Marta Calull

Determination of quinolones in plasma samples by capillary electrophoresis using solid-phase extraction.

The potential of capillary zone electrophoresis (CZE) and micellar electrokinetic capillary chromatography (MEKC) have been investigated for the separation and quantitative determination of 10 quinolone antibiotics. The influence of different conditions, such as the buffer and pH of the electrolyte, the surfactant and the ion-pairing agents added to the electrolyte and the organic modifier were studied. A buffer consisting of 40 mM sodium tetraborate at pH 8.1 containing 10% (v/v) methanol was found to be a highly efficient electrophoretic system for separating lomefloxacin, enoxacin, norfloxacin, pipemidic acid, ofloxacin, piromidic acid, flumequine, oxolinic acid, cinoxacin and nalidixic acid. A solid-phase extraction method to remove the sample matrix (pig plasma samples) was developed on a C(18) cartridge using a mixture of methanol-water (70:30, v/v). The method is specific and reproducible and mean recoveries were in the range 94.0+/-4.2% and 123.3+/-4.1% for pig plasma samples over the range used. A linear relationship between concentration and peak area for each compound in pig plasma samples was obtained in the concentration range 5-20 mg l(-1) and detection limits were between 1.1 and 2.4 mg l(-1).

Determination of ciprofloxacin, enrofloxacin and flumequine in pig plasma samples by capillary isotachophoresis--capillary zone electrophoresis.

Quinolones are a group of synthetic antibiotics that are widely used in veterinary medicine. Their residues may remain in tissues, milk, etc. intended for human consumption. The European Union fixes the maximum residue limits (MRLs) of veterinary medicinal products in foodstuffs of animal origin. Analytical methods are therefore needed to determine them in biological samples. In this study, we describe capillary isotachophoresis-capillary zone electrophoresis (ITP-CZE) to analyze three quinolones, enrofloxacin (ENR), ciprofloxacin (CPR) and flumequine (FLU), in pig plasma samples. We used solid-phase extraction with Oasis HLB cartridges as a sample pretreatment clean-up step. Capillary zone electrophoresis (CZE) requires low amounts of sample and is not as sensitive as one would wish. ITP-CZE is an easy way to increase the sample loadability and sensitivity. With this system sensitivity increases 40-fold. The detection limits for CPR, ENR and FLU were 70, 85 and 50 microg l(-1), respectively, which were lower than their MRLs in different kinds of samples. This method is simple and sensitive, and is therefore an alternative tool to the existing HPLC methods for analyzing the residuals of these quinolones in biological samples.

Separation of eleven priority phenols by capillary zone electrophoresis with ultraviolet detection

The separation and detection of eleven priority phenols using capillary zone electrophoresis with UV detection are described. Using a 70 cm x 75 μm I.D. capillary at 15 kV and an electrophoretic buffer of 20 mM sodium borate (pH 9.9 ± 0.1), the eleven compounds could be completely separated in less than 14 min. The different variables that affect separation were studied and optimized, and good linearity was obtained between 0.5 and 20 mg l−1 for 2,4-dimethylphenol (2,4-DMP) and between 0.25 and 20 mg l−1 for the other compounds, and the detection limits were 0.1 mg l−1 for all compounds except 2,4-DMP (0.25 mg l−1). Previous analyses of real samples, an off-line solid-phase extraction process with a highly cross-linked styrene-divinylbenzene copolymer cartridge was used to determine the priority phenolic compounds at low μg l−1 levels. The method was tested with tap and Ebro river waters.

Solid-phase extraction coupling to capillary electrophoresis with emphasis on environmental analysis.

This article reviews the status of solid-phase extraction (SPE) coupled with capillary electrophoresis (CE). It focuses on some of the organic pollutants which have captured the interest of analytical chemists--phenols, surfactants, dyes, polynuclear aromatic hydrocarbons (PAHs), aromatic and aliphatic amines, aromatic acids and aromatic sulfonic acids--and, in particular, on monitoring pesticides from different sources. It shows that the coupling of SPE to CE has considerable potential in the analysis of environmental pollutants.

Analysis of antibiotics in biological samples by capillary electrophoresis

Antibiotics are widely used to treat and prevent diseases in humans and animals. It is therefore important to monitor their residues in biological samples. This is a review of some of the most important antibiotic groups used in medicine: β-lactam antibiotics (penicillins and cephalosporins); aminoglycosides; quinolones; and, tetracyclines. We describe how capillary electrophoresis (CE) is used to analyze these antibiotics in biological samples. We also discuss how the biological samples are pre-treated before they are analyzed and describe several ways in which the sensitivity of CE systems can be improved.

Sorbent preconcentration procedures coupled to capillary electrophoresis for environmental and biological applications.

Sorbent preconcentration offers good strategies to overcome the poor detection limits of capillary electrophoresis (CE). The present review focuses on the recent trends of the coupling between sorbent preconcentration techniques, namely solid-phase extraction (SPE) and solid-phase microextraction (SPME), to capillary electrophoresis (CE). Special attention is given to their environmental and biological application. We also discuss the most important advantages and disadvantages of the different methodologies and briefly outline the new trends of the coupling between sorbent preconcentration and CE.

Determination of phenolic compounds at low μg 1−1 levels by various solid-phase extractions followed by liquid chromatography and diode-array detection

Abstract An off-line solid-phase extraction was carried out to determine thirteen phenolic compounds, which included eleven EPA priority phenols, using reversed-phase liquid chromatography and diode-array detection. Two different sorbents, carbon and a highly cross-linked styrene-divinylbenzene copolymer, were compared for the preconcentration process. To increase the retention of the most polar compounds, mainly phenol, tetrabutylammonium bromide was used as an ion-pair reagent in the extraction system. Better recoveries were obtained for the copolymer sorbent and the performance of the method was tested with tap and Ebro river water. Recoveries higher than 90% were obtained for all compounds when a 500-ml sample was preconcentrated using the optimum conditions found with the copolymer sorbent. The R.S.D. for a river water sample spiked at 1 μg l−1 was lower than 10% (n = 4) and the detection limits were between 65 and 100 ng l−1.

Recent trends in analytical methods and separation techniques for drugs of abuse in hair

Hair analysis of drugs of abuse has been a subject of growing interest from a clinical, social and forensic perspective for years because of the broad time detection window after intake in comparison to urine and blood analysis. Over the last few years, hair analysis has gained increasing attention and recognition for the retrospective investigation of drug abuse in a wide variety of contexts, shown by the large number of applications developed. This review aims to provide an overview of the state of the art and the latest trends used in the literature from 2005 to the present in the analysis of drugs of abuse in hair, with a special focus on separation analytical techniques and their hyphenation with mass spectrometry detection. The most recently introduced sample preparation techniques are also addressed in this paper. The main strengths and weaknesses of all of these approaches are critically discussed by means of relevant applications.

Comparative study of a solid-phase extraction system coupled to capillary electrophoresis in the determination of haloacetic compounds in tap water

This study compares four different commercial sorbents, LC-SAX (a quaternary ammonium anion exchanger), LiChrolut EN (a highly crosslinked styrene-divinylbenzene), Envi-Carb (a graphitized carbon black) and Oasis HLB [a macroporous poly(divinylbenzene-co-N-vinylpyrrolidone) copolymer], for the solid-phase extraction (SPE) of various haloacetic compounds from aqueous samples. The recoveries with the different sorbents were studied by coupling an off-line SPE system to capillary electrophoresis with indirect photometric detection. The recoveries were highest when LiChrolut EN was used. The limits of detection for the compounds are in the low microgram per litre range and the recovery values are over 80% for dichloroacetic acid and trichloroacetic acid, two of the most habitual haloacetic acids in chlorinated water, when 500 ml of standard solution was preconcentrated using this sorbent. Finally, the performance of the method with different water samples, the effect of chlorination in a treatment plant and the evolution of the haloacetic acids in the water distribution system were tested and the results were compared with those obtained using liquid-liquid extraction and gas chromatography-mass spectrometry.

Capillary zone electrophoresis with indirect UV detection of haloacetic acids in water

A capillary zone electrophoresis (CZE) system for determining haloacetic acids in water was optimized with indirect photometric detection. Two different carrier electrolytes, potassium hydrogenphthalate and sodium 2,6-naphthalenedicarboxylate, were evaluated in terms of sensitivity and two different electroosmotic flow modifiers, tetradecyltrimethylammonium bromide and hexadecyltrimethylammonium bromide, were tested. Parameters such as electrolyte concentration and pH, and the concentration of the electroosmotic flow modifiers, which affect the CZE separations, were investigated. The method was used to determine haloacetic acids in chlorine tap water using the liquid-liquid extraction process.