A micro-volume electron capture detector for use in high resolution capillary column gas chromatography

A new design for an electron capture detector cell is described. The cell is compatible with the requirements of high resolution capillary columns and is shown to be useful in applications that require high analysis speed. A unique method of sample introduction reduces the problems of sample loss by adsorption on the surfaces of the cell. Previously reported problems of sample loss by adsorption on active surfaces within the cell when using hydrogen carrier gas are shown to have been eliminated. Examples are shown demonstrating the increased speed of analysis that can be obtained when using hydrogen carrier gas and 100 micron diameter columns.     

Evaluation of electron capture cell designs for use in high resolution capillary column gas chromatography

A comparison of the effects on peak shape is made between a 350 and 100 microliter displaced coaxial and a 350 microliter concentric cylinder electron capture cell. Peaks as fast as W_1/2 = 0.5 second were detected using electronics operating in the constant current mode. The measured peak shapes are compared to those obtained by computer simulation assuming either complete mixing or plug-like flow within ECD cell. The advantage of controlling the flow pattern through the cell to obtain plug-like flow is demonstrated. Differences in peak shape between the displaced coaxial and concentric cylinder cells of the same volume are explained in terms of the electrostatic fields within the cells.     

Determination of PCBs in tetrachlorinated quinone using gas chromatography with electron capture detection

A simple, sensitive method for determining polychlorinated biphenyl (PCB) congeners in industrial product 2,3,5,6-tetrachloro-1,4-benzoquinone with GC/ECD detection has been developed. The method based on liquid-liquid extraction from tetrachlorinated quinone dissolved in N,N-dimethylformamide was found to be efficient for the determination of the levels of the investigated pollutants. A series of extraction and purification steps were designed for the sample pretreatment. The congener specific averages of recoveries were 82-96% for Aroclor 1242 and 1254 at a total spiking level of ca. 0.4 mug g(-1) sample. The reproducibilities of replicate determinations of different congeners were typically 5-19% except one with the average 13% R.S.D. (n=3). This method was applied to evaluate the background levels of PCBs in tetrachloro-1,4-benzoquinone, of which the corresponding PCB levels varied from 0.014 to 1.5 mug g(-1).     

Analytical method for dimethenamid-P in selected raw agricultural commodities by gas chromatography with electron capture detection

A sensitive and simple method for the extraction and quantification of the herbicide dimethenamid-P from several raw agricultural commodities (RAC) is presented. The method provides sensitive and well-defined chromatography with baseline resolution in all matrixes tested. Homogenized samples were extracted with methanol-water, filtered, and then extracted with hexanes. A Florisil solid-phase extraction was then applied for the final cleanup. Sample separation and quantification were performed by gas chromatography with an electron capture detector. The instrument detection limit was 0.007 microg/mL, and the practical quantification limit was 0.003 microg/g (w/w) based on a 25 g sample. Recoveries for a series of fortified plant tissues ranged from 69 to 103%. The study demonstrated selective and sensitive recovery of dimethenamid-P from the RAC tested.     

气相色谱-电子捕获检测法测定海水中十氯酮残留

通过考察提取溶剂、毛细管柱、净化条件及共溶出干扰物等因素对十氯酮测定的影响,建立了二氯甲烷液-液富集萃取、硫酸净化分离、气相色谱法(GC)-电子捕获检测器(ECD)测定海水介质中有机氯农药类持久性有机污染物十氯酮残留分析方法。1 L海水经50 mL二氯甲烷萃取富集,浓缩后采用硫酸净化,以1%(体积分数)甲醇/正己烷混合溶液转移定容后,采用DB-5非极性毛细管柱进行GC分离,电子捕获检测器可测定其中十氯酮的含量;该方法采用外标法定量,在5～100 μg/L范围内呈线性,线性相关系数为0.9989。低、中、高3个浓度水平的平均加标回收率为81%～108%,相对标准偏差为1.2%～5.1%(n=6)。方法的检出限为0.6 ng/L。结果表明,该方法灵敏度高,线性关系好,可以满足简便、快速、准确测定海水中十氯酮的要求。     

Determination of methylmercury in biological samples by capillary gas chromatography with electron capture detection

A precise and accurate method has been developed for the determination of methylmercury in biological material using capillary gas chromatography with electron-capture detection. Homogenized fish or mussel samples were digested with acid, spiked with ethylmercury chloride as an internal standard and extracted with toluene. After treatment of the solvent extract with sodium thiosulphate and cupric bromide the alkylmercurials were extracted into benzene as their bromide derivatives and analyzed using an OV-275 coated glass capillary column. The detection limit of the method for methylmercury was 5 g/kg tissue.     

Determination of milk-oxidised ketone bodies as an acetone derivative by electron capture gas chromatography

Following the deproteination of the milk sample by means of zinc hexacyanoferrate, acetoacetic acid was decarboxylated by heating; the acetone originally present was then determined together with the acetone formed. The essence of the determination was that acetone reacted with bromine in the presence of sulphuric acid, following which, the bromoacetone formed was extracted into toluene, separated by gas chromatography and measured using an electron capture detector. The calibration curve was found to be linear up to a concentration of 2 mmol l(-1) acetone. The detection limit calculated from the threefold noise level and the slope of the calibration curve was 9x10(-7) mol l(-1). The reliability of the method meets the practical requirements. Its application may be recommended above all for the establishment of subclinical ketosis.     

Low-temperature clean-up method for the determination of pyrethroids in milk using gas chromatography with electron capture detection

This paper describes a new gas-chrormatography with electron capture detection (GC-ECD) method for determination of some pyrethroids in milk samples. The extraction of the pyrethroids was carried out by liquid–liquid extraction with clean-up by precipitation at low temperature, without additional stages for removal of fat interferences. The method was efficient with recoveries of 93.0 ± 0.1% for cipermethrin and 84.0 ± 0.3% for deltamethrin. The quantification limits were 0.75 μg L⁻¹ for both pyrethroids. The method was simple, of easy execution, and used only small quantities of organic solvent. After optimization and validation, the method was used for the determination of residues of the pyrethroids cipermethrin and deltamethrin in milk and in lactea drink commercialized in Viçosa (MG, Brazil). Some samples presented contamination with deltamethrin at levels below the maximum contamination limits established by the FAO.     

Automated determination of nifedipine in human plasma by capillary gas chromatography with electron capture detection

A rapid, sensitive, and reliable method for the determination of nifedipine in human plasma is described. Using a single-step solvent extraction and capillary gas chromatography combined with electron capture detection, an assay sensitivity of 2 ng/ml is achieved routinely using 0.5 ml of plasma. Intact nifedipine is quantitated and separated from its nitroso- and nitropyridine-derivatives. The suitability of the assay for pharmacokinetic studies is illustrated.     

Trace analysis of ethinyl estradiol in casein diet using gas chromatography with electron capture detection

Ethinyl estradiol (EE2) is an extremely potent synthetic estrogen and a common component in oral contraceptives. The drug has a well-characterized pharmacological profile and is used as a positive control in toxicological investigations of compounds having estrogenic activity. An analytical method developed for the determination of low microg/kg levels of EE2 in a casein-based rodent diet is presented. A methanol extract of casein diet is purified for instrumental analysis by a 3-fold solid-phase extraction process. The sample extract is derivatized with pentafluoropropionic anhydride to the pentafluoropropionyl product and analyzed by capillary gas chromatography with electron-capture detection. Recoveries of EE2 from casein diet fortified at 5, 10, and 50 microg/kg average 88.8% and have a relative standard deviation (%) of 7.2. The method limit of detection in a casein-based diet is 1 microg/kg.     

Determination of eight synthetic pyrethroids in bovine fat by gas chromatography with electron capture detection

Synthetic pyrethroids are among the most widely used classes of insecticides, and their uses are varied, including plant protection, animal dips, and as a treatment for human clothing and bedding in very hot climates. Veterinary applications include ear tags, pour-on formulations, sprays, and dips. Persistent residues have been reported in livestock, and routine monitoring programs in other countries have found detectable residues of various pyrethroids in fat. A method has been developed using solid-phase extraction that reduces the quantities of solvents used, the time required, and the amount of glassware used compared to an earlier method on which it was based. The scope of analytes tested included the 5 compounds cited in the earlier method (flucythrinate, permethrin, cypermethrin, fenvalerate, and deltamethrin) and, in addition, cyfluthrin, lambda-cyhalothrin, and fluvalinate. Sample extracts were analyzed by gas chromatography with electron capture detection using selected chromatographic peaks characteristic of each compound. Limits of quantification for the compounds were from 25-50 microg/kg, with a linear response for all compounds to 200 microg/kg. Recoveries ranged from 80 to 123%.     

Derivatization and determination of arsenic in marine samples by gas chromatography with electron capture detection

Summary Arsenic in marine samples was determined by gas chromatography with electron capture detection after derivatization with 2,3-dimercaptopropanol. Biological tissues and sediments were analyzed after acid decomposition. For sea water, arsenic was preconcentrated by coprecipitation with hydrous iron (III) oxide. The results obtained by this approach compare favourably with the certified values of the reference materials analyzed. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984     

Determination of coumarin in fragrance products by capillary gas chromatography with electron capture detection.

A gas chromatographic (GC) method is described for the determination of coumarin in fragrance products. Coumarin was tentatively identified by retention time and confirmed by GC/mass spectrometry. The amount of coumarin was determined by external standard. The method was validated by conducting recovery studies from fortified fragrance products at several concentrations. Recoveries of coumarin ranged from 99 to 110%, with a relative standard deviation of 3.24. The method was used to survey a variety of fragrance products purchased in the metropolitan Washington, DC area, for coumarin. Seventy one percent of the products were found to contain coumarin at concentrations ranging from 0.002 to 0.61%.     

Quantitative gas chromatography without calibration

Summary Recent developments of a method used since 1954 for accurate quantitative determination of organic substances separated by gas chromatography are described. The method is based on combustion to carbon dioxide and titration of the latter in a non-aqueous medium. Details are given of improved combustion and titration procedures. The accuracy of the method is demonstrated with reference to results obtained on various mixtures. Standard deviations are of the order of 0.1–0.2%.Advantages of the method compared with others are summarized. It is emphasized that the method is particularly suitable for the organic analyst in the research laboratory, as it permits immediate accurate analysis of a mixture even if its components are not available in the pure state.Accurate weighing of the sample on an inexpensive torsion balance allows a check to be made on 100% elution.The low price of a complete apparatus enabled the authors to set up large batteries, ready for immediate use and suitable for solving a wide variety of analytical problems.

---

Zusammenfassung Es werden neuere Entwicklungen einer Methode beschrieben, die seit 1954 zur genauen quantitativen Bestimmung organischer Verbindungen nach gaschromatographischer Trennung benutzt wird. Das Verfahren beruht auf der Verbrennung zu Kohlendioxid und dessen Titration in nichtwäßrigem Medium. Einzelheiten von verbesserten Verbrennungs- und Titrationsmethoden werden gegeben.An verschiedenen Gemischen wird die Genauigkeit des Verfahrens nachgewiesen. Die Standardabweichungen betragen 0,1–0,2%. Im Vergleich zu anderen Methoden werden die Vorteile des Verfahrens aufgezeigt. Es gestattet die sofortige genaue Analyse eines Gemisches, auch wenn seine Bestandteile nicht in reinem Zustand zur Verfügung stehen. Durch genaues Wägen der Probe mit einer billigen Torsionswaage kann die 100% ige Elution kontrolliert werden. Der niedrige Preis der Apparatur erlaubt die Durchführung von Serienanalysen auf verschiedensten Gebieten.