Determination of higher aliphatic amines and cyclohexylamine by TLC after derivatization with 1-fluoro-2,4-dinitrobenzene

Summary Higher aliphatic amines and cyclohexylamine find use on a large scale as inhibitors of corrosion in power stations and in installations for drawing and storing natural gas in underground containers. The determination of active constituents of the inhibitors at the individual technological steps, very important for assessing the efficacy of the anticorosive protection, is complicated by other compounds accompanying the trace amounts of the amines being monitored. This circumstance makes it necessary to use selective methods based on the derivatization of the primary amino group and formation of intensively UV-VIS absorbing or fluorescent derivatives.These demands are met by the detection with ninhydrine [1, 2] or TLC of 2,4-dinitrophenyl-[3,4] or 3,5-dinitrobenzoyl-[5] amine derivatives. We applied a modified derivatization procedure with 1-fluoro-2,4-dinitrobenzene as UV label [6], well known as Sanger's reagent originally developed for the labeling of amino acids and peptides [7]. This reagent forms with amines intensively absorbing N-alkyl-2,4-dinitroaniline derivatives which can be easily separated by TLC.     

Determination of 4-alkylphenols by novel derivatization and gas chromatography-mass spectrometry

A simple and sensitive method for the determination of alkylphenols in water samples has been developed using gas chromatography-mass spectrometry. Alkylphenols were determined after the extractive derivatization with pentafluoropyridine. The derivatization of alkylphenols efficiently proceeded to give the corresponding 4-tetrafluoropyridyl derivatives under the biphasic reaction system. The derivatization conditions including the phase-transfer catalyst, the amount of pentafluoropyridine, the reaction time, the concentration of NaOH and organic solvent were optimized. On the mass spectra of these derivatives, intense specific ion peaks were observed: m/z 256 for 4-n-alkylphenols and m/z 284 for 4-tert.-alkylphenols. Calibration curves were linear in the range of 20-1000 ng/l (200-10,000 ng/l for nonylphenol), and the detection limits varied between 6.93 and 15.7 ng/l (85.2 ng/l for nonylphenol). The average recoveries of the alkylphenols in a fortified river water sample (100 ng/l except for nonylphenol: 1000 ng/l) ranged from 91.1 to 112%. The relative standard deviations were found to be between 5.6 and 16%. This method was successfully applied to the determination of alkylphenols in river water.     

醋酸酐衍生-气相色谱-质谱联用测定葡萄酒中的糖醇

建立了先采用醋酸酐衍生然后用气相色谱-质谱联用仪检测葡萄酒中糖醇的方法。在葡萄酒中加入吡啶涡旋混合均匀,以5000 r/min (4℃)离心10 min。取上清液过有机滤膜,加入吡啶、醋酸酐衍生。加无水硫酸钠吸水后,经DB-5MS毛细管气相色谱柱分离,在选择离子监测(SIM)模式下进行检测。各目标物在0.019~1.25 mg/L (乳糖醇在0.039~2.50 mg/L)范围内线性关系良好,相关系数(r²)均大于0.99。赤藓糖醇、木糖醇、甘露糖醇、山梨糖醇、半乳糖醇和乳糖醇的定量限(信噪比(S/N)=10)分别为0.17、0.29、0.43、0.46、0.47和2.88 mg/L;检出限(S/N=3)分别为0.05、0.08、0.13、0.14、0.14和1.38 mg/L。在40 mg/L和80 mg/L加标水平下,6种糖醇在葡萄酒基质中的回收率为80.15%~108.75%,相对标准偏差(RSD)为2.16%~6.97%。该方法的灵敏度、准确度和精密度均符合相关的技术要求,适合于葡萄酒中糖醇含量的快速检测。     

气相色谱-质谱法测定水中痕量的四乙基铅

建立了气相色谱-质谱(GC-MS)测定水中痕量四乙基铅的分析方法。用正己烷萃取水样中的四乙基铅,萃取液浓缩后加入同位素内标萘-d8,采用GC-MS选择离子方式(SIM)进行检测,在200 mL水样中四乙基铅的检出限可达0.04 μg/L;添加回收率为92.2%～103%,准确度好;平行5次测定的相对标准差为4.4%～13.3%。结果表明: 方法简便、快速、准确、实用,可用于水中痕量四乙基铅的测定。     

Determination of neurotoxin 3-N-oxalyl-2,3-diaminopropionic acid and non-protein amino acids in Lathyrus sativus by precolumn derivatization with 1-fluoro-2,4-dinitrobenzene

A rapid and simple method is presented for determining neuro-excitatory nonprotein amino acid 3-N-oxalyl-2,3-diaminopropionic acid (beta-ODAP) and non-protein amino acids in Lathyrus sativus. Seed and foliage extracts of Lathyrus sativus were treated with 1-fluoro-2,4-dinitrobenzene (FDNB) and a reversed-phase high-performance liquid chromatography method (RP HPLC) for the separation of the derivatives in the pmol range is reported. The RP HPLC method and a colorimetric method were compared for measuring ODAP.     

基于巯基化衍生的气相色谱-质谱法测定有机相及水相中氯化氰

氯化氰(ClCN)是常用的化工中间体,也是《禁止化学武器公约》附表颁布的化学毒剂之一.采用传统的比色法或气相色谱法对ClCN进行分析时,稳定性差且检出限高.研究建立了有机相及水相中ClCN的巯基化衍生过程及气相色谱-质谱(GC-MS)的检测方法.经比较后选择1-丁基硫醇作为衍生试剂,有机相中ClCN的衍生条件为衍生温度...     

Determination of chlorine dioxide in water by gas chromatography-mass spectrometry

A sensitive gas chromatographic method has been established for the determination of chlorine dioxide in water. With weak basic conditions (pH 9.0), chlorine dioxide reacts with iodide to form iodine, which reacts with 2,6-dialkylphenol to form 4-iodo-2,6-dialkylphenol. The volatile organic derivative was extracted with ethyl acetate, and then measured by gas chromatography-mass spectrometry (GC-MS). The reaction of the active proton of 2,6-dialkylphenols (2,6-dimethylphenol, 2,6-di-isopropylphenol and 2,6-di-tert-butylphenol) with iodine was tested, and compared to each other in terms of reactivity and stability of the derivatives. 2,6-dimethylphenol showed rapid reaction with iodine, and its derivative was stable for 2 weeks. The detection limit of chlorine dioxide in water was about 1.0 ng/mL, and the calibration curve showed good linearity with r2 = 0.998. The existent concentration of chlorine dioxide in water was calculated from multiplying the concentration calculated from the calibration curve of 4-iodo-2,6-dimethylphenol by 0.544. The method was sensitive, reproducible and simple enough to permit the reliable analysis of chlorine dioxide at the low ng/mL level in water.     

Determination of naphthalenesulfonic acid isomers by large-volume on-line derivatization and gas chromatography-mass spectrometry

This work presents a modified method to analyze polar and water-soluble naphthalene monosulfonic acid (NS) isomers in industrial effluents and river water samples. The method involves extraction of samples by a styrene-divinylbenzene copolymer solid-phase extraction cartridge, and on-line derivatization in the GC injection port using a large-volume (10 microl) sample injection with tetrabutylammonium salts. The analytes were then identified and quantitatively determined by GC-MS. The large-volume injection-port derivatization technique provides sensitivity, fast and reproducible results for NS isomers, to quantitation at 0.05 microg/l in 200 ml of water sample. Enhanced extracted mass chromatograms of molecular ion and [M-56]+ ion of butylated NS isomers by electron impact ionization MS allows us to determine residues at trace levels in environmental samples. Recoveries of the NS isomers in spiked water samples ranged from 70 to 82% with RSDs around 10%. Naphthalene-2-sulfonic acid was found as a major pollutant and propagated in surface water and industrial effluents.     

Estimation of residues of carbofuran and its metabolites in sugarcane and soil by derivatization with 1-fluoro-2,4-dinitrobenzene and gas chromatography with nitrogen-phosphorus detection

Residues of carbofuran and its metabolites were studied in sugarcane plants and soil after application at 1 and 2 kg/ha. The residues of carbofuran and its metabolites were extracted by refluxing with 0.25N HCI, partitioned into dichloromethane, and cleaned up on acidic alumina. The respective 7-phenols of carbofuran, 3-ketocarbofuran, and 3-hydroxycarbofuran were destroyed by treatment with ceric ammonium sulfate, and the residues were derivatized with 1-fluoro-2,4-dinitrobenzene. The derivatives were estimated by gas chromatography with nitrogen-phosphorus detection. The concentration of 3-hydroxycarbofuran in sugarcane plants remained higher and persisted longer than that of the parent compound. Carbofuran-derived residues were not detected in cane juice. Soil samples were found to contain only carbofuran, which declined at a very fast rate that followed a first-order kinetics rate of reaction.     

硝基氟苯柱前衍生HPLC测定减肥药中芬氟拉明

诺贝尔奖获得者F．sange使用2,4-二硝基氟苯(DNFB)确定了蛋白质中氨基酸排列次序以来,DNFB常用作为胺类化合物的衍生试剂。在碱性溶液中,DNFB与胺反应生成强紫外吸收的硝基苯胺类化合物。芬氟拉明(Fenfluramine,FFA)化学名为N-乙基-α-甲基-3-三氟甲基苯乙胺,属苯乙胺类食欲抑制剂,对人体健康有潜在危害。HPLC分析FFA的报道,检测限仅为20．6ng。本文用DNFB为衍生试剂,研究衍生化条件,色谱分析检测限降至1．02ng。     

Determination of chloropropanols in foods by one-step extraction and derivatization using pressurized liquid extraction and gas chromatography-mass spectrometry

3-Chloropropane-1,2-diol (3-MCPD) and 1,3-dichloro-2-propanol (1,3-DCP) were determined for the first time in bakery foods using pressurized liquid extraction (PLE) combined with in situ derivatization and GC-MS analysis. This one-step protocol uses N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) as silylation reagent. Initially, screening experimental design was applied to evaluate the effects of the variables potentially affecting the extraction process, namely extraction time (min) and temperature (°C), number of cycles, dispersant reagent (diatomaceous earth in powder form and as particulate matter with high pore volume Extrelut NT) and percent of flush ethyl acetate volume (%). To reduce the time of analysis and improve the sensitivity, derivatization of the compounds was performed in the cell extraction. Conditions, such as the volume of BSTFA, temperature and time for the in situ derivatization of analytes using PLE, were optimized by a screening design followed to a Doehlert response surface design. The effect of the in-cell dispersants/adsorbents with diatomaceous earth, Florisil and sodium sulfate anhydrous was investigated using a Box-Behnken design. Using the final best conditions, 1 g of sample dispersed with 0.1 g of sodium sulfate anhydrous and 2.5 g diatomaceous earth was extracted with ethyl acetate. 1 g of Florisil, as clean-up adsorbent, and 70 μL of BSTFA were used for 3 min at 70°C. Under the optimum conditions, the calibration curves showed good linearity (R(2)>0.9994) and precision (relative standard deviation, RSD≤2.4%) within the tested ranges. The limits of quantification for 1,3-DCP and 3-MCDP, 1.6 and 1.7 μg kg(-1), respectively, are far below the established limits in the European and American legislations. The accuracy, precision, linearity, and limits of quantification provided make this analytical method suitable for routine control. The method was applied to the analysis of several toasted bread, snacks, cookies and cereal samples, none of which contained chloropropanols at concentrations above the legislation levels.     

Study of the derivatization of n-alkylamines with 1-fluoro-2,4-dinitrobenzene in the presence of aqueous cetyltrimethylammonium bromide micelles

The use of aqueous cetyltrimethylammonium bromide micelles in the derivatization of n-alkylamines with 1-fluoro-2,4-dinitrobenzene was investigated systematically. The rate constants of derivatization of the n-alkylamines (C1-C8) were analysed using liquid chromatography. Up to butylamine the micellar rate enhancement depends on the electrostatic interactions between the amines and cetyltrimethylammonium bromide, and beyond C4 it depends mainly on the hydrophobic interactions. The reaction rates are also enhanced by a micelle-induced decrease of the pKa of the amines, but to a lesser extent. The derivatization rates for the longer alkylamines are comparable with those in dipolar aprotic solvents. Pharmaceutical and biomedical science is likely to benefit from the use of micellar systems in pre-column derivatization reactions in aqueous solutions.     

Determination of iodide by derivatization to 4-iodo-N,N-dimethylaniline and gas chromatography-mass spectrometry

A real-time determination of iodide is proposed which involves the oxidation of iodide with 2-iodosobenzoate in the presence of N,N-dimethylaniline. The reaction is completed within 1 min to yield 4-iodo-N,N-dimethylaniline, which is extracted in cyclohexane and determined by GC-MS. It was also possible to determine iodine by derivatization in the absence of 2-iodosobenzoate, and iodate by its reduction with ascorbic acid to iodide and subsequent derivatization. A rectilinear calibration graph was obtained for 0.02-50 micrograms l-1 iodide with a correlation coefficient of 0.9998. The limit of detection was 8 ng l-1 iodide. The method was applied to the determination of iodate in iodized table salt and free iodide and total iodine in sea-water, and to spiked samples when the recovery was in the range 96.8-104.3% (RSD 1.9-3.6%). A sample clean-up by solid-phase extraction with a LiChrolut EN cartridge is proposed.     

Optimization of an HPLC method for determination of gabapentin in dosage forms through derivatization with 1-fluoro-2,4-dinitrobenzene

A rapid, sensitive and accurate high performance liquid chromatography with UV detection method was developed and validated for the quantification of gabapentin in dosage forms. Gabapentin was quantified after pre-column derivatization with 1-fluoro-2,4-dinitrobenzene. Amlodipine was used as an internal standard. The chromatographic separation was carried out on a Nova-Pak C(18) column using a mixture of acetonitrile-sodium dihydrogenphosphate (pH 2.5; 0.05 M) (70:30, v/v) as mobile phase with UV detection at 360 nm. The method was linear over the range of 10-500 microg/ml of gabapentin (r(2)>0.999). The within-day and between-day precision values were in the range of 0.86-1.11%. The method was successfully used for quantitative determination and dissolution rate study of Neurontin capsules.     

Determination of low-molecular-weight dicarboxylic acids in atmospheric aerosols by injection-port derivatization and gas chromatography-mass spectrometry

A rapid and environmental-friendly injection-port derivatization with gas chromatography-mass spectrometry (GC-MS) method was developed to determine selected low-molecular weight (LMW) dicarboxylic acids (from C2 to C10) in atmospheric aerosol samples. The parameters related to the derivatization process (i.e., type of ion-pair reagent, injection-port temperature and concentration of ion-pair reagent) were optimized. Tetrabutylammonium hydroxide (TBA-OH) 20 mM in methanol gave excellent yield for di-butyl ester dicarboxylate derivatives at injection-port temperature at 300 °C. Solid-phase extraction (SPE) method instead of rotary evaporation was used to concentrate analytes from filter extracts. The recovery from filter extracts ranged from 78 to 95% with relative standard deviation (RSD) less than 12%. Limits of quantitation (LOQs) ranged from 25 to 250 pg/m³. The concentrations of di-carboxylated C2-C5 and total C6-C10 in particles of atmospheric aerosols ranged from 91.9 to 240, 11.3 to 56.7, 9.2 to 49.2, 8.7 to 35.3 and n.d. to 37.8 ng/m³, respectively. Oxalic acid (C2) was the dominant LMW-dicarboxylic acids detected in aerosol samples. The quantitative results were comparable to the results obtained by the off-line derivatization.     

Determination of anti-inflammatory drugs in water samples, by in situ derivatization, solid phase microextraction and gas chromatography-mass spectrometry

In this work, the reactions of various copper ions with 1,3,3-trimethyl-2-[5-(1,3,3-trimethyl-1,3-dihydro-indol-2-ylidene)-penta-1,3-dienyl]-3H-indolium--more commonly known as dimethylindodicarbocyanine polymethyne dye (DIDC)--as well as the application of the results obtained for the development of a spectrophotometric method for the determination of Cu(I), Cu(II) and Cu(III) are described. Cu(I) and Cu(II) in the presence of chloride ions and DIDC reagent are extractable by a variety of organic solvents. It is important to emphasize that Cu(I) was extracted under considerably different experimental conditions than Cu(II). The optimum conditions for the extraction of the Cu ion associates with DIDC by amyl acetate and the determination of Cu(I) and Cu(II) were found to be: pH 3-5 and pH 3-6 and chloride concentrations of 0.5-0.8 mol L(-1) and 3-6 mol L(-1) for Cu(I) and Cu(II), respectively. The molar absorptivities for Cu(I) and Cu(II) are 1.8x10(5) L mol(-1) cm(-1) and 1.2x10(5) L mol(-1) cm(-1), respectively. A reaction mechanism is suggested. Cu(III) does not extract in the presence of chloride ions. However, Cu(III) is a strong oxidative agent which can cause the decolourisation of the DIDC reagent. The optimum conditions for Cu(III) determination were found to be: 2x10(-5) mol L(-1) DIDC; pH 8; water:acetone 4:1 medium. The developed procedures were tested for the determination of Cu(I), Cu(II) and Cu(III) in semiconductor samples.     

Full automatic determination of chlorophenols in water using solid-phase microextraction/on-fiber derivatization and gas chromatography-mass spectrometry

A fully automated combination of solid-phase microextraction and on-fiber derivatization coupled with gas chromatography-mass spectrometry was developed to determine 17 chlorophenols in aqueous samples. Optimal parameters for the automated process, such as fiber coating (polyacrylate), derivatization reagent (N,O-bis(trimethylsilyl) trifluoroacetamide), extraction time (60 min), derivatization time (5 min), incubation temperature (35°C), sample pH (3), and ionic strength (300 g L(-1) of NaCl), as well as desorption time (5 min) and desorption temperature (270°C) were established. The whole procedure took only 90 min and was performed automatically. The shortcomings of silylation derivatives, like incompleteness and instability, were overcome by using solid-phase microextraction on-fiber silylation in this study. The results from both pure water and river water samples showed that the method had a good linearity (r(2) = 0.9993-1.0000), ranging from 0.01 to 100 μg L(-1). The related standard deviations were between 3.6 and 10.0%. The limits of detections and qualifications ranged from 0.03 to 3.11 ng L(-1) and 0.09 to 10.4 ng L(-1) for the CPs, respectively. The proposed method is superior to traditional solid phase extraction procedure.