Chromatography-electron Capture Negative Ionization Mass Research Articles

Short- and medium-chain chlorinated paraffins in sediment from the Haihe River Basin: Sources, distributions, and ecological risk assessment

Chlorinated paraffins (CPs) can accumulate in sediment and pose risks to ecological systems and human health. The Haihe River Basin is one of the seven main river basins in China and is mainly in the Beijing–Tianjin–Hebei region, which is densely populated and very urbanized. There is therefore a high probability of CP pollution in the Haihe River Basin. However, CP pollution and the environmental risks posed by CPs in the Haihe River are not well understood. In this study, the concentrations of short-chain CPs (SCCPs) and medium-chain CPs (MCCPs) in sediment from six rivers in the Haihe River Basin system were determined using two-dimensional gas chromatography electron-capture negative ionization mass spectrometry. The total SCCP and MCCP concentrations in the sediment samples ranged from 131.83 to 1767.71 and from 89.72 to 1442.82 ng/g dry weight, respectively. The total organic carbon content did not significantly correlate with the CP concentrations. The dominant SCCP congener groups were C10Cl6–7 and the dominant MCCP congener groups were C14Cl7–8. Significant relationships (R = 0.700, p < 0.05) were found between the SCCP and MCCP concentrations, indicating that SCCPs and MCCPs may have similar sources. Hierarchical cluster analysis and principal component analysis indicated that sediment in the study area was contaminated with CPs through the use of the CP-42 and CP-52 commercial products in industrial processes and human activities. The ecological risks posed by CPs were assessed and SCCPs were found to pose high risks in the Yongding New River but moderate risks in the other rivers. MCCPs were found to pose minimal risks to the aquatic environment at most of the sampling points.

Parameters optimization using experimental design for headspace solid phase micro-extraction analysis of short-chain chlorinated paraffins in waters under the European water framework directive

The water framework directives (WFD 2000/60/EC and 2013/39/EU) force European countries to monitor the quality of their aquatic environment. Among the priority hazardous substances targeted by the WFD, short chain chlorinated paraffins C10–C13 (SCCPs), still represent an analytical challenge, because few laboratories are nowadays able to analyze them. Moreover, an annual average quality standards as low as 0.4μgL−1 was set for SCCPs in surface water. Therefore, to test for compliance, the implementation of sensitive and reliable analysis method of SCCPs in water are required. The aim of this work was to address this issue by evaluating automated solid phase micro-extraction (SPME) combined on line with gas chromatography-electron capture negative ionization mass spectrometry (GC/ECNI–MS).Fiber polymer, extraction mode, ionic strength, extraction temperature and time were the most significant thermodynamic and kinetic parameters studied. To determine the suitable factors working ranges, the study of the extraction conditions was first carried out by using a classical one factor-at-a-time approach. Then a mixed level factorial 3×23 design was performed, in order to give rise to the most influent parameters and to estimate potential interactions effects between them. The most influent factors, i.e. extraction temperature and duration, were optimized by using a second experimental design, in order to maximize the chromatographic response.At the close of the study, a method involving headspace SPME (HS-SPME) coupled to GC/ECNI-MS is proposed. The optimum extraction conditions were sample temperature 90°C, extraction time 80min, with the PDMS 100μm fiber and desorption at 250°C during 2min. Linear response from 0.2ngmL−1 to 10ngmL−1 with r2=0.99 and limits of detection and quantification, respectively of 4pgmL−1 and 120pgmL−1 in MilliQ water, were achieved. The method proved to be applicable in different types of waters and show key advantages, such as simplicity, automation and sensitivity, required for the monitoring programs linked to the WFD.

Optimization of the determination of polybrominated diphenyl ethers in human serum using solid-phase extraction and gas chromatography-electron capture negative ionization mass spectrometry

A simple, rapid, sensitive and reproducible method based on solid-phase extraction (SPE) and acidified silica clean-up was developed for the measurement of 12 polybrominated diphenyl ethers (PBDEs), including BDE 209, and 2,2',4,4',5,5'-hexabromobiphenyl (BB 153) in human serum. Several solid-phase sorbents (Empore C(18), Isolute Phenyl, Isolute ENV+ and OASIS HLB) were tested and it was found that OASIStrade mark HLB (500 mg) gives the highest absolute recoveries (between 64% and 95%, R.S.D.<17%, n=3) for all tested analytes and internal standards. Removal of co-extracted biogenic materials was performed using a 6 ml disposable cartridge containing (from bottom to top) silica impregnated with sulphuric acid, activated silica and anhydrous sodium sulphate. PBDEs and BB 153 were quantified using a gas chromatograph coupled with a mass spectrometer (MS) operated in electron-capture negative ionization mode. The method limits of quantification (LOQ) ranged between 0.2 and 25 pg/ml serum (0.1 and 4 ng/g lipid weight). LOQs were dependent on the analyte levels in procedural blanks which resulted in the highest LOQs for PBDE congeners found in higher concentrations in blanks (e.g. BDE 47, 99 and 209). The use of OASIS HLB SPE cartridge allowed a good method repeatability (within- and between-day precision<12% for all congeners, except for BDE 209<17%, n=3). The method was applied to serum samples from a random Belgian population. The obtained results were within the range of PBDE levels in other non-exposed population from Europe.

Determination of dimetridazole and metronidazole in poultry and porcine tissues by gas chromatography–electron capture negative ionization mass spectrometry

A sensitive and selective method using gas chromatography–electron capture negative ionization mass spectrometry (GC–ECNI-MS) for analysis of dimetridazole (DMZ) and metronidazole (MNZ) in poultry muscles, porcine kidney and liver, and chicken liver, was developed and validated for the purpose of food surveillance testing of the residues of these two nitroimidazoles in various types of animal tissues in the Hong Kong Special Administrative Region. Before homogenization and extraction with toluene, [2H 3]dimetridazole-(DMZ-d 3) and secnidazole (SNZ) were added to tissue samples as internal standards. The organic extracts were mixed with n-hexane and subject to solid-phase extraction cleanup by amine extraction columns. MNZ and SNZ were derivatized with BSA prior to GC–ECNI-MS determination. Good recovery and precision were obtained and the limit of detection was below parts per billion levels for poultry and porcine tissues. The method could also be applied for the detection of the hydroxylated metabolite of DMZ.

Determination of quinoxaline-2-carboxylic acid, the major metabolite of carbadox, in porcine liver by isotope dilution gas chromatography–electron capture negative ionization mass spectrometry

A sensitive and robust method using isotope dilution gas chromatography–electron capture negative chemical ionization mass spectrometry (GC–ECNI-MS) was developed and validated for the analysis of quinoxaline-2-carboxylic acid (QCA) in porcine liver. [ 2H 4]QCA was added to liver samples which were then deproteinated with 2% metaphosphoric acid in 20% methanol. Followed by sequential extraction with water-saturated ethyl acetate and phosphate buffer, the buffer extracts were subject to solid-phase extraction clean-up by mixed mode anion-exchange columns. QCA was derivatized with N-methyl- N- tert-butyldimethylsilyltrifluoroacetamide (MTBSTFA) prior to GC–ECNI-MS determination. For unambiguous identification, a second GC–ECNI-MS experiment was performed on suspected positive samples which were derivatized independently with another derivatization agent, trimethylsilyldiazomethane. Excellent recovery and precision were obtained and the limit of quantitation was 0.7 μg/kg (S/N>60). Method ruggedness by Taguchi orthogonal array technique is also presented.

Trace Quantification of the Oxidative Damage Products,meta- andortho-Tyrosine, in Biological Samples by Gas Chromatography–Electron Capture Negative Ionization Mass Spectrometry

Oxygen radicals damage biomolecules and may contribute to cellular aging and degenerative disease. We describe a sensitive method for the quantification of two endogenous biomarkers of oxidative damage:meta-tyrosine (m-Tyr) andortho-tyrosine (o-Tyr). The assay can be applied to direct analysis of free amino acids or protein-bound amino acids following hydrolysis. The assay involves derivatization with pentafluorobenzyl bromide and extraction inton-decane, followed by gas chromatography–mass spectrometry. Stable isotope labeledm- ando-Tyr (2H4) and phenylalanine [i.e., Phe (2H5)] were added as internal standards to improve analytical accuracy. Quantification of as little as 50 pg ofm- ando-Tyr in 100 μg protein is possible and the data are expressed as a molar ratio ofm- ando-Tyr to native Phe. The assay was used to determine the levels ofm- ando-Tyr in freshly isolated human plasma protein (4.05 ± 0.67m-Tyr per 104Phe, 0.35 ± 0.07o-Tyr per 104Phe). Exposure of human plasma to reactive oxygen species significantly increased the levels ofm-Tyr (56.4 ± 1.1m-Tyr per 104Phe,P< 0.0001) ando-Tyr (48.9 ± 1.3o-Tyr per 104Phe,P< 0.0001). The mild hydrolysis and derivatization conditions caused no artifactual formation of eitherm- oro-Tyr.

Characterization of technical toxaphene using combined high-performance liquid chromatography-gas chromatography-electron capture negative ionization mass spectrometry techniques

More than 300 congeners in technical toxaphene were distinguished by combined HPLC-GC/electron capture negative ionization mass spectrometry (ECNIMS) techniques. Good separation of most congeners on a 60-m DB-5 GC column was achieved when the mixture was pre-separated into five fractions by silica gel HPLC. ECNI spectra of high chlorinated congeners were dominated by M  Cl while both M and M  Cl ions were important in low chlorinated ones. Other ions such as M - 3Cl, M  Cl  HCl and M  Cl - 2HCl can be used to distinguish congeners. Peaks referred to as T2 and T12 in the environment by many authors coelute with several congeners in toxaphene. The 2,5-exo-3,6-endo tetrachloro partial structure existing in both T2 and T12 may be responsible for their persistency in living systems. Results from EI-SIM mode indicated many other low chlorinated congeners not detectable by ECNI in the mixture.