Voltammetric determination of nitroaromatic and nitramine explosives contamination in soil

The contamination of soil by nitroaromatic and nitramine explosives is widespread during the manufacture, testing and disposal of explosives and ammunitions. The analysis for the presence of trace explosive contaminants in soil becomes important in the light of their effect on the growth of different varieties of plants and crops. 2,4,6-Trinitrotoluene (TNT), cyclotrimethylene trinitramine (Research Department explosive, RDX) and cyclotetramethylene tetranitramine (high melting point explosive, HMX), other related explosive compounds and their by-products must be monitored in soil and surrounding waterways since these are mutagenic, toxic and persistent pollutants that can leach from the contaminated soil to accumulate in the food chain. In this study, a voltammetric method has been developed for the determination of explosive such as RDX, HMX and TNT. The electrochemical redox behavior of RDX, HMX and TNT was studied through cyclic voltammetry and quantitative determination was carried out by using square wave voltammetry technique. Calibration curves were drawn and were linear in the range of 63-129 ppm for RDX with a detection limit of 10 ppm, 49-182 ppm for HMX with a detection limit of 1 ppm and 38-139 ppm for TNT with a detection limit of 1 ppm. This method was applied to determine the contaminations in several soil samples that yielded a relative error of 1% in the concentrations.     

洋葱中多种农药残留的双柱双检测器气相色谱分析法

洋葱中含有许多对人类有用的成分包括:水分、蛋白、脂肪、膳食纤维、碳水化合物、胡萝卜素、视黄醇、硫胺素、核黄素、抗坏血酸、维生素总E、K、Na、Ca、Mg、Fe、Mn、Zn等[1].近来的许多研究表明,洋葱具有消炎抑菌,预防心血管疾病、糖尿病等生物活性[2].由于洋葱的医疗价值和保健作用,洋葱现在已经成为人们喜爱的蔬菜,受到人们的重视,尤其在欧美,洋葱被称为"蔬菜皇后".目前,国内外对洋葱的研究越来越多,但是主要集中在研究它的生物活性和成分上[2-4].由于洋葱中合有油类物质,因此给农药残留分析带来许多困难.至今,对洋葱中的农药残留分析还未有成熟的方法.目前,用气相色谱分析多组分农药残留的报道已经有了很多[5,6],关于用双检测器分析多组分农药残留的研究,已越来越引起研究人员的关注[7-9].Jatiender Kumar Dubey等[7]用GC-NPD和GC-ECD检测了食品中乙烯基硫脲的含量.Jiménez等[8]利用GC-NPD和GC-ECD分析了蜂蜜中的农药残留.但是用GC-FPD和GC-ECD分析洋葱中的农药残留还未见报道.本文报道了一种简便、快速的洋葱中多种有机磷和菊酯类农药残留的提取净化及其双柱双检测器测定方法.采用乙睛提取洋葱中的农药,二氯甲烷/乙酸乙酯(20:1,V:V)为淋洗剂,经过Florisil和活性炭净化后,用气相色谱-火焰光度检测器和气相色谱-电子捕获检测器分别直接测定各种农药残留含量.结果表明,采用程序升温,所测定的有机磷和菊酯类农药在DB-1701和BPX608弹性石英毛细管柱上得到了很好的分离,且方法快速、灵敏,完全符合实际应用需要.各种农药的加标回收率范围为86.3～103%,变异系数范围为0.67～4.6%,最低检测浓度范围为0.001～0.005 mg/kg.     

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 nitroaromatic and nitramine explosives from a PTFE wipe using thermal desorption-gas chromatography with electron-capture detection

A method for the detection of nitroaromatic and nitramine explosives from a PTFE wipe has been developed using thermal desorption andgas chromatography with electron-capture detection (TD-GC-ECD). For method development a standard mixture containing eight nitroaromatic and two nitramine (HMX and RDX) explosive compounds was spiked onto a PTFE wipe. Explosives were desorbed from the wipe in a commercial thermal desorption system and trapped onto a cooled injection system, which was incorporated into the injection port of the GC. A dual column, dual ECD configuration was adopted to enable simultaneous confirmation analysis of the explosives desorbed. For the desorption of 50 ng of each explosive, desorption efficiencies ranged between 80.0 and 117%, for both columns. Linearity over the range 2.5-50 ng was demonstrated for each explosive on both columns with r2 values ranging from 0.979 to 0.991 and limits of detection less than 4 ng. Desorption of HMX from a PTFE wipe has also been demonstrated for the first time, albeit at relatively high loadings (100 ng).     

Use of porous graphitic carbon for the analysis of nitrate ester, nitramine and nitroaromatic explosives and by-products by liquid chromatography-atmospheric pressure chemical ionisation-mass spectrometry

A new LC/MS method was developed for the analysis of sixteen different analytes including the most common organic explosives encountered in forensic investigations. The separation was achieved using a porous graphitic carbon (PGC) column with a binary gradient elution. Molecular modeling suggested a possible interpretation for the elution order of explosive compounds on PGC. The introduction of ammonium formate in the mobile phase resulted in the formation of characteristic adduct ions thus enhancing the mass spectrometric detection of nitrate ester and nitramine compounds. Atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) were compared in terms of sensitivity. The final LC/APCI-MS method allowed easy identification of investigated compounds with limits of detection ranging from 0.04 to 1.06 ng/microl. The analysis of simulated forensic samples confirmed the performance of the method.     

Determination of chloramphenicol residue in chicken tissues by immunoaffinity chromatography cleanup and gas chromatography with a microcell electron capture detector

A rapid and sensitive gas chromatography (GC) method was developed to detect chloramphenicol in chicken tissues. The extracted samples were cleaned up using the immunoaffinity column prepared by coupling antichloramphenicol monoclonal antibody with cyanogen bromide-activated Sepharose 4B. The dynamic column capacity of chloramphenicol was 3265 ng/mL gel. The eluate was evaporated to dryness, and residues were derivatized and determined by GC with a microcell electron capture detector. Average recoveries were 86.6 to 96.9% for chicken muscle and 74.3 to 96.1% for chicken liver. The limit of quantitation of the method was 0.05 ng/g for chicken muscle and 0.1 ng/g for chicken liver.     

气相色谱-微池电子捕获器检测尿液中的三唑仑

建立了气相色谱-微池电子捕获检测器(GC-μECD)检测尿液中三唑仑的方法。筛选了pH值、提取溶剂、涡旋时间,优化了液-液萃 取条件。在0.2～50 ng/mL范围内,线性关系良好,相关系数为0.9995;方法的检出限为0.1 ng/mL,日内和日间测定的相对标准偏差分 别为4.17%和5.31%,平均回收率为93.9%。该方法操作简便、灵敏度高、线性范围广、回收率高,完全能够满足日常检测工作的需要。     

Determination of chloramphenicol residue in fish and shrimp tissues by gas chromatography with a microcell electron capture detector

A gas chromatography method with microcell electron capture detection was developed for the determination of chloramphenicol residue in fish and shrimp muscle tissues. The tissue samples were extracted with ethyl acetate, defatted with hexane, and derivatized with Sylon BFT [N,O-bis (trimethylsilyl) trifluoroacetamide-trimethylchlorosilane (99 + 1)]. The limit of detection was 0.04 ng/g and the limit of quantitation 0.1 ng/g. Average recoveries were 70.8-90.8% for fish and 69.9-86.3% for shrimp, respectively. The method was validated for the determination of practical samples.     

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.     

微波辅助萃取-衍生气相色谱-电子捕获检测器法测定电子电气产品中的四溴双酚A

以N,O-双(三甲基硅烷基)三氟乙酰胺(BSTFA)作衍生化试剂,采用微波辅助萃取-衍生气相色谱-电子捕获检测器法(GC-ECD)测定电子电气产品中的四溴双酚A。使用V(甲苯)∶V(甲醇)=10∶1微波辅助萃取电子电气样品,用正己烷沉淀萃取液中的高聚物,净化后,将萃取液进行衍生化反应,采用ECD检测器进行定量测定。对衍生化时间、衍生化温度、衍生化试剂用量、沉淀试剂用量等前处理条件进行了优化,并进行了线性、回收率、精密度等试验。结果表明,方法线性范围为0.005~5 mg/L,相关系数为0.9985,方法的检测下限为0.02 mg/kg。采用样品加标的方式进行四溴双酚A的精密度及回收率实验,回收率在81.7%~110%之间,相对标准偏差RSD(n=7)小于7.2%。所建方法能很好的应用于电子电气产品中四溴双酚A的检测。     

The use of the electron capture detector in human and equine doping analysis by gas chromatography

Summary The possibilities, applications and limitations of the electron capture detector (ECD) in human and equine doping analysis are considered. As many stimulants and/or their metabolites possess and amino group the introduction of halogen containing groupings by acylation results in improved chromatographic performance almost combined with enhanced sensitivity and selectivity when using the ECD. Several examples of the confirmation of doping agents like amphetamines, ephedrine, phenylbutazone, pemoline and procaine by GC/ECD are given.Presented at the 7^th International Symposium on Biomedical Applications of Chromatography, Hradec Králové, Czechoslovakia; 6–9 Sept. 1982.     

Determination of nitro aromatic, nitramine, and nitrate ester explosive compounds in explosive mixtures and gunshot residue by liquid chromatography and reductive electrochemical detection

Reductive and oxidative electrochemical detection with liquid chromatography is applied to the determination of nitro aromatics, nitrate esters, nitramines, and diphenylamines in military explosives and single and double base smokeless gunpowders. A sensitive and highly selective method is presented for the detection of organic “gunshot residue” on the hand of individuals who have discharged a weapon. The detection limits at S/N = 3 are of the order of 0.5, 1, 2, and 0.3 picomol for nitro aromatic, nitramine and nitrate ester explosive compounds, and diphenylamines, respectively.     

Rapid determination of acrylamide contaminant in conventional fried foods by gas chromatography with electron capture detector

Gas chromatography coupled with electron capture detector (GC-ECD) was successfully developed and applied for the rapid determination of acrylamide in conventional fried foods, such as potato crisps, potato chips, and fried chicken wings. The method included defatting with n-hexane, extraction with aqueous solution of sodium chloride (NaCl), derivatization with potassium bromate (KBrO3) and potassium bromide (KBr), and liquid-liquid extraction with ethyl acetate. The final acrylamide extract was analyzed by GC-ECD for quantification and by GC-MS for confirmation. The chromatographic analysis was performed on the HP-INNOWax capillary column, and good retention and peak response of acrylamide were achieved under the optimal conditions (numbers of theoretical plates N = 83,815). The limit of detection (LOD) was estimated to be 0.1 microg kg(-1) on the basis of ECD technique. Recoveries of acrylamide from conventional samples spiked at levels of 150, 500 and 1000 microg kg(-1) (n = 4 for each level) ranged between 87 and 97% with relative standard deviations (RSD) of less than 4%. Furthermore, the GC-ECD method showed that no clean-up steps of acrylamide derivative would be performed prior to injection and was slightly more sensitive than the MS/MS-based methods. Validation and quantification results demonstrated that this method should be regarded as a new, low-cost, and robust alternative for conventional investigation of acrylamide.     

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.     

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.     

Determination of polychlorinated biphenyls and organochlorine pesticides in human serum by gas chromatography with micro-electron capture detector

A method for determination of concentrations of polychlorinated biphenyl congeners (PCB-28, 52, 101, 118, 138, 153, 156, and 187) and organochlorine pesticides (hexachlorobenzene, alpha-hexachlorocyclohexane, beta-hexachlorocyclohexane, gamma-hexachlorocyclohexane, delta-hexachlorocyclohexane, p,p'-dichlorodiphenyl dichloroethylene, o,p'-dichlorodiphenyl trichloroethane, p,p'-dichlorodiphenyl dichloroethane, p,p'-dichlorodiphenyl trichloroethane, alpha-chlordane, gamma-chlordane, heptachlor, heptachlor epoxide, and aldrin) in human serum is developed. Recovery is assessed with artificial serum, in which PCBs and OCPs could not be detected. The method is then confirmed with pooled human serum. Experiments are performed by adding two concentrations of analytes (0.5 μg/L and 1.0 μg/L) to both matrices. The sample pretreatment process involves denaturing with a mixture of water-1-propanol (v:v, 85:15), extraction with a C-18 cartridge, and cleanup with an Alumina B cartridge. This process required about 2 mL of serum. The limit of detection ranged from 0.05-0.35 μg/L for all the analytes. Recovery of analytes at low and high spiking concentrations varied from 63-122% and 61-124% for artificial serum and pooled human serum, respectively. Relative standard deviation was lower than 16% and 18% for artificial serum and pooled human serum, respectively. Stability of the method, expressed as relative standard deviation, was lower than 14%. The method has been applied in epidemiological research.     

气相色谱-双柱双电子捕获检测器测定土壤及沉积物中23种有机氯农药

建立了微波萃取,弗罗里硅土固相萃取柱及铜粉除硫净化,双柱双电子捕获检测器(ECD)-气相色谱法(GC)测定5种不同质地土壤及5处不同来源沉积物中的23种有机氯农药(OCPs)。采用内标法定量,在0.005～0.5 mg/L的质量浓度范围内,替代物和各种农药标准品的线性相关系数(r2)均大于0.997。5种土壤及5处沉积物中23种OCPs的平均加标回收率分别为50%～119%和52%～120%,相对标准偏差分别为0.9%～16.1%(n=6)和0.3%～28.4%(n=6),检出限为0.00005～0.0005 mg/kg。结果表明,该方法重现性好、灵敏度高、线性关系好,可以满足简便、快速、准确测定农药残留的要求,可大范围推广使用。     

Risk assessment,dissipation behavior and persistence of quinalphos in/on green pea by gas chromatography with electron capture detector

Chemical investigation was carried out to examine the risk assessment, dissipation behavior, persistence, and half‐life period of quinalphos in/on green pea fruit by spraying quinalphos at fruiting stage followed by another application after 10‐day interval. The samples were extracted by using the quick, easy, cheap, effective, rugged, and safe method, and the residues of quinalphos were analyzed by gas chromatography with electron capture detector. Herein, we report a novel, accurate, and cost‐effective gas chromatography method for the determination of average deposits of quinalphos in/on green pea. The initial deposits and half‐life of quinalphos were found to be 1.20 mg/kg and 2.77 days, respectively, following the application of insecticide. Residues of quinalphos reached below detection limit of 0.05 mg/kg after 10 days at recommended dosage. For risk assessment studies, the tenth day will be safe for consumers for consumption of green pea. The developed method is simple, selective, and repeatable, and it can be extended for quinalphos‐based standardization of herbal formulations containing green pea and its use in pesticide industries.