Electron Capture Negative Ionization Research Articles

Comparative evaluation of liquid chromatography–mass spectrometry versus gas chromatography–mass spectrometry for the determination of hexabromocyclododecanes and their degradation products in indoor dust

Domestic and office dust samples ( n = 37) were analyzed for hexabromocyclododecanes (HBCDs) using gas chromatography–electron-capture negative ionization–mass spectrometry (GC–ECNI/MS) and liquid chromatography–electrospray tandem mass spectrometry (LC–ESI/MS/MS). To determine the best method to quantify HBCDs using GC–ECNI/MS, BDE 128 was used as internal standard (I.S.) in all samples, while 13C-labeled α-HBCD was used as I.S. in some samples. Total HBCD concentrations (sum of α-, β-, and γ-HBCD diastereomers) were calculated using response factors (RFs) for α- and γ-HBCD as individual diastereomers and using an average RF for both diastereomers. Statistical comparison showed that concentrations obtained via GC–ECNI/MS were statistically indistinguishable ( p > 0.05) from those obtained using LC–ESI/MS/MS. The closest match between the two techniques was obtained using [ 13C]α-HBCD as I.S. and the average RF for α- and γ-HBCDs. Excellent linear correlations (Pearson coefficient values r > 0.9) were obtained between the GC–ECNI/MS and LC–ESI/MS/MS results, with slopes ranging from 0.76 to 1.36. Pentabromocyclododecenes (four isomers) and tetrabromocyclododecadienes (two isomers) were detected in the studied samples and were identified as degradation products of HBCDs after separation from the parent compound on the basis of both retention time and mass spectrum. This finding suggests that the elimination of HBr is the major degradation pathway for HBCDs in dust.

Electron Impact and Electron Capture Negative Ionization Mass Spectra of Polybrominated Diphenyl Ethers and Methoxylated Polybrominated Diphenyl Ethers

This review presents the electron impact (EI) and electron capture negative ionization (ECNI) mass spectra of the polybrominated diphenyl ether (PBDE) flame retardants and of their methoxy derivatives. Data from the literature are reviewed, and full spectra from our laboratory are reported to correct some of the errors that have crept into some previously published data. The EI spectra of the PBDEs are dominated by molecular ions and by singly and doubly charged ions due to the loss of Br2 from the molecular ion. The ECNI spectra of PBDEs with seven or less bromines are dominated by Br(-) and by HBr2(-); the spectra of those with eight or more bromines are dominated bytetra- or pentabromophenoxide ions due to cleavage of the phenyl-ether linkage. The EI mass spectra of methoxy-PBDEs can easily distinguish the position of the methoxy group relative to the phenyl-ether linkage. The ECNI spectra of these compounds are also dominated by Br(-) and HBr2(-). In both ionization modes and for both compound groups, there are some subtle features, which often allow one to rule in or out substitution at one or more of the ortho-ring positions.

Historical Profiles of Chlorinated Paraffins and Polychlorinated Biphenyls in a Dated Sediment Core from Lake Thun (Switzerland)

A dated sediment core from Lake Thun covering the last 120 years was analyzed to get an overview of the historical trend of the chlorinated paraffin (CP) and polychlorinated biphenyl (PCB) deposition, because CPs and PCBs have/had similar applications as plasticizers and flame retardants. Total CP concentrations (sum of short chain (SCCP), medium chain (MCCP), and long chain CPs (LCCP)) showed a steep increase in the 1980s and a more-or-less stable level of 50 ng g(-1) dry weight (dw) since then. The concentration-time profile is in good agreement with the available information on global production data. The quantification of higher chlorinated SCCPs using electron capture negative ionization low resolution mass spectrometry (ECNI-LRMS) revealed an increase in recent years. In addition, the degree of chlorination of SCCPs has strongly increased during the past 40 years, which may indicate its use as an additive for plastics, paints, and coatings. Furthermore, PCBs were analyzed in dated sediment slices. The PCB concentrations (sum of the six indicator congeners) peaked around 1969 (18 ng g(-1) dw) and decreased to 1.3 ng g(-1) dw in the surface layer corresponding to 2004. The peak level of CPs exceeded those of PCBs by about a factor of 3.

Simultaneous determination of bisphenol A, triclosan, and tetrabromobisphenol A in human serum using solid-phase extraction and gas chromatography-electron capture negative-ionization mass spectrometry

This study aimed at optimizing and validating a sensitive method for simultaneous determination of bisphenol A (BPA), triclosan (TCS), and tetrabromobisphenol A (TBBPA) in human serum using solid-phase extraction (SPE) and gas chromatography coupled to electron-capture negative-ionization mass spectrometry (GC-ECNI/MS). Sample preparation involved denaturation of serum proteins with formic acid followed by SPE on an Oasis HLB cartridge. Fractionation was performed on Florisil from which the phenolic compounds were eluted with methanol-dichloromethane (DCM) (5:1, v/v). The phenolic fraction was further derivatized with pentafluoropropionic acid anhydride (30 min at 70 degrees C). Further liquid-liquid partitioning using hexane-DCM (4:1, v/v) and K(2)CO(3) 3% aqueous solution was used to eliminate excess reagent and acidic by-products formed during derivatization. The cleaned extract was injected into a GC-ECNI/MS system operated in selected ion monitoring mode. For thorough method validation, each step of the procedure was rigorously optimized. The method limits of quantitation for BPA, TCS, and TBBPA were 0.28 ng mL(-1), 0.09 ng mL(-1) and 0.05 ng mL(-1), respectively. Furthermore, the method was applied to 21 Belgian human serum samples. The median concentrations obtained for BPA (0.71 ng mL(-1)) and TCS (0.52 ng mL(-1)) in Belgian human serum samples were similar to previously reported data for human fluids. Slightly higher levels of TBBPA (0.08 ng mL(-1)) were found in Belgium samples compared to Norwegian serum.

Isolation and Recovery of Selected Polybrominated Diphenyl Ethers from Human Serum and Sheep Serum: Coupling Reversed-Phase Solid-Phase Disk Extraction and Liquid-Liquid Extraction Techniques with a Capillary Gas Chromatographic Electron Capture Negative Ion Mass Spectrometric Determinative Technique

Polybrominated diphenyl ethers (PBDEs) are isolated and recovered with acceptable percent recoveries from human serum via liquid-liquid extraction and column chromatographic cleanup and fractionation with quantitation using capillary gas chromatography-mass spectrometry with electron capture negative ion and selected ion monitoring. PBDEs are found in unspiked serum. An alternative sample preparation approach is developed using sheep serum that utilizes a formic acid pre-treatment followed by reversed-phase solid-phase disk extraction and normal-phase solid-phase cleanup using acidified silica gel that yields>50% recoveries. When these percent recoveries are combined with a minimized phase ratio for human serum and very low instrument detection limits, method detection limits below 500 parts-per-trillion are realized.

Biological transformation, kinetics and dose-response assessments of bound musk ketone hemoglobin adducts in rainbow trout as biomarkers of environmental exposure

Low levels (ng/g) of musk ketone (MK), used as a fragrance additive in the formulation of personal care products, are frequently detected in the water and other environment. Thus, aquatic organisms can be continuously exposed to MK. In this study, kinetics and dose-response assessments of 2-amino-MK (AMK) metabolite, bound to cysteine-hemoglobin (Hb) in rainbow trout, formed by enzymatic nitro-reduction of MK have been demonstrated. Trout were exposed to a single exposure of 0.010, 0.030, 0.10, and 0.30 mg MK/g fish. Twenty-seven Hb samples were collected from exposed- and control fish subsequent to exposure intervals of 1 d (24 h), 3 d (72 h), and 7 d (168 h). Basic hydrolysis released bound AMK metabolite was extracted into n-hexane and then concentrated and analyzed by gas chromatography (GC) electron capture negative ion chemical ionization (NICI) mass spectrometry (MS) using selected ion monitoring (SIM). The presence of the AMK metabolite in Hb extracts was confirmed by agreement of similar mass spectral features and retention time with a standard. In the dose-response study, maximum adduct formation was obtained at the 0.10 mg/g dose with an average AMK metabolite concentration of 2.2 ng/g. For kinetics, the highest concentration of the AMK metabolite was found to be 32.0 ng/g at 0.030 mg/g dose in 3-d sample. Further elimination of the metabolite showed kinetics with a half-life estimated to be 2 d, assuming first-order kinetics. The metabolite was not detected in the control samples, non-hydrolyzed Hb, and reagent blank extracts. The detection limit for AMK in the Hb was approximately 0.30 ng/g, based on a signal to noise ratio of 3 (S/N = 3).

Identification of the Novel Cycloaliphatic Brominated Flame Retardant 1,2-Dibromo-4-(1,2-dibromoethyl)cyclohexane in Canadian Arctic Beluga (Delphinapterus leucas)

1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (TBECH) is used primarily as an additive flame retardant. Technical grade TBECH consists of near equimolar amounts of two (of a possible four) diastereoisomers: rac-(1R,2R)-1,2-dibromo-(4S)-4-((1S)-1,2-dibromoethyl)cyclohexane ((alpha-TBECH) and rac-(1R,2R)-1,2-dibromo-(4S)-4-((1R)-1,2-dibromoethyl)cyclohexane (beta-TBECH). The two other possible isomers, gamma- and delta-TBECH, appear in the technical mixture when heated at temperatures above 120 degrees C. Careful selection of GC-capillary column length was critical in resolution of the two main diastereoisomers. Column lengths of 60 or 30 m (0.25 microm film thickness) resulted in incomplete separation of the alpha- and beta-isomers, while on a 10 m column, the isomers were baseline separated. The gamma- and delta-isomers could not be resolved on any column length in this study. Increased injector port temperature induced thermal conversion of the alpha- and beta-isomers to gamma- and delta-TBECH. Electron impact ionization (EI) was used to provide specificity because no characteristic ions in the electron capture negative ionization (ECNI) mass spectrum of TBECH were evident. In EI, the dominant ions in the mass spectrum corresponded to a concomitant loss of HBr and Br from the molecular ion; the biggest peak in this ion cluster (m/z 266.9208) was used for quantitation and the second biggest peak (m/z 264.9227) was used for confirmation. Beluga (Delphinapterus leucas) blubber extracts of animals from the Canadian Arctic (n=29) were analyzed using low resolution (LR) MS and high resolution (HR) MS run at a resolving power of 10,000. beta-TBECH was the only isomer observed in the samples and was detected in 17 samples. The LRMS technique appeared to overestimate beta-TBECH concentrations compared to HRMS, suggesting a small interference arose at the nominal mass monitored. This potential interference also led to some false positive and negative values (n=7) based on the expected ion ratio of the quantitation and confirmation ions. Observed concentrations of the beta-isomer as measured by HRMS ranged from 1.1 to 9.3 ng/g (lipid weight).

Occurrence of polychlorinated naphthalenes, polychlorinated biphenyls and short-chain chlorinated paraffins in marine sediments from Barcelona (Spain)

Polychlorinated naphthalenes (PCNs), short-chain chlorinated paraffins (SCCPs) and polychlorinated biphenyls (PCBs) were analysed in marine sediment samples collected from the coastal area of Barcelona (Spain) and near of a submarine emissary coming from a waste water treatment plant located at the mouth of the Besòs River (Barcelona). An integrated sample treatment based on Soxhlet extraction followed by a simple clean-up with Florisil and graphitized carbon cartridge was employed. Gas chromatography coupled to ion-trap tandem mass spectrometry (GC–MS/MS) and gas chromatography–mass spectrometry in electron capture negative ionization mode, were used for PCN and SCCP determinations, respectively, while for PCB analysis gas chromatography with electron capture detection (GC-ECD) was used. The method developed provided low limits of detection (0.001–0.003 ng g −1 dry weight (dw) for PCNs, 1.8 ng g −1 for SCCPs and 0.006–0.014 ng g −1 dw for PCBs) and good run-to-run precisions (lower than RSD 8%) for the analysis of sediment samples. Concentration levels ranging from 0.17 to 3.27 ng g −1 dw for PCNs, between 0.21 and 1.17 μg g −1 dw for SCCPs, and from 2.33 to 44.00 ng g −1 (dw) for PCBs, were found in the coastal sediments, while for samples collected near to the submarine emissary higher levels (from 2.02 to 6.56 ng g −1 dw for PCNs, between 1.25 and 2.09 μg g −1 dw for SCCPs and from 22.34 to 37.74 ng g −1 dw for PCBs) were obtained. The results obtained provide new data about the occurrence of PCN and SCCP in the coastal area of Barcelona.

Fast analysis of decabrominated diphenyl ether using low-pressure gas chromatography–electron-capture negative ionization mass spectrometry

This paper reports the applicability of low-pressure gas chromatography–mass spectrometry operated in electron-capture negative ionization mode (LP-GC–ECNI-MS) for the analysis of decabrominated diphenyl ether (BDE-209). Particular attention was paid to find optimal injector and oven conditions for minimal thermal degradation of BDE-209. The analytical characteristics were compared for LP-GC columns (10 m × 0.53 mm) with different film thicknesses ( d f 0.15 μm versus 0.25 μm) and for a conventional GC column (15 m × 0.25 mm, 0.10 μm d f). Short residence times (6.5 and 9.8 min) of BDE-209 were found for the LP-GC systems with 0.15 and 0.25 μm d f, respectively, resulting in a low elution temperature and minimal degradation. Additionally, baseline separation of 22 polybrominated diphenyl ether (PBDE) congeners (major components of PBDE technical mixtures) was possible in less than 12 min using the LP-GC–ECNI-MS system with 0.15 μm d f. The optimized method was applied for the determination of PBDEs in Belgian indoor dust samples. The obtained concentrations of BDE-209 (range 8–292 ng/g dry weight) were in the same range or lower than concentrations in dust from other European countries.

Analysis of nitroaromatic compounds in complex samples using solid-phase microextraction and isotope dilution quantification gas chromatography–electron-capture negative ionisation mass spectrometry

A solid-phase microextraction (SPME) method using gas chromatography–electron-capture negative ionisation mass spectrometry (GC–ECNI-MS) and isotope dilution quantification for the analysis of nitroaromatic compounds in complex, water based samples has been optimised. For ionisation, ECNI was the most sensitive and selective method. SPME was compared to solid-phase extraction (SPE) and found to be more sensitive for these small volume samples. LODs were in the range 0.02–38 ng L −1 for SPME and 6–184 ng L −1 for SPE, respectively. The SPME method was applied on samples in the ng L −1 level from artificial reed beds treated with sludge containing residues from explosives and pharmaceuticals.

Feasibility of electron impact and electron capture negative ionisation mass spectrometry for the trace determination of tri- to deca-brominated diphenyl ethers in human samples

The applicability of two different MS ionisation modes (EI and ECNI) for the determination of PBDEs at low-trace levels in small-size (up to 1 mL) human samples was compared. The instrumental precision, expressed as R.S.D., obtained for both ionisation modes was similar and lower than 6% (repeatability) and 12% (intermediate precision) for all congeners investigated, except PBDE 209. The LODs obtained when using the ECNI-MS operation mode (6–507 fg) were lower than those found in EI-MS experiments (9 and 10,909 fg), mainly for those congeners with a high bromination degree, i.e., hepta- to deca-BDEs. The selectivity of the ECNI-MS method proposed in the present work was improved by using two ions of the [M−H x Br y ] − cluster as both qualifier and quantifier ions. For the final validation of the methods, serum and breast milk samples from two different inter-laboratory exercises were analysed. A good agreement was found between the results obtained using the proposed methods and the results provided by the different inter-laboratory organisations, but only ECNI-MS provided the low-LODs necessary for the quantification of high brominated congeners (mainly, PBDEs 196, 197 and 209) at low concentration levels in small-size human samples. Finally, the ECNI-MS method was applied to real-life samples obtained from the Spanish population and the preliminary results obtained were in the same range as those found in other European and Asian regions and lower than the concentrations reported in USA populations.

Quantitation of phenylalanine and its trans‐cinnamic, benzoic and hippuric acid metabolites in biological fluids in a single GC‐MS analysis

We describe a sensitive, simple and convenient stable isotope dilution assay developed to study endogenous metabolism of administered stable isotope-labeled phenylalanine (Phe) in phenylketonuric (PKU) mice treated experimentally with phenylalanine ammonia lyase (PAL). Mouse urine and plasma containing endogenous and administered labeled Phe together with internal standard Phe bearing a different pattern of labeling are converted by in situ diazotization to 2-chloro-3-phenylpropionic acid (CPP). A single solvent extraction is then used to isolate the isotopomers of CPP along with the trans-cinnamic acid (TCA) produced from Phe by PAL, as well as the TCA metabolites benzoic and hippuric acids. This procedure eliminates the need for a separate ion-exchange isolation step for Phe on a second sample aliquot and separate GC-MS analysis. Extracted CPP and the Phe metabolites are then measured by conversion to the pentafluorobenzyl esters and a single analysis by electron capture negative ion GC-MS. The estimated lower limit of quantitation is 0.1 microM.

Pulsed Large Volume Injection Gas Chromatography Coupled with Electron-Capture Negative Ionization Quadrupole Mass Spectrometry for Simultaneous Determination of Typical Halogenated Persistent Organic Pollutants

A pulsed large-volume injection gas chromatography coupled with electron-capture negative ionization quadrupole mass spectrometry (pLVI-GC/ECNI-qMS) was developed for the simultaneous determination of typical halogenated persistent organic pollutants (H-POPs). By monitoring the characteristic ions of large mass-to-charge ratio (m/z) for each of the H-POPs rather than the chlorine and/or bromine ions, this method avoided the possible interferences arising from the H-POPs themselves and from complex matrices encountered frequently in current GC/qMS methods; and allowed, on the other hand, the use of (13)C-labeled and perdeuterated analogues as internal standards for reliable quantification. pLVI up to 120 microL improved the instrumental detection limits down to pg-fg mL(-1), comparable to or lower than those obtained by the recognized GC/high-resolution MS methods reported so far. The H-POPs including 12 polybrominated diphenyl ethers, 1 polybrominated biphenyl, 10 polychlorinated biphenyls (PCBs), 4 hexachlorocyclohexane isomers, and hexachlorobenzene were involved in this study. The method developed demonstrated good linearity (r(2) = 0.9904-0.9999) within 0.5 to 50,000 pg mL(-1) for PCBs and 0.05 to 5000 pg mL(-1) for other H-POPs, and was satisfactory in terms of both repeatability (0.07%-2.2%) and reproducibility (2.1%-8.4%). It was validated by analyzing a NIST standard reference material SRM-1946 of Lake Superior fish tissue with low 0.01 to 63 pg g(-1) method detection limits, and successfully applied to the determination of the H-POPs in five reference materials of different matrices.

Highly selective and sensitive gas chromatography–electron-capture negative-ion mass spectrometry method for the indirect enantioselective identification of 2- and 3-hydroxy fatty acids in food and biological samples

A gas chromatographic (GC) method is described for the indirect enantioresolution of 2- and 3-hydroxy fatty acids (OH-FAs). It combines the derivatization of each alkylated enantiomer and the subsequent transfer with ( R)-(−)- α-methoxy- α-trifluoromethylphenylacetyl chloride [( R)-(−)-MTPA-Cl, Mosher's reagent] into a diastereomeric ( S)-MTPA derivative. The enantiomers of each derivatized OH-FA were well separated on three non-chiral GC-columns (CP-Sil 2, CP-Sil 8/20% C18 and VF-5 ms). The derivatives were detected with high sensitivity by GC with electron-capture detection (GC/ECD) and electron-capture negative-ion mass spectrometry (GC/ECNI-MS) because of their enhanced electron-capturing properties. When applied to sunflower oil spiked with a small amount of a racemic 2-OH-FA, the present method allowed for a highly selective identification without influence from the sample matrix. For more complex samples such as wool wax, GC/ECNI-MS was superior to GC/ECD, since the high sensitivity of this method was linked with high selectivity. Using GC/ECNI-MS in the selected ion monitoring (SIM) mode, 16 enantiopure 2-OH-FAs were detected in a wool wax sample.

Gas chromatography–mass spectrometry/mass spectrometry analysis to determine natural and post-administration levels of oestrogens in bovine serum and urine

A novel analytical approach has been developed and shown to be capable of detecting the isomers of oestradiol in the low ppt (pgmL−1) range in bovine serum and urine. Following extractive derivatisation the analytes were detected as their 3-pentafluorobenzoyl 17-trimethylsilyl ether derivatives by gas chromatography–mass spectrometry/mass spectrometry (GC–MS/MS), using electron capture negative ion chemical ionisation. The isomers of oestradiol were quantified in both blank and post-administration urine and serum samples, with a view to setting action/threshold levels for these compounds, to allow discrimination between normal samples and samples from animals treated with growth promoting ear implants. A non-parametric statistical assessment of the data resulted in proposed action levels (with a false positive probability of 1 in 1000) of 1.6 and 2.7ngmL−1 for 17α-oestradiol, in male and female urine, respectively, and 40 and 44pgmL−1 for 17β-oestradiol, in male and female urine, respectively. An action level of 20pgmL−1 was proposed for 17α- and 17β-oestradiol in male serum. In female serum the proposed action levels were 40 and 20pgmL−1 for 17α- and 17β-oestradiol, respectively.

Structure Elucidation of an Artifact Discharging from Rubber-Based Vial Closures by Means of Gas Chromatography/Tandem Mass Spectrometry

The use of vial closures equipped with butyl rubber septa may lead to sample contamination by rubber additives discharging from the septum material. In this study, the structure elucidation of an artifact causing intense signals in gas chromatography/electron capture negative ion mass spectrometry (GC/ECNI-MS) and gas chromatographic analyses with electron capture detection is described. Tentative identification of the leached compound was achieved by employing tandem mass spectrometric techniques both in electron capture negative ion and in electron ionization modes. The artifact could thus be characterized as 2-benzothiazolyl-N,N-dimethyl dithiocarbamate, which is a known vulcanization accelerator for rubber. It is conceivable that the identified compound or related substances are also used in other applications. Therefore, two food-related matrixes were investigated for a possible migration of this compound into foods. During these analyses, the tentatively identified rubber additive was detected in an aqueous extract of a rubber seal ring for canning jars. GC/ECNI-MS provided better sensitivity and selectivity than GC/EI-MS for the determination of the rubber additive and other mercaptobenzothiazole-derived substances.

Fast gas chromatographic/mass spectrometric determination of diuretics and masking agents in human urine: Development and validation of a productive screening protocol for antidoping analysis

An analytical procedure was developed for the fast screening of 16 diuretics (acetazolamide, althiazide, amiloride, bendroflumethiazide, bumetanide, canrenoic acid, chlorthalidone, chlorthiazide, clopamide, ethacrynic acid, furosemide, hydrochlorthiazide, hydroflumethiazide, indapamide, triamterene, trichlormethiazide) and a masking agent (probenecid) in human urine. The whole method involves three analytical steps, including (1) liquid/liquid extraction of the analytes from the matrix, (2) their reaction with methyl iodide at 70 °C for 2 h to form methyl derivatives, (3) analysis of the resulting mixture by fast gas chromatography/electron impact mass spectrometry (fast GC/EI-MS). The analytical method was validated by determining selectivity, linearity, accuracy, intra and inter assay precision, extraction efficiencies and signal to noise ratio (S/N) at the lowest calibration level (LCL) for all candidate analytes. The analytical performances of three extraction procedures and five combination of derivatization parameters were compared in order to probe the conditions for speeding up the sample preparation step. Limits of detection (LOD) were evaluated in both EI-MS and ECNI-MS (electron capture negative ionization mass spectrometry) modes, indicating better sensitivity for most of the analytes using the latter ionization technique. The use of short columns and high carrier gas velocity in fast GC/MS produced efficient separation of the analytes in less than 4 min, resulting in a drastic reduction of the analysis time, while a resolution comparable to that obtained from classic GC conditions is maintained. Fast quadrupole MS electronics allows high scan rates and effective data acquisition both in scan and selected ion monitoring modes.

Detailed Polybrominated Diphenyl Ether (PBDE) Congener Composition of the Widely Used Penta-, Octa-, and Deca-PBDE Technical Flame-retardant Mixtures

Polybrominated diphenyl ethers (PBDEs) have been widely used to flame-retard products common in homes and the workplace, and subsequently, they have become widely dispersed in the environment. Detailed compositional knowledge of these complex PBDE mixtures is crucial to a fuller understanding of their toxicological potencies and environmental fate due to selective congener biomagnification, degradation, and transport. Utilizing recenttechnical enhancements and newly available commercial standards, we developed a method capable of analyzing a larger suite of mono- through deca-BDEs. We then characterized the congener composition of six common technical flame-retardant mixtures: two penta-BDE products (DE-71 and Bromkal 70-5DE) two octa-BDE products (DE-79 and Bromkal 79-8DE) and two deca-BDE products (Saytex 102E and Bromkal 82-0DE). PBDEs were analyzed by gas chromatography/mass spectrometry (GC/MS). Structural conformations based on fragmentation patterns and molecular ions were established by electron-capture negative ionization (ECNI) and electron ionization (El). Sixty-four commercially available PBDE standards were chromato-graphed on two GC columns (DB-1HT and DB-5HT) and relative retention indexes (RRI) calculated. Thirty-nine PBDEs were identified in these products, 29 at concentrations >0.02% by weight. Of these, 12 previously unreported congeners have been confirmed as commercial mixture components. Four of these congeners were detected >0.02% w/w (BDE-144, -171, -180, and -201) and three (BDE-75, -184, and -194) at <0.02%. Five other congeners (four <0.02% by weight) were tentatively identified based on their molecular ion and ECNI fragmentation in the absence of corresponding analytical standards.

Biotransformation of musk xylene in trout haemoglobin: dose–response and toxicokinetics of musk xylene metabolites haemoglobin adducts by gas chromatography-mass spectrometry

Musk xylene (MX) is frequently used as a fragrance in commercial toiletries. Biotransformation of MX into 4-amino-MX (4-AMX) and 2-amino-MX (2-AMX) metabolites in rainbow trout haemoglobin (Hb) has been described. The dose–response relationship and toxicokinetics of the metabolites as adducts in the Hb were determined by gas chromatography (GC)–electron capture negative chemical ionization (NCI)–mass spectrometry (MS), and GC–electron ionization (EI)–MS/MS, using selected ion monitoring (SIM). The trout were subjected to a single exposure of 0.010, 0.030, 0.10, and/or 0.30 mg MX/g of fish. Hb samples were collected from exposed and control fish, and analysed subsequent to exposure at intervals of 24, 72, and 168 h. Alkaline hydrolysis released 4-AMX and 2-AMX metabolites from the Hb, and the solutes were extracted into n-hexane. The extracts were preconcentrated and analysed. The presence of the metabolites in the Hb extracts was confirmed based on agreement of similar mass spectral features from NCI/MS and EI-MS/MS spectra, and retention times of the metabolites with standards. The NCI/MS results were used for dose–response and toxicokinetics measurements. For dose–response, the concentrations of adducts of the metabolites increased with dosage, and a maximum adduct formation was observed at 0.10 mg g−1, beyond which it decreased. The average concentrations of 4-AMX and 2-AMX at a dosage of 0.10 mg g−1 were 700 and 7.4 ng g−1, respectively. For toxicokinetics, the concentration of the metabolites in the Hb reached a maximum in the 3 day sample after administration of MX. Further elimination of the metabolites exhibited kinetics with a half-life estimated to be 1–2 days, assuming first-order kinetics. Quantitations were made based on an internal standard and a calibration plot. In control samples, non-hydrolysed Hb, and reagent blank extracts, the metabolites were not detected. The limits of detection for 4-AMX and 2-AMX in the Hb were approximately 1.7 and 1.4 µg L−1, respectively, based on a signal-to-noise ratio of 3 with NCI/MS.

Determination of Triclosan as Its Pentafluorobenzoyl Ester in Human Plasma and Milk Using Electron Capture Negative Ionization Mass Spectrometry

A sensitive method for the determination of triclosan in plasma and milk is presented. Following hydrolysis of possible conjugates, triclosan is extracted with n-hexane/acetone, partitioned into alcoholic potassium hydroxide, and converted into its pentafluorobenzoyl ester. After sulfuric acid cleanup, sample extracts are analyzed by gas chromatography/electron capture negative ionization mass spectrometry. The limit of quantification was 0.009 ng/g for a 5-g plasma sample and 0.018 ng/g for a 3-g milk sample. The coefficient of variation for the method was 6%. The method was tested on more than 70 human plasma and milk samples, of which all plasma samples and more than half of the milk samples were above the limit of quantification. The presented method has lowered the limit of quantification for triclosan in human matrixes significantly as compared to previous methods and makes possible the analysis of triclosan in humans under normal exposure conditions.