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.

Determination of kanamycin in serum by solid-phase extraction, pre-capillary derivatization and capillary electrophoresis.

An effective method based on solid-phase extraction (SPE) and capillary electrophoresis (CE) for the determination of kanamycin in human serum was developed and validated. Off-line SPE was employed for the isolation of kanamycin from serum on a carboxypropyl-bonded phase (CBA) weak cation-exchange cartridge. A mixture of 0.2 M borate (pH 10.5)-methanol (50:50, v/v) was used as analyte eluting solvent. After pre-capillary derivatization with o-phthalaldehyde/mercaptoacetic acid reagent, the sample was analyzed by CE with a separation buffer of 30 mM borax, pH 10.0, containing 16% (v/v) methanol. A linear response over the concentration range 5-40 microgram/ml was obtained with a detection limit of 2 microgram/ml. Intra-day and inter-day precision were 6.2 and 10.3% RSD, respectively. Recoveries of approximately 90% were found. For the determination of lower levels of kanamycin (<5 microgram/ml), NH(4)OH (25%, w/v)-methanol (30:70, v/v) was used for analyte elution. After evaporation, reconstitution and derivatization, the sample was analyzed by on-line field-amplified sample stacking (FASS) CE. Good linearity in the concentration range 0.4-5 microgram/ml was obtained with a detection limit of 0.1 microgram/ml. Intra-day and inter-day RSD were 3.4 and 11.2%, respectively. Recoveries of approximately 60% were found. The method was successfully applied to the analysis of kanamycin in sera of tuberculosis patients at peak level and trough level concentrations.

Large-volume sample stacking for on-capillary sample enrichment in the determination of naphthalene- and benzenesulfonates in real water samples by capillary zone electrophoresis.

We investigated the on-line preconcentration of a test mixture of 15 substituted and unsubstituted naphthalene(NSs) and benzenesulfonates (BZSs) by large-volume sample stacking (LVSS). Analyses were carried out by capillary zone electrophoresis (CZE) with on-column UV detection. In particular, we focused on how experimental variables such as the inside diameter of the capillary, the volume of sample introduced and polarity switching influenced the enrichment procedure. The best results were obtained when 300 nl were injected and stacked using a bubble cell capillary. Under these conditions, LVSS increased the detector response of conventional hydrodynamic injection by a factor of 40. The limits of detection of the method were between 5 and 10 microg l(-1). Determinations were reproducible, in terms of peak area and migration time, under such conditions. The performance of the method was examined by determining NS and BZS in real samples, such as tap, river and surface waters and inflow/outflow waters from a water treatment plant. Real samples were injected directly into the CZE column with little or no preparation.

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).

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.

Comparative study of capillary zone electrophoresis and micellar electrokinetic capillary chromatography for the separation of naphthalenedisulfonate isomers.

We investigated the separation of a test mixture of nine substituted and unsubstituted naphthalenedisulfonate isomers by capillary electrophoresis with a UV diode array detector. In particular, we focused on how the composition of the running buffer affected the separation selectivity. When capillary zone electrophoresis was carried out, the best results were obtained when organic solvents such as ethanol or propan-2-ol were added. Eight peaks were baseline separated but in no case were all the unsubstituted isomers separated. Therefore, capillary electrophoretic separation of the compounds was examined in the presence of micellar agents, such as sodium dodecyl sulfate, polyethylene glycol dodecyl ether (Brij 35) and cetyltrimethylammonium bromide. All the substituted isomers and two of the unsubstituted isomers were well resolved within 20 min by micellar electrokinetic capillary chromatography when Brij 35 was used as micellar agent. Separations were reproducible, in terms of peak area and migration time, under these conditions.

Determination of amoxicillin in plasma samples by capillary electrophoresis.

We have developed a capillary zone electrophoresis (CZE) method for determining amoxicillin in animal plasma samples. Sample clean-up involved solid-phase extraction onto Sep-Pak C18 cartridges followed by elution with water-methanol (85:15). This paper describes two different techniques to increase the sensitivity of the CZE method: field-amplified sample injection (FASI) and electrokinetic injection. We have enhanced the detection limit to 280 micrograms l-1 by the FASI technique.

Evaluation of different electrolyte systems and on-line preconcentrations for the analysis of haloacetic acids by capillary zone electrophoresis.

This study compares the sodium chromate, potassium hydrogenphthalate, 2,6-naphthalenedicarboxylic acid dipotassium and sodium tetraborate electrolyte systems, for determining haloacetic acids using capillary zone electrophoresis with and without modified electroosmotic flow. In order to detect low concentrations of these compounds, an on-line preconcentration step was carried out. Results were good when standard solutions were analysed, but when the method was applied to real samples, the sample had to be pretreated to decrease the interference of the matrix. For this reason, a solid-phase extraction process with LiChrolut EN cartridges was applied to clean up the sample before the injection.

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.

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.

Determination of carboxylic acids, sugars, glycerol and ethanol in wine and grape must by ion-exchange high-performance liquid chromatography with refractive index detection.

Method to determine the major carboxylic acids, sugars, glycerol and ethanol in wine and grape must was developed using an ion-exchange column and refractive index detector. A solid-phase extraction method with a strong anion exchanger was used to determine these compounds in sweet wines and in grape musts. With this method it is possible to determine malic acid in sweet wines and in grape musts without interference from sugars. This high-performance liquid chromatographic method was compared with standard methods of analysis. There was good agreement in the accuracy and precision of the compared methods.