–105.5%.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Selective electronalysis of peracetic acid in the presence of a large excess of H2O2 at Au(111)-like gold electrode

Publication year: 2012
Source:Analytica Chimica Acta, Volume 730

M.I. Awad

Peracetic acid (PAA) has been selectively electroanalyzed in the presence of a large excess of hydrogen peroxide (H2O2), about 500 fold that of PAA, using Au (111)-like gold electrode in acetate buffer solutions of pH 5.4. Au(111)-like gold electrode was prepared by a controlled reductive desorption of a previously assembled thiol, typically cysteine, monolayer onto the polycrystalline gold (poly-Au) electrode. Cysteine molecules were selectively removed from the Au(111) facets of the poly-Au electrode, keeping the other two facets (i.e., Au(110) and Au(100)) under the protection of the adsorbed cysteine. It has been found that Au(111)-like gold electrode positively shifts the reduction peak of PAA, while, fortunately, shifts the reduction peak of H2O2 negatively, achieving a large potential separation (around 750mV) between the two reduction peaks as compared with that (around 450mV) obtained at the poly-Au electrode. This large potential separation between the two reduction peaks enabled the analysis of PAA in the presence of a large excess of H2O2. In addition, the positive shift of the reduction peak of PAA gives the present method a high immunity against the interference of the dissolved oxygen.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Disposable screen-printed sensors modified with bismuth precursor compounds for the rapid voltammetric screening of trace Pb(II) and Cd(II)

Publication year: 2012
Source:Analytica Chimica Acta, Volume 728

Nikolitsa Lezi, Anastasios Economou, Panagiotis A. Dimovasilis, Pantelis N. Trikalitis, Mamas I. Prodromidis

In this article, a study of novel screen-printed electrodes bulk-modified with five potential bismuth precursor compounds (bismuth citrate, bismuth titanate, bismuth oxide, bismuth aluminate and bismuth zirconate) is presented for the determination of Cd(II) and Pb(II) by anodic stripping voltammetry. During the electrolytic deposition step, the precursor was reduced and served as the source of bismuth. Different key parameters were investigated in detail such as the nature of the bismuth precursor compound, the precursor content in the carbon ink, the polarisation range of the sensors, the supporting electrolyte, the stripping waveform, the deposition time, the deposition potential and the long-term stability of the sensors under continuous use. Using bismuth citrate as the precursor, the limit of detection was 0.9?gL^?1 for Pb(II) and 1.1?gL^?1 for Cd(II). The reproducibility on the same sensor (expressed as % relative standard deviation, (n =8)) was 5.4% for Pb(II) and 7.2% for Cd(II) at the 20?gL^?1 level. Finally, the sensors were applied to the determination of Cd(II) and Pb(II) in water samples.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

High-throughput quantification of palladium in water samples by ion pair based-surfactant assisted microextraction

Publication year: 2012
Source:Analytica Chimica Acta, Volume 728

Yadollah Yamini, Morteza Moradi, Elham Tahmasebi

A novel method for the determination of palladium as a metal ion model was developed by ion pair based surfactant-assisted microextraction (IP-SAME) and inductively coupled plasma-optical detection (ICP-OES). In this methodology, a cationic surfactant was used in extraction process. It has two fundamental functions: (1) the formation of an emulsified phase and (2) the ion pair formation with Pd(II) in the presence of iodide ions and making $\text{Pd}{{\text{I}}_4}^{2?}$ extractable into organic phase (active microextraction). The effective parameters on the extraction recovery such as the types of extraction solvent and the surfactant, surfactant concentration, KI amount and HCl concentration of the sample were investigated and optimized. In the proposed approach, tetradecyl trimethyl ammonium bromide (TTAB) was used as emulsifier and ion pairing agent, and 1-octanol was selected as extraction solvent. Under the optimum conditions, the enhancement factor as large as 146 was obtained. The detection limit for palladium was 0.2?gL^?1, and the relative standard deviation (RSD) was 4.1% (n =5, C =10.0?gL^?1). The proposed method was applied for extraction and determination of palladium in different water samples.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Poly(o-phenylenediamine)-carried nanogold particles as signal tags for sensitive electrochemical immunoassay of prolactin

Publication year: 2012
Source:Analytica Chimica Acta, Volume 728

Huafeng Chen, Yuling Cui, Bing Zhang, Bingqian Liu, Guonan Chen, Dianping Tang

A novel class of redox-active molecular tags, poly(o-phenylenediamine)-carried nanogold particles (GPPDs), was first synthesized and functionalized with horseradish peroxidase-anti-prolactin conjugates (HRP-anti-PRL). Thereafter, a specific sandwich-type electrochemical immunoassay was designed for determination of prolactin (PRL) by using GPPD-labeled HRP-anti-PRL conjugates as molecular tags on anti-PRL antibody-modified glassy carbon electrode. Compared with pure gold nanoparticles and poly(o-phenylenediamine) microspheres, the as-prepared GPPDs increased the surface coverage of the nanostructures, and enhanced the immobilization amount of biomolecules. Several labeling protocols compromising GPPD-labeled HRP-anti-PRL, nanogold particles-labeled HRP-anti-PRL and poly(o-phenylenediamine) microspheres-labeled HRP-anti-PRL, were investigated for detection of PRL, and improved analytical features were obtained with the GPPD-based strategy. With the GPPD labeling method, dependence of the electrochemical signals on the incubation time and pH of the assay solution were also studied. The strong attachment of HRP-anti-PRL to the GPPDs resulted in a good repeatability and intermediate reproducibility down to 9.8%. The dynamic concentration range spanned from 0.5 to 180ngmL^?1 PRL with a detection limit of 0.1ngmL^?1 at the 3S blank level. No significant differences at the 95% confidence level were encountered in the analysis of 10 spiked blank cattle serum samples between the developed immunoassay and enzyme-linked immunosorbent assay method for determination of PRL.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Thermodynamic evaluation of the stability of the bone-seeking radiopharmaceutical [177Lu]Lu(III)–DOTP under simulated blood plasma conditions

Publication year: 2012
Source:Analytica Chimica Acta, Volume 730

Lebogang C. Sepini, Neil V. Jarvis, David R. Jansen, Jan Rijn Zeevaart

The stability and in vivo robustness of [¹⁷⁷Lu]Lu–DOTP as a potential bone-targeting radiopharmaceutical was determined with the aid of thermodynamic blood plasma modeling simulations. Glass electrode potentiometry was employed to measure the stability constants of the complexes of Lu³⁺ with DOTP. Similarly, the complexes of DOTP with a selection of the important physiological metal ions: Ca²⁺, Mg²⁺, and Cu²⁺ were determined, representing the typical interactions that the ligand would encounter upon administration. This made possible the construction of a blood plasma model of DOTP, aiding in establishing the potential susceptibility of the radiopharmaceutical. The ligand binds predominantly to calcium in vivo, accounting for 59.6% of that initially introduced as a component of the Lu–DOTP complex. Furthermore, due to a preference of the DOTP to bind to Cu²⁺ it causes mobilization of the ions in blood plasma, and would therefore indicate a deficiency if the ligand is administered at a concentration of 8.5×10^?5 moldm^?3. The lutetium-ions are preferentially bound to DOTP, with as much as 98.1% of the Lu³⁺ occupying the ligand under physiological conditions.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Air-assisted liquid–liquid microextraction method as a novel microextraction technique; Application in extraction and preconcentration of phthalate esters in aqueous sample followed by gas chromatography–flame ionization detection

Publication year: 2012
Source:Analytica Chimica Acta, Volume 728

Mir Ali Farajzadeh, Mohammad Reza Afshar Mogaddam

A novel microextraction technique, air-assisted liquid–liquid microextraction (AALLME), which is a new version of dispersive liquid–liquid microextraction (DLLME) method has been developed for extraction and preconcentration of phthalate esters, dimethyl phthalate (DMP), diethyl phthalate (DEP), di-iso-butyl phthalate (DIBP), di-n-butyl phthalate (DNBP), and di-2-ethylhexyl phthalate (DEHP), from aqueous samples prior to gas chromatography–flame ionization detection (GC–FID) analysis. In this method, much less volume of an organic solvent is used as extraction solvent in the absence of a disperser solvent. Fine organic droplets were formed by sucking and injecting of the mixture of aqueous sample solution and extraction solvent with a syringe for several times in a conical test tube. After extraction, phase separation was performed by centrifugation and the enriched analytes in the sedimented phase were determined by GC–FID. Under the optimum extraction conditions, the method showed low limits of detection and quantification between 0.12–1.15 and 0.85–4ngmL^?1, respectively. Enrichment factors (EFs) and extraction recoveries (ERs) were in the ranges of 889–1022 and 89–102%, respectively. The relative standard deviations (RSDs) for the extraction of 100ngmL^?1 and 500ngmL^?1 of each phthalate ester were less than 4% for intra-day (n =6) and inter-days (n =4) precision. Finally some aqueous samples were successfully analyzed using the proposed method and three analytes, DIBP, DNBP and DEHP, were determined in them at ngmL^?1 level.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

An infrared spectroscopic based method for mercury(II) detection in aqueous solutions

Publication year: 2012
Source:Analytica Chimica Acta, Volume 728

Asela Chandrasoma, Amer Al Abdel Hamid, Alice E. Bruce, Mitchell R.M. Bruce, Carl. P. Tripp

A new method that uses solid phase extraction (SPE) coupled with FTIR spectroscopy to detect Hg(II) in aqueous samples is described. The technique is envisioned for on-site, field evaluation rather than lab-based techniques. This paper presents the “proof of principle” of this new approach toward measurements of Hg(II) in water and identifies mass transport issues that would need to be overcome in order to migrate from a lab based method to field operation. The SPE material supported on a Si wafer is derivatized with an acylthiosemicarbazide, which undergoes a reaction in the presence of aqueous Hg(II) to form an oxadiazole ring. The progress of the reaction is monitored by IR spectroscopy. Following EPA guidelines, the method of detection limit (MDL) for the SPE/IR was 5?g of Hg(II)cm^?2. In a 1L sample and a 1cm² Si wafer, this translates to a detection limit of 5ppb. This system shows a high selectivity toward aqueous Hg(II) over other thiophilic heavy metal ions such as Pb(II), Cd(II), Fe(III), and Zn(II) and other metal ions such as Ni(II), Mn(II), Co(II), Cu(II), In(III), Ru(III), Na(I), and Ag(I) in aqueous solutions.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

A comparative study of glycoprotein concentration, glycoform profile and glycosylation site occupancy using isotope labeling and electrospray linear ion trap mass spectrometry

Publication year: 2012
Source:Analytica Chimica Acta, Volume 728

Chih-Yu Lin, Yi-Chun Ma, Pei-Jing Pai, Guor-Rong Her

A strategy is presented for comparative analysis of glycoproteins in which the variation of protein concentration, variation of glycosylation site occupancy and variation of glycoform profile can be determined. A comparative study was performed using stable isotope labeling of glycopeptides and peptides by formaldehyde-H2 and formaldehyde-D2 and analysis by ESI-MS analysis. The relative intensity of the nonglycosylated peptide provided information about protein concentration variation. Variation of the glycoform profile was obtained by comparing the glycoform profile of d0- and d4-dimethyl labeled glycopeptides. By knowing the variation of protein concentration and the variation of glycoform profile, the variation of glycosylation site occupancy could be calculated. The utility of the proposed strategy was demonstrated with ribonuclease B with different protein concentrations, different levels of glycosylation site occupancy and different glycoform profiles.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

The use of multi-channel silicone rubber traps as denuders for polycyclic aromatic hydrocarbons

Publication year: 2012
Source:Analytica Chimica Acta, Volume 730

Patricia B.C. Forbes, Erwin W. Karg, Ralf Zimmermann, Egmont R. Rohwer

Atmospheric polycyclic aromatic hydrocarbons are ubiquitous environmental pollutants, which may be present both in the gaseous phase and adsorbed onto the surface of particles. Denuders are sampling devices which have been effectively employed in such partitioning applications. Here we describe and characterise a novel miniature denuder consisting of two multi-channel silicone rubber traps (each 178mm long, 6mm o.d. containing 22 silicone tubes), separated by a quartz fibre filter for particle phase collection. The denuder only requires a small portable personal sampling pump to provide sampling flow rates of ?0.5Lmin^?1. Theoretical considerations indicated that the air flow through the denuder was expected to be laminar, and the linear velocity arising from longitudinal diffusion was found to be negligible. The calculated particle transmission efficiency through the denuder was found to be essentially 100% for particles>50nm, whilst the experimental overall efficiency, as determined by CPC and SMPS measurements, was 92±4%. The size resolved transmission efficiency was <60% for particles below 20nm and 100% for particles larger than 200nm. Losses could have been due to diffusion and electrostatic effects. Semi-volatile gaseous analytes are pre-concentrated in the silicone of the trap and may be thermally desorbed using a commercially available desorber, allowing for total transfer and detection of the collected analytes by GC–MS. This enhances detection limits and allows for lower sampling flow rates and shorter sampling times, which are advantageous for studies requiring high temporal resolution.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Label-free detection of C-reactive protein using reflectometric interference spectroscopy-based sensing system

Publication year: 2012
Source:Analytica Chimica Acta, Volume 728

Hyung Woo Choi, Yasuhiko Sakata, Yoshikazu Kurihara, Tooru Ooya, Toshifumi Takeuchi

Reflectometric interference spectroscopy (RIfS) is a label-free, time-resolved technique, and suitable for detecting antibody–antigen interaction. This work describes a continuous flow biosensor for C-reactive protein (CRP), involving an effective immobilization method of a monoclonal antibody against CRP (anti-CRP) to achieve highly sensitive RIfS-based detection of CRP. The silicon nitride-coated silicon chip (SiN chip) for the RIfS sensing was first treated with trimethylsilylchloride (TMS), followed by UV-light irradiation to in situ generation of homogeneous silanols on the surface. Following amination by 3-aminopropyltriethoxysilane, carboxymethyldextran (CMD) was grafted, and subsequently, protein A was immobilized to create the oriented anti-CRP surface. The immobilization process of protein A and anti-CRP was monitored with the RIfS system by consecutive injections of an amine coupling reagent, protein A and anti-CRP, respectively, to confirm the progress of each step in real time. The sensitivity was enhanced when all of the processes were adopted, suggesting that the oriented immobilization of anti-CRP via protein A that was coupled with the grafted CMD on the aminated surface of TMS-treated SiN chip. The feasibility of the present sensing system was demonstrated on the detection of CRP, where the silicon-based inexpensive chips and the simple optical setup were employed. It can be applied to other target molecules in various fields of life science as a substitute of surface plasmon resonance-based expensive sensors.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Dynamic labeling of diagnostically significant microbial cells in cerebrospinal fluid by red chromophoric non-ionogenic surfactant for capillary electrophoresis separations

Publication year: 2012
Source:Analytica Chimica Acta, Volume 728

Marie Horká, Filip R?ži?ka, Anna Kubesová, Karel Šlais

During bacterial infections of the central nervous system the number of microorganisms in the cerebrospinal fluid is often ranging from few up to hundreds of cells per milliliter. The electrophoretic techniques with the UV-detection reach a detection limit for whole cells of approximately 10⁷ cells per milliliter. The coupling of the filtration cartridge with capillary isoelectric focusing can improve the detection limit by four orders of magnitude. In order to improve the detection limit the red non-ionogenic surfactant 1-[[4-(phenylazo)phenyl]azo]-2-hydroxy-3-naphthoic acid polyethylene glycol ester, PAPAN 1000, has been prepared and used for the dynamic labeling of analytes before filtration of the sample with a concentration modulation in the analysis of proteins or microorganisms. Values of isoelectric points of labeled analytes have been calculated using pI markers detectable at 515nm and have been found comparable with pI of the native compounds. Minimum detectable amounts of proteins and microorganisms were lower than nanograms and a hundred labeled cells, respectively. The introduced method, coupling of the filtration cerebrospinal fluid spiked with microorganisms and labeled by PAPAN, facilitates their rapid CIEF separation in the pH gradient pH range of 2–5 at their clinically important level 10¹ to 10² cells per milliliter.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

A ratiometric fluorescence sensor for Be2+ based on Beryllon II/layered double hydroxide ultrathin films

Publication year: 2012
Source:Analytica Chimica Acta, Volume 728

Xiaolan Ji, Wenying Shi, Shitong Zhang, Min Wei, David G. Evans, Xue Duan

A ratiometric fluorescence sensor for Be²⁺ has been fabricated via alternate assembly of 2-(3,6-disulfo-8-hydroxynaphthylazo)-1,8-dihydroxynaphthalene-3,6-disulfonate (Beryllon II) and MgAl-LDH nanosheets on quartz substrates using the layer-by-layer (LBL) deposition technique. UV–vis absorption and the fluorescence emission spectroscopy indicate a stepwise and regular growth of the Beryllon II/LDH UTFs upon increasing deposition cycle. The film of Beryllon II/LDH possesses a periodic layered structure perpendicular to the substrate revealed by X-ray diffraction and scanning electron microscopy. Atomic force microscopy images show that the film surface is continuous and uniform. The Beryllon II/LDH UTFs display ratiometric fluorescence response for Be²⁺ with a linear response range in 1.0×10^?7–1.9×10^?6 molL^?1 and a detection limit of 4.2×10^?9 molL^?1. Furthermore, the ratiometric sensor exhibits good repeatability, high stability (thermal, storage and mechanical) as well as excellent selectivity toward Be²⁺. XPS and Raman measurements demonstrate that the specific response of the sensor is attributed to the coordination between Be²⁺ and Beryllon II in the UTF. The Beryllon II/LDH UTFs in this work can be potentially used as a chemosensor for the detection of Be²⁺ in the environmental and biomedical field.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Development of a dispersive liquid–liquid microextraction method for the determination of fluoroquinolones in chicken liver by high performance liquid chromatography

Publication year: 2012
Source:Analytica Chimica Acta, Volume 730

D. Moema, M.M. Nindi, S. Dube

A simple and cost effective sample pre-treatment method, dispersive liquid–liquid microextraction (DLLME), has been developed for the extraction of six fluoroquinolones (FQs) from chicken liver samples. Clean DLLME extracts were analyzed for fluoroquinolones using liquid chromatography with diode array detection (LC-DAD). Parameters such as type and volume of disperser solvent, type and volume of extraction solvent, concentration and composition of phosphoric acid in the disperser solvent and pH were optimized. Linearity in the concentration range of 30–500?gkg^?1 was obtained with regression coefficients ranging from 0.9945 to 0.9974. Intra-day repeatability expressed as % RSD was between 4 and 7%. The recoveries determined in spiked blank chicken livers at three concentration levels (i.e. 50, 100 and 300?gkg^?1) ranged from 83 to 102%. LODs were between 5 and 19?gkg^?1 while LOQs ranged between 23 and 62?gkg^?1. All of the eight chicken liver samples obtained from the local supermarkets were found to contain at least one type of fluoroquinolone with enrofloxacin being the most commonly detected. Only one sample had four fluoroquinolone antibiotics (ciprofloxacin, difloxacin, enrofloxacin, norfloxacin). Norfloxacin which is unlicensed for use in South Africa was also detected in three of the eight chicken liver samples analyzed. The concentration levels of all FQs antibiotics in eight samples ranged from 8.8 to 35.3?gkg^?1, values which are lower than the South African stipulated maximum residue limits (MRL).

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Active Cellular Sensing with Quantum Dots: Transitioning from Research Tool to Reality

Publication year: 2012
Source:Analytica Chimica Acta

James B. Delehanty, Kimihiro Susumu, Rachel L. Manthe, W. Russ Algar, Igor L. Medintz

The application of luminescent semiconductor quantum dots (QDs) within a wide range of biological imaging and sensing formats is now approaching its fifteenth year. The unique photophysical properties of these nanomaterials have long been envisioned as having the potential to revolutionize biosensing within cellular studies that rely on fluorescence. However, it is only now that these materials are making the transition towards accomplishing this goal. With the idea of understanding how to actively incorporate QDs into different types of cellular biosensing, we review the progress in many of the areas relevant to achieving this goal. This includes the synthesis of the QDs themselves, with an emphasis on minimizing potential toxicity, along with the general methods for making these nanocrystalline structures stable in aqueous media. We next survey some methods for conjugating QDs to biomolecules to allow them to participate in active biosensing. Lastly, we extensively review many of the applications where QDs have been demonstrated in an active role in cellular biosensing. These formats cover a wide range of possibilities including where the QDs have contributed to: monitoring the cell's interaction with its extracellular environment; elucidating the complex molecular interplay that characterizes the plasma membrane; understanding how cells continuously endocytose and exocytose materials across the cellular membrane; visualizing organelle trafficking; and, perhaps most importantly, monitoring the intracellular presence of target molecules such as nucleic acids, nutrients, cofactors, and ions or, alternatively, intracellular responses to external changes in the environment. We illustrate these processes with examples from the recent literature and focus on what QDs can uniquely contribute along with discussing the benefits and liabilities of each sensing strategy. A perspective on where this field is expected to develop in both the near and long-term is also provided.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Foreword for Analytica Chimica Acta Volume 750

Publication year: 2012
Source:Analytica Chimica Acta

Paul Worsfold, Ulli Krull, Alan Townshend

Posted on 28 May 2012 | 12:44 pm

Photoactivation by visible light of CdTe quantum dots for inline generation of reactive oxygen species in an automated multipumping flow system

Publication year: 2012
Source:Analytica Chimica Acta

David S.M. Ribeiro, Christian Frigerio, João L.M. Santos, João A.V. Prior

Quantum dots (QD) are semiconductor nanocrystals able to generate free radical species upon exposure to an electromagnetic radiation, usually in the ultraviolet wavelength range. In this work, CdTe QD were used as highly reactive oxygen species (ROS) generators for the control of pharmaceutical formulations containing epinephrine. The developed approach was based on the chemiluminometric monitoring of the quenching effect of epinephrine on the oxidation of luminol by the produced ROS. Due to the relatively low energy band-gap of this chalcogenide a high power visible light emitting diode (LED) lamp was used as photoirradiation element and assembled in a laboratory-made photocatalytic unit. Owing to the very short lifetime of ROS and to ensure both reproducible generation and time-controlled reaction implementation and development, all reactional processes were implemented inline by using an automated multipumping micro-flow system. A linear working range for epinephrine concentration of up to 2.28×10^?6 molL^?1 (r=0.9953; n=5) was verified. The determination rate was about 79 determinations per hour and the detection limit was about 8.69×10^?8 molL^?1. The results obtained in the analysis of epinephrine pharmaceutical formulations by using the proposed methodology were in good agreement with those furnished by the reference procedure, with relative deviations lower than 4.80%.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

A study of the removal of heavy metals from aqueous solutions by Moringa oleifera seeds and amine-based ligand 1,4-bis[N,N-bis(2-picoyl)amino]butane

Publication year: 2012
Source:Analytica Chimica Acta, Volume 730

Veronica Obuseng, Florence Nareetsile, Habauka M. Kwaambwa

Uptake for lead, copper, cadmium, nickel and manganese from aqueous solution using the Moringa oleifera seeds biomass (MOSB) and amine-based ligand (ABL) was investigated. Experiments on two synthetic multi-solute systems revealed that MOSB performed well in the biosorption and followed the decreasing orders Pb(II)>Cu(II)>Cd(II)>Ni(II)>Mn(II) and Zn(II)>Cu(II)>Ni(II). The general trend of the heavy metal ions uptake by the amine-based ligand followed decreased in the order Mn>Cd>Cu>Ni>Pb, which is the reverse trend for what was observed for MOSB. Comparing the single- and multi-metal solutions, there was no clear effect in the biosorption capacity of MOSB suggesting the presence of sufficient active binding sites for all metal ions studied. The MOSB performance is also not affected by pH in the range 3.5–8.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Development of an oxidative dehydrogenation-based fluorescent probe for Cu2+ and its biological imaging in living cells

Publication year: 2012
Source:Analytica Chimica Acta

Jiangli Fan, Xiaojian Liu, Mingming Hu, Hao Zhu, Fengling Song, Xiaojun Peng

Based on a boron dipyrromethene (BODIPY) derivative containing an N, O and S tridentate ligand, a Cu²⁺ fluorescent probe BTCu was developed. The detection mechanism was verified as Cu²⁺-promoted oxidative dehydrogenation of an amine moiety, leading to a formation of a fluorescent Cu⁺–Schiff base complex. Free BTCu exhibited a maximum absorption wavelength at 496nm, and a very weak maximum emission at 511nm. Upon addition of various metals ions, it showed large fluorescence enhancement toward Cu²⁺ (417-fold in MeCN and 103-fold in MeCN/HEPES solution, respectively) with high selectivity. The detection limits are as low as 1.74×10^?8 M and 4.96×10^?8 M in the two different solutions, respectively. And BTCu could work in a wide pH range with an extraordinary low pK a of 1.21±0.06. Using fluorescence microscopy, the probe was shown to be capable of penetrating into living cells and imaging intracellular Cu²⁺ changes.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Potentiometric stripping analysis of methyl and ethyl parathion employing carbon nanoparticles and halloysite nanoclay modified carbon paste electrode

Publication year: 2012
Source:Analytica Chimica Acta

Bankim J. Sanghavi, Gary Hirsch, Shashi P. Karna, Ashwini K. Srivastava

Carbon nanoparticles (CNPs) and halloysite nanoclay (HNC) modified carbon paste electrode (HNC-CNP-CPE) was developed for the determination of methyl parathion (MP) and ethyl parathion (EP). The electrochemical behavior of these molecules was investigated employing cyclic voltammetry (CV), chronocoulometry (CC), electrochemical impedance spectroscopy (EIS) and potentiometric stripping analysis (PSA). After optimization of analytical conditions employing this electrode at pH 5.0 in acetate buffer (0.1M), the peak currents were found to vary linearly with its concentration in the range of 1.55 × 10^?9 to 3.67 × 10^?6 M and 1.21 × 10^?9 to 4.92 × 10^?6 M for MP and EP respectively. The detection limits (S/N=3) of 4.70 × 10^?10 M and 3.67 × 10^?10 M were obtained for MP and EP respectively using PSA. The prepared modified electrode showed several advantages such as simple preparation method, high sensitivity, very low detection limits and excellent reproducibility. The proposed method was employed for the determination of MP and EP in fruits, vegetables, water and soil samples.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Quantum Dot-enhanced Detection of Dual Short RNA Sequences via One-step Template-Dependent Surface Hybridization

Publication year: 2012
Source:Analytica Chimica Acta

Wenqing Song, Xue Qiu, Choiwan Lau, Jianzhong Lu

A novel multiplexed method for short RNA detection is reported that employs a design strategy in which capture and reporter probes anneal to each other in the presence of a short RNA target via the formation of a stable three-component complex. Quantum dots (QDs) functionalized with reporter DNA are thus specifically bound onto a capture probe-modified 96-well plate by one-step hybridization for simple RNA detection. In comparison with conventional organic dye-modified reporter probes, the use of reporter DNA-modified QD conjugates increase the melting temperature and lead to the detection of short RNA without the need for a ligation reaction. Moreover, QD properties allow multiple short RNA sequences to be simultaneously determined via rapid and simple one-step hybridization, as exemplified herein. The present results clearly demonstrate that this new strategy can be used to detect dual-short ssRNA sequence at concentrations of 10 pM in 100?L.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

35Cl/37Cl isotope effects in 103Rh NMR of [RhCln(H2O)6?n]3?n complex anions in hydrochloric acid solution as a unique ‘NMR finger-print’ for unambiguous speciation

Publication year: 2012
Source:Analytica Chimica Acta, Volume 730

Theodor E. Geswindt, Wilhelmus J. Gerber, D. Jacobus Brand, Klaus R. Koch

A detailed analysis of the ³⁵Cl/³⁷Cl isotope effects observed in the 19.11MHz ¹⁰³Rh NMR resonances of [RhCl n (H2O)6?n ]^3?n complexes (n =3–6) in acidic solution at 292.1K, shows that the ‘fine structure’ of each ¹⁰³Rh resonance can be understood in terms of the unique isotopologue and in certain instances the isotopomer distribution in each complex. These ³⁵Cl/³⁷Cl isotope effects in the ¹⁰³Rh NMR resonance of the [Rh^35/37Cl6]^3? species manifest only as a result of the statistically expected ³⁵Cl/³⁷Cl isotopologues, whereas for the aquated species such as for example [Rh^35/37Cl5(H2O)]^2?, cis-[Rh^35/37Cl4(H2O)2]^? as well as the mer-[Rh^35/37Cl3(H2O)3] complexes, additional fine-structure due to the various possible isotopomers within each class of isotopologues, is visible. Of interest is the possibility of the direct identification of stereoisomers cis-[RhCl4(H2O)2]^?, trans-[RhCl4(H2O)2]^?, fac-[RhCl3(H2O)3] and mer-[RhCl3(H2O)3] based on the ¹⁰³Rh NMR line shape, other than on the basis of their very similar ?(¹⁰³Rh) chemical shift. The ¹⁰³Rh NMR resonance structure thus serves as a novel and unique ‘NMR-fingerprint’ leading to the unambiguous assignment of [RhCl n (H2O)6?n ]^3?n complexes (n =3–6), without reliance on accurate ?(¹⁰³Rh) chemical shifts.

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm

Liquid-phase microextraction in a microfluidic-chip–High enrichment and sample clean-up from small sample volumes based on three-phase extraction

Publication year: 2012
Source:Analytica Chimica Acta

María D. Ramos Payán, Henrik Jensen, Nickolaj Jacob Petersen, Steen Honoré Hansen, Stig Pedersen-Bjergaard

In this work, a microfluidic-chip based system for liquid-phase microextraction (LPME-chip) was developed. Sample solutions were pumped into the LPME-chip with a micro-syringe pump at a flow rate of 3-4?L/min. Inside the LPME chip, the sample was in direct contact with a supported liquid membrane (SLM) composed of 0.2?L dodecyl acetate immobilized in the pores of a flat membrane of polypropylene (25?m thickness). On the other side of the SLM, the acceptor phase was present. The acceptor phase was either pumped at 1?L/min during extraction, or was kept stagnant (stop-flow). Amitriptyline, methadone, haloperidol, loperamide, and pethidine were selected as model analytes, and they were extracted from alkaline sample solution, through the SLM, and into 10mM HCl or 100mM HCOOH functioning as acceptor phase. Subsequently, the acceptor phase was either analyzed off-line by capillary electrophoresis for exact quantification, or on-line by UV detection or electrospray ionization mass spectrometry for time profiling of concentrations. The LPME-chip was found to be highly effective, and extraction efficiencies were in the range of 52-91%. When the flow of acceptor phase was turned off during extraction (stop-flow), analyte enrichment increased linearly with the extraction time. After 10minutes as an example, amitriptyline was enriched by a factor of 42 from only 30?L sample solution, and after 120minutes amitriptyline was enriched by a factor of 500 from 320?L sample solution. This suggested that the LPME-chip has great potentials for very efficient analyte enrichments from limited sample volumes in the future

Graphical abstract

Graphical abstract Highlights

Posted on 28 May 2012 | 12:44 pm