Negative Chemical Ionization Mass Spectrometry Research Articles

Exposure to polybrominated diphenyl ethers among workers at an electronic waste dismantling region in Guangdong, China

Polybrominated diphenyl ethers (PBDEs) are widely used as flame retardants. The aim of the present study was to evaluate the PBDE serum levels in residents from an electronic waste dismantling region, residents living within 50 km of the dismantling region, and a referent group with no occupational PBDE exposure. Fourteen PBDE congeners including BDE-28, BDE-47, BDE-99, BDE-100, BDE-153, BDE-154, BDE-183, BDE-196, BDE-197, BDE-203, BDE-206, BDE-207, BDE-208 and BDE-209 were quantified in these three groups by gas chromatography–negative chemical ionization (NCI) mass spectrometry in selected ion monitoring (SIM) mode. We found that the levels of all PBDE congeners in serum of residents from electronic waste dismantling region were significantly higher than those in the two other groups. The referents showed the lowest PBDE levels. Concentrations of congeners with a high number of bromine substituents, i.e., hepta- to decaBDEs in occupational exposure workers were 11–20 times higher than those in the referent group. BDE-209 was the dominant congener. The highest concentration of BDE-209 was observed among the electronic waste dismantling workers, and it was 3436 ng g−1 lipid weight (ng g−1 l.w.), which is the highest concentration of BDE-209 in humans worldwide. Some higher brominated PBDE congeners such as BDE-197, BDE-207 and BDE-208 also showed elevated concentrations in dismantling workers. This study confirms that BDE-209 is released to the environment and can bioaccumulate in the blood of electronic waste dismantling workers, and extensive occupational exposure to PBDEs leads to elevated concentrations of all PBDE congeners in serum.

Analysis of aldehydes in excipients used in liquid/semi-solid formulations by gas chromatography–negative chemical ionization mass spectrometry

Monitoring of low-molecular-weight aldehyde levels in excipients used in liquid/semi-solid based capsule (LFC) dosage forms plays a critical role in the development of these pharmaceutical products. A simple, sensitive and specific method based on gas chromatography coupled with mass spectrometry (GC–MS) utilizing an Rtx-5MS capillary column was developed and validated for the detection and quantification of C 1–C 8 aliphatic aldehydes in LFC excipients at sub-μg/g levels. The proposed procedure is based on the derivatization of aldehydes in 10:1 (v/v) acetonitrile:water with O-2,3,4,5,6-(pentafluorobenzyl) hydroxylamine hydrochloride (PFBHA), followed by direct GC analysis of aldehyde-PFBHA-oxime derivatives with negative chemical ionization (NCI) MS detection. The method developed was successfully applied to the analysis of short chain aldehydes in 30 typical LFC excipients. An example case study on the formation and growth of aldehydes in these excipients under accelerated storage conditions is also reported.

Simultaneous determination of safflor yellow A, puerarin, daidzein, ginsenosides (Rg 1, Rb 1, Rd), and notoginsenoside R 1 in rat plasma by liquid chromatography–mass spectrometry

A liquid chromatograph/mass spectrometry (LC/MS) method was developed for the simultaneous quantitation of seven compounds (safflor yellow A, puerarin, daidzein, ginsenosides (Rg 1, Rb 1, Rd), and notoginsenoside R 1) in rat plasma samples with sufficient sensitivity to facilitate analysis of samples collected after an intravenous injection of Naodesheng. The plasma samples were subjected to protein precipitation with acetone, and analyzed using negative atmospheric pressure chemical ionization mass spectrometry in selected ion monitoring (SIM) mode with baicalin as an internal standard. Good linearity for all the seven compounds was observed. The intra- and inter-day precision of analysis was <15.0% for each compound, and the accuracy ranged from 90.0% to 109.0%. This quantitation method was successfully applied to a pharmacokinetic study of following intravenous injection of rats with Naodesheng.

Simultaneous determination of homoeriodictyol-7- O-β- d-Glccopyranoside and its metabolite homoeriodictyol in rat tissues and urine by liquid chromatography–mass spectrometry

A liquid chromatographic–mass spectrometric (LC–MS) method was developed and validated for the simultaneous determination of homoeriodictyol-7- O-β- d-glycoside (HEDT-Glc) and its active metabolite homoeriodictyol (HEDT) in rat tissues and urine. The analytes and internal standard (dihydromyricetin, IS) were detected by using negative atmospheric pressure chemical ionization mass spectrometry in selected ion monitoring (SIM) mode at m/ z 464, 301 and 319 for HEDT-Glc, HEDT and IS, respectively. These compounds were eluted on a Luna reverse phase column. The mobile phase was a methanol–water mixture (70:30, v/v) containing 0.1% of formic acid at a flow rate of 0.8 ml/min. The limit of quantification (LOQ) for both HEDT-Glc and HEDT was 10 ng/ml and their limit of detection (LOD) was 1 ng/ml. Calibration curves were linear ( r > 0.995) over a wide range of the analytes in tissues and urine. The mean extraction recoveries were ≥75.6% for HEDT-Glc and ≥82.4% for HEDT from biological matrixes. Accuracy, expressed as the relative error, ranged from −4.0% to 3.8% for HEDT-Glc and from −2.8% to 4.7% for HEDT. The method was successfully applied to the estimation of HEDT-Glc and its metabolite HEDT in rat tissues and urine.

Quantification of low levels of organochlorine pesticides using small volumes (≤100 μl) of plasma of wild birds through gas chromatography negative chemical ionization mass spectrometry

A solid phase extraction and gas chromatography with negative chemical ionization mass spectrometry in scan mode (GC-NCI-MS) method was developed to identify and quantify for the first time low levels of organochlorine pesticides (OCs) in plasma samples of less than 100 μl from wild birds. The method detection limits ranged from 0.012 to 0.102 pg/μl and the method reporting limit from 0.036 to 0.307 pg/μl for α, γ, β and δ-hexachlorocyclohexane (HCH), heptachlor, aldrin, heptachlor epoxide, endosulfan I, 1,1-dichloro-2,2-bis( p-chlorophenyl)ethylene ( p, p′-DDE), dieldrin, endrin, endosulfan-II, endrin-aldehyde and endosulfan-sulfate. Pesticide levels in small serum samples from individual Falco sparverius, Sturnella neglecta, Mimus polyglottos and Columbina passerina were quantified. Concentrations ranged from not detected (n/d) to 204.9 pg/μl for some OC pesticides. All levels in the food web in and around cultivated areas showed the presence of pesticides notwithstanding the small areas for agriculture existing in the desert of Baja California peninsula.

Determination of five nitrobenzoic acids in groundwater by solid-phase extraction and liquid chromatography–mass spectrometry

A method involving solid-phase extraction (SPE) and reversed-phase liquid chromatography-mass spectrometry (LC-MS) has been developed for determination, in groundwater, of nitrobenzoic acids associated with 2,4,6-trinitrotoluene production. Pre-concentration on a co-polymer-based SPE cartridge enabled quantitative extraction of the analytes from water. Investigation of negative ion electrospray and atmospheric-pressure chemical ionization mass spectrometry indicated the sensitivity of APCI was more than twice that of ESI. An 15N-labeled internal standard was used to achieve more accurate quantitation and mass assignment. Recovery was better than 80% when 10 mL water was extracted with the SPE cartridge. Combination of SPE with LC-MS analysis resulted in method detection limits of less than 5 microg L-1. The method has been used for analysis of groundwater samples collected from a site of a former ammunition plant. Contamination with nitrobenzoic acids was determined at microg L-1 levels.

Multi-analyte approach for the determination of ng L−1 levels of steroid hormones in unidentified aqueous samples

Since the 1970s, many analytical methods for the detection of illegal growth promoters, such as thyreostats, anabolics, β-agonists and corticosteroids have been developed for a wide range of matrices of animal origin, including meat, fat, organ tissue, urine and faeces.The aim of this study was to develop an analytical method for the determination of ngL−1 levels of estrogens, gestagens, androgens (EGAs) and corticosteroids in aqueous preparations (i.e. drinking water, drinking water supplements), commercially available on the ‘black’ market. For this, extraction was performed with Bakerbond C18 speedisk, a technique commonly used in environmental analysis. After fractionation, four fractions were collected using a methanol:water gradient program. Gas chromatography coupled to electron impact multiple mass spectrometry (GC–EI-MS2) screening for the EGAs was carried out on the derivatized extracts. For the detection of corticosteroids, gas chromatography coupled to negative chemical ionization mass spectrometry (GC–NCI-MS) was used after oxidation of the extracts. Confirmation was done by liquid chromatography coupled to electrospray ionization multiple mass spectrometry (LC–ESI-MS2). The combined use of GC and LC coupled to MS enabled the identification and quantification of anabolics and corticosteroids at the low ngL−1 level. This study demonstrated the occurrence of both androgens and corticosteroids in different commercial aqueous samples.

Electron affinities of polynuclear aromatic hydrocarbons and negative-ion chemical-ionization sensitivities

Negative-ion chemical-ionization mass spectrometry (NICI MS) has the potential to be a very useful technique in identifying various polycyclic aromatic hydrocarbons (PAHs) in soil and sediment samples. Some PAHs give much stronger signals under NICI MS conditions than others. On the other hand, positive-ion signals are largely comparable under the same source conditions. An extensive set of newly re-evaluated experimental electron affinities (EAs), or free energies of electron attachment, are now available, as well as reliable predicted electron affinities from quantum theoretical calculations or from solution reduction potentials and theoretically predicted solvation energies. In order to show a high negative-ion sensitivity, a PAH must have an EA that exceeds a threshold of approximately of 0.5 eV. Comparisons between the negative-ion to positive-ion sensitivities ( N/ P ratios) and these new electron affinities show a rough correlation between the two, but naphthacene and perylene are exceptions to this relationship with much lower sensitivities than expected from their high EA values. By calculating the EA for a PAH, one can predict whether a sensitivity enhancement under NICI MS conditions is to be expected. Since aliphatic hydrocarbons and many other substances have negative or very low EAs, NICI MS is expected to be a good technique for detecting PAHs in samples contaminated with other hydrocarbons or compounds with low EAs.

Automated analysis of 2-methyl-3-furanthiol and 3-mercaptohexyl acetate at ng L −1 level by headspace solid-phase microextracion with on-fibre derivatisation and gas chromatography–negative chemical ionization mass spectrometric determination

A fast and automated method for the analysis at ng L −1 level of aroma-powerful polyfunctional thiols has been developed and applied to wine. The sample is just poured in a 20 mL vial and its vapour extracted with a poly(dimethylsiloxane)–divinylbenzene (PDMS–DVB) solid-phase microextraction fibre (65 μm thickness) previously exposed to vapours of the reactive (pentafluorobenzyl bromide) and of an alkali (tributylamine). The derivatised compounds are subsequently desorbed in the GC system and determined by negative chemical ionization mass spectrometry. The method is fully automated by using a Combi-Pal autosampler conveniently programmed. The analysis takes 50 min, which contrasts to the long and tedious methods previously proposed. The development of an optimal procedure is constrained by the aggressive character of the reagent (towards the fibre and the chromatographic column), its volatility and the quality of the blanks that can be obtained. Therefore, a critical step was fixing in the fibre a “safe” and repetitive amount of reagent. This was achieved by exposing the fibre (5 min) to the vapours of a water:acetone (9:1) solution containing 200 mg L −1 of reagent. Under these conditions, the extraction-derivatisation of analytes improves with time and temperature, and the best working conditions are dictated by a compromise between sensitivity, speed and chromatographic performance. Although analytes studied were 2-methyl-3-furanthiol, 4-mercapto-4-methyl-2-pentanone, 3-mercaptohexanol, 2-furanmethanethiol and 3-mercaptohexyl acetate, a good analytical performance could be achieved only for these two last compounds. Both of them can be repetitively (10% < RSD < 20%) determined in wine at concentrations below 0.1 ng L −1. Other aspects considered in the method setup were the oxidation of analytes during the process, and the electron-capture detection (ECD) and MS properties of the pentafluorobenzyl derivatives of different polyfunctional thiols.

Rapid and simplified method for the analysis of polychloronaphthalene congener distributions in environmental and human samples by gas chromatography coupled to negative ion chemical ionization mass spectrometry

A method for the analysis of congener-specific polychloronaphthalene mixtures in sediments and human sera based on combined applications of gas chromatography coupled to negative ion chemical ionization mass spectrometry (GC–NICI-MS) is described. Separation, identification and quantification of the constituent congeners is achieved in both types of samples. Besides the octa- and heptachloronaphthalenes the method allows the identification of 9 hexachloronaphthalene congeners, 12 pentachloronaphthalenes and 8 tetrachloronaphthalenes. Detection and quantification limits were in the order of 0.4–0.7 ng g −1 dry weight and 0.9–1.3 ng g −1 dry weight in sediments, respectively, and 0.06–0.11 ng mL −1 and 0.18–0.21 ng mL −1 in human sera, respectively. Application of the method to study the distributions of these compounds nearby a chlor-alkali plant located at the shore of the Ebro River has shown that whereas the most chlorinated compounds, octachloronaphthalene and the two heptachloronaphthalenes were dominant in the sediments, tri-, tetra-, penta- and hexachloronaphthalenes were the most abundant congeners found in human sera.

Effects of garlic ingestion in humans on the formation of urinary nitrosoproline

In vitro and animal studies suggest that compounds found in garlic may play a role in mediating the bioactivation of some carcinogens. N-nitrosoproline (NPRO) has been used in feeding studies as a biomarker for the formation of N-alkylnitrosamines. A controlled-feeding study was performed at Penn State University to test the hypothesis that garlic consumption inhibits nitrosamine formation. In this study, subjects (3 to 5 per group) consumed either 0 (control) 1, 3 or 5 grams of fresh garlic, 3 grams Kyolic (a commercial garlic supplement) or 500 mg vitamin C for 1 day following a 3 day run-in period in which 300 mg nitrate and 500 mg proline was consumed daily with a standard meal. Urine was collected during the last 24 hours and analyzed for NPRO. Aliquots were diluted with mobile phase, fractionated by isocratic reversed phase HPLC, and the fraction containing NPRO was dried and derivatized with pentafluorobenzyl bromide (PFB). The NPRO-PFB derivative was isolated using a second, gradient reversed-phase HPLC step and quantified by gas chromatography/ negative chemical ionization mass spectrometry. 13C5NPRO was used as the internal standard. Preliminary analysis of the samples indicates that NPRO excretion was reduced to nearly undetectable levels by treatments with 5 grams garlic, 3 grams Kyolic, and 500 mg vitamin C compared to controls. Analysis of the remaining samples is underway. In conclusion, the consumption of a single dose of prepared garlic, either fresh or as a supplement, reduced the excretion of NPRO under controlled-feeding conditions as much as a vitamin C supplement.

Polychlorinated biphenyls and toxaphene in preferred prey fish of coastal southeastern U.S. bottlenose dolphins (Tursiops truncatus)

Legacy organochlorine (OC) contaminants continue to pose a potential risk to ecological and human health in coastal aquatic ecosystems of the southeastern United States. Polychlorinated biphenyls (PCBs) and toxaphene (TOX) were analyzed by gas chromatography with electron capture detection and negative chemical ionization mass spectrometry in 77 composites of four inshore fish species commonly preyed upon by bottlenose dolphins (Tursiops truncatus) from estuaries near Savannah, Georgia (SAV), Brunswick, Georgia (BRN), and Jacksonville, Florida (JAX), USA. Whereas seasonal and species-specific differences were minimal, differences among mean total PCB concentrations (sigmaPCBs) by estuary (42.0 +/- 48.3, 1.59 +/- 1.24, and 0.281 +/- 0.075 microg/g lipid for BRN, JAX, and SAV, respectively) were highly significant. This estuary-specific trend also held true for mean total toxaphene concentrations (sigmaTOX): 49 +/- 100 (BRN), 1.2 +/- 0.52 (JAX), and 0.40 +/- 0.19 microg/g lipid (SAV). Congener profiles of PCBs also were found to be significantly different among estuaries, with BRN and (to a lesser extent) JAX samples enriched with highly chlorinated homologs associated with Aroclor 1268, a legacy OC linked to a historical point source in Brunswick. The observed spatial heterogeneity in OC concentrations and PCB congener profiles suggests that contaminated fish from Brunswick pose the greatest risk to ecological and human health via biomagnification and seafood consumption; highly chlorinated PCBs (and possibly toxaphene) are transported in a southerly, alongshore direction; and the uniqueness of Aroclor 1268 underscores its utility as a signature proxy in future regional ecotoxicological studies.

Presence of Chlorinated Paraffins in Sediments from the North and Baltic Seas

Chloroparaffins (CPs) were determined in sediments collected from the North and Baltic Seas during monitoring campaigns in 2001-2003. Electron ionization tandem mass spectrometry (MS/MS) was used for a first screening. It allowed the simultaneous determination of short (SCCP) and medium chain chlorinated paraffins (MCCP). SCCP+MCCP concentrations between 5 and 499 ng/g dry weight were found. In general, Baltic Sea sediments were more highly contaminated by CPs than the North Sea was. However, concentrations related to the total organic carbon content were on the same order of magnitude due to the higher organic content in the Baltic Sea. Additional information about the congener and homologue pattern was obtained for selected samples from the Baltic Sea by high-resolution gas chromatography combined with negative ion chemical ionization and low-resolution mass spectrometry, Concentrations in the North Sea were in general too low for this approach. In the Baltic Sea, MCCP concentrations were 1.7-2.4 times higher than for SCCPs. Lower chlorinated C(13) and C(14) compounds were the main CP compounds. The CP congener and homologue patterns showed similarities with technical SCCP and MCCP mixtures when compared using principal component analysis.

Analysis of 7‐methylguanine using isotope dilution and gas chromatography/electron‐capture negative chemical ionization mass spectrometry

This paper presents results obtained for in vivo endogenous and exogenous 7-methylguanine (7-MG) analyzed using a method incorporating gas chromatography with electron-capture negative chemical ionization mass spectrometry and isotope dilution (GC/EC-ID-MS). 13C4-Labeled 7-MG was synthesized to serve as an internal standard to improve accuracy of quantitation, and was used to analyze 7-MG in livers of control mice and dacarbazine-treated mice. The results confirm that 7-MG in tissue DNA can be measured using this GC/EC-ID-MS method with excellent sensitivity and specificity. Administration of 0, 30, and 60 mg/kg dacarbazine to mice led to dose-dependent increases in the formation of 7-MG. The results indicate that this method could be applied to the analysis of endogenous and exogenous 7-MG in human tissues for future molecular epidemiology studies on potential health effects caused by methylating agents.

Negative Ion Chemical Ionization Mass Spectrometry for the Analysis of 3,5,6‐Trichloro‐2‐pyridinol in Saliva of Rats Exposed to Chlorpyrifos

Organophosphorus (OP) insecticides (e.g. chlorpyrifos) are widely used in a variety of applications, and the potential exists for significant occupational and environmental exposures. They have been associated with more occupational poisoning cases than any other class of insecticides. One of the best approaches for accurately assessing human dosimetry and determining risk from both occupational and environmental exposure is biomonitoring. Biological matrices such as blood and urine have been routinely used for biomonitoring; however, other matrices such as saliva represent a simple and readily obtainable fluid. As a result, saliva has been suggested as an alternative biological matrix for the evaluation of a broad range of biomarkers such as environmental contaminants, drugs of abuse, hormones, chemotherapeutics, heavy metals, and pesticides. Chlorpyrifos (CPF), and its major metabolite, 3,5,6‐trichloro‐2‐pyridinol (TCP), have been quantified in urine and blood as a biomarker for exposure to OP insecticides. The purpose of this study was to develop an analytical approach for detecting and quantitating the levels of TCP in saliva obtained from rats exposed to CPF and to evaluate the potential of saliva as a noninvasive biomonitoring matrix for the determination of exposure to OP insecticides. Adult male rats were administered CPF, and blood and saliva were humanely collected for analysis of TCP and CPF. The TCP was detected and quantitated in saliva using negative ion chemical ionization mass spectrometry with selected ion monitoring. Initial results indicate that saliva potentially may be utilized as a noninvasive biomonitoring matrix to determine exposure to organophosphate insecticides. The authors would like to thank Ms. K. Brzak and Dr. M. Bartels of Dow Chemical Company for their helpful input. This work was partially supported by the U.S. Environmental Protection Agency's STAR program through grant R828608. It has not been subject to any EPA review and, therefore, does not necessarily reflect the views of the agency, and no public endorsement should be inferred. This publication was also partially supported by grant 1 R01 OH03629‐01A2 from the Centers for Disease Control and Prevention (CDC). Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the CDC.

Optimization of quadrupole ion storage mass spectrometric conditions for the analysis of selected polybrominated diphenyl ethers. Comparative approach with negative chemical ionization and electron impact mass spectrometry.

Gas chromatography coupled to quadrupole ion storage mass spectrometry (QISTMS) operating in the non-resonant mode is presented as an innovative approach for the analysis of selected polybrominated diphenyl ethers (PBDEs). Although reductions in complexity and time needed for optimization are achieved in comparison with the resonant option, precise adjustment of the mass spectrometric conditions is required. Differences in isolation and fragmentation patterns of target species with degree of bromination were observed. The reliability of the method was confirmed by using standard solutions through the evaluation of certain quality parameters such as accuracy (92-108%), injection repeatability and reproducibility (coefficient of variation below 10% and 15%, respectively). Detection limits ranged from 62 to 621 fg, providing sensitivity similar to that of negative chemical ionisation (NCIMS) and greater than that of electron ionization mass spectrometry. The applicability of QISTMS method to real samples and matrix effects were evaluated through the analysis of some PBDE congeners in a sewage sludge sample from a Spanish waste-water treatment plant. Comparable results were obtained using QISTMS and NCIMS. According to these observations, QISTMS performed in the non-resonant mode may constitute a low-cost, rapid and reliable alternative to high-resolution devices for the analysis of selected PBDEs in environmental samples.

Reduction of brain lipid peroxidation by CSF drainage in Alzheimer's disease patients.

Alzheimer's disease (AD) is associated with an increase in cerebrospinal fluid (CSF) levels of the isoprostane 8,12-iso-iPF2alpha-VI, a specific marker of in vivo lipid peroxidation. Poor cerebral clearance of end products of oxidative reactions via CSF circulation may contribute to and sustain ongoing stress. CSF drainage via a low-flow ventriculoperitoneal (VP) shunt may improve removal of these products, reducing oxidative stress. We quantified this biomarker in patients with AD undergoing to VP shunt placement at baseline and after one-year period. CSF sampling occurred at baseline and quarterly visits for one year. Levels of this isoprostane were determined simultaneously at the end of the study by gas chromatography negative ion chemical ionization mass spectrometry. Over one-year, CSF 8,12-iso-iPF2alpha-VI levels consistently decreased versus baseline (51% of initial level), while CSF protein, glucose, cell count and IgG concentrations remained within normal limits. This finding supports the hypothesis that improving CSF drainage enhances extra-cellular clearance of end products of oxidative reactions and lowers brain lipid peroxidation.

Microwave-assisted extraction versus Soxhlet extraction for the analysis of short-chain chlorinated alkanes in sediments

Microwave-assisted extraction (MAE) was evaluated as a possible alternative to Soxhlet extraction for analysing short-chain chlorinated alkanes (commonly called short-chain chlorinated paraffins, SCCPs) in river sediment samples, using gas chromatography coupled to negative chemical ionisation mass spectrometry. For MAE optimisation, several extraction parameters such as solvent extraction mixture, extraction time and extraction temperature were studied. Maximum extraction efficiencies for SCCPs (90%) and for 12 polychlorinated biphenyl (PCB) congeners (91–95%) were achieved using 5 g of sediment sample, 30 ml of n-hexane–acetone (1:1, v/v) as solvent extraction, and 15 min and 115 °C of extraction time and temperature, respectively. Activated Florisil was used to clean-up the extracts, allowing highly selective separation of SCCPs from other organic contaminants such as PCBs. MAE was compared with a conventional extraction technique such as Soxhlet and good agreement in the results was obtained. Quality parameters of the optimised MAE method such as run-to-run (R.S.D. 7%) and day-to-day precision (R.S.D. 9%) were determined using spiked river sediment samples, with LODs of 1.5 ng g −1. This method was successfully applied to the analysis of SCCPs in river sediment samples at concentrations below the ng g −1 level.

Microwave-assisted extraction versus Soxhlet extraction for the analysis of short-chain chlorinated alkanes in sediments☆

Microwave-assisted extraction (MAE) was evaluated as a possible alternative to Soxhlet extraction for analysing short-chain chlorinated alkanes (commonly called short-chain chlorinated paraffins, SCCPs) in river sediment samples, using gas chromatography coupled to negative chemical ionisation mass spectrometry. For MAE optimisation, several extraction parameters such as solvent extraction mixture, extraction time and extraction temperature were studied. Maximum extraction efficiencies for SCCPs (90%) and for 12 polychlorinated biphenyl (PCB) congeners (91-95%) were achieved using 5 g of sediment sample, 30 ml of n-hexane-acetone (1:1, v/v) as solvent extraction, and 15 min and 115 degrees C of extraction time and temperature, respectively. Activated Florisil was used to clean-up the extracts, allowing highly selective separation of SCCPs from other organic contaminants such as PCBs. MAE was compared with a conventional extraction technique such as Soxhlet and good agreement in the results was obtained. Quality parameters of the optimised MAE method such as run-to-run (R.S.D. 7%) and day-to-day precision (R.S.D. 9%) were determined using spiked river sediment samples, with LODs of 1.5 ng g(-1). This method was successfully applied to the analysis of SCCPs in river sediment samples at concentrations below the ng g(-1) level. O 2004 Elsevier B.V. All rights reserved.

Determination of polybrominated diphenyl ethers in human milk samples in the Czech Republic: Comparative study of negative chemical ionisation mass spectrometry and time-of-flight high-resolution mass spectrometry

In the Czech Republic no study on the levels of brominated flame retardants in human milk has been conducted, yet. In the first step analytical method for determination of PBDEs in this bioindicator matrix was implemented. Liquid–liquid extraction (LLE) (hexane, diethyl ether), followed by gel permeation chromatography was employed for isolation of PBDEs. Identification and quantification of PBDEs was carried out by GC–MS operated in negative chemical ionisation (NCI). Two mass spectrometric technologies, one employing quadrupole and the other one high resolution (HR) time-of-flight (TOF) analyzer, etc. were used in our study. Detection limits (LODs) obtained by quadrupole analyzer ranged from 0.02 to 0.05 ng g −1 lipid weight, using high resolution time-of-flight analyzer LODs were significantly lower, ranging from 0.002–0.005 ng g −1 lipid weight, what enabled detection of minor PBDE congeners. Within this pilot study 103 breast milk samples, obtained from mothers living in Olomouc region, were examined. Ten PBDE congeners were determined. All samples examined till now contained PBDEs residues, the dominating contaminant representing this group was congener BDE 47. In most of analysed samples levels of this compound ranged from 0.2 to 2 ng g −1 of lipid weight. Three exceptionally contaminated samples, containing levels of PBDEs 5–10 times higher than other samples, were found.