Self-aggregates of deoxycholic acid-modified chitosan as a novel carrier of adriamycin

A novel and simple method for delivery of adriamycin (ADR) was developed using self-aggregates of deoxycholic acid-modified chitosan. Deoxycholic acid was covalently conjugated to chitosan via EDC-mediated reaction to generate self-aggregated chitosan nanoparticles. ADR was physically entrapped inside the self-aggregates and the characteristics of ADR-loaded chitosan self-aggregates were analyzed by dynamic light scattering, fluorescence spectroscopy, and atomic force microscopy (AFM). The maximum amount of entrapped ADR reached 16.5 wt% of chitosan self-aggregates, suggesting a loading efficiency of 49.6 wt%. The size of ADR-loaded self-aggregates increased with increasing the loading content of ADR. AFM images showed spherical shape of ADR-loaded self-aggregates, and ADR was slowly released from chitosan self-aggregates in PBS solution (pH 7.2). Received: 24 April 2000/Accepted: 11 July 2000     

Aconityl-derived polymers for biomedical applications. Modeling study of cis–trans isomerisation

 Soluble polymers have been prepared that are designed to undergo enhanced rates of hydrolysis at pH values less than that observed in blood circulation. The degradable element in the polymer mainchain is derived from cis-aconityl acid and is defined by a carboxylic acid pendent functionality (C-4) that is cis across a double bond to an amide at C-1 in the polymer mainchain. While degradation studies in vitro have confirmed these polymers do undergo enhanced rates of degradation at acidic pH values, there is also increasing evidence that during the degradation process the double bond isomerises to the trans configuration and thus prevents the full degradation of a polymer. From a molecular modelling perspective we are seeking to understand the propensity for this cis–trans isomerisation and the mechanism of this cis–trans isomerisation is discussed. Received: 29 April 2002 / Accepted: 6 September 2002 / Published online: 14 February 2003     

Determination of tributyltin in marine sediment: Comité Consultatif pour la Quantité de Matière (CCQM) pilot study P-18 international intercomparison

The capabilities of National Metrology Institutes (NMIs—those which are members of the Comité Consultatif pour la Quantité de Matière (CCQM)of the CIPM) and selected outside "expert" laboratories to quantitate (C₄H₉)₃Sn⁺ (TBT) in a prepared marine sediment were assessed. This exercise was sanctioned by the 7th CCQM meeting, April 4–6, 2001, as an activity of the Inorganic Analysis Working Group and was jointly piloted by the Institute for National Measurement Standards of the National Research Council of Canada (NRC) and the Laboratory of the Government Chemist (LGC), UK. A total of 11 laboratories submitted results (7 NMIs, and 4 external labs). Two external laboratories utilized a standard calibration approach based on a natural abundance TBT standard, whereas all NMIs relied upon isotope dilution mass spectrometry for quantitation. For this purpose, a species specific ¹¹⁷Sn-enriched TBT standard was supplied by the LGC. No sample preparation methodology was prescribed by the piloting laboratories and, by consequence, a variety of approaches was adopted by the participants, including mechanical shaking, sonication, accelerated solvent extraction, microwave assisted extraction and heating in combination with Grignard derivatization, ethylation and direct sampling. Detection techniques included ICP–MS (with GC and HPLC sample introduction), GC–MS, GC–AED and GC–FPD. Recovery of TBT from a control standard (NRCC CRM PACS-2 marine sediment) averaged 93.5±2.4% (n=14). Results for the pilot material averaged 0.680±0.015 µmol kg^–1 (n=14; 80.7±1.8 µg kg^–1) with a median value of 0.676 µmol kg^–1. Overall, performance was substantially better than state-of-the-art expectations and the satisfactory agreement amongst participants permitted scheduling of a follow-up Key comparison for TBT (K-28), a Pilot intercomparison for DBT (P-43), and certification of the test sediment for TBT content and its release as a new Certified Reference Material (HIPA-1) with a TBT content of 0.679±0.089 µmol kg^–1 (expanded uncertainty, k=2, as Sn) (80.5±10.6 µg kg^–1).Electronic Supplementary Material Supplementary material is available in the online version of this article at .     

An immunoassay for a urinary metabolite as a biomarker of human exposure to the pyrethroid insecticide permethrin

Permethrin is the most popular synthetic pyrethroid insecticide used in agriculture and public health. For the assessment of human exposure to permethrin, a competitive indirect enzyme-linked immunosorbent assay (ELISA) for the detection of the glycine conjugate of a major metabolite, cis-/trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid (DCCA), of permethrin was developed based on a polyclonal antibody. An assay based on an antibody with a high sensitivity was optimized and characterized. The IC₅₀ value and the detection range for trans-DCCA–glycine, in the assay buffer were 1.2 and 0.2−7.0 μg/L, respectively. The antibody recognized trans-DCCA–glycine and the mixture of cis-/trans-DCCA–glycine with an isomer range from 30:70 to 50:50 nearly equally. Little or no cross-reactivity to permethrin and its other free metabolites or glycine conjugates was measured. The integration of the ELISA and solid-phase extraction which was used to reduce the matrix effect from human urine samples provided for analysis of total cis-/trans-DCCA–glycine at low parts per billion levels in the samples. The limit of quantitation of the target analyte was 1.0 μg/L in urine with a limit of detection of 0.1 μg/L in buffer. This assay might be a useful tool for monitoring human exposure to permethrin.     

Use of Experimental Design to Develop a Method for Analysis of 1,3-Dichloropropene Isomers in Water by HS-SPME and GC–ECD

A simple and reliable method has been established for determination of cis and trans-1,3-dichloropropene (1,3-DCP) in water by headspace solid-phase microextraction (HS-SPME) then GC–ECD. An experimental design with two steps was performed to determine the best experimental conditions for extraction of the 1,3-DCP isomers. First, a 2⁶⁻² fractional factorial design was conducted to screen for significant conditions. Second, a central composite design (CCD) was performed to optimise the variables. The best experimental extraction conditions were: polydimethylsiloxane–divinylbenzene (PDMS–DVB)-coated fibre, 20-min extraction time, 12 °C extraction temperature, 300 g L⁻¹ NaCl, and 20 mL headspace volume in 40-mL vial. Under these conditions the method detection limit (MDL) was 0.5 ng L⁻¹ for cis-1,3-DCP and 1.0 ng L⁻¹ for trans-1,3-DCP. The method quantification limit (MQL) was 1.2 ng L⁻¹ for cis-1,3-DCP and 3.0 ng L⁻¹ for trans-1,3-DCP. For both isomers the relative standard deviation (RSD) for analysis of 50 ng L⁻¹ or 0.5 μg L⁻¹ of the isomer mixture was less than 8%. When the proposed method was applied to surface (river) water and tapwater samples from Gipuzkoa province (Spain) the target analytes were not detected. The method was also used to investigate the presence of the isomers in leachates from agricultural soil. A mixed solution was added to samples of two different soils and 1,3-DCP isomers were quantified in leachate obtained from the samples.     

Process for detecting <Emphasis Type="Italic">Helicobacter pylori</Emphasis> using aliphatic amides

Helicobacter pylori diagnosis is fundamental in the management of gastrointestinal pathologies, whose current clinical guidelines support a non-invasive ‘test-and-treat’ strategy. As such, the present work reports the basis of a new, low-cost, specific breath test based on the detection of volatile carboxylic acids resulting from the hydrolysis of short-chain aliphatic amides by H. pylori amidases. Propionamide and butyramide, which are metabolized by amidases to propionic and butyric acids, were elected for this study. Conditions for the extraction of these acids from a vapour phase were optimized concerning the use of solid-phase microextraction (SPME) followed by gas chromatography–quadrupole mass spectrometry (GC–qMS) analysis. SPME–GC–qMS was then used to detect the acids released into a vapour phase upon incubation of a H. pylori reference strain J99 or a clinical specimen with the amides. These experiments have demonstrated that the administration of less than 9 mg of propionamide and/or butyramide to H. pylori cultures, in loads recognized to cause infection (10⁶–10⁹ cells), resulted in the formation of detectable and/or quantifiable amounts of propionic and/or butyric acids after 30 min incubation. As such, propionic and butyric acids can be used as biomarkers for H. pylori upon incubation with the corresponding amides. SPME–GC–qMS was also used to verify the hepatic stability of the acids. These experiments were conducted in mouse liver cells and revealed no signs of metabolization that could compromise their bioavailability in future in vivo assays. Moreover, SPME–GC–qMS permitted the detection of both acids in amounts as low as 0.8 μg in systems mimicking exhaled breath, demonstrating the sensitivity of the method for these compounds.     

Development of a multianalyte method for the determination of anabolic hormones in bovine urine by isotope-dilution GC–MS/MS

A sensitive, specific and selective multianalyte GC–MS/MS method has been developed for the determination of 11 anabolic hormones in bovine urine. After adjusting the urine pH to 4.8, the samples were spiked with deuterated internal standards and submitted to enzymatic hydrolysis with β-glucuronidase/arylsulfatase. Hormones were eluted with methanol through a C18 solid phase cartridge and submitted to a liquid–liquid extraction. Analytes were derivatized by adding N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) with 1% trimethylchlorosilane and GC–MS data were obtained in the positive electron impact tandem mass mode. Under these conditions, no matrix effects were observed and limit of detection values were in the range of 0.005 ng/mL (diethylstilbestrol) to 0.38 ng/mL (17α-methyltestosterone and 17α-ethynylestradiol). Recoveries from 81% (α-zeranol) to 149% (17α-methyltestosterone) were found under the selected conditions. These results were better than those found using heptafluorobutyric anhydride (HFBA) as derivative reagent and those measured in full scan and selective ion monitoring modes.     

A Stopped-flow Study on the Kinetics and Mechanism of CO2 Uptake by the cis-[Cr(1,10-phenanthroline)2(OH2)2]3+ Complex Ion

The kinetics of the reaction between gaseous CO₂ and the cis-[Cr(phen)₂(OH₂)₂]³⁺ ion leading to the formation of the carbonato complex ion, have been studied over the pH and temperature ranges: 3 < pH < 6 and 5 < T < 25 °C, respectively, at a constant ionic strength of 1 m (NaClO₄). Investigations were carried out using the stopped-flow spectrophotometry technique in the UV–Vis range: 340–700 nm. The major reactant species in the pH range studied was cis-[Cr(phen)₂(OH)(OH₂)]²⁺ ion, which underwent reaction with CO₂ to form cis-[Cr(phen)₂(OH₂)(HCO₃)]²⁺ ion. Subsequently, slower ring closure of the latter species to form the bidentate carbonato chelate was observed. The possible mechanism has been discussed and the activation parameters ΔH^† and ΔS^† were also determined for the reaction studied.     

Combined FT–Raman spectroscopic and mass spectrometric study of ancient Egyptian sarcophagal fragments

The application of combined Raman spectroscopic and GC–MS analytical techniques for the characterisation of organic varnish residues from Egyptian Dynastic funerary sarcophagal and cartonnage fragments from the Graeco-Roman period, ca. 2200 BP, is described. The nondestructive use of Raman spectroscopy was initially employed to derive information about the specific location of organic material on the specimens, which were then targeted in specific areas using minimal sampling for GC–MS analysis. In the case of the sarcophagal fragment, a degraded yellow-brown surface treatment was identified as a Pistacia spp. resin; this provides additional evidence for the use of this resin, which has previously been identified in Canaanite transport amphorae, varnishes and “incense” bowls in an Egyptian Late Bronze Age archaeological context. The cartonnage fragment also contained an organic coating for which the Raman spectrum indicated a degradation that was too severe to facilitate identification, but the GC–MS data revealed that it was composed of a complex mixture of fatty acid residues. The combined use of GC–MS and Raman spectroscopy for the characterisation of organic materials in an archaeological context is advocated for minimisation of sampling and restriction to specifically identified targets for museum archival specimens.     

Bacterial Biotransformation of Isoprene and Related Dienes

Summary.  The bacterium Pseudomonas putida ML 2 was used in the oxidative biodegradation of the acyclic dienes isoprene, trans-piperylene, cis-piperylene, and 1,3-butadiene. Regioselective dioxygenase-catalyzed dihydroxylation of alkenes yielded vicinal diols in the preferred sequence monosubstituted > cis-disubstituted > gem-disubstituted > trans-disubstituted. The isolated diol metabolites had an excess of the R configuration (9–97%ee), and further diol oxidation was controlled by addition of propylene glycol as an inhibitor. Stereoselectivity using the ML2 strain resulted from both enzymatic asymmetric alkene dihydroxylation and kinetic resolution of diols. Enantioselective oxidation of the allylic secondary alcohol group of R configuration yielded the corresponding unsaturated ketoalcohol; the residual diol was recovered with a large excess (≥ 93%ee) of the S configuration. In addition to the enzymatic diene oxidation steps yielding unsaturated diols and ketoalcohols, evidence was also found of enzymatic alkene hydrogenation to yield saturated ketoalcohols and diols. Received December 20, 1999. Accepted (revised) February 7, 2000     

Development of Electro Solid-Phase Microextraction and Application to Methamphetamine Analysis

A new electro solid-phase microextraction (El-SPME) technique using homemade pencil-lead fibers has been developed as an effective means of selective extraction of methamphetamine before analysis by gas chromatography (GC) and gas chromatography–mass spectrometry (GC–MS). The methamphetamine was extracted by use of a laboratory-made El-SPME cell with three electrodes—the pencil-lead SPME fiber, Ag/AgCl, and platinum as working, reference, and auxiliary electrodes, respectively. A negative potential was applied to the homemade pencil-lead fiber during extraction. Experimental conditions, for example type of pencil-lead fiber, conditions for modification of the fiber, extraction time, applied potential, pH, and gas chromatographic conditions were optimized. Methamphetamine was identified by GC–MS. Screening of the extracted compounds showed that the proposed El-SPME technique is much more selective than direct SPME using a commercially available polyacrylate fiber. Under the optimum conditions the calibration plot for the compound was linear in the range 50–3,200 ng mL⁻¹ and the detection limit was 34 ng mL⁻¹.     

Identification of organic sulfur compounds in coal bitumen obtained by different extraction techniques using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometric detection

The determination of organic sulfur compounds (OSC) in coal is of great interest. Technically and operationally these compounds are not easily removed and promote corrosion of equipment. Environmentally, the burning of sulfur compounds leads to the emission of SO _x gases, which are major contributors to acid rain. Health-wise, it is well known that these compounds have mutagenic and carcinogenic properties. Bitumen can be extracted from coal by different techniques, and use of gas chromatography coupled to mass spectrometric detection enables identification of compounds present in coal extracts. The OSC from three different bitumens were tentatively identified by use of three different extraction techniques: accelerated solvent extraction (ASE), ultrasonic extraction (UE), and supercritical-fluid extraction (SFE). Results obtained from one-dimensional gas chromatography (1D GC) coupled to quadrupole mass spectrometric detection (GC–qMS) and from two-dimensional gas chromatography with time-of-flight mass spectrometric detection (GC × GC–TOFMS) were compared. By use of 2D GC, a greater number of OSC were found in ASE bitumen than in SFE and UE bitumens. No OSC were identified with 1D GC–qMS, although some benzothiophenes and dibenzothiophenes were detected by use of EIM and SIM modes. GC × GC–TOFMS applied to investigation of OSC in bitumens resulted in analytical improvement, as more OSC classes and compounds were identified (thiols, sulfides, thiophenes, naphthothiophenes, benzothiophenes, and benzonaphthothiophenes). The roof-tile effect was observed for OSC and PAH in all bitumens. Several co-elutions among analytes and with matrix interferents were solved by use of GC×GC.     

Bacterial Biotransformation of Isoprene and Related Dienes

 The bacterium Pseudomonas putida ML 2 was used in the oxidative biodegradation of the acyclic dienes isoprene, trans-piperylene, cis-piperylene, and 1,3-butadiene. Regioselective dioxygenase-catalyzed dihydroxylation of alkenes yielded vicinal diols in the preferred sequence monosubstituted > cis-disubstituted > gem-disubstituted > trans-disubstituted. The isolated diol metabolites had an excess of the R configuration (9–97%ee), and further diol oxidation was controlled by addition of propylene glycol as an inhibitor. Stereoselectivity using the ML2 strain resulted from both enzymatic asymmetric alkene dihydroxylation and kinetic resolution of diols. Enantioselective oxidation of the allylic secondary alcohol group of R configuration yielded the corresponding unsaturated ketoalcohol; the residual diol was recovered with a large excess (≥ 93%ee) of the S configuration. In addition to the enzymatic diene oxidation steps yielding unsaturated diols and ketoalcohols, evidence was also found of enzymatic alkene hydrogenation to yield saturated ketoalcohols and diols.     

Analysis of captan, folpet, and captafol in apples by dispersive liquid–liquid microextraction combined with gas chromatography

A novel method was developed for the determination of captan, folpet, and captafol in apples by dispersive liquid–liquid microextraction (DLLME) coupled with gas chromatography–electron capture detection (GC–ECD). Some experimental parameters that influence the extraction efficiency, such as the type and volume of the disperser solvents and extraction solvents, extraction time, and addition of salt, were studied and optimized to obtain the best extraction results. Under the optimum conditions, high enrichment factors for the compounds were achieved ranging from 824 to 912. The recoveries of fungicides in apples at spiking levels of 20.0 μg kg⁻¹ and 70.0 μg kg⁻¹ were 93.0–109.5% and 95.4–107.7%, respectively. The relative standard deviations (RSDs) for the apple samples at 30.0 μg kg⁻¹ of each fungicide were in the range from 3.8 to 4.9%. The limits of detection were between 3.0 and 8.0 μg kg⁻¹. The linearity of the method ranged from 10 to 100 μg kg⁻¹ for the three fungicides, with correlation coefficients (r ²) varying from 0.9982 to 0.9997. The obtained results show that the DLLME combined with GC–ECD can satisfy the requirements for the determination of fungicides in apple samples. Figure Dispersive liquid–liquid microextraction (DLLME) coupled with gas chromatography–electron capture detection (GC–ECD) allows satisfactory determination of fungicides in apple samples     

Analytical method for assessing potential dermal exposure to pesticides of a non-agricultural occupationally exposed population

To measure dermal exposure of a non-agricultural occupationally exposed population to pesticides, a new method has been developed for analysis of 13 pesticides from different classes (fungicides, herbicides, insecticides) on dermal patches. The method includes extraction of the patches and analysis of the pesticides by GC–MS and/or HPLC–fluorescence. Water-soluble pesticides (glyphosate and glufosinate) on patches were ultrasonically extracted twice with ultra-pure water for 10 min and analysed by HPLC–fluorescence after derivatisation with FMOC. Organic-soluble pesticides (bifenthrin, cyprodinil, difufenicanil, fludioxonil, oxadiazon, pyriproxyfen, clopyralid, 2,4-D, fluroxypyr, 2,4-MCPA, and triclopyr) were extracted ultrasonically twice for 10 min with 70:30 dichloromethane–acetonitrile and analysed by GC–MS directly or after derivatisation with N-methyl-N-tert-butyldimethylsilyltrifluoroacetamide. Detection limits varied between 3 and 4 μg L⁻¹ for water-soluble pesticides and between 1 and 10 μg L⁻¹ for organic-soluble pesticides.     

Determination of diketopiperazines of Burkholderia cepacia CF-66 by gas chromatography–mass spectrometry

Bacteria communicate with each other by a process termed “quorum sensing” (QS), and diffusible, low-molecular-weight chemicals, called signal molecules, are used as the communication languages. In cell-free Burkholderia cepacia CF-66 culture supernatants, five compounds suspected of being signal molecules were identified. The gene (cepI) related with AHLs synthesis were not detected by polymerase chain reaction (PCR) using specific primers. Gas chromatography–mass spectrometry (GC–MS) revealed that these compounds were not AHLs but the diketopiperazines (DKPs) cyclo(Pro–Phe), cyclo(Pro–Tyr), cyclo(Ala–Val), cyclo(Pro–Leu), and cyclo(Pro–Val), all of which were both d and l-type. Four kinds of DKPs had been isolated from other Gram-negative bacteria, but the other was a novel kind discovered in CF-66, and l-cyclo (Pro–Phe) was quantified by GC–MS. It was found that exogenous DKPs had a negative effect on the candidacidal activity of the culture supernatant extracts.     

Probing the Interaction Between a Surfactant–Cobalt(III) Complex and Bovine Serum Albumin

The mechanism of binding of the surfactant–cobalt(III) complex, cis-[Co(phen)₂(C₁₄H₂₉NH₂)Cl](ClO₄)₂⋅3H₂O (phen = 1,10-phenanthroline, C₁₄H₂₉NH₂ = tetradecylamine) with bovine serum albumin (BSA) was investigated by UV–vis absorption, circular dichroism (CD) and fluorescence spectroscopic techniques. The results of fluorescence titration revealed that the surfactant–cobalt(III) complex quenched the intrinsic fluorescence of BSA through a combination of static and dynamic quenching. The apparent binding constant (K _a) and number of binding sites (n) were calculated below and above the critical micelle concentration (CMC). The thermodynamic parameters determined by the van’t Hoff analysis of the constants (ΔH ^∘=14.87 kJ⋅mol⁻¹; ΔS ^∘=152.88 J⋅mol⁻¹⋅K⁻¹ below the CMC and 25.70 kJ⋅mol⁻¹ and 243.14 J⋅mol⁻¹⋅K⁻¹, respectively, above the CMC) clearly indicate that the binding is entropy-driven and enthalpically disfavored. Based on F?rster’s theory of non-radiation energy transfer, the binding distance, r, between donor (BSA) and the acceptor (surfactant–cobalt(III) complex) was evaluated. UV–vis, CD and synchronous fluorescence spectral results showed that the binding of the surfactant–cobalt(III) complex to BSA induced conformational changes in BSA.     

Analysis of hormonal steroids in fish plasma and bile by coupling solid-phase extraction to GC/MS

An analytical procedure for the simultaneous determination of twelve endogenous steroids (testosterone, androstenedione, 17β-estradiol, estrone, pregnenolone, progesterone, dihydroandrostenedione, dihydrotestosterone, 11α-ketotestosterone, 17α-hydroxyprogesterone, 17α-hydroxypregnenolone, 17α,20β-dihydroxy-4-pregnen-3-one) in plasma and bile samples by solid-phase extraction (SPE) and gas chromatography/mass spectrometry (GC–MS) has been developed. After enzymatic hydrolysis for bile samples only, samples were concentrated and purified using two successive SPE (C₁₈ and NH₂) cartridges. Analytes were derivatized with a mixture of N-methyl-N-(trimethylsilyl)trifluoroacetamide (MSTFA) / mercaptoethanol / ammonium iodide (NH₄I) and determined by GC–MS in selective ion monitoring mode. For most of the steroids monitored, recoveries were in the range 90–120% in plasma and in the range 60–70% in bile, and the reproducibility was below 10% for the complete procedure. Limits of detection obtained ranged from 0.1 to 0.4 ng/g in fish plasma and from 1.6 to 14 ng/g in fish bile. The developed method was successfully applied to the determination of plasma steroids in flounders (Platichthys flesus) collected from two French estuaries.     

Correction of discrepancies in dioxin quantification between immunoassay and gas chromatography–high-resolution mass spectrometry

Due to the toxicity of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F), efforts are made to quantify their emission into the environment. Typically, this quantification is done using gas chromatography–high-resolution mass spectrometry (GC–HRMS). However, GC–HRMS is extremely expensive and time consuming, and GC–HRMS facilities are overly requested. In order to decrease the workload on GC–HRMS, another alternative is to use an enzyme-linked immunosorbent assay (ELISA) as a semi-quantitative screening tool. One problem of this solution is that ELISA measures the total PCDD/F content of a sample differently than GC–HRMS; a disparity exists between the two techniques. This paper introduces a congener correction factor that adjusts ELISA results for this incompatibility. The importance of the correction factor is explored by examining the congener profiles of 27 different dioxin sources. The congener profiles for many of these sources are such that large incompatibilities in predicted PCDD/F content would likely exist between uncorrected ELISA and GC–HRMS. The effect that the correction factor has on the correlation between ELISA and GC–HRMS for samples from a test site with dioxin-contaminated soils was also examined. The congener profile at this site was such that the inconsistencies between uncorrected ELISA and GC–HRMS results were relatively small. However, application of the congener correction factor still improved the correlation between ELISA and GC–HRMS by 11% when using sample-specific correction factors and by 5% when using an average site-wide correction factor. The findings of this paper suggest that application of the correction factor is necessary to remove incompatibilities between ELISA and GC–HRMS—particularly when the congener profile at a site would lead to incompatibilities that are large.     

A comparison of three solvent-free techniques coupled with gas chromatography for determining trihalomethanes in urine samples

The analysis of volatile organic compounds in samples of biological fluids characterized by complex matrices is highly challenging. This paper presents a comparison of the results obtained in this field using three solvent-free techniques: thin-layer headspace with autogenous generation of liquid sorbent (TLHS) and membrane separation of the trace substances (pervaporation, PV), both of which are coupled to direct aqueous injection gas chromatography–electron capture detection (TLHS–DAI–GC–ECD and PV–DAI–GC–ECD), as well as conventional static headspace analysis followed by GC analysis with ECD detection (HS–GC–ECD). Basic validation parameters of the HS–GC–ECD, TLHS–DAI–GC–ECD and PV–DAI–GC–ECD procedures were calculated for water and urine samples. The calibration curves for all procedures were linear within the concentration range examined. The intermediate precisions of the procedures were good and reached about 10% (for all analytes) for HS–GC–ECD and TLHS–DAI–GC–ECD. The poorest results were obtained for PV–DAI–GC–ECD: about 20% for all analytes. The lowest method detection limits were obtained for the TLHS–DAI–GC–ECD procedure: below 0.0022 μg/L for all analytes. The enrichment factors did not differ significantly between water and urine samples, indicating little or no matrix effect in all procedures.