Separation of polycyclic aromatic hydrocarbon metabolites by gamma-cyclodextrin-modified micellar electrokinetic chromatography with laser-induced fluorescence detection

[Chemical methods for determination of hydroxylated metabolites of polycyclic aromatic hydrocarbons and polychlorinated biphenyls in biological material]

This review presents methods for the analysis of hydroxylated metabolites of polycyclic aromatic hydrocarbons and polychlorinated biphenyls in humans and animals. These metabolites serve as biomarkers of human and animal exposure to the mentioned pollutants, but some metabolites also have toxic properties. Most are analysed in urine, which is the most accessible sample, but they can also be analysed in human and animal liver, bile, and adipose tissue.Their analysis is important for assessing bioavailability of aromatic pollutants and their toxicity in human organism, but also the toxicity of metabolites themselves. Advancements in analytical methods have made it possible to analyse multiple metabolites in a sample at the same time. New extraction techniques and more precise and selective qualitative and quantitative analyses can now detect very low metabolite concentrations. An extra advantage is that these simple techniques require less chemicals and time.

Environmental analysis based on luminescence in organized supramolecular systems

The use of organized supramolecular systems-including micellar media and cyclodextrin inclusion complexes-combined with luminescence techniques in the study and determination of compounds and elements of environmental interest from 1990 to 2005 is reviewed. Analyses of environmental samples performed using fluorescence, photochemically induced fluorescence and phosphorescence spectroscopy as well as liquid chromatography, capillary electrophoresis and flow injection with luminescence detection in the presence of these organized media are described in detail.

Determination of nateglinide in animal plasma by micellar electrokinetic chromatography and on-line sweeping technique

A micellar electrokinetic chromatography (MEKC) method was developed for the determination of nateglinide in animal plasma by on-line sweeping technique, in which plasma samples were simply deproteinized with acetonitrile, and analyzed with 16 mmol/L NaH2PO4 + 6 mmol/L Na2B4O7 + 60 mmol/L sodium dodecyl sulfate (SDS) (pH 7.14) as the running buffer, a fused-silica capillary as the separation tube, 21 kV as the running voltage and UV detection at 214 nm. Under these conditions, more than 100-fold enrichment of nateglinide was obtained with the good linear relation in the range of nateglinide plasma concentration 0.2-7 mg/L (R = 0.998). The method could be applied successfully to determine trace drugs in clinical analysis.

Biomonitoring of polycyclic aromatic hydrocarbons in human urine

Measurement of polycyclic aromatic hydrocarbons (PAH) metabolites in human urine is the method of choice to determine occupational and/or environmental exposure of an individual to PAH, in particular, when multiple routes of exposure have to be taken into account. Requirements for methods of biomonitoring PAH metabolites in urine are presented. Studies using 1-hydroxypyrene or phenanthrene metabolites including its phenols and dihydrodiols are summarized. The role of these PAH metabolites as established biomarkers and also more recent developments of PAH biomonitoring are discussed.

Separation of monomethyl-benz[a]anthracene isomers using cyclodextrin-modified electrokinetic chromatography

Cyclodextrin-modified electrokinetic chromatography (CD-EKC) was investigated for the separation of 12 monomethylbenz[a]anthracene (MBA) isomers. Combined use of a polymeric surfactant, poly(sodium 10-undecenyl sulfate) (poly-SUS), with various types of neutral cyclodextrins (CDs) [beta-CD, gamma-CD, dimethyl-beta-CD (DM-beta-CD), trimethyl-beta-CD (TM-beta-CD) and hydroxypropyl-beta-CD (HP-beta-CD)] were successful in CD-EKC separation of the MBA isomers. Baseline resolution of 10 of the 12 isomers, except for 9-MBA and 2-MBA, was achieved with gamma-CD at pH 9.75. The beta-CD, gamma-CD, and beta-CD derivatives (DM-beta-CD, TM-beta-CD, HP-beta-CD) were found to have different resolution and selectivity. Additionally, the tR/t0 values of isomers were found to be dependent on the type and concentration of the CD additives. In general, tR/t0 values of MBA isomers decrease with an increase in the concentration of beta-CD derivatives, whereas the reversed was true when the concentrations of native beta-CD and gamma-CD were varied. The combination of 5 mM gamma-CD, 0.5% (w/v) poly-SUS, 35% (v/v) acetonitrile at a pH of 9.75 provided the best selectivity and resolution of the MBA isomers with a separation time of 110 min. However, the use of 30 mM DM-beta-CD under similar EKC conditions resulted in much faster separation (ca. 16 min) of 10 MBA isomers.

Laser-induced fluorescence detection at 266 nm in capillary electrophoresis. Polycyclic aromatic hydrocarbon metabolites in biota

The separation of five phenolic polycyclic aromatic hydrocarbon metabolites (hydroxy-PAHs) has been performed by cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) using a 30 mM borate buffer (pH 9.0) containing 60 mM sodium dodecyl sulfate and varying concentrations of gamma-cyclodextrin (gamma-CD). A concentration of 12.5 mM gamma-CD was found to provide a baseline separation of the five hydroxy-PAHs. We applied conventional fluorescence and laser-induced fluorescence (LIF) detection, using a new, small-size, quadrupled Nd-YAG laser emitting at 266 nm. The best limits of detection, in the low ng/ml range, were achieved using LIF detection. For all analytes, linearity was observed up to ca. 100 ng/ml. As an application, conjugated pyrene metabolites in hepatopancreas samples from the terrestrial isopods Oniscus asellus and Porcellio scaber were separated and detected. Finally, flatfish bile samples from individuals exposed to polluted sediment or crude oil, which were part of an interlaboratory study, were analyzed by CD-MEKC with conventional fluorescence and LIF detection to determine the 1-hydroxypyrene concentrations.

Approaching a million-fold sensitivity increase in capillary electrophoresis with direct ultraviolet detection: cation-selective exhaustive injection and sweeping

A novel method that combines two on-line concentration techniques in capillary electrophoresis (CE), namely, sample stacking with electrokinetic injection (field-enhanced sample injection, FESI) and sweeping, afforded the detection of positively chargeable analytes in parts per trillion (ppt) levels. The main idea is to selectively introduce by FESI as many molecules of cationic analytes as possible from a very dilute sample solution and focus the resulting zone by sweeping. Limit of detection values (signal-to-noise ratio 3) of 4.1 and 8.0 ppt-the lowest concentration reported by direct UV detection in CE-with average plate numbers of 3.6 x 10(5) and 4.4 x 10(5) are obtained for laudanosine and naphthylamine (standard solutions), respectively. This translates to improvements in peak heights compared with usual injection approaching a million-fold. Optimization schemes and application to quantitative and qualitative analyses are also investigated.

Biomonitoring of environmental polycyclic aromatic hydrocarbon exposure by simultaneous measurement of urinary phenanthrene, pyrene and benzo[a]pyrene hydroxides

A high-performance liquid chromatographic method with fluorescence detection was developed which enables the simultaneous determination of the urinary polycyclic aromatic hydrocarbon metabolites 3-hydroxyphenanthrene, 1-hydroxypyrene and 3-hydroxybenzo[a]pyrene. The method has small solvent consumption because of the use of a microbore RP C18 column and a relatively short run time. Low detection limits of 0.02 nmol/l for 3-hydroxypyrene to 0.19 nmol/l for 3-hydroxybenzo[a]pyrene were attained. In contrast, the detection limits of alpha-naphthol and 9,10-dihydroxy-9,10-dihydrophenanthrene were not adequate for the determination of environmental exposure. The developed method was successfully used for the analysis of urine samples from children.

Capillary electrophoresis and capillary electrochromatography of organic pollutants

Capillary electrophoresis (CE) has a unique capability for separation of analytes of environmental concern, particularly those that are more polar and ionic, based on the complementary separation principle of electrophoresis. In the past few years, CE has been selectively used to analyze various classes of compounds having current or potential environmental relevance. This review outlines the current status of CE for the determination of environmental pollutants, based predominantly on research results published from the beginning of 1997 to early 1999. Covered are environmental pollutants of all types except pesticides and inorganics. Certain naturally produced toxins are also covered because of their significant impacts upon human health and the environment. CE methods, as with all methods, must be judged on their ability to provide approaches that are reliable, sensitive, selective, and rapid, while meeting "green chemistry" initiatives for pollution prevention. We also compare CE methods to benchmark environmental techniques involving gas chromatography-mass spectrometry (GC-MS), liquid chromatography-mass spectrometry (LC-MS), and high performance liquid chromatography (HPLC).

Electrokinetic chromatography

The important features of electrokinetic chromatography are critically reviewed. Special emphasis is given to systems using micelles as pseudostationary phase. Short and comprehensive overviews are given on the subjects of separation, comparison with capillary electrochromatography, on-line coupling with mass spectrometry, and developments that are expected in the future. A greater coverage on the subject of improvement of detection sensitivity, specifically by on-line concentration was also contributed.