Optimization in sample stacking for the measurement of short chain organic acids in serum of natural rubber latex by capillary electrophoresis

It is of interest to measure the short chain organic acid content in natural latex serum, and capillary electrophoresis (CE) has proved to be a good tool for this study. However, for some acids, a higher sensitivity than that provided by the standard methods was needed. Therefore, a stacking effect was optimised and applied both for standards and real samples. Large-volume injection of sample solutions prepared in low conductivity matrices containing 50% acetonitrile (v/v) and 0.5% NaCl (w/v) gave the best results with enhancement factors over 17 and recoveries ranging from 83±14 to 122±4%.     

Speciation and detection of arsenic in aqueous samples: A review of recent progress in non-atomic spectrometric methods

Inorganic arsenic (As) displays extreme toxicity and is a class A human carcinogen. It is of interest to both analytical chemists and environmental scientists. Facile and sensitive determination of As and knowledge of the speciation of forms of As in aqueous samples are vitally important. Nearly every nation has relevant official regulations on permissible limits of drinking water As content. The size of the literature on As is therefore formidable. The heart of this review consists of two tables: one is a compilation of principal official documents and major review articles, including the toxicology and chemistry of As. This includes comprehensive official compendia on As speciation, sample treatment, recommended procedures for the determination of As in specific sample matrices with specific analytical instrument(s), procedures for multi-element (including As) speciation and analysis, and prior comprehensive reviews on arsenic analysis. The second table focuses on the recent literature (2005–2013, the coverage for 2013 is incomplete) on As measurement in aqueous matrices. Recent As speciation and analysis methods based on spectrometric and electrochemical methods, inductively coupled plasma-mass spectrometry, neutron activation analysis and biosensors are summarized. We have deliberately excluded atomic optical spectrometric techniques (atomic absorption, atomic fluorescence, inductively coupled plasma-optical emission spectrometry) not because they are not important (in fact the majority of arsenic determinations are possibly carried out by one of these techniques) but because these methods are sufficiently mature and little meaningful innovation has been made beyond what is in the officially prescribed compendia (which are included) and recent reviews are available.     

Chiral separation of agricultural fungicides

Fungicides are very important and diverse environmental and agricultural concern species. Their determination in commercial formulations or environmental matrices, requires highly efficient, selective and sensitive methods. A significant number of these chemicals are chiral with the activity residing usually in one of the enantiomers. The different toxicological and degradation behavior observed in many cases for fungicide enantiomers, results in the need to investigate them separately. For this purpose, separation techniques such as GC, HPLC, supercritical fluid chromatography (SFC) and CE have widely been employed although, at present, HPLC still dominates chromatographic chiral analysis of fungicides. This review covers the literature concerning the enantiomeric separation of fungicides usually employed in agriculture grouping the chiral separation methodologies developed for their analysis in environmental, biological, and food samples.     

Single-drop microextraction as a powerful pretreatment tool for capillary electrophoresis: A review

Single drop microextraction (SDME) is a convenient and powerful preconcentration and sample cleanup method for capillary electrophoresis (CE). In SDME, analytes are typically extracted from a sample donor solution into an acceptor drop hanging at the inlet tip of a capillary. The enriched drop is then introduced to the capillary for CE analysis. Since the volume of the acceptor drop can be as small as a few nanoliters, the consumption of solvents can be minimized and the preconcentration effect is enhanced. In addition, by covering the acceptor phase with an organic layer or by using an organic acceptor phase, inorganic ions such as salts in the sample solution can be blocked from entering the acceptor phase, providing desalting effects. Here, we describe the basic principles and instrumentation for SDME and its coupling with CE. We also review recent developments and applications of SDME-CE.     

Atmospheric pressure photoionization for coupling liquid-chromatography to mass spectrometry: A review

This review presents the state-of-the-art techniques that couple liquid chromatography (LC) and mass spectrometry (MS) via atmospheric pressure photoionization (APPI). The different ionization mechanisms are discussed as well as the influence of the mobile phase composition, the nature of the dopant, etc. A comparison with other ionization sources, such as electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI), is reported, and the combination of APPI with these sources is also discussed. Several applications, covering the time period of 2005-2008, for the analysis of drugs, lipids, natural compounds, pesticides, synthetic organics, petroleum derivatives, and other substances are presented.     

Development and validation of a nonaqueous capillary electrophoretic method for the enantiomeric purity determination of a synthetic intermediate of new 3,4-dihydro-2,2-dimethyl-2H-1-benzopyrans using a single-isomer anionic cyclodextrin derivative and an ionic liquid

The enantiomeric purity determination of a synthetic intermediate of new 3,4-dihydro-2,2-dimethyl-2H-1-benzopyrans, i.e. 4-amino-2,2-dimethyl-6-ethoxycarbonylamino-3,4-dihydro-2H-1-benzopyran, was successfully carried out using an anionic cyclodextrin (CD) derivative combined with a chiral ionic liquid (IL). In order to obtain high resolution and efficiency values, the addition of a chiral IL, i.e. ethylcholine bis(trifluoromethylsulfonyl)imide (EtChol NTf₂), to the background electrolyte containing heptakis(2,3-di-O-methyl-6-O-sulfo)-β-CD (HDMS-β-CD) was found to be essential. A simultaneous increase in separation selectivity and enantioresolution seems to indicate a synergistic effect of HDMS-β-CD and EtChol NTf₂. The best enantioseparation of the key intermediate was achieved using a methanolic solution of 0.75 M formic acid, 10 mM ammonium formate, 1.5 mM HDMS-β-CD and 5 mM EtChol NTf₂. Levamisole was selected as internal standard. The optimized conditions allowed the determination of 0.1% of each enantiomer in the presence of its stereoisomer using the method of standard additions. The NACE method was then fully validated with respect to selectivity, response function, trueness, precision, accuracy, linearity and limits of detection and quantification.     

Capillary zone electrophoresis and capillary electrophoresis-mass spectrometry for analyzing qualitative and quantitative variations in therapeutic albumin

The present study describes a reproducible and quantitative capillary zone electrophoresis (CZE) method, which leads to the separation of nine forms (native, oxidized and glycated) of human serum albumin (HSA). In an attempt to identify the different species separated by this CZE method, the capillary electrophoresis was coupled to mass spectrometry using a sheath liquid interface, an optimized capillary coating and a suitable CE running buffer. CE-MS analyses confirmed the heterogeneity of albumin preparation and revealed new truncated and modified forms such as Advanced Glycation End products (AGEs). Assignment of the CZE peaks was carried out using specific antibodies, carboxypeptidase A or sample reduction before or during the CE separation. Thus, five HSA forms were unambiguously identified. Using this CZE method several albumin batches produced by slightly different fractionation ways could be discriminated. Furthermore, analyses of HSA preparations marketed by five pharmaceutical industries revealed that two therapeutic albumins, including that marketed by LFB, contained the highest proportion of native form and lower levels of oxidized forms.     

New development in in-capillary electrophoresis techniques for kinetic and inhibition study of enzymes

Enzymes are often quantified by measuring their biological activity. Capillary electrophoresis is gaining its position in this field due to the ongoing trend to miniaturize biochemical assays.     

Chiral separation of metalaxyl and benalaxyl fungicides by electrokinetic chromatography and determination of enantiomeric impurities

The enantiomers of two acylamine fungicides (metalaxyl and benalaxyl) were separated by EKC using CDs as chiral selectors. The use of 15 mM succinyl-γ-CD for metalaxyl and 5 mM succinyl-β-CD for benalaxyl dissolved in a 50 mM 2-morpholinoethanesulfonic acid buffer (pH 6.5), enabled the chiral separation of metalaxyl enantiomers in 11.5 min with a resolution of 3.1 and the enantiomeric separation of benalaxyl in 7.5 min with a resolution close to 15. Under these conditions, the two enantiomers of each of the chiral compound studied were also separated from folpet, very commonly present in fungicide formulations containing metalaxyl or benalaxyl. The analytical characteristics of the two developed methods were studied in terms of precision, linearity, selectivity, limits of detection (LODs) and limits of quantitation (LOQs) showing their suitability for the determination of these compounds in commercial agrochemical formulations. Finally, the development of an in-capillary preconcentration strategy allowed the detection of enantiomeric impurities up to 1.2% in commercial products labeled as enantiomerically pure in metalaxyl-M.