Determination of organochlorine pesticide residues by solid phase extraction and dual-column HRGC

Organochlorine pesticide residues have been extracted from samples of animal feed by a solid phase extraction clean-up procedure using an octadecyl-bonded column. The proposed method gave recoveries ranging from 70 to 100 % for ppb levels of the fifteeen pesticides studied. Analytes were identified by dual-column capillary gas chromatography employing DB-1 and DB-1701 columns in parallel; identities were confirmed by calculation of retention indexes with the cubic spline interpolation method.     

Analysis of a mixture of polychlorinated biphenyls and chlorinated pesticides in human serum by column fractionation and dual-column capillary gas chromatography with electron capture detection

An analytical method is presented for precise identification and quantitation of 29 specific polychlorinated biphenyl (PCB) congeners and 15 chlorinated pesticides in human serum. Analyte surrogates PCB 30, PCB 204, 2,2',4,4',5,5'-hexabromo-biphenyl, perthane, alpha-hexachlorocyclohexane, and dichlorobenzophenone were added to each sample. The serum was extracted with an organic solvent and separated by adsorption chromatography into 3 elution fractions for high-resolution gas chromatographic analysis. Each fraction was analyzed by dual-column capillary chromatography followed by electron capture detection. Two capillary columns, DB-5 and DB-1701, with different polarities were used to increase selectivity for each analyte. Quantitation was performed by selecting 2 sets of calibration standard mixtures and 1,2-dichloronaphthalene as an internal standard. Mean recoveries ranged from 39 to 126% for selected analytes and from 31 to 88% for surrogates. Detection limits for specific congeners and pesticides are reported. Typical chromatographic profiles of calibration standard mixtures, as well as a human sample, are illustrated. Verification of each analyte is assessed, and results of analyses of selected human samples and quality control criteria used to ensure data validity also are presented.     

多氯联苯分子结构参数与色谱焓、熵变化的定量关系

 通过理论分析与研究,提出了描述多氯联苯(PCBs)氯原子数目与取代位置有关的分子拓扑指数结构参数JG以及描述多氯联苯分子中氯原子之间相邻关系的分子拓扑指数邻接参数LJ,并推导出PCBs在色谱过程中的焓变(ΔH)、似溶解熵变(ΔS′)与结构参数JG、邻接参数LJ的关系式。在DB-1,DB-5,DB-1701等3种固定相上测定了140余种PCB的ΔH、ΔS′数值,并运用所推导出的关系式对ΔH和ΔS′进行了预测,收到良好的效果,ΔH和ΔS′的理论计算值与实验值的平均相对偏差分别为0.56%~0.97%和0.55%~1.06%，接近实验数据本身的相对偏差。     

Prediction of gas chromatographic retention indices of polychlorinated dibenzothiophenes on non-polar columns

Polychlorodibenzothiophenes (PCDTs) have been found in several kinds of environmental samples. The lack of reference compounds has meant that very little is known about their gas chromatographic behavior. Here we discuss the retention of 19 authentic PCDTs and their sulfones on the widely used gas chromatographic stationary phases DB-5 and DB-5ms. The retention order is different from that of the polychlorodibenzofurans. The data generated allowed us to carry out a multiple linear regression to generate parameters for predicting the retention indices of unknown congeners based only on their structural features.     

GC and MS Properties of β-Blockers as tert-Butyldimethylsilyl Derivatives and as Ethoxycarbonyl/Trimethylsilyl Derivatives

Fourteen β-blockers in pre-dried free base forms were simultaneously converted into tert-butyldimethylsilyl (TBDMS) derivatives in one-step. As a different approach, β-blockers were directly transformed into N-ethoxycarbonyl (EOC) derivatives in aqueous solution, followed by extraction and trimethylsilyl (TMS) derivatization. The retention index sets measured by DB-5 and DB-17 dual-column GC were characteristic for each β-blocker as TBDMS- and EOC/TMS derivatives. Their characteristic fragmentation patterns obtained by GC–MS facilitated easier peak identification of each β-blocker. The overall EOC/TMS method for assays of 14 β-blockers in aqueous solution was linear with acceptable precision and accuracy.     

西兰花中13种有机含磷农药在不同色谱柱上的色谱保留行为

应用Agilent GC 6890气相色谱仪(附FPD检测器)对13种残留于西兰花中的有机含磷农药(OPP′s)在4种不同极性的毛细管色谱柱(即DB-1、DB-5、DB-1701及DB-35MS)上的保留行为作了研究。结果表明:采用由DB-5及DB-1701串联组成的色谱柱单元,西兰花中13种残留OPP′s可达到有效分离和测定。     

Gas chromatographic retention indices of sulfur vesicants and related compounds

Temperature-programmed retention indices, relative to a n-alkane homologous series, were determined for 37 sulfur vesicant or vesicant-related compounds using DB-1, DB-5 and DB-1701 fused-silica capillary columns. Many of the compounds, including long chain dichloro, vinylchloro, vinylalcohol and macrocyclic compounds have either not been previously identified or have not been associated with sulfur vesicant analysis. Reproducibility of the retention indices, based on Van den Dool's equation, was excellent over the course of the study. In addition, changes in retention index (delta RI), which may enable the prediction of uncharacterized homologue chromatographic behaviour, were calculated for several homologous series.     

Dual low thermal mass gas chromatography–mass spectrometry for fast dual-column separation of pesticides in complex sample

A method is described for fast dual-column separation of pesticides by use of dual low thermal mass gas chromatography–mass spectrometry (dual LTM-GC–MS) with different temperature programming. The method can provide two total ion chromatograms with different separation on DB-5 and DB-17 in a single run, which allows improved identification capability, even with short analysis time (<17 min). Also simultaneous detection with MS and elemental selective detector, e.g. pulsed flame photometric detection (PFPD) was evaluated for fast dual-column separation of 82 pesticide mixtures including 27 phosphorus pesticides. Dual LTM-GC–MS/PFPD was applied to analysis of pesticides in a brewed green tea sample with dual stir bar sorptive extraction method (dual SBSE).     

Peak tailoring concept in gas chromatographic analysis of volatile organic pollutants in the atmosphere

An automated gas chromatographic system aiming at performing unattended analysis of volatile organic compounds (VOCs) was developed in laboratory. To encompass VOCs of a wide range of volatility, two different designs of enrichment and separation methods were adopted and compared with performance in analyzing ozone precursors of C3-C12. In the dual-trap dual-column design, lower boiling species (C3-C6) are enriched and separated by one set of trap and column (porous layer open tubular (PLOT)), whereas the enrichment and separation for the higher boiling species (C6-C12) are performed by the other set (wall-coated open tubular (WCOT)). Undesired peaks also inevitably appear on both chromatograms often causing annoyances. To reduce complexity of both the apparatus and the resulting chromatograms, the heart-cut technique was adopted as a base for developing a system, which only uses one trap and one flame ionization detector for constructing two-dimensional GC with PLOT and DB-1. Methods were developed to allow the auxiliary flow pressure in the heart-cut device to be programmed to create dual effects, which not only can perform regular heart-cut actions but can also temporally hold up species in the precolumn for prescribed time intervals. Because it is characteristic for PLOT chromatograms to have reproducible blank retention time windows, segments of a DB-1 trace are produced by the auxiliary flow program aligning perfectly in time with the gaps of the PLOT trace. Subsequently, the two column flows are merged and channeled into single flame ionization detector to produce a very condensed "tailored" chromatogram which is equivalent to overlaying a PLOT and a DB-1 chromatogram on top of each other, except that no peaks are overlapped. This innovative "peak tailoring" concept based on the heart-cut technique is simple in design, easy to build, and extremely rugged for long-term continuous operation as fewer moving parts are involved, which is beneficial for deploying in remote monitoring stations.     

Analysis of compounds of environmental concern: II. Diphenyl ethers

Nineteen halogenated and/or nitrated diphenyl ethers (currently listed in EPA Method 8111) have been separated on a DB-5/ DB-1701 column pair connected to an inlet splitter and separate electron capture detectors. Retention times are included for 10 additional compounds evaluated for their suitability as internal standards or surrogate compounds for incorporation into Method 8111. Method reproducibility and linearity are discussed, and results are presented for extracts of two real samples spiked with the 19 diphenyl ethers and analyzed using the dual-column dual-detector arrangement.     

Analysis of classes of compounds of environmental concern: III. Organochlorine pesticides

Forty five organochlorine pesticides (currently listed in EPA Method 8081A) have been chromatographed on DB-5/DB-1701 and SPB-5/SPB-1701 column pairs which were in each case connected to an inlet splitter and separate electron capture detectors. Thirteen additional compounds were evaluated for their suitability as internal standards or surrogate compounds for incorporation into Method 8081A. Method reproducibility and linearity are discussed, and results are presented for extracts of six real samples spiked with fifteen organochlorine pesticides and analyzed using the dual-column, dual-detector arrangement.     

多氯联苯的正辛醇-空气分配系数与气相色谱保留参数的关联

通过对19种多氯联苯（PCBs）在DB-1,DB-5和DB-1701等3种色谱柱上的气相色谱（GC）保留参数A,B值与正辛醇-空气分配系数(Koa)的相关分析,发现GC保留参数A,B与Koa存在明显的线性关系。采用了逐步回归的方法,建立了保留参数A,B与Koa的二元回归方程,相关系数的平方达到了0.99以上,标准偏差小于0.11。此外,根据实验测定的153个PCBs的GC保留参数以及定量构效关系（QSAR）研究中的56个预测值,对剩余190种PCBs的Koa值进行了预测。     

A new gas chromatographic retention index for pesticides and related compounds

A new gas chromatographic (GC) retention index based on a homologous series of tri-n-alkylamines is proposed for use in the detection of pesticides and related compounds because the standard n-paraffin hydrocarbons used for the Kovats index do not show up well on the nitrogen-phosphorus detectors commonly used in pesticide analysis. Using fused silica bonded phase capillary columns (DB-1 or DB-5), the trialkylamine indices of 106 selected pesticides and related compounds were measured and their relationship to the Kovats index determined.     

Use of SE-30 as a stationary phase for the gas-liquid chromatography of drugs.

The dimethyl silicone elastomer SE-30 has been chosen as the preferred liquid phase for the gas-liquid chromatographic analysis of drugs, and retention index data have been compiled for 480 drugs and commonly occurring chemicals such as plasticisers. The inter-laboratory variation in measurement of retention indices has been measured for three drugs in eleven laboratories and the standard deviations were between 20 and 15 retention index units.     

Gas chromatographic separation of substituted pyridines

Capillary gas chromatographic methodology for separation of complex mixtures of substituted pyridines has been demonstrated on polar (CAM) and non-polar (DB-5) columns. Separations are characterized by high resolution, high sensitivity, a wide dynamic detector range, and good reproducibility. For the first time, Kováts retention indices have been calculated for pyridine and substituted pyridines. Correlations of retention indices with physico-chemical properties, such as hydrogen bonding, pyridine pKa and Hammett substituent constants are discussed.     

High-performance liquid chromatography systems for the separation of benzodiazepines and their metabolites

The high-performance liquid chromatographic (HPLC) retention characteristics of 21 benzodiazepine drugs and some of their metabolites have been examined on both silica and ODS-silica packing materials. Four HPLC systems have been considered and retention data are presented for the drugs on these systems. The correlation of retention data on the systems is considered with reference to the problem of identifying unknown benzodiazepines.     

几种苯甲酰胺类抗精神病药物的手性色谱拆分及其对映体含量的测定

采用直链淀粉-三(5-氯-2-甲基苯基氨基甲酸酯)手性固定相(CSP),以0.1%二乙胺正己烷和0.1%二乙胺乙醇为流动相梯度洗脱,以舒必利、阿米舒必利和莫沙必利为目标物,利用高效液相色谱法研究了这3种苯甲酰胺类药物的手性色谱分离行为。分别考察了流动相组成、添加剂及柱温对3种药物对映体分离的影响,从热力学和结构上探讨了色谱拆分的机理。结果表明: 在优化的色谱条件下,舒必利、阿米舒必利和莫沙必利对映体的分离度Rs＞1.5;计算了3种药物对映体的色谱保留因子k和分离因子α,以及与CSP相互作用的热力学函数,其相互作用大小依次为舒必利＞阿米舒必利＞莫沙必利。已将该方法成功地应用于上述3种药物片剂和血清中其对映体的测定,方法简便、准确、可靠。