Untargeted metabolomics of human keratinocytes reveals the impact of exposure to 2,6-dichloro-1,4-benzoquinone and 2,6-dichloro-3-hydroxy-1,4-benzoquinone as emerging disinfection by-products.

INTRODUCTION: The 2,6-dichloro-1,4-benzoquinone (DCBQ) and its derivative 2,6-dichloro-3-hydroxy-1,4-benzoquinone (DCBQ-OH) are disinfection by-products (DBPs) and emerging pollutants in the environment. They are considered to be of particular importance as they have a high potential of toxicity and they are likely to be carcinogenic. OBJECTIVES: In this study, human epidermal keratinocyte cells (HaCaT) were exposed to the DCBQ and its derivative DCBQ-OH, at concentrations equivalent to their IC20 and IC50, and a study of the metabolic phenotype of cells was performed. METHODS: The perturbations induced in cellular metabolites and their relative content were screened and evaluated through a metabolomic study, using 1H-NMR and MS spectroscopy. RESULTS: Changes in the metabolic pathways of HaCaT at concentrations corresponding to IC20 and IC50 of DCBQ-OH involved the activation of cell membrane α-linolenic acid, biotin, and glutathione and deactivation of glycolysis/gluconeogenesis at IC50. The changes in metabolic pathways at IC20 and IC50 of DCBQ were associated with the activation of inositol phosphate, pertaining to the transfer of messages from the receptors of the membrane to the interior as well as with riboflavin. Deactivation of biotin metabolism was recorded, among others. The cells exposed to DCBQ exhibited a concentration-dependent decrease in saccharide concentrations. The concentration of steroids increased when cells were exposed to IC20 and decreased at IC50. Although both chemical factors stressed the cells, DCBQ led to the activation of transporting messages through phosphorylated derivatives of inositol. CONCLUSION: Our findings provided insights into the impact of the two DBPs on human keratinocytes. Both chemical factors induced energy production perturbations, oxidative stress, and membrane damage.

Matrix solid-phase dispersion based on magnetic ionic liquids: An alternative sample preparation approach for the extraction of pesticides from vegetables.

In this study, we propose, for the first time, the direct use of a magnetic ionic liquid (MIL) in a matrix solid-phase extraction procedure. Because of the magnetic properties, the MIL can be harvested directly after the extraction step, using a magnet, while its hydrophobic nature makes feasible the extraction of analytes. Raw vegetables of high water content can be analyzed without any pretreatment. The viscous nature of the selected MIL assists in blending with the matrix, while its hydrophobicity facilitates easier separation and retrieval. Additionally, no solid dispersing materials or co-sorbents are needed. A simple, low-cost analytical method for the determination of multi-class pesticides residues in raw vegetables was developed, with satisfactory recoveries.

Melamine Sponge Functionalized with Urea-Formaldehyde Co-Oligomers as a Sorbent for the Solid-Phase Extraction of Hydrophobic Analytes.

A new procedure for the functionalization of melamine sponge (MeS) with urea-formaldehyde (UF) co-oligomers is put forward. The procedure differs from the typical synthesis of the UF co-polymer, as it employs a base-catalyzed condensation step at certain concentrations of urea and formaldehyde. The produced melamine-urea-formaldehyde (MUF) sponge cubes are hydrophobic, despite the presence of hydrophilic groups in the oligomers. The MUF sponge developed herein is used as a sorbent for the solid-phase extraction of 10 analytes, from 6 different classes (i.e., non-steroidal anti-inflammatory drugs, benzophenones, parabens, phenols, pesticides and musks) and an analytical method is developed for their liquid chromatographic separation and detection. Low limits of quantification (0.03 and 1.0 µg L-1), wide linear ranges and excellent recoveries (92⁻100%) are some of the benefits of the proposed procedure. The study of the synthesis conditions of MUF cubes reveals that by altering them the hydrophilic/lipophilic balance of the MUF cubes can be tuned, hinting towards a strong potential for many other applications.

Magnetic octadecyl-based matrix solid-phase dispersion coupled with gas chromatography with mass spectrometry in a proof-of-concept determination of multi-class pesticide residues in carrots.

A novel procedure is put forward based on the combination of the well-established matrix solid-phase dispersion and the magnetic and sorption properties of magnetic octadecyl in the presence of n-octanol and was employed in a proof-of-concept sample preparation and determination of several classes of pesticide residues in carrots. The procedure does not require the transfer of blend to cartridge and subsequent packing, nor any co-sorbent for extract clean up. The hydrophobic magnetic nanoparticles utilized as a sorbent, can be retrieved by n-octanol under the application of a magnetic field due to hydrophobic interactions. Elution of pesticide residues is then carried out with an organic solvent. A total of 26 pesticides were included in this procedure and the target compounds were analyzed using gas chromatography with mass spectrometry in the selective ion monitoring mode. The average extraction recoveries obtained from carrot samples fortified at three different concentrations (20, 50, and 500 µg/kg) were 77-107%. The estimated limits of quantitation for most target analytes were in the low µg/kg level. The study demonstrates that the proposed extraction procedure is simple and effective, avoiding a clean-up step for the sample preparation of vegetable.

Octyl-modified magnetic graphene as a sorbent for the extraction and simultaneous determination of fragrance allergens, musks, and phthalates in aqueous samples by gas chromatography with mass spectrometry.

An effective, simple, and low-cost sample preparation method based on dispersive SPE followed by GC with MS is developed for the multianalyte determination of fragrance allergens, musks, and phthalates, at sub-ppb levels. The extraction procedure is based on a novel magnetic graphene sorbent, which is functionalized with octylamine, taking advantage of the functionalization's hydrophobic properties and π-π interactions with the analytes. Two alkyl amines, the octylamine and octadecylamine are studied to introduce alkyl chains in the basal plane of graphene. Magnetic graphene- octadecylamine is proved to be highly hydrophobic to such a degree that is hard to disperse in the bulk aqueous matrixes. Because of this behavior, its extraction efficiency for the target analytes is low. The synthesis and applicability of the magnetic graphene-octylamine as more favored sorbent are optimized in terms of the most determining experimental conditions. The detection and quantification limits, which are calculated based on S/N ratio of 3 and 10, respectively, ranged from 0.29 to 3.2 ng L(-1) and from 0.89 to 9.6, respectively. The dispersive SPE is successfully applied to routine analysis for the determination of the target analytes in samples from municipal treatment plant of Ioannina (Greece), from Pamvotis Lake and baby bathwater. The reproducibility of the spiked biological treatment plant water sample is evaluated and the relative standard deviation values range between 2.1 and 9.4%.

Graphene-coated cotton fibers as a sorbent for the extraction of multiclass pesticide residues from water and their determination by gas chromatography with mass spectrometry.

A straightforward functionalization procedure is proposed for synthesizing a cotton-supported graphene as an extraction material, which is effectively employed for the extraction of multiclass pesticides from environmental waters prior to their determination by gas chromatography with mass spectrometry. Different experimental parameters that affect the extraction efficiency, including pH of the extraction, stirring rate, extraction time, ionic strength, presence of humic acid, sample volume, amount of sorbent, and elution conditions, were investigated and properly established. The advantages of the present extraction method are the simplicity of implementation, rapidity, and low consumption of sorbent per extraction. Moreover, the pesticides on the adsorbent are stable, under certain storage conditions, rendering the cotton-supported graphene suitable for environmental field studies. The applicability of the cotton-graphene-based procedure for routine analysis was demonstrated by the determination of pesticides in a lake water sample. The recoveries ranged from 83 to 107%, the limits of quantitation were in the range of 0.02-0.09 µg/L, and the calculated relative standard deviations varied from 3 to 8% (data obtained with the same batch of sorbent). Because of the acceptable analytical characteristics, the developed method shows great prospects in determining certain classes of pesticides in water.

Evaluation of magnetic nanoparticles to serve as solid-phase extraction sorbents for the determination of endocrine disruptors in milk samples by gas chromatography mass spectrometry.

A rapid magnetic solid-phase extraction (MSPE) is proposed based on C18-functionalized magnetic silica nanoparticles as sorbents, for the determination of endocrine disruptors - 20 organochlorine pesticides and 6 polychlorinated biphenyls - in milk samples. Magnetic nanoparticles are characterized by several techniques, such as Scanning Electron Microscopy, X-Ray diffraction, Brunauer-Emmett-Teller and Fourier transform-infrared. The MSPE is performed by dispersion of the Fe3O4@SiO2@C18 nanoparticles in milk samples with sonication, after protein precipitation. Then, the sorbent is collected by applying an external magnetic field and the analytes are desorbed by n-hexane. Several parameters affecting the extraction efficiency of target analytes by the magnetic nanoparticles are investigated, including washing and elution solvents, amount of sorbents, time of extraction and elution, sample and elution solvent volume. The proposed method is optimized by means of experimental design and response surface methodology. When coupled with gas chromatography-mass spectrometry detection and under optimum extraction conditions, average recoveries of target analytes are found to be in the range of 79% to 116%. The proposed MSPE-GC-MS analytical method has a linear calibration curve for all target analytes with coefficients of determination to range from 0.9950 to 0.9999. The limits of quantification are found to be between 0.2 and 1µg/L ensuring compliance with the maximum residue limits established by European Commission and Codex Alimentarius, for OCPs and PCBs residues in milk. The proposed method is applied to the determination of target analytes in milk samples from local markets.

Fluoroacetylation/fluoroethylesterification as a derivatization approach for gas chromatography-mass spectrometry in metabolomics: preliminary study of lymphohyperplastic diseases.

Metabolic fingerprinting in combination with gas chromatography and multivariate analysis is being extensively employed for the improved understanding of biological changes induced by endogenous or exogenous factors. Chemical derivatization increases the sensitivity and specificity of gas chromatography-mass spectrometry (GC-MS) for polar or thermally labile biological compounds, which bear derivatizable groups. Thus, there is a constant demand for simple methods of derivatization and separation that satisfy the need for metabolite analysis, identifying as many chemical classes of compounds as possible. In this study, an optimized protocol of extraction and derivatization is established as a generally applicable method for the analysis of a wide range of classes of metabolites in urine, whole blood and saliva. Compounds of biological relevance bearing hydroxyl- carboxyl- and amino-groups are derivatized using single-step fluoroacetylation/fluoroethylesterification after proper optimization of the protocol. Subsequently, the developed derivatization procedure is engaged in finding blood metabolic biomarkers, induced by lymphohyperplastic disease, through the metabolomic fingerprinting approach, the multivariate modeling (hierarchical cluster analysis) and GC-MS. Our preliminary, GC-MS-based metabolomic fingerprinting study underlines the contribution of certain metabolites to the discrimination of patients with lymphohyperplastic diseases.

Zero-valent iron/iron oxide-oxyhydroxide/graphene as a magnetic sorbent for the enrichment of polychlorinated biphenyls, polyaromatic hydrocarbons and phthalates prior to gas chromatography-mass spectrometry.

A composite magnetic material consisting of zero-valent iron, iron oxide-oxyhydroxide and graphene was synthesized and used successfully as a sorbent for the micro solid-phase extraction of PAHs, PCBs and phthalic acid esters. The components endow the composite with multiple characteristics such as adsorption capability and facile removal due to its magnetic properties. Due to the π-π electrostatic stacking property of graphene, the high specific surface area and the adsorption capability of both components, the resulting black flaky Fe(0)/iron oxide-oxyhydroxide/graphene composite showed high extraction efficiency for the target analytes from water samples. Compared with the neat graphene, the composite material has improved properties in terms of microextraction capabilities as both the hydrophobic graphene and zero-valent iron participate in the adsorption of the hydrophobic molecules. The precision from the extraction of all three groups of compounds was lower than 7% and the recoveries were from 90 to 93% from a spiked lake water sample. The high recoveries in relation to the low final volume of the desorption solvent ensure high preconcentration efficiency and a promising sorbent for analytical applications.

A layered magnetic iron/iron oxide nanoscavenger for the analytical enrichment of ng-L(-1) concentration levels of heavy metals from water.

Magnetically driven separation techniques have received considerable attention in recent decade because of their great potential application. In this study, we investigate the application of an unmodified layered magnetic Fe/Fe(2)O(3) nanoscavenger for the analytical enrichment and determination of sub-parts per billion concentrations of Cd(II), Pb(II), Ni(II), Cr(VI) and As(V) from water samples. The synthesized nanoscavenger was characterized by BET, TGA, XRD and IR and the parameters influencing the extraction and recovery of the preconcentration process were assessed by atomic absorption spectrometry. The possible mechanism of the enrichment of heavy metals on Fe/Fe(2)O(3) was proposed, which involved the dominant adsorption and reduction. The nanoscale size offers large surface area and high reactivity of sorption and reduction reactions. The obtained limits of detection for the metals studied were in the range of 20-125 ng L(-1) and the applicability of the nanomaterial was verified using a real sample matrix. The method is environmentally friendly as only 15 mg of nanoscavenger are used, no organic solvent is required for the extraction and the experiment is performed without the need for filtration or preparation of packed preconcentration columns.

Sensitive determination of pesticides residues in wine samples with the aid of single-drop microextraction and response surface methodology.

The multi-residue trace-level determination of six pesticides (diazinon, dimethoate, chlorpyrifos, vinclozolin, fenthion and quinalphos) in wine samples, after their single-drop microextraction (SDME) is presented herein. The extraction procedure was optimized using the multivariate optimization approach following a two-stage process. The first screening experimental design brought out the significant parameters and was followed by a central composite design (CCD) experiment, which revealed the simultaneous effect of the significant factors affecting the SDME process. High level of linearity for all target analytes was recorded with r(2) ranging between 0.9978 and 0.9999 while repeatability (intra-day) and reproducibility (inter-day) varied from 5.6% to 7.4% and 4.9% to 12.5%, respectively. Limits of detection (LODs) and limits of quantification (LOQs) were found to range in the low microg L(-1) level. In general, the developed methodology presented simplicity and enhanced sensitivity, rendering it appropriate for routine wine screening purposes.

Microwave-assisted phase-transfer catalysis for the rapid one-pot methylation and gas chromatographic determination of phenolics.

Microwave-assisted phase-transfer catalysis (PTC) is reported for the first time, for the one-step extraction-derivatization-preconcentration and gas chromatographic determination of twenty phenols and ten phenolic acids. The well established phase-transfer catalytic methylation is largely accelerated when heating is replaced with the "greener" microwave irradiation. The overall procedure was thoroughly optimized and the analytes were determined by GC/MS. The method presented adequate analytical characteristics being more sensitive in analyzing phenols than phenolic acids. The limits of detection without any additional preconcentration steps (e.g. solvent evaporation) were adequate and ranged from 0.4 to 15.8ng/mL while limits of quantitation were between 1.2 and 33.3ng/mL. The method was applied to the determination of phenols, in spiked environmental samples and phenolic acids in aqueous infusions of commercially available pharmaceutical dry plants. The recoveries of fortified composite lake water samples and Mentha spicata aqueous infusions ranged from 89.3% to 117.3% for phenols and 93.3% to 115.2% for phenolic acids.

Measurements of benzene and formaldehyde in a medium sized urban environment. Indoor/outdoor health risk implications on special population groups.

In the present study, the results of a measurement campaign aiming to assess cancer risk among two special groups of population: policemen and laboratory technicians exposed to the toxic substances, benzene and formaldehyde are presented. The exposure is compared to general population risk. The results show that policemen working outdoor (traffic regulation, patrol on foot or in vehicles, etc.) are exposed at a significantly higher benzene concentration (3-5 times) than the general population, while the exposure to carbonyls is in general lower. The laboratory technicians appear to be highly exposed to formaldehyde while no significant variation of benzene exposure in comparison to the general population is recorded. The assessment revealed that laboratory technicians and policemen run a 20% and 1% higher cancer risk respectively compared to the general population. Indoor working place air quality is more significant in assessing cancer risk in these two categories of professionals, due to the higher Inhalation Unit Risk (IUR) of formaldehyde compared to benzene. Since the origin of the danger to laboratory technicians is clear (use of chemicals necessary for the experiments), in policemen the presence of carbonyls in indoor air concentrations due to smoking or used materials constitute a danger equal to the exposure to traffic originated air pollutants.

Ion-pair single-drop microextraction versus phase-transfer catalytic extraction for the gas chromatographic determination of phenols as tosylated derivatives.

The environmental fate of phenols represents a diachronic scientific consideration mainly due to their high toxicity and diverse physicochemical properties rendering them difficult to be analyzed as unity. Ion-pair-assisted extraction and microextraction techniques in association with a dedicated derivatization reaction are possible to lead to enhanced selectivity and sensitivity in gas chromatography. Phase-transfer catalytic liquid-liquid extraction-derivatization and ion-pair-assisted single-drop microextraction with in-drop derivatization are successfully employed for the analysis of 15 phenolic compounds. The analytes that react at room temperature with p-toluenesulfonyl chloride into the bulk of the organic phase are subsequently determined by GC-MS in selective-ion monitoring mode. Aiming at maximizing the derivatization yields obtained from the 15 analytes in a reasonable time period, the optimum experimental parameters were established along with the figures of merit of the methods. The limits of detection ranged from 0.48 to 1.5 ng/ml and from 0.20 to 0.28 ng/ml respectively, while the limits of quantitation ranged from 1.4 to 4.5 ng/ml and from 0.59 to 0.84 ng/ml for the two methods with the techniques under study. The overall procedure presented satisfactory analytical features with the liquid-liquid extraction protocol being easier to carry out while the single-drop one, presented higher sensitivity and significant reduction of the organic solvent employed. By comparison with other methods for the analysis of phenols, the proposed methods exhibit adequately low detection limits, good precision, short derivatization time and low solvent, sample and reagent consumption.

Gas chromatographic determination of carbonyl compounds in biological and oil samples by headspace single-drop microextraction with in-drop derivatisation.

A suitable method for the gas chromatographic determination of 10 characteristic carbonyls in biological and oil samples based on the in-drop formation of hydrazones by using 2,4,6-trichlorophenylhydrazine (TCPH), has been developed. The derivatisation-extraction procedure was optimized separately for aqueous and oil samples with respect to the appropriate organic drop solvent, drop volume, in-drop TCPH concentration, sample stirring rate, temperature during single-drop microextraction (SDME), reaction time and headspace-to-sample volume ratio. The optimization showed differentiation of optimum values between the studied matrices. The limits of detection were found to range from 0.001 to 0.003microgmL(-1) for the aqueous biological samples and from 0.06 to 0.20microgmL(-1) for the oil samples. The limits of quantification were in the range of 0.003-0.010microgmL(-1) and 0.020-0.059microgmL(-1) for aqueous and oil samples, respectively. The overall relative standard deviations of the within-day repeatability and between-day reproducibility were <4.4% and <8.2% for the aqueous biological samples and <3.9% and <7.4% for the oxidized oil samples.

In-drop derivatisation liquid-phase microextraction assisted by ion-pairing transfer for the gas chromatographic determination of phenolic endocrine disruptors.

A novel in-drop derivatisation liquid-phase microextraction procedure with an ion-pairing agent is developed and optimised for the extraction of endocrine-disrupting chemicals. The ethyl esters of the analytes were rapidly formed in the organic drop and analysed by gas chromatography. The effects of various parameters such as rate and time of agitation, ion-pairing agent and reactant concentration, pH and temperature were studied systematically to optimise the process and bring out the locale of reaction in the organic drop. A study of the mechanistic pathways of the overall procedure is attempted leading to interesting findings and delineating important points of the kinetics and mechanism. A mechanistic model is proposed on the basis of the theory of mass transfer with chemical reaction in two liquid phases. The O-ethoxycarbonyl derivatisation appears to take place in the bulk organic phase. The system provides insight into the first reported analytical case of single-drop extraction-preconcentration-derivatisation assisted by an ion-pairing transfer and has all of the interesting facets of chemical reaction in which the role of mass transfer comes into picture. The analytical features of the method are acceptable and the overall relative standard deviations of the intra-day repeatability (n=5) and inter-day reproducibility were <3.9% and <5.4%, respectively, for gas chromatography-mass spectrometry analyses and <4.3% and <7.1% for gas chromatography-flame ionisation detection analyses. The method was applicable to urine and surface water samples. The LODs ranged between 0.2-1.3 ng mL(-1) and 8.5-26.5 ng mL(-1) for GC/MS and GC/FID analyses, respectively.

Improved method for the in vitro assessment of antioxidant activity of plant extracts by headspace solid-phase microextraction and gas chromatography-electron capture detection.

The simultaneous monitoring of malondialdehyde, pentanal and hexanal, final products of lipid peroxidation is reported, using a headspace solid-phase microextraction (HS-SPME) technique with on-fibre derivatisation. The aldehydes are extracted and subjected to on-sorbent derivatisation into stable hydrazones with 2,4,6-trichlorophenylhydrazine (TCPH) and analyzed. The degree of inhibition of oxidation is performed by monitoring the chlorinated hydrazones after thermal desorption, by gas chromatography-electron capture detection. The procedure was employed to evaluate in vitro the antioxidant activity of Hypericum perforatum L. extracts and of the well-known antioxidant vitamin E following induction of oxidation of sunflower oil, as a model lipid system. Prior to the measurement of antioxidant activity, the optimal process conditions, i.e. headspace volume, temperature, agitation, extraction/derivatisation time and desorption time and temperature were properly established. Aqueous extracts of H. perforatum L. exhibited the highest antioxidative effect. The method is shown to be promising for screening purposes for antioxidant substances and natural extracts.

Gas chromatographic determination of amino acids via one-step phase-transfer catalytic pentafluorobenzylation-preconcentration.

The gas chromatographic determination of amino acids via their simultaneous extraction, preconcentration and pentafluorobenzylation is reported. Using phase-transfer catalysis (PTC), the amino acids under study were transformed to their pentafluorobenzyl adducts. The method was tested for different catalysts and tetrabutylammonium bromide provided favorable features in comparison to the other PTCs. The derivatization procedure was optimized and the best reaction conditions are given. With the exception of arginine, 19 amino acids were converted to volatile derivatives and analyzed with GC/MS and GC/FID at low concentration levels with acceptable sensitivity and good reproducibility. The LODs were found to range from 0.7 to 2.3microM for the GC/MS analyses and from 1.7 to 6.9microM for GC/FID analyses. The method practicability and applicability were confirmed by the analysis of urine, fruit juice and wheat flour for the determination of the amino acids under study. Protein-bound amino acids were analyzed after an alkaline hydrolysis step with 5M NaOH applying this method to wheat flour with an overall procedure duration less than 12h. The optimized protocol was applied to these samples without any pretreatment and their amino acid concentrations were calculated from the appropriate calibration plots.

The lipophilic extract of Hypericum perforatum exerts significant cytotoxic activity against T24 and NBT-II urinary bladder tumor cells.

Hypericum perforatum L. (St. John's wort) is a medicinal plant used for many pathologies, especially for the treatment of mild to moderate depression. In the present study we have investigated the cytotoxic activity of the locally collected (Epirus region) Hypericum perforatum L. against cultured T24 and NBT-II bladder cancer cell lines. The lipophilic extract of the herb, prepared using petroleum ether, induced apoptosis displaying LC(50) values at concentrations as low as 4 and 5 microg/mL. A fraction of this extract displayed 60 % cell growth inhibition at a concentration of 0.95 microg/mL. Evaluating the importance of various biologically active components of the extract, it was found that hypericins (hypericin, pseudohypericin, etc.) were identified only in the methanolic (lipophobic) extract of the herb, and not in the active lipophilic extract. In addition, hyperforin concentrations in the lipophilic extract and its most active fraction, were 0.94 microg/mL, and 0.17 microg/mL, respectively, while the active cytotoxic concentration of pure hyperforin appeared in the range of 1.8 microg/mL - 5.0 microg/mL. Therefore, pure hyperforin does not seem to contribute significantly to the cytotoxicity activity. Chlorophylls were identified in low, not significantly different, concentrations in all extracts and fractions and were not correlated to the biological activity. Owing to the combination of significant cytotoxic activity, natural abundance and low toxicity, the lipophilic extract of Hypericum perforatum holds the promise of being an interesting, new, antiproliferative agent against bladder cancer that deserves further investigation.

Determination of plasma, urine, and bovine serum albumin low-molecular-weight carbonyl levels by capillary gas chromatography with electron-capture and mass-selective detection.

Peroxidation of lipids produces low-molecular-weight carbonyl compounds, which are reactive with biological nucleophiles. The analysis of these compounds is often difficult. A multicomponent method for the determination of 11 of them in biological samples is reported. The samples are subjected to a pretreatment-derivatization procedure followed by gas chromatographic analysis with either electron-capture detection (ECD) or mass-selective detection (MSD) in the selected-ion monitoring mode. The procedure involves derivatization of the analyte with 2,4,6-trichlorophenylhydrazine, extraction with n-hexane, and separation of the derivatization products on a nonpolar gas chromatographic column. The concentration of the derivatization reagent, pH, reaction time, temperature, and presence of extraneous ions were investigated to determine the optimal derivatization conditions. Under these conditions, the method allows for the selective detection of low-molecular-weight carbonyl compounds at femtomole levels in several biological materials such as plasma, urine, and bovine serum albumin without interferences. The limits of detection were in the ranges 0.01-0.2 microM for ECD and 0.15-1.5 microM for MSD. The mean procedural recoveries obtained during the method validation were within the range 85-95% and the intra- and interassay standard deviations do not exceed 4.6 and 6.1%, respectively.