SPME 涂层中硅烷化反应机理的研究

建立了SPME 涂层中硅烷化衍生化样品预处理方法,并用于葡萄酒中白黎芦醇的测定.SPME 硅烷化的反应动力学过程研究表明,涂层中硅烷化反应遵循假一级反应动力学,高温条件下硅烷化试剂会破坏极性聚丙烯酯(PA)涂层.     

气相色谱中的衍生试剂及新进展

硅烷化试剂,烷基化试剂,酰基化试剂,缩合反应试剂等是气相色谱中常用的几种主要衍生试剂,本文对这几类常用的衍生试剂及新进展作了较为全面的阐述。     

不同有机体系中3种烷基膦酸类化合物的硅烷化衍生方法研究

应用人工神经网络原理,考察了吡啶-甲苯、乙腈-甲苯和四氢呋喃(THF)3种体系中,温度、时间、衍生化试剂及其用量对甲基膦酸(MPA)硅烷化衍生效率的影响,确定主要影响因素为衍生化试剂及其用量;在此基础上建立了MPA、异丙基膦酸(IPA)和甲基膦酸频哪酯(PMPA)的三甲基硅(TMS)衍生法和特丁基二甲基硅(TBDMS)衍生法;在3种体系中,选用N,O-双(三甲基硅烷基)三氟乙酰胺(BSTFA)或N-甲基-N-叔丁基二甲基硅烷基三氟乙酰胺(MTBSTFA)作衍生化试剂,选用体积分数为10%的衍生化试剂.稳定性实验表明:3种化合物的TBDMS衍生产物均比其TMS衍生产物稳定.采用核磁共振氢去耦磷谱技术(31P{1H} -NMR)对TBDMS衍生法进行了评价,衍生接近完全.     

细胞培养液中多溴联苯醚以及代谢产物的GC-MS/MS测定方法

利用柱前衍生化耦合气相/质谱/质谱(GC/MS/MS),建立了细胞培养液中13种多溴联苯醚(PBDEs)、8种甲氧基化多溴联苯醚(MeO-PBDEs)和5种羟基化多溴联苯醚(HO-PBDEs)的分析方法.采用氯甲酸甲酯作为HO-PBDEs的衍生化试剂,相比传统重氮甲烷作为衍生化试剂的方法,其衍生化时间明显缩短.同时,衍...     

气相色谱-质谱法分析乳制品中的三种乳化剂

运用气相色谱-质谱(GC-MS)联用技术,建立了乳制品中的乳化剂单棕榈酸甘油酯、单油酸甘油酯和单硬脂酸甘油酯分析新方法.乳制品中目标物用二氯甲烷提取,经硅烷化试剂(BSTFA+1％TMCS)进行衍生,对提取及衍生化条件进行了优化.在优化条件下,单棕榈酸甘油酯、单油酸甘油酯和单硬脂酸甘油酯分别在1～20 mg/L、5～1...     

手印残留物质中油脂成分的衍生化气质联用法分析

建立了以二氯甲烷-N,N-二甲基甲酰胺(体积比1 ∶ 1)为提取剂,二十一烷为内标,N-甲基-N-三甲基硅烷基三氟乙酰胺(MSTFA)为衍生化试剂,气质联用(GC-MS)测定手印残留物质中油脂成分的分析方法.系统地考察了该方法的回收率、重复性、检出限(0.5 ng)及线性关系.采用的衍生化试剂MSTFA可在室温下衍生迅速、完全.     

气质联用测定DON和NIV及其衍生方法的比较研究

建立了气相色谱-质谱联用检测单端孢霉烯族B类中的脱氧雪腐镰刀菌烯醇(DON)和雪腐镰刀菌烯醇(NIV)的方法。该方法采用七氟丁酰咪唑(HFBI),三甲基硅烷咪唑(TMSI)-双三甲基硅基乙酰胺(BSA)-三甲基氯硅烷(TMCS)(3∶3∶2,V/V/V)(TBT)两种衍生试剂分别与毒素进行衍生反应后用GC-MS检测。方法的线性范围为4~1 300 mg/mL,RSD≤1.52%。此外,对两种衍生方式进行了比较,指出氟化衍生后检测灵敏度高,而硅烷化衍生不需加热,在室温下即可完成,且生成物稳定。分析应用应根据不同检测要求选择相应的衍生试剂。     

气相色谱-质谱法测定血浆中双氯芬酸钠的含量

提出了应用气相色谱-质谱法测定血浆中双氯芬酸钠含量。血浆样品中双氯芬酸钠经盐酸提取,并加入三甲基硅烷衍生化试剂进行衍生化,所得衍生化产物经萃取、净化后供气相色谱分离及质谱测定。采用选择离子质谱扫描方式,供试品双氯芬酸钠-三甲基硅烷衍生物定量选择离子检测质荷比为m/z367,内标物布洛芬-三甲基硅烷衍生物定量选择离子检测质荷比为m/z263。双氯芬酸钠的线性范围为0.005～5.0mg·mL-1,检出限(3S/N)为0.5μg.L-1。方法回收率在94.6%～97.4%之间,日内、日间相对标准偏差(n=6)均小于5%。     

硅烷化衍生／气相色谱／电子捕获检测水产品中羟基多氯联苯的研究

以贻贝为实验样品,采用正己烷-乙酸乙酯(体积比1:1)为萃取溶剂,超声提取,硫酸、活性硅胶柱净化去除脂质及蛋白干扰物质,以双(三甲基硅烷基)三氟乙酰胺-三甲基氯硅烷(BSTFA-TMCS,体积比 99:1)为衍生试剂对羟基多氯联苯进行硅烷化衍生,确定了最佳衍生参数,并研究了气相色谱/电子捕获检测水产品中羟基多氯联苯的分析条件.研究得出,硅烷化衍生最佳衍生温度为60 ℃,最佳衍生时间为40 min;阴性空白贻贝样品在1、2、4 μg/kg的添加水平下,3-OH-PCB101、4-OH-PCB112、4-OH-PCB106的平均回收率为72% ～84%,RSD为0.4% ～10.6%,检出限为1.0 μg/kg.该方法可用于水产品中羟基多氯联苯的检测.     

硅烷化环糊精和硅烷化聚合物环糊精的衍生物制备及其色谱行为

１引言环糊精作为一种选择性固定相发展十分迅速。天然环糊精熔点高，成膜性差，常将其进行衍生化，但是一般衍生化方法非常繁琐。本文提出一种新的β－环糊精修饰方法，用硅烷化试剂对环糊精进行衍生。此法操作简便，与其它固定液混合制柱，能对异构体进行很好的分离。另外，利用此种方法还制备了硅烷化的低聚环糊精．将这两种硅烷化修饰的环糊精涂渍在硫酸钡改性的毛细管上，获得了高的柱效，对异构体显示了较强的分离能力。２实验部分２．１仪器和试剂５０２气相色谱仪（鲁南化工仪器厂）；ＮＥＹ１００超声振荡器（美国）；ＭＣＴ－１Ａ…     

6-Oxy-(acetyl ethylenediamine) fluorescein, a novel fluorescent derivatization reagent for carboxylic acids and its application in HPLC

A novel fluorescent derivatization reagent for carboxylic acids, 6-oxy-(acetyl ethylenediamine) fluorescein (AEF), was well designed, synthesized, and applied to HPLC. The derivatization reaction with 12 fatty acids, including n-valeric acid (C5), n-hexanoic acid (C6), n-heptanoic acid (C7), n-octanoic acid (C8), n-nonanoic acid (C9), n-decanoic acid (C10), lauric acid (C12), myristic acid (C14), palmitic acid (C16), stearic acid (C18), oleic acid (C18:1), and linoleic acid (C18:2), was completed at 55 degrees C within 40 min. The derivatives of fatty acids were separated on a C18 RP column and detected by fluorescence detection. The LODs attained were 0.4-1.2 nM (S/N of 3). It has been demonstrated that AEF is a prominent derivatization reagent for carboxylic acids which is suitable for HPLC.     

A microfluidic device for the automated derivatization of free fatty acids to fatty acid methyl esters

Free fatty acid (FFA) compositions are examined in feedstock for biodiesel production, as source-specific markers in soil, and because of their role in cellular signaling. However, sample preparation of FFAs for gas chromatography-mass spectrometry (GC-MS) analysis can be time and labor intensive. Therefore, to increase sample preparation throughput, a glass microfluidic device was developed to automate derivatization of FFAs to fatty acid methyl esters (FAMEs). FFAs were delivered to one input of the device and methanolic-HCl was delivered to a second input. FAME products were produced as the reagents traversed a 29 μL reaction channel held at 55 °C. A Design of Experiment protocol was used to determine the combination of derivatization time (T(der)) and ratio of methanolic-HCl:FFA (R(der)) that maximized the derivatization efficiencies of tridecanoic acid and stearic acid to their methyl ester forms. The combination of T(der) = 0.8 min and R(der) = 4.9 that produced optimal derivatization conditions for both FFAs within a 5 min total sample preparation time was determined. This combination of T(der) and R(der) was used to derivatize 12 FFAs with a range of derivatization efficiencies from 18% to 93% with efficiencies of 61% for tridecanoic acid and 84% for stearic acid. As compared to a conventional macroscale derivatization of FFA to FAME, the microfluidic device decreased the volume of methanolic-HCl and FFA by 20- and 1300-fold, respectively. The developed microfluidic device can be used for automated preparation of FAMEs to analyze the FFA compositions of volume-limited samples.     

Spectrofluorometric determination of kynurenic acid with horseradish peroxidase in the presence of hydrogen peroxide.

The catalytic activity of horseradish peroxidase (HRP) in the presence of hydrogen peroxide has been investigated for the fluorescent derivatization of kynurenic acid under conditions with no exposure to light. Non-fluorescent kynurenic acid was converted into a fluorescent compound (Ex: 367 nm, Em: 470 nm) with HRP in the presence of hydrogen peroxide, and the optimum conditions of this fluorescent derivatization were investigated. Moreover, this fluorescent derivatization was developed for a spectrofluorometric determination of trace amounts of kynurenic acid by measuring the fluorescence intensity of the fluorescent compound. The calibration curve obtained was linear from 1.0 to 10.0 nmol of kynurenic acid in a 1.0 mL sample solution. The relative standard deviation at 5.0 nmol of kynurenic acid was 5.71% (n=5). By adjusting the bandwidths for both the excitation and emission to 15 nm, the calibration curve was also linear in the range between 0.1 to 1.0 nmol of kynurenic acid in a 1.0 mL sample solution. This method was applied to the fluorometric determination of trace amounts of kynurenic acid in the control sera.     

High-performance liquid chromatographic determination of valproic acid in plasma using a micelle-mediated pre-column derivatization

A method for the determination of valproic acid (2-propylpentanoic acid) in plasma by high-performance liquid chromatography (HPLC) after pre-column derivatization is described. The derivatization of valproic acid with a fluorophore and UV label, 4-bromomethyl-7-methoxycoumarin, is performed in plasma diluted with an aqueous micellar system. No extraction or solvent evaporation steps are required. The mechanism of the derivatization of the carboxylic acid is based on phase-transfer catalysis. The sample preparation, including the derivatization step, is rapid and very simple. The proposed HPLC-method was evaluated and compared with a standard immunological assay used for the determination of valproic acid in plasma.     

Indirect enantioseparation of alpha-amino acids by reversed-phase liquid chromatography using new chiral derivatizing reagents synthesized from s-triazine chloride

Ten chiral dichloro- and monochloro-s-triazines were prepared by the nucleophilic displacement of chlorine atom(s) in s-triazine chloride and its 6-methoxy derivative with different amino acid amides. Dichloro-s-triazines (DCTs) were used as CDRs for derivatization of alpha-amino acids under basic conditions at room temperature (30 degrees C) while derivatization with monochloro-s-triazine (MCT) reagents was carried out at 80 degrees C. The resultant diastereomers were separated on a reversed-phase C(18) column using mixtures of acetonitrile and aqueous-trifluoroacetic acid (TFA). The separation results for the two were compared. One DCT reagent was optimized for derivatization kinetics with respect to the effects of pH, reagent excess, temperature and reaction time on derivatization yield. In most of the cases, DCT reagents provided better separation of diastereomers in comparison to MCT reagents. One DCT reagent was also validated for limit of detection, linearity, recovery and robustness. Effects of structural modifications in reagents on chromatographic properties were investigated. Separation mechanism of diastereomers was proposed in light of both MCT and DCT reagents.     

Continuous on-line derivatization and selective separation of D-aspartic acid by a capillary electrophoresis system with a continuous sample introduction interface

A rapid and selective method is described for the separation of D-aspartic acid (D-Asp) using a continuous on-line derivatization system coupled to capillary electrophoresis (CE). D-Asp was derivatized using o-phthaldialdehyde/N-acetyl-L-cysteine (OPA/NAC). By on-line derivatization, amino acid enantiomers were automatically and reproducibly converted to the UV-absorbing diastereomer derivatives which were separated by capillary zone electrophoresis (CZE) in the presence of 10 mmol/L beta-cyclodextrin (beta-CD). Under the investigated separation conditions, D-Asp is resolved from L-aspartic acid (L-Asp) and other amino acids in a standard mixture of amino acids. The separation could be achieved within 4 min and the sample throughput rate can reach up to 16 h(-1). The repeatability (defined as relative standard deviation, RSD) was 3.21%, 3.58% with peak area evaluation and 3.72%, 4.03% with peak height evaluation for L-Asp and D-Asp.     

Comparison of Reverse-Phase High-Performance Liquid Chromatographic Methods for Precolumn-Derivatized Amino Acids

Abstract

A comparison was made among five precolumn derivatization techniques for amino acid analysis using reverse-phase high-performance liquid chromatography (HPLC). All chromatographic analyses were conducted using the same instrumentation and a C₁₈ Ultrasphere ODS column (5 μm, 250 × 4.6 mm). The precolumn derivatization methodologies studied included the formation of OPA (o-phthaldialdehyde), DANSYL (dimethylaminonaphthalenesulphonyl), DABSYL (dimethylaminoazobenzenesulphonyl), PTH (phenylthiohydantoin), and PTC (phenylthiocarbamyl) derivatives. The derivatization procedures were evaluated for simplicity, time required, and derivative stability. HPLC analyses of the amino acid derivatives were compared in terms of resolution, sensitivity, reproducibility, and time of analysis.     

Gas chromatographic/mass spectrometric analysis of the essential oil of Houttuynia cordata Thunb by using on-column methylation with tetramethylammonium acetate

This paper describes a simple and novel on-column derivatization procedure used with gas chromatography/mass spectrometry (GC/MS) for the analysis of essential oil of Houttuynia cordata Thunb (HCT), a traditional Chinese medicine. In the procedure, the essential oil was obtained by hydrodistillation, and the fatty acid components were derivatized with tetramethylammonium acetate (TMAA) at 250 degrees C and identified by GC/MS. Methylation improved the determination of both the fatty acids and the other components in the essential oil of HCT. To obtain optimum methylation conditions, several important factors were investigated with pentadecane as the internal standard and a GC inlet temperature of 250 degres C. Tetramethylammonium hydroxide (TMAH) and TMAA were compared as the derivatization agent, and a 2:1 ratio of TMAA to capric acid was evaluated. Fatty acid methyl esters produced good chromatographic peak shapes and did not interfere with the determination of dodecanal and caryophyllene. TMAA is a neutral methylation reagent, and it yielded no side reactions during derivatization. It was found that the fatty acid content of the essential oil was about 81%; among the methylated fatty acids found were capric acid, methyl (43.66%), methyl laurate (16.15%), methyl hexadecanoate (9.27%), undecanoic acid, methyl (5.62%), methyl oleate (1.98%), and methyl linoleate (1.40%). Other major constituents were (-)-beta-pinene (1.02%), beta-myrcene (1.62%), 1-terpinen-4-ol (1.59%), decanal (1.49%), and 2-undecanone (1.47%). The results obtained demonstrated good efficiency for the procedure. Pure chromatograms allowed quantitation, which was obtained by total volume integration. The on-column derivatization procedure was simple to perform, and it improved the sensitivity, the peak resolution, and the selectivity of the GC/MS determination.     

Application of amino acid analysis by high-performance liquid chromatography with phenyl isothiocyanate derivatization to the rapid determination of free amino acids in biological samples.

An amino acid analysis by reversed-phase high-performance liquid chromatography after precolumn derivatization with phenyl isothiocyanate was adapted to the determination of free amino acids in plasma or other biological fluids and in tissue homogenates. Preparation of samples included deproteinization by 3% sulphosalicylic acid, and careful removal under high vacuum of residual phenyl isothiocyanate after derivatization. A Waters Pico-Tag column (15 cm long) was used, immersed in a water-bath at 38 degrees C. In rat or human plasma, separation of 23 individual amino acids, plus the unresolved pair tryptophan and ornithine, was obtained within 13 min. Including the time for column washing and re-equilibration, samples could be chromatographed at 23-min intervals. Variability was tested for each amino acid by calculating the coefficients of variation of retention times (less than 1% in the average) and peak areas (less than 4% for both intra-day and inter-day determinations). The linearity for each standard amino acid was remarkable over the concentration range 3-50 nmol/ml. The mean recovery of amino acid standards added to plasma prior to derivatization was 97 +/- 0.8%, except for aspartate (82%) and glutamate (81%). This method is rapid (almost three samples per hour can be analysed, more than in any other reported technique), with satisfactory precision, sensitivity and reproducibility. Therefore, it is well suited for routine analysis of free amino acids in both clinical and research work.     

Determination of residual solvents in isobutylboronic acid: Masking derivatization improves stability of GC column

Masking derivatization was introduced for the determination of residual solvents in samples containing a volatile reactive matrix component(s). Isobutylboronic acid, used in the last step of Bortezomib synthesis, represents a compound passing to the gas phase and deteriorating a chromatographic column during a headspace analysis. The masking derivatization with 1,8‐diaminonaphthalene allowed a simple and straightforward conversion of isobutylboronic acid to a stable nonvolatile derivative and thus prevented gas chromatography column deterioration. The method was successfully validated according to the guidelines of International Committee for Harmonization (Q3C (R6) Guideline for Residual Solvents) and international pharmacopoeias (Ph. Eur., USP) and approved by Teva Czech Industries for routine application.