Development of a solid-phase extraction and derivatization method for polar carboxylic acids from aqueous extracts of inorganic multi-component incineration residues

A rapid and reliable GC/MS (EI and CI) method was developed for the identification of short-chain mono- and dicarboxylic acids in complex and strongly alkaline residues of municipal waste incineration. Such residues contain organic carboxylic acids in the mg/kg to μg/kg range, which may contribute to the mobilization of heavy metals. However, the alkalinity and the high salt loads of the matrix were found to be a serious problem in the analysis of short chain acids. Extraction with water, solid phase extraction, and derivatization were studied under these conditions. Solid-phase extraction with polymeric sorbents and derivatization with diazomethane can be combined in a reproducible manner to yield a robust and simple method which can be applied for screening unknown solids due to its wide applicability and the well identifiable methyl esters. Absolute recovery rates varied between 20 and 85% depending on the individual acids.     

Extraction of polar and hydrophobic pollutants using accelerated solvent extraction (ASE)

Accelerated solvent extraction (ASE) shows higher recoveries for PAHs in comparison with traditional Soxhlet extraction, but in a fraction of time and with less solvent consumption. Better recoveries are especially achieved with PAHs of high reactivity, the latter being expressed by the structure-to-count ratio (SCR). To estimate polar pollutants including phenols/benzenediols, the sample was subjected to a combined in-situ derivatization/extraction approach using 2% v/v acetic anhydride in toluene. The main reason for the better recovery obtained in this way, in comparison with the classical ASE approach, is to overcome strong matrix-analyte interactions. Analogously, fatty acids were analyzed as methyl esters obtained by in-situ derivatization/extraction using boron trifluoride. Received: 28 December 1998 / Revised: 16 February 1999 / Accepted: 21 February 1999     

Application of matrix solid-phase dispersion and high-performance liquid chromatography for determination of sulfonamides in honey

A novel method for simultaneous determination of 8 sulfonamide residues (sulfathiazole, sulfapyridine, sulfadiazine, sulfamerazine, sulfamonome-thoxine, sulfachloropyridazine, sulfamethoxazole, and sulfadimethoxine) in honey samples by high-performance liquid chromatography (HPLC) has been developed on the basis of precolumn derivatization with 9-fluorenylmethyl-chloroformate (FMOC-Cl). Sulfonamide residues in honey samples were extracted and purified by matrix solid-phase dispersion with C18 as the solid support. The residues were derivatized by FMOC-CI, and the FMOC-sulfonamide derivatives were further purified by solid-phase extraction with silica gel as the solid support prior to HPLC analysis. The average recoveries for most sulfonamide compounds at different spiking levels (from 10 to 250 microg/kg) were > 70% with relative standard deviations < 16%, and their limits of detection were 4.0 microg/kg. The established analytical method has high sensitivity and repeatability and can be applicable for determining the sulfonamide residues in various honey matrixes.     

Simplified derivatization method for the speciation analysis of organolead compounds in water and peat samples using in-situ butylation with tetrabutylammonium tetrabutylborate and GC-MIP AES

A simplified derivatization method for the speciation analysis of organolead compounds in environmental samples followed by gas chromatography-microwave induced plasma atomic emission detection is developed. An in-situ butylation using tetrabutylammonium tetrabutylborate in an acetate buffer medium of pH 4.0 with simultaneous extraction of the derivatized organolead species into hexane was performed; for the analysis of the peat samples, the desorption of the different species from the matrix by acid leaching was also included. Detection limits at the sub-ng L^–1 range, comparable to those achieved by Grignard-alkylation, were obtained for the different species. The accuracy of the method was confirmed by analysis of a standard reference material (BCR-CRM 605, road dust). Examples of applications for the analysis of tap water and peat are given. Received: 16 February 1998 / Revised: 25 May 1998 / Accepted: 29 May 1998     

Simplified derivatization method for the speciation analysis of organolead compounds in water and peat samples using in-situ butylation with tetrabutylammonium tetrabutylborate and GC-MIP AES

A simplified derivatization method for the speciation analysis of organolead compounds in environmental samples followed by gas chromatography-microwave induced plasma atomic emission detection is developed. An in-situ butylation using tetrabutylammonium tetrabutylborate in an acetate buffer medium of pH 4.0 with simultaneous extraction of the derivatized organolead species into hexane was performed; for the analysis of the peat samples, the desorption of the different species from the matrix by acid leaching was also included. Detection limits at the sub-ng L^–1 range, comparable to those achieved by Grignard-alkylation, were obtained for the different species. The accuracy of the method was confirmed by analysis of a standard reference material (BCR-CRM 605, road dust). Examples of applications for the analysis of tap water and peat are given. Received: 16 February 1998 / Revised: 25 May 1998 / Accepted: 29 May 1998     

Analytical selenoamino acid studies by chromatography with interfaced atomic mass spectrometry and atomic emission spectral detection

Consumption of selenium enriched plants or yeast-based nutritional supplements has been reported to provide anticarcinogenic benefits which are selenium compound dependent. Separation and identification of these selenium compounds is critical to understand the activity. Plants and yeast convert inorganic selenium in the soil or growth media into organoselenium compounds, probably following a route similar to the sulfur assimilatory pathway. Non-volatile selenium compounds produced include selenoamino acids, some of which have shown anticarcinogenic activity. Volatile compounds produced by chemical reaction of involatile precursors have also been found. An ion pair chromatographic method with ICP-MS detection for the separation of selenoamino acid standards potentially present in real samples is given. The method allows separation of selenoamino acids including such analytes as the cis-trans isomers of Se-1-propenyl-dl-selenocysteine. The method also provides the capability of determining the presence of selenoxides and possibly selenones, and tracking of other functionalities and reactions by selective derivatization. Alternatively, selenoamino acids are treated with ethylchloroformate to produce stable volatile derivatives which are amenable to GC separation with element specific atomic emission detection (GC-AED). Results of total selenium determination and speciation of selenium enriched yeast-based nutritional supplements, selenium enriched allium vegetables and bioremediation samples are presented. Received: 16 February 1998 / Revised: 4 June 1998 / Accepted: 9 June 1998     

Determination of methylmalonic acid and glutaric acid in urine by aqueous-phase derivatization followed by headspace solid-phase microextraction and gas chromatography-mass spectrometry

In this work, a novel technique of aqueous-phase derivatization followed by headspace solid-phase microextraction and gas chromatography-mass spectrometry was developed for the determination of organic acids in urine. The analytical procedure involves derivatization of organic acids to their ethyl esters with diethyl sulfate, headspace sampling, and GC/MS analysis. The proposed method was applied to the determination of methylmalonic acid and glutaric acid in urine. The experimental parameters and method validation were studied. Optimal conditions were obtained: PDMS fiber, extraction temperature 55 degrees C, extraction time 30 min, and 60 microL of diethyl sulfate as derivatization reagent with 2 mg of the ion pairing agent tetrabutylammonium hydrogensulfate. The method was linear over three orders of magnitude, and detection limits were 21 nM for methylmalonic acid and 34 nM for glutaric acid, respectively. Consequently, in-situ derivatization/HS-SPME/GC/MS is an alternative and powerful method for determination of organic acids as biomarkers in biological fluids.     

柱前衍生-超高效液相色谱-串联四极杆质谱法测定茶叶中乙撑硫脲的残留

建立了茶叶中乙撑硫脲残留的柱前衍生-超高效液相色谱-串联四极杆质谱检测方法。样品采用乙腈提取,提取液经QuEChERS基质分散固相萃取净化后采用9-芴基甲基氯甲酸酯（FMOC-CL）柱前衍生;衍生溶液经BEH-C18色谱柱（100 mm×2.0 mm,1.7 μm）分离后进入串联四极杆质谱仪检测,采用同位素内标法定量;流动相为0.1%（v/v）甲酸-乙腈。该方法对茶叶样品检出限为1.3 μg/kg,定量限为4.2 μg/kg;加标回收率在97.7%~107.5%之间,相对标准偏差（RSD,n=6）在2.1%~10.0%之间;在1.0~203.4 μg/L范围内线性回归系数r为0.9993。该方法灵敏度高,重现性好,定性定量准确,可有效满足对茶叶中乙撑硫脲残留检测的要求。     

微波消解衍生化气相色谱-质谱法测定鲨鱼软骨中的脂肪酸

 研究了用微波技术消解衍生化气相色谱 质谱法 (GC MS)快速测定鲨鱼软骨中脂肪酸的分析方法。用正交设计试验优化消解衍生化条件 ,以盐酸 甲醇 (体积比为 1∶4)体系作消解衍生化溶液 ,在 60 0W微波功率作用下加热 4min进行样品的前处理 ,将样品的消解、脂肪酸的衍生化及脂肪酸甲酯的萃取融于一体。方法具有灵敏度高、省时、省试剂、操作方便等特点。该法适用于大批量固体样品中脂肪酸的测定。     

Effect of background derivatization on the signal enhancement of pesticide residues extracted from edible oils

The effect of background derivatization on the signal enhancement of pesticide residues extracted from edible oil samples was studied by GC with negative chemical ionization MS. The analytes were extracted by a solvent extraction process, and the extract was subjected to rapid low‐temperature fat precipitation. The residual fatty acids were silylated by derivatization with N,O‐bis(trimethylsilyl)trifluoroacetamide. The chromatograms obtained from the derivatized samples showed higher signal intensity and lower detection levels when compared to the direct analysis without derivatization. The sensitivity levels of the method are either better or comparable to that of previously reported methodologies. The LODs of the analyzed organochlorine, organophosphorus, and synthetic pyrethroid residues in sunflower, rice bran, and ground oil samples were in the range of 0.02–0.5 ng/g, and the LOQs were in the range of 0.1–2 ng/g. The intraday and interday accuracies were in the range of 81–116% with RSDs less than 14%. The recoveries obtained were in the range of 53–89% with the RSD values less than 13% for all the studied pesticide residues.     

气相色谱-质谱法同时检测动物组织中多种激素类兽药的残留量

建立了不同动物基质(肌肉、肝脏、肾脏)中己烷雌酚、己烯雌酚、己二烯雌酚、还原尿睾酮、表睾酮、雌酮、雌二醇、炔雌醇和雌三醇激素残留量的气相色谱-质谱联用(GC-MS)检测方法。以乙腈为提取溶剂,固相萃取柱净化,微波辅助衍生化,用双(三甲基硅烷基)三氟乙酰胺(BSTFA)与甲基氯硅烷(TMCS)(体积比为99 :1)的硅烷化试剂在吡啶存在下进行衍生化反应。实验结果表明,9种激素的检出限为0.1～1 μg/kg。3种动物基质中9种激素的平均回收率为68.8%～93.1%,实验室内相对标准偏差(RSD)为4.1%～22.3%,实验室间RSD为3.1%～17.9%。方法的技术指标满足动物组织中激素类兽药残留分析的要求。     

Analysis of fatty acids in lung tissues using gas chromatography-mass spectrometry preceded by derivatization-solid-phase microextraction with a novel fiber

In this article, a laboratory-made sol-gel derived fiber with butyl methacrylate/hydroxy-terminated silicone oil (BMA/OH-TSO) coating was first used for headspace solid-phase microextraction (HS-SPME) of medium and long chain fatty acids after derivatization and applied to the analysis of fatty acids in lung tissues by coupling to gas chromatography-mass spectrometry (GC-MS). The experimental parameters for derivatization, HS-SPME and desorption were optimized. Fatty acids in cancerous lung tissues from five patients with lung cancer were determined under the optimized conditions. Normal lung tissues from the same five patients were used as controls. This fiber showed higher extraction efficiency for fatty acids after derivatization when compared with commercial polydimethylsiloxane (PDMS) and polydimethylsiloxane-divinylbenzene (PDMS/DVB) fibers due to the three-dimensional network in the coating. The method presented in this paper showed satisfactory precision, accuracy, linearity and limits of detection (LODs). The relative standard deviation values were below 13.3% (n = 5) and the recoveries obtained ranged from 76.35% to 107.0%. The results obtained using the SPME method were also compared with those got by using liquid-liquid extraction (LLE) technique. It was found that the sensitivity could be enhanced by the SPME method. The analysis of the cancerous lung tissues and normal controls from five patients with lung cancer indicated that the main components of lung tissue were palmitic acid (C_16:0), stearic acid (C_18:0) and lignoceric acid (C_24:0). A comparison between the levels of the fatty acids in cancerous lung tissues and normal controls from the same a patient with lung cancer shows that most of the saturated fatty acids showed higher levels in cancerous lung tissues, while unsaturated fatty acids showed higher levels in normal controls on the whole.     

An internal surface reversed phase column for the effective removal of humic acid interferences in the trace analysis of mecoprop in soils with coupled-column RPLC-UV

In the development of a screening method for the determination of residues of mecoprop in soils involving coupled-column RPLC-UV (228 nm) the cleanup performance of a 5 μm GFF-II internal surface reversed phase (ISRP, Pinkerton) analytical column (50 × 4.6 mm I.D.) as a first column was investigated. In comparison to an analytical C18 column the ISRP column substantially improved the separation between acidic analyte and co-extracted humic substances. Under the selected coupled-column conditions soil extracts obtained after hydrolysis with an aqueous alkaline solution, acidifying and centrifugation could be analyzed directly allowing the determination of mecoprop in soils to a level of about 0.02 mg/kg. A rapid concentration step on a 100 mg C18 solid phase extraction (SPE) cartridge was adopted into the procedure providing a limit of detection (S/N = 3) of 0.01 mg/kg of mecoprop in soil. The method was validated by analyzing freshly spiked soil samples and samples with aged residues. In case of freshly spiked samples the overall recovery was 87% (n = 18, spiked level 0.02–8.0 mg/kg) with a repeatability of 6.8% and a reproducibility of 8.3%. No significant decrease of the recovery was observed for samples with aged residues (n = 15, spiked level 0.1 and 8.0 mg/kg) during a storage of 29 days in the refrigerator at about 4 °C; a storage of 67 days provided a mean recovery of 76% (n = 14, spiked level 8.0 mg/kg). Received: 4 May 1998 / Revised: 11 July 1998 / Accepted: 18 July 1998     

Determination of volatile organic acids in oriental tobacco by needle-based derivatization headspace liquid-phase microextraction coupled to gas chromatography/mass spectrometry

A method coupling needle-based derivatization headspace liquid-phase microextraction with gas chromatography-mass spectrometry (HS-LPME/GC-MS) was developed to determine volatile organic acids in tobacco. The mixture of N,O-bis(trimethylsilyl)trifluoroacetamide and decane was utilized as the solvent for HS-LPME, resulting that extraction and derivatization were simultaneously completed in one step. The solvent served two purposes. First, it pre-concentrated volatile organic acids in the headspace of tobacco sample. Second, the volatile organic acids extracted were derivatized to form silyl derivatives in the drop. The main parameters affecting needle-based derivatization HS-LPME procedure such as extraction and derivatization reagent, microdrop volume, extraction and derivatization time, and preheating temperature and preheating time were optimized. The standard addition approach was essential to obtain accurate measurements by minimizing matrix effects. Good linearity (R(2)> or =0.9804) and good repeatability (RSDs< or =15.3%, n=5) for 16 analytes in spiked standard analytes sample were achieved. The method has the additional advantages that at the same time it is simple, fast, effective, sensitive, selective, and provides an overall profile of volatile organic acids in the oriental tobacco. This paper does offer an alternative approach to determine volatile organic acids in tobacco.     

GC–MS analysis of organic acids in rat urine: A protocol of direct ultrasound-assisted derivatization

The aim of the present study was to develop a novel ultrasound-assisted derivatization method for analysis of urine that can be used for preliminary screening and monitoring of metabolic disorders. Here we describe an ultrasound-assisted derivatization method followed by GC–MS analysis to quantify 26 organic acids in urine. The optimum levels of the variables affecting the yield of derivatization were investigated, including urease doses, derivatization reagents and derivatization conditions (duration time, reaction temperature and sonic power). The method exhibited the best results with 80 μl urease. The optimal reaction conditions were 100 μl BSTFA, 80% ultrasound power, 70°C and 40 min. This method showed satisfactory linearity, good reproducibility and an acceptable limit of detection and accuracy. Therefore, it could potentially be used to as a standard method to enable comparisons between laboratories. Finally, we applied our method to urine samples from pregnant rats administered 2 or 10 mg/kg folic acid supplementation.     

Fast,sensitive and highly discriminant gas chromatography–mass spectrometry method for profiling analysis of fatty acids in serum

A method for the determination of fatty acids in serum based on GC–MS (micro-SIS detection mode) has been developed and the separation and cis/trans isomers have been identified. A prior two-step extraction/derivatization procedure accelerated by ultrasound allows individual determination of esterified (EFAs) and non-esterified fatty acids (NEFAs), and shortening of the derivatization steps to 5 min for EFAs and 15 min for NEFAs. The total analysis time for 39 fatty acids was 61 min. The minimum LOD and LOQ values were 0.002 and 0.006 μg/ml, respectively. The proposed method was validated for EFAs and NEFAs using two different methods and the results show no statistical differences between the proposed method and those used as reference. The proposed derivatization–extraction methodology is suitable for fatty-acid analysis of human serum, and can be applied to nutritional and epidemiological studies.     

Determination of phosmet and its metabolites in olives by matrix solid-phase dispersion and gas chromatography-mass spectrometry

An accurate method based on matrix solid-phase dispersion (MSPD), and gas chromatography-mass spectrometry (GC/MS) was developed for determination of phosmet residues and its metabolites (phosmet-oxon, phthalimide, N-hydroxymethylphthalimide, and phthalic acid) in olive fruits. After testing different sorbents and eluents for MSPD extraction, C₁₈ and acetonitrile were found to be the most appropriate for clean-up of the samples, in terms of yields and efficient removal of interfering compounds. All analytes were determined in selective ion monitoring (SIM) mode following a derivatization step with N,O-bis-trimethylsilyltrifluoroacetamide (BSTFA) containing 1% of trimethylchlorosilane (TMCS), except for phosmet and phosmet-oxon which were analyzed directly. The method showed suitable linearity (correlation coefficients higher than 0.8919 for all the compounds) and suitable sensitivity (limit of detection lower than 0.06 mg/kg). It was successfully applied in the analysis of olive fruits collected during the preharvest interval and olive oil. Phosmet residues found in all samples were lower than the maximum residue limits established by legislation (2 mg/kg).     

Determination of the plasticizer N-butylbenzenesulfonamide and the pharmaceutical Ibuprofen in wastewater using solid phase microextraction (SPME)

A rapid, inexpensive and solvent-free method for the simultaneous determination of the polyamide plasticizer N-butylbenzenesulfonamide (NBBS) and the widely used pharmaceutical Ibuprofen by solid phase microextraction (SPME) combined with gas chromatography/mass spectrometry (GC/MSD) in wastewater samples was developed. Besides the optimized analytical conditions, results of investigations with varying analytical parameters are reported. Problems, which may occur during the analytical procedure (e.g. salt deposits, adsorption phenomena, carry-over), are discussed. For the determination of Ibuprofen, it is important to carry out the extraction under acidic conditions with sufficiently buffered samples; the GC/MSD system must be very clean and well maintained. SPME allows an extraction of Ibuprofen without derivatization of its carboxylic group. For quantification in complex matrices, the standard addition technique is necessary. Limit of detection and limit of determination are 0.1 μg/L for both analytes. NBBS and Ibuprofen were detected in several raw and treated wastewater samples from municipal wastewater treatment plants in the range from < 0.1 to 3.5 μg/L. Received: 13 March 1998 / Revised: 16 June 1998 / Accepted: 19 June 1998     

柱后衍生高效液相色谱法测定虾中14种磺胺类药物残留量

建立了虾中14种磺胺类药物残留量的柱后衍生高效液相色谱检测方法。样品在加入内标物磺胺吡啶后用乙酸乙酯提取,提取液浓缩后用4 mL乙酸乙酯溶解残余物,用盐酸溶液反萃取,正己烷去脂,盐酸溶液经滤膜过滤后,加入乙腈、甲醇和3.5 mol/L乙酸钠溶液（体积比为5：5：20）的混合溶液混匀后,经高效液相色谱分离,用荧光胺衍生试剂进行柱后衍生,荧光检测器检测。采用基质标样添加法绘制标准曲线,内标法定量。对柱后衍生系统参数进行了优化,确定了荧光胺溶液的浓度、流速和反应温度分别为0.2 g/L、0.15 mL/min和50℃。14种磺胺类药物在5~200 μg/L范围内具有良好的线性。磺胺类药物的定量限（LOQ,S/N=10）为1.0~5.0 μg/kg。在1.0~100.0 μg/kg添加水平内,磺胺类药物的平均回收率为77.8%~103.6%,相对标准偏差（RSD）为2.9%~9.1%（n=6）。实验结果表明该方法灵敏、准确,重复性好,适用于虾中磺胺类药物的残留检测。     

Determination of carbaryl in foods by solid-phase room-temperature phosphorimetry

A phosphorimetric solid phase assay is proposed for the determination of the pesticide carbaryl (CBL) at room temperature. CBL was spotted on filter paper together with Tl(I) as heavy metal, and dried for 3 min, after which the diffuse transmitted phosphorescence was measured using two quartz plates to avoid the quenching effect produced by atmospheric oxygen. The linear dynamic range was 0.5–4.0 μg/mL and the detection and quantification limits were 0.09 and 0.31 μg/mL, respectively. The precision of the method, expressed as relative standard deviation, was 2.3% for a sample containing 2.0 μg/mL of CBL. The method was applied to the determination of CBL residues in cereals, potatoes and waters, obtaining recoveries ranging between 92 and 105%. Received: 10 October 1997 / Revised: 2 February 1998 / Accepted: 7 February 1998