Comprehensive two-dimensional gas chromatography in the screening of persistent organohalogenated pollutants in environmental samples

Separations of eight persistent organohalogenated classes of pollutants, organochlorinated pesticides (OCPs), polychlorinated biphenyls (PCBs), polychlorinated diphenyl ethers (PBDEs), polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated naphthalenes (PCNs), polychlorinated terphenyls (PCTs) and toxaphene (CTT) by comprehensive two-dimensional gas chromatography (GC x GC) were evaluated. Columns with different polarity and selectivity, including ZB-5, HT-8, DB-17 and BP-10, were selected as first dimension and combined with columns of increasing polarity in the second dimension, i.e. HT-8, BPX-50 and Carbowax (or Supelcowax-10). In total nine column combinations were tested. Because the main interest of the study was fast screening of the test xenobiotic families in complex matrices, in all cases, attention was primarily focussed on group-type separation. Nevertheless, within-group separation was also considered, especially for those classes containing particularly toxic congeners, such as PCBs and PCDD/Fs. Although none of the assayed column sets allowed the simultaneous and complete separation of all pollutants classes, some column combinations provided satisfactory separations among selected families and the rest of pollutants investigated. That was, for instance, the case of HT-8 x BPX-50 for PBDEs and PCDD/Fs, DB-17 x HT-8 for PCNs and OCPs and BP-10 x BPX-50 for CTT, PCDD/Fs and PBDEs. The feasibility of the proposed approach for the fast screening of the target classes of pollutants in complex samples was illustrated by the analysis of food and marine fat samples prepared using simplified miniaturised sample treatment methods.     

加速溶剂萃取-硅胶柱净化-碱性氧化铝柱分离-气相色谱三重四极杆质谱法测定土壤中的二噁英类化合物

建立了加速溶剂萃取(ASE),酸性硅胶柱、复合硅胶柱及碱性氧化铝柱纯化分离,气相色谱-三重四极杆质谱测定土壤中二噁英/呋喃(PCDD/Fs)、多氯联苯(PCBs)、多氯萘(PCNs)的分析方法.选用正己烷-二氯甲烷(50∶50, V/V)作为ASE的提取溶剂,设定提取温度为120℃,加标回收实验表明本方法可行.用100 mL正己烷-二氯甲烷(95∶5, V/V)及50 mL正己烷-二氯甲烷(50∶50, V/V)依次淋洗碱性氧化铝柱,得到组分A(PCBs及PCNs)与组分B(PCDD/Fs),实现了PCDD/Fs与另外两种化合物的分离,排除了同系物间及其它杂质的干扰.使用同位素稀释-气相色谱三重四极杆质谱法(GC-MS/MS), 在选择反应监测(Selected reaction monitoring, SRM)模式下测定PCDD/Fs、PCBs和PCNs,3种化合物的仪器检出限(LOD)范围分别为0.04~0.25 μg/L, 0.10~0.20 μg/L和0.01~0.05 μg/L,目标物平均相对响应因子(RRF)的相对标准偏差(RSD)均小于13%.基质土加标实验中,3种化合物13C标记的同位素内标回收率的范围分别为50%~95%,51%~103%, 49%~74%.实际样品的分析结果表明,PCDD/Fs、PCBs及PCNs在土壤样品中的总含量范围分别为16.1~1148 pg/g、6.6~152.6 pg/g及10.9~99.5 pg/g,且样品测定结果与高分辨质谱测定结果相吻合.     

Group separation of organohalogenated compounds by means of comprehensive two-dimensional gas chromatography

Separations of 12 compound classes, polychlorinated biphenyls (PCBs), diphenyl ethers (PCDEs), naphthalenes (PCNs), dibenzothiophenes (PCDTs), dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), terphenyls (PCTs) and alkanes (PCAs), toxaphene, organohalogenated pesticides (OCPs), and polybrominated biphenyls (PBBs) and diphenyl ethers (PBDEs) by comprehensive two-dimensional gas chromatography were evaluated. Five column combinations, DB-1 x 007-210, DB-1 x HT-8, DB-1 x LC-50, DB-1 x 007-65HT and DB-1 x VF-23ms were used to study, primarily, group-type separations, but attention was devoted also to within-class separation, especially for those classes which were not addressed in much detail before, the PCNs, OCPs, PBBs and PCTs. The DB-1 x 007-210 column set did not offer any extra separation compared to one-dimensional GC. For the DB-1 x HT-8 column combination, the useful principle of congener separation on the basis of number of halogen substituents in a molecule was confirmed (PCBs, toxaphene) and extended (PCTs, PBDEs). No practically useful group-type separation was observed for this column combination. The DB-1 x LC-50 set provides group separation based on planarity: planar compounds such as PCDDs, PCDFs, PCDTs and PCNs are much more retained than, and therefore separated from, non-planar analytes. Within the classes of PCBs, PBBs and PCTs highly useful separation of planar from non-planar compounds was also observed. The DB-1 x 007-65HT column set effectively separates PCAs and PBDEs from all other compound classes, and provides a good separation of brominated and chlorinated analogue classes from each other. This column set was the most efficient one for within-class separation of OCPs and PCNs. Finally, DB-1 x VF-23ms yields excellent within-class separations, especially of non-aromatic compounds, viz. OCPs, toxaphene and PCAs. No group separation was observed here. The applicability of the approach was demonstrated for a sediment extract and a dust extract. In the sediment extract, PCDDs, PCDFs, PCAs and PCNs were identified and their efficient separation was achieved. In the dust sample, separation of PCAs and PBDEs was achieved and several new PBDE congeners were identified.     

Matrix Solid-Phase Dispersion Combined with GC–MS/MS for the Determination of Organochlorine Pesticides and Polychlorinated Biphenyls in Marketed Seafood

An analysis method based on matrix solid-phase dispersion (MSPD) and gas chromatography tandem mass spectrometry was developed and applied for the analysis for organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in the marketed seafood such as fish, shrimp and shellfish. The parameters of the method including the type and amount of the absorbent, as well as the type and volume of the elution solution were optimized. The recoveries were between 70 and 120% with RSDs less than 20%, and the LODs and LOQs were 0.011–0.046 and 0.037–0.153 ng g^?1 under optimized conditions. The results showed that most of the OCPs and PCBs were detectable in the marketed samples with the average concentration range of 0.722–14.206 and 0.034–1.184 ng g^?1, respectively. Among the 21 OCPs detected, DDTs had a relatively higher concentration level. And in the PCBs, the concentration of PCB28 was over 45% of the total PCBs determined in all the samples. The developed method was simple, fast and effective, and could successfully be applied for trace amount of OCPs and PCBs determination in seafood matrixes.     

Trace-level analysis of polychlorinated biphenyls,organochlorine pesticides and polycyclic aromatic hydrocarbons in human plasma or serum by dispersive liquid–liquid microextraction and gas chromatography–tandem mass spectrometry

A method to determine 8 polychlorinated biphenyls (PCBs), 23 organochlorine pesticides (OCPs) and 16 polycyclic aromatic hydrocarbons (PAHs) was described using dispersive liquid–liquid microextraction (DLLME) of a small amount of plasma or serum sample and gas chromatography–tandem mass spectrometry (GC–MS/MS). The appropriate selection of the extraction solvent and dispersing solvent contributes to a high extraction yield and a clean extract. To verify the developed method, the interference, linearity of the calibration curve, detection limit, precision and accuracy were evaluated. The calibration curves were linear by 2–3 orders of magnitude with correlation coefficients above 0.997 in all cases. The LODs of PCBs, OCPs and PAHs were measured in the ranges of 0.0006–0.0029, 0.001–0.029 and 0.0002–0.012 ng/mL. The intraday precision achieved by this method was 2.19–10.3% (PCBs), 1.65–14.3% (OCPs) and 0.91–12.8% (PAHs), and the intraday accuracy 1.56–7.37% (PCBs), 2.34–19.6% (OCPs) and 1.49–15.7% (PAHs). The advantage of this method is that the analysis of PCBs, OCPs, and PAHs can be performed in a single chromatographic run, and the low detection limit enables monitoring of target substances in low exposure general public samples, and the analysis procedure is relatively simple and fast.     

气相色谱-三重四极杆质谱同位素内标法测定鱼样中20种多氯联苯

建立了一种气相色谱-三重四极杆质谱结合双稳定性同位素内标检测鱼样中多氯联苯的方法。采用自动索氏提取器提取样品中的多氯联苯,经一根复合净化柱净化后,采用质谱多反应监测模式检测,选取两个独立的离子对。分析了20种多氯联苯,包含7种指示性多氯联苯,从三氯联苯到八氯联苯每族3个化合物,九氯联苯和十氯联苯各一个,每族使用一个相同氯代程度的¹³C₁₂标记多氯联苯作为定量内标、2种回收内标。20种多氯联苯在33 min内流出,分离良好,线性范围为0.05~10 μg/L,相关系数r均在0.99以上,低、中、高3种水平的加标回收率均在80.3%~117.6%之间,相对标准偏差（RSD,n=6）在5.09%~18.5%之间,方法检出限为0.01~0.02 μg/kg。20种多氯联苯总量在1.2~8.8 μg/kg（湿重）范围内,7个指示性多氯联苯总量在0.68~6.4 μg/kg（湿重）范围内。该方法缩短了分析时间,减少了有机溶剂的使用量,适合鱼样中多氯联苯的测定。     

Polychlorinated naphthalene concentrations and profiles in cheese and butter,and comparisons with polychlorinated dibenzo-p-dioxin,polychlorinated dibenzofuran and polychlorinated biphenyl concentrations

Polychlorinated naphthalenes (PCNs) are candidates for inclusion in the Stockholm Convention on persistent organic pollutants. PCNs are structurally and toxicologically similar to 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) and its analogues. Intake in food is considered to be an important human exposure pathway for PCNs. In this preliminary study, cheese and butter samples were analysed for PCNs, polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) using an isotope dilution gas chromatography high-resolution mass spectrometry method. The aim of this study was to evaluate the PCN concentrations in the cheese and butter samples and to compare them with the PCDD, PCDF and PCB concentrations. The PCN concentrations were 5.6–103 pg g^?1 of wet weight in the seven cheese samples tested and 5.0–199 pg g^?1 of wet weight in the seven butter samples tested. The mass concentrations of lower chlorinated congeners were greater than those of the higher chlorinated congeners. Congeners of CN45/36, CN27/30 and CN33/34/37 were much more abundant than other congeners found in tetrachlorinated PCNs. Congeners of CN51, CN66/67 and CN73 were determined to be the predominant congeners in penta-, hexa- and heptachlorinated homologs, respectively. The PCNs contributed around 5% of the total PCN, PCDD, PCDF and PCB toxic equivalence (TEQ) values. CN73 was found to be the dominant PCN congener and contributed more than 40% to the PCN TEQ value. Congeners CN66/67, CN69 and CN63 were also found at relatively high levels. The PCB congener CB118 was the predominant congener (by mass-based concentration) of the 12 dioxin-like PCBs (dl-PCBs). The PCBs contributed 53.8% of the total TEQ, and congener CB126 contributed more than any other compound that was analysed to the total TEQ. The PCDDs and PCDFs contributed 11.6% and 29.7% of the total TEQ values, respectively.     

Supercritical fluid extraction and clean-up of organochlorine pesticides and polychlorinated biphenyls in mussels

The simultaneous extraction and clean-up of mussel samples followed by gas chromatography with electron-capture detection and mass spectrometric confirmation of 15 organochlorine pesticides (OCPs) and 11 polychlorinated biphenyls (PCBs) is developed using Florisil sorbent in the supercritical fluid extraction cell. The method detection limits vary from 1 to 10 ng/g for OCPs and from 2 to 15 ng/g for PCBs. Mean reproducibilities of 11% and 10% and mean recoveries of 80% and 53%, respectively, for OCPs and PCBs are obtained. The feasibility of the proposed supercritical fluid extraction method was confirmed by analyzing a certified reference material and mussels collected from Taiwan region. The method is simple, rapid and requires only small amounts of samples and solvents. It may serve as a screening protocol for the determination of OCPs and PCBs in mussels on a routine basis.     

A Rapid Method for the Determination of Organochlorine, Pyrethroid Pesticides and Polychlorobiphenyls in Fatty Foods Using GC with Electron Capture Detection

A new, single-step extraction and purification method was developed for the separation of 26 organochlorine pesticides (OCPs), three pyrethroid pesticides (PPs) and six polychlorinated biphenyls (PCBs) from fatty foods of either animal or vegetable origin. The method includes homogenisation of extracted fat and diatomaceous earth. Separation was achieved using a mini Pasteur pipette where a matrix solid-phase dispersion extraction was carried out with only 5 mL of dimethyl sulphoxide as an eluting solvent. A Pasteur pipette was joined to a prepacked slurry filled Florisil column, water deactivated to 15% where a liquid–liquid extraction and adsorption chromatography successively took place. The elution of OCPs, PPs and PCBs was performed with n-hexane/diethyl ether. Recoveries for PCBs were from 81 to 86% and for OCPs 68 to 94%, except for β-HCH, which gave lower, more variable recoveries. Excellent recoveries were obtained for pyrethroid pesticides, mostly more than 80%. The method was applied to 509 fatty samples for monitoring of these compounds. GC, with two columns connected to two electron capture detectors (ECD), was used.     

加速溶剂萃取同步净化-同位素内标-气相色谱-高分辨质谱测定水产品中32种多氯联苯

建立了加速溶剂萃取同步净化-同位素内标-气相色谱-高分辨质谱同时测定水产品中32种多氯联苯含量的方法。通过在加速溶剂萃取仪中加入2 g无水硫酸钠、1 g弗罗里硅土、50 g中性氧化铝作为吸附剂实现同步净化的效果，萃取溶剂为二氯甲烷-正己烷（1:1，v/v），萃取温度为100℃，循环2次。萃取结束后分别用0.5 mL浓硫酸净化两次，净化液浓缩定容后，采用气相色谱-高分辨质谱测定，同位素内标法定量。32种多氯联苯在0.1~20 μg/L范围内平均相对响应因子（RRF）的相对标准偏差（RSD）值（n=7）均小于15%，定量限（S/N=10）为0.3~1.9 ng/kg。在草鱼和海鲈鱼空白基质中做加标回收试验，添加水平为5、20和50 ng/kg，得到的平均回收率为71.9%~119.0%（n=6），RSD为3.5%~19.6%。该方法背景干扰低，灵敏度高，重现性好，回收率稳定，适用于水产品中多氯联苯的检测。     

Analysis of polychlorinated dibenzo-p-dioxins, dibenzofurans and dioxin-like polychlorinated biphenyls in vegetable oil samples by gas chromatography-ion trap tandem mass spectrometry

Gas chromatography coupled to ion trap tandem mass spectrometry (CG-MS-MS) has been evaluated for the analysis of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (dl-PCBs) in vegetable oil samples containing different concentration levels (0.2-6 pg WHO-TEQ g(-1) for both PCDD/Fs and dl-PCBs) of the 29 toxic congeners of PCDD/F and dioxin-like PCBs. The effect of potential interfering compounds such as polychlorinated naphthalenes (PCNs), polychlorinated biphenyls (PCBs) and polychlorinated diphenylethers (PCDEs) on the quantification of mono-ortho PCBs has been investigated. In addition, the influence of the clean-up procedure on the final determination by CG-MS-MS was studied, showing that the quality of the results depends to a great extent on this analytical step. Quality parameters have been established and good precisions (CV: 3-19%) and low limits of detection for PCDD/Fs (0.04-0.20 pg g(-1) oil) and dl-PCBs (0.08-0.64 pg g(-1) oil) were obtained. The method was validated by a comparison of the CG-MS-MS results with those obtained by GC-HRMS.     

Multiresidue determination of organochlorine pesticides and polychlorinated biphenyls in milk by gas chromatography with electron-capture detection after extraction by matrix solid-phase dispersion

A multiresidue analytical method based on matrix solid-phase dispersion was developed to analyze liquid milk for 22 organochlorine pesticides (OCPs) and 6 polychlorinated biphenyls (PCBs). Initial extraction is performed by loading 3 mL milk onto a 2.0 g octadecyl (C18)-bonded silica cartridge with n-hexane as the eluant. Neutral alumina column chromatography with sodium sulfate as the drying agent is used for further cleanup. The eluate is concentrated to 0.5 mL, and target analytes are determined by capillary gas chromatography with electron-capture detection. The optimized method was validated by determining accuracy (recovery percentages), precision (repeatability and reproducibility), and sensitivity (detection and quantitation limits) from analyses of milk samples fortified at 10 and 1 microg/L levels. Average recoveries were between 74 and 106% for all residues except beta-HCH, beta-endosulfan, and endosulfan sulfate. Both repeatability and reproducibility relative standard deviation values were < 22% for all residues. Detection limits ranged from 0.02 to 0.12 microg/L and quantitation limits were between 0.02 and 0.62 microg/L. The proposed analytical method may be used as a fast and simple procedure in routine determinations of OCPs and PCBs in milk.     

Analytical methods for PCBs and organochlorine pesticides in environmental monitoring and surveillance: a critical appraisal

Analytical methods for the analysis of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) are widely available and are the result of a vast amount of environmental analytical method development and research on persistent organic pollutants (POPs) over the past 30–40 years. This review summarizes procedures and examines new approaches for extraction, isolation, identification and quantification of individual congeners/isomers of the PCBs and OCPs. Critical to the successful application of this methodology is the collection, preparation, and storage of samples, as well as specific quality control and reporting criteria, and therefore these are also discussed. With the signing of the Stockholm convention on POPs and the development of global monitoring programs, there is an increased need for laboratories in developing countries to determine PCBs and OCPs. Thus, while this review attempts to summarize the current best practices for analysis of PCBs and OCPs, a major focus is the need for low-cost methods that can be easily implemented in developing countries. A “performance based” process is described whereby individual laboratories can adapt methods best suited to their situations. Access to modern capillary gas chromatography (GC) equipment with either electron capture or low-resolution mass spectrometry (MS) detection to separate and quantify OCP/PCBs is essential. However, screening of samples, especially in areas of known use of OCPs or PCBs, could be accomplished with bioanalytical methods such as specific commercially available enzyme-linked immunoabsorbent assays and thus this topic is also reviewed. New analytical techniques such two-dimensional GC (2D-GC) and “fast GC” using GC–ECD may be well-suited for broader use in routine PCB/OCP analysis in the near future given their relatively low costs and ability to provide high-resolution separations of PCB/OCPs. Procedures with low environmental impact (SPME, microscale, low solvent use, etc.) are increasingly being used and may be particularly suited to developing countries. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Environmental analysis of chlorinated and brominated polycyclic aromatic hydrocarbons by comprehensive two-dimensional gas chromatography coupled to high-resolution time-of-flight mass spectrometry

A method for the analysis of chlorinated and brominated polycyclic aromatic hydrocarbon (Cl-/Br-PAHs) congeners in environmental samples, such as a soil extract, by comprehensive two-dimensional gas chromatography coupled to a high resolution time-of-flight mass spectrometry (GC×GC-HRTOF-MS) is described. The GC×GC-HRTOF-MS method allowed highly selective group type analysis in the two-dimensional (2D) mass chromatograms with a very narrow mass window (e.g. 0.02Da), accurate mass measurements for the full mass range (m/z 35-600) in GC×GC mode, and the calculation of the elemental composition for the detected Cl-/Br-PAH congeners in the real-world sample. Thirty Cl-/Br-PAHs including higher chlorinated 10 PAHs (e.g. penta, hexa and hepta substitution) and ClBr-PAHs (without analytical standards) were identified with high probability in the soil extract. To our knowledge, highly chlorinated PAHs, such as C(14)H(3)Cl(7) and C(16)H(3)Cl(7), and ClBr-PAHs, such as C(14)H(7)Cl(2)Br and C(16)H(8)ClBr, were found in the environmental samples for the first time. Other organohalogen compounds; e.g. polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), and polychlorinated dibenzofurans (PCDFs) were also detected. This technique provides exhaustive analysis and powerful identification for the unknown and unconfirmed Cl-/Br-PAH congeners in environmental samples.     

Rapid multiresidue determination of organochlorine and organophosphorus compounds in human serum by solid-phase extraction and gas chromatography coupled to tandem mass spectrometry

A rapid analytical method for the multiresidue determination of several organochlorine and organophosphorus pesticides and polychlorinated biphenyls in human serum samples has been developed. Analytes were isolated by solid-phase extraction using C18 cartridges with subsequent analysis by GC-MS/MS using a glass liner packed with CarboFrit in the GC injection port. Labelled surrogate internal standards (fenitrothion D6, HCB (13)C6, p, p'-DDE D8 and PCB 138 (13)C12) were added to the samples before the extraction and were used for quantitation and for quality control in the analysis of real-world samples. Accuracy and precision were evaluated by using serum samples fortified at two concentration levels for the three families of compounds, with satisfactory results in the majority of cases. The high selectivity and sensitivity of GC-MS/MS allowed low detection limits of 0.05-0.5 ng mL(-1) for most of the analytes investigated. The developed procedure improves other current methodologies for the analysis of pesticides and PCBs in biological fluids, especially as regards to analysis time and simplicity of sample treatment. The method was applied to several serum samples obtained from farmers devoted to citrus crop production. Chlorpyrifos, HCB, p, p'-DDE and the higher chlorinated PCBs (153, 138 and 180) were the most frequently detected compounds.     

同位素稀释气相色谱/三重四极杆串联质谱法分析环境样品中的多氯萘

采用稳定同位素标记的多氯萘(PCNs)同类物为内标,建立了同位素稀释气相色谱/三重四极杆串联质谱技术测定环境样品中20种高关注的PCNs同类物的方法。结果表明:PCNs同类物的校正曲线在0.5~200 μg/L范围内线性良好(R²>0.99),检出限(LOD)为0.04~0.48 μg/L,相对标准偏差(RSD)小于15%。采用基质加标法评价该方法对实际环境样品中PCNs测定的回收率为45.2%~87.9%。为验证方法的适用性,以河流沉积物和再生铝冶炼排放的烟道气样品为对象,利用所建立的方法测定了20种PCNs同类物,并将结果与高分辨气相色谱/高分辨质谱方法的测定结果进行了比对,两种方法测定结果的RSD为0.5%~41.4%,表明所建立的同位素稀释气相色谱/三重四极杆串联质谱方法可用于实际环境样品中PCNs的定性、定量分析。     

Feasibility of gas chromatography--ion trap tandem mass spectrometry for the determination of polychlorinated biphenyls in food

The different parameters affecting the ionisation and fragmentation of selected polychlorinated biphenyls (PCBs) in an IT detector working in the MS/MS mode, ITD(MS/MS), have been optimised for maximum selectivity and sensibility. The low LODs (in the range 0.03-0.3 microg/L), the satisfactory repeatability (RSDs in general below 11%) and reproducibility (RSDs below 17%) obtained when analysing standard solutions ensured proper determination of the PCBs studied at the concentrations typically found in food samples. Foodstuffs naturally contaminated with varying levels of PCBs have been analysed using the optimised GC-ITD(MS/MS) method. The results obtained compared favourably with those found using more conventional detectors, such as (micro-)electron capture detection (for ortho-PCBs) and high-resolution MS (for non-ortho-PCBs), as well as with the consensus PCB levels established for these particular samples via an international interlaboratory exercise. The relative merits of these three detectors have been discussed.     

A method to circumvent the lot number of activated carbon affecting the performance of activated carbon silica gel columns used for cleanup of blood samples for analysis of 29 hazardous organochlorine compounds

We have previously described the use of a tandem simplified multilayer silica gel-activated carbon dispersed silica gel (TS-ML-AC) column for the cleanup of blood samples for the analysis of 29 hazardous organochlorine compounds (OCs)--the 17 major polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDDs/DFs) and 4 non-ortho- and 8 mono-ortho-polychlorinated biphenyls (PCBs). We noted that the performance of the activated carbon-silica gel (ACS) column (lower column) varied with the lot number of the ACS. In this study, we compared the elution profiles of OCs eluted on 5 ACS columns, each with a different ACS lot number, and found that only mono-ortho-PCBs #114 and #123 were affected by lot number. The problem was that the 50 ml of n-hexane required to elute all the OCs from the simplified multilayer silica gel (MLS) column (upper column) into the AC column (lower column) also eluted varying amounts of PCBs #114 and #123 from the ACS column by ACS lot number. Although we could prevent PCBs #114 and #123 from being eluted from the ACS column by reducing the n-hexane volume to 10 ml, this volume was not sufficient to elute all the OCs from the MLS column. We solved this by separating the two columns; the sample solution was eluted with 50 ml of n-hexane from the MLS column, this eluate was concentrated to about 0.3 ml using a rotary evaporator, and then the concentrated solution was cleaned up on the ACS column. The recovery rates of #114 and #123 from blood samples were above 70% and the relative standard deviations of their concentration were below 10%, irrespective of the lot number, compared with recovery rates of 45-79% for #114 and 59-89% for #123, and relative standard deviations of their concentration above 15% when 50 ml of n-hexane was run through the tandem column. Our modified method affords reliable and reproducible cleanup of blood samples for analysis of 29 OCs, irrespective of the ACS lot number.     

双重净化-气相色谱法测定植物油中指示性多氯联苯

为了考察食用油中7种指示性多氯联苯(PCBs)的残留情况,建立了食用油中痕量多氯联苯测定的双重净化-气相色谱法。以乙腈提取样品,提取液浓缩至干后用正己烷溶解,经浓硫酸、硅胶分散固相萃取双重净化后进行气相色谱分析,外标法定量。优化的色谱条件为:HP-5石英毛细管柱(30 m×0.32 mm×0.25 μm)程序升温分离,流速0.8 mL/min,进样量1.00 μL,电子捕获检测器检测。结果表明:在优化的条件下,7种多氯联苯在10~500 μg/L范围内线性良好,相关系数大于0.999,不同基质中的检出限(S/N=3)范围为1.8~8.9 μg/kg,定量限(S/N=10)范围为5.9~29.8 μg/kg。在橄榄油、花生油和棕榈油空白样品中添加10、20、100 μg/kg 3个水平的7种多氯联苯,其加标回收率范围为71.0%~105.5%,相对标准偏差(RSD)范围为4.0%~11.3%。该方法具有操作简便、快速、准确的特点,可用于植物油中指示性多氯联苯残留量的日常检测。     

Comprehensive two-dimensional gas chromatography with isotope dilution time-of-flight mass spectrometry for the measurement of dioxins and polychlorinated biphenyls in foodstuffs. Comparison with other methods

A comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC x GC-TOF-MS) experimental setup was tested for the measurement of seven 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins (PCDDs), ten 2,3,7,8-substituted polychlorinated dibenzofurans (PCDFs), four non-ortho-polychlorinated biphenyls (PCBs), eight mono-ortho-PCBs, and six indicator PCBs (Aroclor 1260) in foodstuff samples. A 40m RTX-500 (0.18mm I.D., 0.10 microm df) was used as the first dimension (1D) and a 1.5 m BPX-50 (0.10mm I.D., 0.10 microm df) as the second dimension (2D). The GC x GC chromatographic separation was completed in 45 min. Quantification was performed using 13C-label isotope dilution (ID). Isotope ratios of the selected quantification ions were checked against theoretical values prior to peak assignment and quantification. The dynamic working range spanned three orders of magnitude. The lowest detectable amount of 2,3,7,8-TCDD was 0.2 pg. Fish, pork, and milk samples were considered. On a congener basis, the GC x GC-ID-TOF-MS method was compared to the reference GC-ID high resolution mass spectrometry (HRMS) method and to the alternative GC-ID tandem-in-time quadrupole ion storage mass spectrometry (QIST-MS/MS). PCB levels ranged from low picogram (pg) to low nanogram (ng) per gram of sample and data compared very well between the different methods. For all matrices, PCDD/Fs were at a low pg level (0.05-3 pg) on a fresh weight basis. Although congener profiles were accurately described, RSDs of GC x GC-ID-TOF-MS and GC-QIST-MS/MS were much higher than for GC-ID-HRMS, especially for low level pork and milk. On a toxic equivalent (TEQ) basis, all methods, including the dioxin-responsive chemically activated luciferase gene expression (DR-CALUX) assay, produced similar responses. A cost comparison is also presented.