Miniaturised selective pressurised liquid extraction of polychlorinated biphenyls from foodstuffs

The feasibility of miniaturised pressurised liquid extraction (PLE) with in-cell purification and subsequent gas chromatography with micro-electron capture detection (GC-micro-ECD) for the determination of prioritary and toxic polychlorinated biphenyls (PCBs) in a variety of foodstuffs (fat contents in the range 22-49%, w/w, on a freeze-dried basis) has been investigated. After optimisation of the several experimental parameters affecting the efficiency of the selective PLE process, the developed method provided quantitative recoveries of the endogenous PCBs studied and complete fat elimination in a single step using n-hexane as extraction solvent. A total solvent volume of 3.5 mL was used for the two consecutive 7 min static PLEs of 100-mg samples. Detection limits using GC-micro-ECD were below 0.2 ng/g freeze dried sample for all 22 PCBs investigated in real-life foodstuffs, and the repeatability of the complete PLE plus GC-micro-ECD method as calculated for the analysis of the endogenous PCBs in general was better than 14%. Comparison of the miniaturised PLE method developed with either conventional Soxhlet extraction or matrix solid phase dispersion with subsequent (off-line) clean-up for the analysis of non-spiked samples showed that the efficiency of PLE was similar to or better (recoveries in the range 83-133%, as calculated for the endogenous analytes) than for the other two extraction methods assayed.     

气相色谱-串联质谱法测定贝类中指示性多氯联苯

研究并建立了测定贝类中多氯联苯残留的气相色谱-串联质谱(GC-MS/MS)方法.通过正己烷和丙酮的混合溶液超声提取,硅胶柱净化,旋转蒸发浓缩,采用GC-MS/MS多反应监测(MRM)方式测定,可同时对贝类中的7种指示性多氯联苯进行定性和定量.研究结果表明:7种指示性多氯联苯的检出限(S/N=3)为0.0066～0.0098μg/kg,定量限(S/N=10)为0.02 μg/kg;在0.1～50.0 ng/mL时峰强度与质量浓度的线性关系良好(r>0.99).方法的平均回收率为73%～113%.该法简便快捷,降低了分析成本,在一定程度上实现了持久性污染物的快速检测和确证.     

离子阱串联质谱法检测鱼肉中指示性多氯联苯

建立了使用离子阱串联质谱技术和同位素稀释技术准确测定鱼肉中的7种指示性多氯联苯（PCB）单体的方法。方法的检出限为0．025—0．068ng／g,6个加标鱼样（添加水平1ng／g）中7个单体的回收率为87.2％～103.7％,RSD为3．2％-8．7％（n=6）。本方法定量准确可靠,可用于食品中指示性PCB的测定。     

气相色谱/高分辨质谱联用测定环境样品中的二噁英和类二噁英多氯联苯

样品采用索氏抽提,抽提液依次经酸性硅胶床、多段混合硅胶柱和凝胶渗透色谱柱(GPC)净化后,用Florisil硅藻土柱分离出样品中的二噁英(PCDD/Fs)和类二噁英多氯联苯(dioxin-like PCBs),采用同位素稀释法和气相色谱/高分辨质谱联用仪(GC/HRMS)测定了其中的17个2,3,7,8-氯取代二噁英类化合物和12个类二噁英多氯联苯。结果表明,用该法分析二噁英和多氯联苯标准溶液,平行4次的分析结果为:RSD(PCDD/Fs)<8.9%,RSD(PCBs)<11.4%;回收率可达60%-105%。PCDD/Fs和PCBs的检出限分别为0.1-0.8 pg/g和0.05-0.6 pg/g。应用本方法成功测定了沉积物、淤泥、土壤和飞灰中的二噁英和类二噁英多氯联苯,并计算出它们的毒性当量。     

Method development for the analysis of polybrominated diphenyl ethers, polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins and dibenzo-furans in single extract of sediment samples

A comprehensive method was developed for quantitative analysis of polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins and dibenzo-furans (PCDD/Fs) in one single extract of environmental samples. The sample preparation procedure included two fractionation steps using silver nitrate silica chromatography to separate PBDEs from PCBs and PCDD/Fs and florisil column to separate PCBs from PCDD/Fs. Acidic silica, acidic alumina and gel permeation chromatography (GPC, for PCBs) or activated carbon column (for PCDD/Fs) were used for further clean-up. The sample extracts were analyzed by using high-resolution gas chromatography/high-resolution mass spectrometry. The entire method was validated from the analysis of mixed standards of PBDEs, PCBs and PCDD/Fs (n = 3); the analysis of certified reference biota (WMF-01). The method was applied for the analysis of 10 sediment samples collected from Haihe River and Dagu Drainage River in Tianjin City. No significant PBDEs pollution was found in the areas.     

Determination of chlorinated paraffins in cutting fluids and lubricants

An analytical routine procedure to classify chlorinated paraffins in technical products such as cutting fluids and lubricants is presented. Classification is based on chain length and chlorination degree (short chain, highly chlorinated congeners being subject to legal restrictions). After sample clean up with solid phase extraction over silica, screening is performed with gas chromatography and electron capture detection (ECD). Positive identification and quantitation is then performed with gas chromatography/mass spectrometry using negative chemical ionisation (NCI). Both methods show good reproducibility and repeatability and the average recovery of the chlorinated paraffins with the NCI method is 98%. The detection limits for restricted paraffins in samples range between 0.02–0.08% (w/w) for the ECD method and between 0.2–2.6% (w/w) for the NCI method. The procedure has been applied successfully to the analysis of 37 cutting fluids or lubricants. Short chain, highly chlorinated paraffins were detected in 8 (21%) samples in concentrations from 1 to 70% (w/w). The described procedure can be recommended as an analytical routine method for supervising future legal restrictions on the use of chlorinated paraffins in cutting fluids and lubricants. Received: 13 January 1997 / Revised: 20 March 1997 / Accepted: 3 April 1997     

Determination of chlorinated paraffins in cutting fluids and lubricants

An analytical routine procedure to classify chlorinated paraffins in technical products such as cutting fluids and lubricants is presented. Classification is based on chain length and chlorination degree (short chain, highly chlorinated congeners being subject to legal restrictions). After sample clean up with solid phase extraction over silica, screening is performed with gas chromatography and electron capture detection (ECD). Positive identification and quantitation is then performed with gas chromatography/mass spectrometry using negative chemical ionisation (NCI). Both methods show good reproducibility and repeatability and the average recovery of the chlorinated paraffins with the NCI method is 98%. The detection limits for restricted paraffins in samples range between 0.02–0.08% (w/w) for the ECD method and between 0.2–2.6% (w/w) for the NCI method. The procedure has been applied successfully to the analysis of 37 cutting fluids or lubricants. Short chain, highly chlorinated paraffins were detected in 8 (21%) samples in concentrations from 1 to 70% (w/w). The described procedure can be recommended as an analytical routine method for supervising future legal restrictions on the use of chlorinated paraffins in cutting fluids and lubricants. Received: 13 January 1997 / Revised: 20 March 1997 / Accepted: 3 April 1997     

Determination of N-nitrosodimethylamine in fish products using gas chromatography with nitrogen-phosphorus detection

A simple and rapid gas chromatographic method for the determination of N-nitrosodimethylamine (NDMA) in fish products is described. NDMA is extracted from a dried sample with methylene chloride, mixed with n-hexane and passed through a silica gel column. NDMA adsorbed on silica gel is eluted with methylene chloride-diethyl ether (7:3) and the eluate is passed through a Sep-Pak alumina A cartridge column, on which NDMA is adsorbed. NDMA is eluted from the cartridge with diethyl ether-methanol (2:1) and the solution is injected into a gas chromatograph with nitrogen-phosphorus detection. This method does not use solvent evaporation and concentration in the clean-up procedure, which eliminates the loss of volatile NDMA and artifactual formation of NDMA in the analytical procedure. The detection limit is 0.5-1 micrograms/kg and recoveries from salted pollack roe spiked at 40 and 4 micrograms/kg were 96.7% [relative standard deviation (R.S.D.) 3.6%] and 85.0% (R.S.D. 6.8%) respectively.     

Glycidyl fatty acid esters in food by LC-MS/MS: method development

An improved method based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the analysis of glycidyl fatty acid esters in oils was developed. The method incorporates stable isotope dilution analysis (SIDA) for quantifying the five target analytes: glycidyl esters of palmitic (C16:0), stearic (C18:0), oleic (C18:1), linoleic (C18:2) and linolenic acid (C18:3). For the analysis, 10 mg sample of edible oil or fat is dissolved in acetone, spiked with deuterium labelled analogs of glycidyl esters and purified by a two-step chromatography on C18 and normal silica solid phase extraction (SPE) cartridges using methanol and 5% ethyl acetate in hexane, respectively. If the concentration of analytes is expected to be below 0.5 mg/kg, 0.5 g sample of oil is pre-concentrated first using a silica column. The dried final extract is re-dissolved in 250 μL of a mixture of methanol/isopropanol (1:1, v/v), 15 μL is injected on the analytical C18 LC column and analytes are eluted with 100% methanol. Detection of target glycidyl fatty acid esters is accomplished by LC-MS/MS using positive ion atmospheric pressure chemical ionization operating in Multiple Reaction Monitoring mode monitoring 2 ion transitions for each analyte. The method was tested on replicates of a virgin olive oil which was free of glycidyl esters. The method detection limit was calculated to be in the range of 70-150 μg/kg for each analyte using 10 mg sample and 1-3 μg/kg using 0.5 g sample of oil. Average recoveries of 5 glycidyl esters spiked at 10, 1 and 0.1 mg/kg were in the range 84% to 108%. The major advantage of our method is use of SIDA for all analytes using commercially available internal standards and detection limits that are lower by a factor of 5-10 from published methods when 0.5 g sample of oil is used. Additionally, MS/MS mass chromatograms offer greater specificity than liquid chromatography-mass spectrometry operated in selected ion monitoring mode. The method will be applied to the survey of glycidyl fatty acid esters in food products on the Canadian market.     

Determination of two oxy-pyrimidine metabolites of diazinon in urine by gas chromatography/mass selective detection and liquid chromatography/electrospray ionization/mass spectrometry/mass spectrometry

An analytical method was developed for the determination in urine of 2 metabolites of diazinon: 6-methyl-2-(1-methylethyl)-4(1H)-pyrimidinone (G-27550) and 2-(1-hydroxy-1-methylethyl)-6-methyl-4(1H)-pyrimidinone (GS-31144). Two of the urine sample preparation procedures presented rely on gas chromatography/mass selective detection (GC/MSD) in the selected ion monitoring mode for determination of G-27550. For fast sample preparation and a limit of quantitation (LOQ) of 1.0 ppb, urine samples were purified by using ENV+ solid-phase extraction (SPE) columns. For analyte confirmation at an LOQ of 0.50 ppb, classical liquid/liquid partitioning was used before further purification in a silica SPE column. An SPE sample preparation procedure and liquid chromatography/electrospray ionization/mass spectrometry/mass spectrometry (LC/ESI/MS/MS) were used for both G-27550 and GS-31144. The limit of detection was 0.01 ng for G-27550 with GC/MSD, and 0.016 ng when LC/ESI/MS/MS was used for both G-27550 and GS-31144. The LOQ was 0.50 ppb for G-27550 when GC/MSD and the partitioning/SPE sample preparation procedure were used, and 1.0 ppb for the SPE only sample preparation procedure. The LOQ was 1.0 ppb for both analytes when LC/ESI/MS/MS was used.     

高效液相色谱-串联质谱法同时测定血液中的15种减肥药物

建立了一种专属、灵敏的同时测定血液中咖啡因、盐酸西布曲明等15种减肥药的高效液相色谱-串联质谱(HPLC-MS/MS)分析方法。样品经乙腈沉淀后,进入HPLC-MS/MS中分析检测。以甲醇和含0.1%(v/v)冰醋酸的20 mmol/L醋酸铵溶液作为流动相,采用梯度洗脱方式,以UltimateXB-C18为色谱柱进行HPLC分析;质谱分析采用电喷雾离子源,正负离子快速切换扫描,选择反应监测模式检测。15种减肥药的定量限在0.001～0.05 mg/L内,各种药物的灵敏度较高,各成分的线性相关系数均大于0.99,精密度均小于12.3%,回收率范围为77.3%～110.8%。研究了这15种药物的质谱特征。该方法灵敏、简便、快捷、专属性强,可用于动物实验样品中减肥药物的含量测定,并且对其他药品、食品中目标减肥药物的测定具有借鉴意义。     

Rapid assays of clozapine and its metabolites in dried blood spots by liquid chromatography and microextraction by packed sorbent procedure

A novel analytical approach has been developed for the determination of clozapine and its metabolites in dried blood spots on filter paper, using a chromatographic method coupled with a microextraction by packed sorbent procedure. The analytes were separated on a RP-C18 column using a mobile phase composed of 20% methanol, 16% acetonitrile and 64% aqueous phosphate buffer. Coulometric detection was used, setting the guard cell at +0.050 V, the first analytical cell at -0.200 V and the second analytical cell at +0.500 V. Clozapine and its metabolites were extracted from dried blood spots with phosphate buffer and, then, a microextraction by packed sorbent procedure for the sample clean-up was implemented obtaining good extraction yields. The calibration curve was linear over the 2.5-1000 ng mL(-1) blood concentration ranges for all the analytes. The method validation gave satisfactory results in terms of sensitivity, precision, selectivity and accuracy. The analytical method was successfully applied to dried blood spots from several psychiatric patients for therapeutic drug monitoring purpose.     

Determination of trialkyllead species in water samples

An analytical compound procedure is described for the determination of trimethyl- and triethyllead in water samples like rain, melted snow, and surface waters. The method consists of an enrichment step (adsorption onto and elution from silica gel), a chromatographic separation with column switching (HPLC including pre-column enrichment), and a spectrophotometric detection (chemical reaction detector). The detection limits for the whole procedure, starting with 500 ml sample volume, are 15 pg/ml and 20 pg/ml for trimethyl- and triethyllead resp. The standard deviation for repeated analysis of a sample containing 90 pg Et3Pb+/ml is calculated to +/- 4%. The method also covers the analysis of the chemically mixed trialkyllead species Me2EtPb+ and MeEt2Pb+. The investigation of several water samples taken from different locations shows the presence of trimethyl- and triethyllead in the concentration range of 20-100 pg/ml.     

A routine accredited method for the analysis of polychlorinated biphenyls,organochlorine pesticides,chlorobenzenes and screening of other halogenated organics in soil,sediment and sludge by GCxGC-μECD

The analysis of persistent organic pollutants is a real challenge due to the large number of compounds with varying chemical and physical properties. Gas chromatography with electron capture detection or mass spectrometry has been the method of choice for the past 50 years. Comprehensive two-dimensional gas chromatography (GCxGC) coupled with micro-electron capture detector (μECD) is a new method that can analyze polychlorinated biphenyls (PCBs), organochlorine pesticides (OCs) and chlorobenzenes (CBz) in a single analytical run with enhanced selectivity and sensitivity over single column methods and can also be used to screen for other halogenated organics in environmental samples. An accredited routine method using commercially available LECO GCxGC-μECD and a column combination DB-1 × Rtx-PCB has been developed to analyse PCBs/OCs/CBz in soils, sediments and sludges. The method provides quantification of Aroclors and Aroclor mixtures to within 15% of target values and sub-nanogrammes per gramme detection limits.     

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.     

Detection of low-abundance impurities in synthetic thyroid hormones by stationary phase optimized liquid chromatography–mass spectrometry

The transfer of a gradient method to an isocratic or multistep gradient method employing stationary phase optimized liquid chromatography facilitated a reduction in analysis time by 50% and significantly improved the mass spectrometric detectability of impurities in synthetic thyroid hormones. Four column segments packed with different stationary phases were combined into a single chromatographic column, which allowed the separation and photometric as well as mass spectrometric detection of thyroid compounds in less than 30 min under isocratic- or step gradient elution conditions with 0.10% acetic acid/acetonitrile. Signal instability and baseline drift during detection by negative electrospray ionization time-of-flight mass spectrometry were minimized by optimizing the spray parameters for each individual elution step. This resulted in improved detectabilities and higher mass spectral quality, especially for low-abundance components in the sample mixture. The method was applied to the separation and detection of the low-abundance impurities formed upon the thermal stressing of a sample of synthetic levothyroxine.     

Analysis of organochlorines in harbor seal (Phoca vitulina) tissue samples from Alaska using gas chromatography/ion trap mass spectrometry by an isotopic dilution technique

A gas chromatography/ion trap mass spectrometry (GC/ITMS) method was developed for the determination of organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs) and polychlorinated naphthalenes (PCNs) in harbor seal (Phoca vitulina) tissues. Tissue samples were homogenized, lyophilized and fortified with (13)C-PCBs 28, 123, 169 and 170, and then extracted with an accelerated solvent extractor with a mixture of hexane and methylene chloride (1:1, v/v). After lipid removal using a 40% H(2)SO(4)-modified silica gel column, all organochlorines were collected in one fraction and further fractionated with an activated carbon/silica gel (1:20) column into a first fraction containing OCPs, non-coplanar PCBs and (13)C-PCBs 28, 123 and 170, and a second containing PCNs, coplanar PCBs and (13)C-PCB 169. Prior to GC/MS/MS analysis, (13)C-PCB 169 was added into the first fraction as an injection standard and (13)C-PCB 170 into the second fraction to calibrate the recoveries of the fortified internal standards. This method can effectively eliminate matrix interferences, and has high selectivity and sensitivity. Recoveries averaged 45-86% for OCPs with relative standard deviations (RSDs) of 2-14%, 52-137% for PCBs with RSDs of 3-29% and 36-152% for PCNs with RSDs of 7-29% from lard and chicken heart samples, which were used as alternative matrices to harbor seal samples in recovery studies. The limits of detection for OCPs, PCBs and PCNs were 0.7-1.9, 1.5-8.9 and 0.5-10 pg/g dry weight, respectively. This method can be used to analyze OCPs, PCBs and PCNs in harbor seal blubber, liver and kidney samples.     

Rapid bioanalysis of vancomycin in serum and urine by high-performance liquid chromatography tandem mass spectrometry using on-line sample extraction and parallel analytical columns

A novel high-performance liquid chromatography tandem mass spectrometry (LC/MS/MS) method is described for the determination of vancomycin in serum and urine. After the addition of internal standard (teicoplanin), serum and urine samples were directly injected onto an HPLC system consisting of an extraction column and dual analytical columns. The columns are plumbed through two switching valves. A six-port valve directs extraction column effluent either to waste or to an analytical column. A ten-port valve simultaneously permits equilibration of one analytical column while the other is used for sample analysis. Thus, off-line analytical column equilibration time does not require mass spectrometer time, freeing the detector for increased sample throughput. The on-line sample extraction step takes 15 seconds followed by gradient chromatography taking another 90 seconds. Having minimal sample pretreatment the method is both simple and fast. This system has been used to successfully develop a validated positive-ion electrospray bioanalytical method for the quantitation of vancomycin. Detection of vancomycin was accurate and precise, with a limit of detection of 1 ng/mL in serum and urine. The calibration curves for vancomycin in rat, dog and primate were linear in a concentration range of 0.001-10 microg/mL for serum and urine. This method has been successfully applied to determine the concentration of vancomycin in rat, dog and primate serum and urine samples from pharmacokinetic and urinary excretion studies.     

A highly automated 96-well solid phase extraction and liquid chromatography/tandem mass spectrometry method for the determination of fentanyl in human plasma

A high-throughput bioanalytical method based on automated sample transfer, automated solid phase extraction, and fast liquid chromatography/tandem mass spectrometry (LC/MS/MS) analysis, has been developed for the determination of the analgesic fentanyl in human plasma. Samples were transferred into 96-well plates using an automated sample handling system. Automated solid phase extraction (SPE) was carried out using a 96-channel programmable liquid-handling workstation using a mixed-mode sorbent. The extracted samples were then dried down, reconstituted and injected onto a silica column using an aqueous/organic mobile phase with tandem mass spectrometric detection. The method has been validated over the concentration range 0.05-100 ng/mL fentanyl in human plasma, based on a 0.25-mL sample size. The assay is sensitive, specific and robust. More than 2000 samples have been analyzed using this method. The automation of the sample preparation steps not only increased the analysis throughput, but also facilitated the transfer of the method between different bioanalytical laboratories of the same organization.     

Limitations of porous graphitic carbon as stationary phase material in the determination of catecholamines

A fast and sensitive capillary liquid chromatography (cLC) column-switching method with electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) detection for the simultaneous determination of dopamine (D), epinephrine (E), norepinephrine (NE) and serotonin (SE) was pursued. A sample volume of 100 microl was loaded with a mobile phase containing 0.1% pentafluoropropionic acid (PFPA) as ion-pairing agent on a 25 mm x 0.32 mm (i.d.) 5 microm Hypercarb column. A water-acetonitrile (AcN) gradient with 0.1% acetic acid (AcOH) backflushed the compounds onto a 34 mm x 0.32 mm (i.d.) 5 microm Hypercarb analytical column. However, during a series of analyses, oxidation of the catecholamines (CAs) was observed. This was suspected to be due to the loading mobile phase composition and precluded the usefulness of this method even though the achievable detection limit was in the range of 0.75-3.0 ng/ml. The combination of the porous graphitic carbon (PGC) material and the fluorinated strong acids which were required to get enough retention for preconcentration of large volumes cannot be used for easily oxidized compounds as the CAs.