A simple gas chromatography method for the determination of ethylcarbamate in spirits

Summary Ethylcarbamate is a toxic component of certain spirits. For its determination, the spirit is concentrated to one-fifth of its volume, extracted with ethylacetate and analysed by capillary gas chromatography (GC) with flame ionization detection (FID). The method saves time and material and has proved to be a reliable test in different laboratories. The ethylcarbamate concentrations in 170 samples of Swiss origin are presented. the mean values were 1.0 mg/l in cherry brandies, 1.5 mg/l in plum brandies and 0.4 mg/l in Williams pear brandies. Ethylcarbamate concentrations may increase during storage, especially under the influence of daylight.

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Eine einfache gaschromatographische Methode zur Bestimmung von Ethylcarbamat in Spirituosen

Zusammenfassung Ethylcarbamat ist ein cancerogener Inhaltsstoff von gewissen Spirituosen. Zu dessen Bestimmung wird die Probe auf 1/5 ihres Volumens eingeengt, mit Ethylacetat extrahiert und durch Capillar-GC mit FID nachgewiesen. Die Methode ist zeitund materialsparend und hat sich bei einem Vergleich mit mehreren Laboratorien als zuverlässig erwiesen. Die Ethylcarbamatgehalte von 170 Spirituosenproben aus der Innerschweiz werden angegeben. Dabei liegen die Mittelwerte für Kirschwasser bei 1,0 mg/l, für Zwetschgen- und Pflümliwasser bei 1,5 mg/1 und für Williamsbranntweine bei 0,4 mg/1. Die Ethylcarbamatgehalte von Spirituosen können bei der Lagerung stark zunehmen, dies vor allem unter dem Einfluß von Tageslicht.

     

A Screening method for total oxalate determination in plant material by gas chromatography

Oxalates in plant material can be methylated directly to from dimethyl oxalate. After addition of water and chloroform, the volatile compoun is extracted into the organic phase and analysed quantitatively by gas chromatography. Some forms of oxalates are difficult to methylise, and this is apparent when 20% boron trifluoride-methanol is used as the methylating reagent. The use of 7% hydrochloric acid-methanol improved methylation, but the best result was obtained by repacing the acid catalyst with sulphuric acid and increasing the acid concentration up to 30%. Using this reagent, recovery from spiked samples was satisfactory (ranging from 92 to 105%), and precision of the method was good (Relative Standard Deviation (RSD) 1.3% at a total oxalate content of 1.95%).     

《气相色谱法测定六六六》检测方法验证

本文通过对《气相色谱法测定六六六》检测方法进行验证,以评价该检测方法是否适用于水中六六六的检测工作,以确保该方法能够满足水中六六六的测定.     

A simple and quick gas chromatographic method for the determination of propham and chlorpropham in potatoes.

This study describes a gas chromatographic method for the quantitative determination of residual propham and chlorpropham in potatoes. Both herbicides are extracted from the foodstuff with methylene chloride. After centrifugation and concentration, propham and chlorpropham are quantitatively determined by gas chromatography thermionic detection using a fused silica capillary column CP Sil 5CB. 2-Chloraniline is used as internal standard. Recoveries of 100 +/- 15% and 99 +/- 10% have been obtained for propham and chlorpropham in blank samples spiked at the level of 0.5, 1.0 and 5.0 mg/kg. The absolute detection limit for both compounds is 1 ng corresponding to 0.1 mg/kg. Of the 161 samples of fresh potatoes analysed using this method, 136 contained residues of these herbicides and 18 of them (11%) exceeded the maximum tolerated value of 5 mg/kg.     

Headspace solid-phase micro-extraction gas chromatography method for the determination of methanol in aspartame sweeteners

A headspace solid-phase micro-extraction (HS-SPME) method for the extraction and determination of residual methanol in artificial sweeteners by capillary gas chromatography with flame ionization detection (GC-FID) is described. A manual SPME holder with an 85-µm polyacrylate fibre was used. The optimized conditions for methanol extraction by SPME were: sample agitation, absorption temperature of 30°C, absorption time of 10 min, desorption time of 2 min and sample volume in the vial of 400.0 µl. Under these conditions the calibration graphs were linear in the range 2.50-31.60 mg l^-1, and the precision was good (relative standard deviation 4.9%). The detection limit was 0.40 mg l^-1; the quantification limit was 2.06 mg l^-1.     

还原型谷胱甘肽简便测定法

对测定还原型谷胱甘肽-四氧嘧啶305法的改进。适合于GSH浓度介于0.02￣0.10mg/mL的样品分析,回归方程为:y=5.77x,R2=0.9970,最大误差不超过4%。该法可用于发酵液中GSH的直接测定,结果满意。     

A gas chromatographic method for the determination of pentosans

A method for the determination of pentosans by gas chromatographic analysis of furfural produced by acid treatment is presented. Samples are treated with 3.85m hydrochloric acid and the furfural produced partitioned in situ into di-butyl ether. Furfural is measured by gas chromatography with acetophenone as internal standard. The method is calibrated against xylose which is taken through an identical hydrolysis procedure. When applied to starch and flour samples, the method showed good precision with a coefficient of variation of 2–4% depending upon sample type.     

A simple method of sample preparation for analysis of biphenyl residues in citrus fruit peels by gas chromatography

A simple method of sample preparation for analysis of residues of the fungicide biphenyl in peels of citrus fruits by gas chromatography (GC) is described. The blended peels are macerated after addition of anhydrous sodium sulphate in dichloromethane for 2 h. After filtration the biphenyl is quantified directly without concentration of the solution by GC with a flame ionization detector (FID) or a mass selective detector (MSD) under single ion mass conditions. Due to the simple method of sample preparation and good average recoveries of 98–103% with standard deviations of 1–4% in the concentration range of 1–10 ppm, the method described is reliable for analysis of biphenyl in citrus fruit peels. In order to avoid loss of the relatively volatile biphenyl no evaporation of the extraction solution occurs.

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Eine einfache Probenvorbereitungsmethode zur Analyse von Biphenyl-Rückständen in Schalen von Citrusfrüchten mit Hilfe der Gaschromatographie

Zusammenfassung Beschrieben wird eine Probenvorbe-reitungsmethode zur Rückstandsanalyse des Fungizids Biphenyl in Schalen von Citrusfrüchten. Die homogenisierten Schalen werden zwei Stunden lang mit wasserfreiem Natriumsulfat in Dichlormethan maceriert und das Biphenyl ohne vorherige Konzentrierung mit Hilfe der Gaschromatographie (GC) mit einem Flammenionisationsdetektor (FID) oder massenselektiven Detektor (MSD-SIM) quantifiziert. Die Methode zeichnet sich durch hohe Wiederfmdungsraten (98–103%) im Konzentrationsbereich von 1–10 ppm mit Standardabweichungen von 1–4% aus.

     

A rapid and simple method for the determination of glycogen in yeast

A rapid, simple, adaptable and widely applicable procedure for the determination of glycogen in yeast is described. The method exploits the known fact that an aqueous solution of iodine/potassium iodide will stain yeast cells. The intensity of staining has been shown to be proportional to the amount of glycogen present in samples of yeast representing four strains of Saccharomyces cerevisiae. Therefore levels of yeast glycogen can be determined quantitatively by measurement of absorbance, or approximated by visual examination of the yeast-iodine suspension. Such a convenient procedure should enable the brewer (i) to compensate for variations in the glycogen content between different batches of pitching yeast, thereby achieving greater reproducibility in fermentations, and (ii) to monitor changes in yeast composition during storage as a basis for developing improved yeast handling procedures.     

Modified determination method of total bromine in agricultural products by gas chromatography

In the official method for determination of total bromine in fruit and grain foods, bromine is derivatized with 3-pentanone for GC analysis. Co-existing substances sometimes interfere with measurement of the derivative, though the method is highly selective. In this study, the notification method was modified to reduce impurity peaks by applying 3-hexanone. Samples were alkalized and reduced to ash in an electric furnace. After ashing, samples were oxidized with potassium permanganate solution and derivatized with 3-hexanone. The calibration curve was linear from 0.1 microg/mL up to 5.0 microg/mL. The detection limit (S/N = 10) was 0.1 microg/mL, i.e., 5 microg/g for herb, 2.5 microg/g for grains and 1.0 microg/g for fruits. The recoveries of bromine from fruit, grain foods and herbs added at the levels of 5 to 25 microg/g ranged from 84.2 to 96.9%. The values of relative standard deviation (RSD) were from 1.4 to 6.3%. This method should be useful for routine examination of total bromine in foods.     

A simple quantitative HPLC method for determination of aflatoxins in cereals and animal feedstuffs using gel permeation chromatography clean-up

A simple and sensitive procedure is described for the analysis of aflatoxins B1, B2, G1 and G2 in cereal and animal feedstuff samples. Aflatoxins are extracted with dichloromethane:water (10:1). Gel permeation chromatography (GPC) using a column packed with Bio-beads S-X3 and dichloromethane:hexane (3:1) as the eluent is used for clean-up of extracts prior to separation and quantification of aflatoxins by HPLC. The eluent fraction containing the aflatoxins is concentrated by evaporation under reduced pressure and the aflatoxins separated by reverse phase HPLC on an ODS column. Quantitative results have been obtained at levels down to 1 microgram/kg, and average recoveries from samples of wheat, maize and compound feed spiked at levels of 10 and 40 micrograms/kg were greater than 80%, 70% and 65% respectively.     

A simple colorimetric method for the determination of sugars in fruit and vegetables

A rapid, manual colorimetric method for determining glucose, fructose and sucrose in fruit and vegetables is described. The method is based on the determination of reducing sugars before and after invertase digestion using p-hydroxybenzoic acid hydrazide (PAHBAH). Total fructose (fructose plus fructose in sucrose) is determined using 2-thiobarbituric acid and the component sugars calculated. Addition of sugars to fruit extracts gave good recoveries (97.4–101.8%) for glucose, fructose and sucrose.     

A multiresidue method for the determination of 107 pesticides in cabbage and radish using QuEChERS sample preparation method and gas chromatography mass spectrometry

A rapid, specific and sensitive multiresidue method based on the modified Quick Easy Cheap Effective Rugged and Safe (QuEChERS) sample preparation method and gas chromatography with the electron impact mass spectrometric detection in the selected ion monitoring mode (GC–MS-SIM) using one target and two qualifier ions for the routine analysis of 107 pesticides in cabbage and radish has been developed. The recoveries for all the pesticides studied were from 80% to 115% with relative standard deviation lower than 15% in the concentration range of 0.030–0.360 mg/kg. The limit of quantitation (LOQ) for most compounds met MRLs for pesticides in cabbage and radish in Korea. This method was successfully applied to analysis commercial cabbage and radish samples.     

A simple and rapid colorimetric method for lactose determination in milk

A simple and rapid technique for the estimation of lactose in fluid milk and whey, utilizing trichloroacetic acid (TCA) as a precipitating agent, is outlined. The color development is based on the reaction of picric acid with lactose in the presence of phenol, sodium hydroxide and sodium bisulfate. This method can be completed within 10 min. There is no significant difference (p ≤ 0·05) between the results obtained by the proposed method and those obtained by the IDF method.     

橄榄油中农药多残留前处理方法研究及其应用于气相色谱、气质联用测定效果评估

建立了串联双柱净化前处理方法用于橄榄油中313种农药多残留的测定。橄榄油样品采用正己烷溶解,正己烷-乙腈-盐水三相分配除去部分杂质,农药组分转移至乙腈中,经串联双柱净化后供气相色谱仪(GC)和气相色谱-质谱仪(GC-MS)分析。气相色谱法采用火焰光度检测器(FPD)和电子捕获检测器(ECD)测试,外标法定量,适用于有机磷、有机氯和拟除虫菊酯等部分农药的测定。气相色谱-质谱法采用选择离子监测方式(SIM),外标法定量,适用于本法中所有313项农药的测定。在优化后的条件下进行分析,气相色谱-质谱法的检出限(S/N≥3)为0.01～0.03 mg/kg,在加标水平为0.01、0.05、0.20 mg/kg时,平均回收率为57.5%～148.4%(百菌清为44.3%),其中回收率在70%～120%之间的占93.9%,相对标准偏差为2.1%～17.8%。方法准确、灵敏、快速,可满足橄榄油中多种农药残留的风险监控需求并可扩展到其他植物油检测。     

气相色谱法应用于复配乳化剂中单脂肪酸甘油酯含量测定的研究

建立复配乳化剂中单脂肪酸甘油酯的含量检测方法,采用了DB-5ht毛细管柱(15m×250μm×0.10μm),BSTFA和TMCS作为硅烷化试剂,十四烷为内标物,内标法定量。结果表明,样品加入1倍量的硅烷化试剂混合液,70℃反应30min达到最佳硅烷化条件,采用DB-5h毛细管柱(15m)能使目标峰与杂质有良好的分离,三个浓度的加标平均回收率在96.6%~102.5%之间,RSD均少于2.5%,精密度(n=7)RSD为2.8%。经证实,本法准确、灵敏、快速、重现性好,可用于复配乳化剂中单脂肪酸甘油酯含量的定量分析。