苯胺及其衍生物的毛细管电泳行为研究

采用紫外吸收检测，毛细管电泳分离，研究了九种苯胺及其衍生物在毛细管区带电泳(CZE)体系和胶束电动毛细管色谱(MECC)体系中的行为特征。讨论了缓冲溶液的浓度与pH、胶束浓度及混合胶束等在不同体系中对分离组分的影响，发现在CZE体系中，控制分离的主要因素是pKb值；在MECC体系中，控制分离的主要因素是溶质分子中碳原子数。建立了一种分离测定九种苯胺及其衍生物的高效毛细管电泳方法。     

超高效液相色谱法快速测定环境空气中13种醛酮类化合物

建立了一种快速、高效分离测定环境空气中13种醛酮类化合物的方法。环境空气中的醛酮类化合物,与采样管中的2,4-二硝基苯肼在强酸性条件下反应生成腙类衍生物。洗脱的衍生物,以乙腈-水为流动相,采用Core-Shell型色谱柱进行分离,二极管阵列检测器检测。在优化的色谱条件下,13种醛酮组分的衍生物在15 min内均达到良好分离,各组分的质量浓度在50～1 000μg/L(以醛酮计)范围内与色谱峰面积线性相关系数均大于0.999。采样体积为50 L时,方法检出限为0.24～1.38μg/m³。样品加标回收率为92.9%～105%,测定值的相对标准偏差为1.2%～7.8%(n=6)。该方法分离快速、定量准确,满足环境空气中痕量醛酮类化合物的分离分析。     

生物碱样品中有效成分的CZE法分离与测定

建立了一种简单的同时分离测定生物碱样品中咖啡因、可可碱和茶碱3种有效成分的区带毛细管电泳法。采用未涂层石英毛细管(75μm i.d.×60 cm,有效长度50 cm),以20 mmol.L-1硼砂-4 mmol.L-1β-CD(pH 9.0)为运行缓冲液,压力(0.5 psi)进样5 s,运行电压16 kV,检测波长273 nm,温度25℃。在优化的实验条件下,3种生物碱的电泳谱图峰面积与其质量浓度在0.036～0.288 g.L-1呈良好线性关系(r≥0.998 4);方法的精密度、重复性和稳定性良好,其峰面积的RSD均不大于3.2%,其检出限均不大于2.7mg.L-1;加标回收率为97%～104%。该方法简单、快速、试剂消耗少,可用于生物碱样品中咖啡因、可可碱和茶碱的分离与测定。     

血卟啉衍生物的色谱分离

本文拟定的纸色谱法是以苯-乙酸乙酯-甲醇-乙酸(9:2:1:1)作展开剂,将血卟啉衍生物(HPD)分离为五部份,分别测定各部份浸取液的荧光发射光谱,作为一种对血卟啉衍生物组份作对比鉴定的参考方法。采用Ward的高效液相色谱程序对比研究结果表明,国产与美国产HPD的组份近似,均以血卟啉为主要组份,而前者血卟啉的含量较高;二者还均含有羟乙基乙烯基衍生物和羟基乙酸酯,初步研究了血卟啉衍生物在甲醇-水溶剂系统中的高效液相色谱行为,进一步将血卟啉衍生物分离为九部份,有利于单一组份研究。     

衍生化毛细管气相色谱法同时测定无糖食品中的多种糖醇类甜味剂

建立了一种同时测定无糖食品中多种糖醇类甜味剂的气相色谱定量分析方法。样品中的糖醇经水提取,净化、脱水后,在吡啶-乙酸酐(1∶1,V/V)存在条件下,于90℃反应20 min,生成的糖醇乙酸酯衍生物用OV-101毛细管色谱柱(50 m×0.25 mm×0.33μm)分离,氢火焰离子化检测器(FID)进行测定及气相色谱-质谱结构鉴定。在优化的色谱分析条件下,实现了赤藓糖醇、木糖醇、甘露糖醇、山梨糖醇和麦芽糖醇衍生物的理想分离,并排除了常见糖类对糖醇测定的干扰。本方法在0.01～1.6 mg/mL范围内,对糖醇浓度与其衍生物峰面积进行线性回归分析,其相关系数在0.9995～0.9999之间。平均回收率为74.6%～113.4%,相对标准偏差在2.4%～8.6%之间。本方法操作简便、快速、可靠,检测限和加标回收率均能满足无糖食品中糖醇的定量分析要求。     

α-CF_3芳香仲醇类对映体的高效液相色谱法分离

利用正相高效液相色谱法在一种纤维素衍生物手性固定相(OJ-H或OD-H)上成功分离了一系列(23个)α位取代的CF3芳香醇及其酯化后的对映异构体。通过考察流动相组成、流速、进样浓度和温度等因素对对映体分离的影响,优化色谱分离条件,并且利用得到的数据计算出对映异构体的分离因子和分离度。     

α位取代的CF_2仲醇及其酯类对映体的高效液相色谱法分离

利用正相高效液相色谱法在一种纤维素衍生物手性固定相(OJ-H或OD-H)上成功分离了一系列α位取代的CF2芳香醇及其酯化后的对映异构体。通过考察流动相组成、流速、进样浓度和温度等因素对对映体分离的影响,优化色谱分离条件。     

毛细管电泳分析检测豆芽中植物生长调节剂残留

建立了一种用于测定豆芽中植物生长调节剂残留的毛细管电泳分析方法。通过3-氨基苯磺酸对10种植物生长剂进行柱前衍生,在16 min内可实现高效的基线分离、测定。实验考察了缓冲溶液pH及浓度对分离的影响,在优化条件下,各标准品衍生物在0.07～5.0μmol/L浓度范围内呈良好的线性关系,相关系数为0.9980～0.9998,保留时间和峰面积的相对标准偏差分别为0.59%～1.09%和0.69%～1.44%,检测限(3倍信噪比)为0.035～0.058μmol/L。该方法准确可靠,对实际样品进行定性定量检测,结果令人满意。     

表面活性剂对NBD-Cl衍生氨基酸的荧光增敏和芯片电泳分离的影响

研究多种表面活性剂以及溶剂对4-氯-7-硝基苯-2-氧-1,3-二唑(NBD-Cl)衍生氨基酸荧光性质的影响。考察并优化了NBD-Cl与氨基酸的衍生反应条件以及芯片毛细管电泳-激光诱导荧光的分离分析条件。结果表明:在临界胶束浓度以上,阳离子表面活性剂十六烷基三甲基溴化胺(CTMAB)对精氨酸、谷氨酸、天冬氨酸的NBD-Cl衍生物,非离子表面活性剂十二烷基聚氧乙烯醚(Brij-35)对苯丙氨酸、精氨酸的NBD-Cl衍生物有荧光增敏效果。在含有5mmol/LBrij-35和20%乙腈添加剂的15mmol/L硼砂缓冲液(pH9.2)中,精氨酸、苯丙氨酸、丙氨酸、甘氨酸、谷氨酸及天冬氨酸等6种氨基酸的NBD-Cl衍生物可以在70s内实现分离,其中较难分离的丙氨酸、甘氨酸的NBD-Cl衍生物分离度为0.91;6种氨基酸衍生物的检出限为0.15～1.6μmol/L。     

两亲性壳聚糖衍生物的合成及其自聚集现象

以壳聚糖为主链, 聚乙二醇单甲醚为亲水性链段, 癸二酸为疏水链段, 合成了一系列两亲性壳聚糖衍生物. 通过FTIR, 1H NMR和X射线粉末衍射等手段对壳聚糖衍生物进行了结构表征, 由元素分析方法计算出衍生物的取代度. 采用直接溶解法制备了壳聚糖衍生物的空白胶束, 通过透射电子显微镜(TEM)观察了胶束的形态. 由动态光散射(DLS)测定了胶束的粒径及分布, 并以芘为分子探针, 通过荧光光谱法测定了壳聚糖衍生物的临界聚集浓度(CAC). 研究结果表明, 壳聚糖主链上疏水链段的取代度越大, 其衍生物的临界聚集浓度越低, 相同浓度下的胶束的粒径也越小.     

Separation of caffeine and theophylline in poly(dimethylsiloxane) microchannel electrophoresis with electrochemical detection

A method for the rapid separation and sensitive determination of caffeine and theophylline was presented in poly(dimethylsiloxane) (PDMS) microchannel electrophoresis integrated with electrochemical detection. By using methanol as an additive, the peak shape and resolution were essentially improved. The analytes were well separated within only 40s in the running buffer of 5.0mM borate solution (pH 9.2) containing 10% (v/v) methanol. The linear ranges were from 6microM to 0.6mM and the detection limits were 4microM for caffeine and theophylline, respectively. The proposed method has been successfully applied to determine caffeine and theophylline in rat serum and urine.     

Separation and fluorodensitometric determination of some purine derivative drugs by thin-layer chromatography on starch and cellulose

Summary Purine derivative drugs, aminophylline, theophylline, xantinolnicotinate, 6-mercaptopurine, 6-thyoguanine, azathioprine, 1-methylxantine, 3-methylxantine, 1-methyluric acid, 1,3-dimethyluric acid, 6-thioxantine, 2-amino-6-methylmercaptopurine, were separated by thin-layer chromatography on rice starch and cellulose by three different solvent systems. Conditions for quantitative fluorodensitometric determination of purine derivatives drugs were investigated.     

Characteristic of theophylline imprinted monolithic column and its application for determination of xanthine derivatives caffeine and theophylline in green tea

Theophylline imprinted monolithic columns were designed and prepared for rapid separation of a homologous series of xanthine derivatives, caffeine, and theophylline by an in situ thermal-initiated copolymerization technique. Caffeine and theophylline were fully separated both under isocratic and gradient elutions on this kind of monolithic molecularly imprinted polymers (MIP) column. The broad peak showed in isocratic elution could be improved in gradient elution. Some chromatographic conditions such as mobile phase composition, flow rate, and the temperature on the retention times were investigated. Hydrogen bonding interaction and hydrophobic interaction played an important role in the retention and separation. The binding capacity was evaluated by static adsorption and Scatchard analysis, which showed that the dissociation constant (KD) and the maximum binding capacity (Qmax) were 1.50 mol/L, and 236 micromol/g for high affinity binding site, and 7.97 mol/L and 785 micromol/g for lower affinity binding site, respectively. Thermodynamic data (DeltaDeltaH and DeltaDeltaS) obtained by Van't Hoff plots revealed an enthalpy-controlled separation. The morphological characteristics of monolithic MIP were investigated by scanning electron microscope, which showed that both mesopores and macropores were formed in the monolith. The present monolithic MIP column was successfully applied for the quantitative determination of caffeine and theophylline in different kinds of green tea.     

Non‐enzymatic Electrochemical Sensor for the Simultaneous Determination of Xanthine,its Methyl Derivatives Theophylline and Caffeine as well as its Metabolite Uric Acid

Xanthine and its methyl derivatives, theophylline and caffeine are purines which find important roles in biological systems. The simultaneous voltammetric behaviour of these purines has been studied on a glassy carbon electrode modified with an electropolymerised film of para amino benzene sulfonic acid. Well defined and well separated peaks were obtained for the oxidation of xanthine, theophylline and caffeine on the polymer modified electrode in the square wave mode. The experimental requirements to obtain the best results for individual as well as simultaneous determination were optimised. The signal for the electro‐oxidation was found to be free of interferences from each other in the range 0.9 – 100 μM in the case of xanthine and from 10–100 μM in the case of theophylline and caffeine with detection limits 0.35 μM, 7.02 μM and 11.95 μM respectively. The simultaneous determination of uric acid, the final metabolic product of xanthine oxidation in biological systems could also be accomplished along with xanthine, theophylline and caffeine atphysiological pH. The mechanistic aspects of the electro‐oxidation on the polymer modified electrode was also studied using linear sweep voltammetry. Chronoamperometry was employed to determine the diffusion coefficient of these xanthines. The developed sensor has been successfully demonstrated to be suitable for the determination of these compounds in real samples without much pre‐treatment.     

Quantitative Densitometric Determination of Theophylline

Abstract

A method for identification and quantification of theophylline in certain dosage forms, that employs TLC-scanner is reported. the method is applied for theophylline either as raw material or in certain dosage forms admixed with other medicamenta. Samples were extracted with methanol, separated and measured in situ on silica gel G plates at about 270 nm using TLC-scanner. the mean recovery (six determinations) was 99.9± 0.57. the developed procedure has been found to be simple, rapid and precise and its application to various dosage forms was demonstrated and yields comparable results with UV measurement after location, scraping and elution from the plates.     

A method for the determination of theophylline in serum by isotope dilution mass spectrometry

Summary A method for the determination of theophylline in human serum by the isotope dilution/mass spectrometric technique is described. As an internal standard labelled (1,3-¹⁵N₂-2-¹³C)theophylline is added to the serum sample. The analyte and internal standard are extracted with chloroform/2-propanol (90:10) and converted to the trimethylsilyl derivatives. The extraction and silylation procedures are checked by adding theophylline and internal standard in various concentrations to blank serum and determining the recovery. The trimethylsilyl derivatives of labelled and non-labelled theophylline are separated and detected by GC-MS with the mass spectrometer set to m/z 252 and 255. The amounts of theophylline in the serum are calculated from the isotope ratios measured by selected ion monitoring. The accuracy, precision and recovery of this GC-MS method are presented and discussed. The coefficient of variation determined from duplicate samples was less than 2.5%. The detection limit was 10 ng/ml at a signal-to-noise ratio of 3:1.Part of the work was presented at the 32th Kongreß der Deutschen Gesellschaft für Laboratoriumsmedizin, Frankfurt 1991     

Rapid separation of tetracycline derivatives and their main degradation products by capillary zone electrophoresis.

A mixture of five tetracycline (TC) derivatives: minocycline (MC), demeclocycline (DMCTC), doxycycline (DC), and sancycline (SC), as well as each TC derivative from its main degradation product were separated by capillary zone electrophoresis (CZE). The influence of the pH and the concentration and nature of the background electrolyte (BGE) on the separations was investigated. Ethylenediaminetetraacetic acid (EDTA; 1 mM) was used as additive in a 25 mM phosphate buffer (pH 2.3) because this BGE enabled the rapid separation of the TC derivatives and of each TC derivative from its respective degradation product in less than 6 min. After optimization of the separation conditions, the analytical characteristics of the method were investigated. The parameters involved were linearity, precision (repeatability and reproducibility), and limits of detection (LODs). LODs obtained for the five TC derivatives studied were about 3 microg/mL. Finally, the CZE method developed was applied to study the stability of TC derivatives and to analyze the TC derivative content in three different pharmaceutical preparations.     

Thermal studies on purine complexes. VII. 8-theophylline derivatives and their silver(I) complexes

Four theophylline derivatives: 8-ethyltheophylline (ETH), 8-isopropyltheophylline (IPH), 8-propyltheophylline (PRH), and 8-phenyltheophylline (FTH) have been synthesized and characterized by spectroscopic techniques and thermal analysis. The melting points of these theophylline derivatives increase with the molecular weight, from 263.8°C (ETH) to 384.7°C (FTH). The values of the fusion enthalpy increase in the same order, from 28.4 kJ mol⁻¹ (ETH) to 36.5 kJ mol⁻¹ (FTH).

The interaction of these theophylline derivatives with Ag(I) has been studied by means of spectroscopic techniques, TG, DTG and DSC. In all cases, the pyrolysis of these compounds gave metallic silver.     

Optimization of fast CE analyses of ecstasy derivatives by use of experimental designs

Summary The separation by capillary electrophoresis of five ecstasy derivatives has been evaluated by means of experimental designs. A full-factorial design and a central composite design were employed to optimize the experimental conditions for a fast separation. With a conventional capillary (62.5 cm length) analytes were separated in less than 8 min. When the capillary length was reduced the analysis time decreased substantially. Comparisons were made between different procedures (e.g. working at a constant field or at constant voltage) and finally, a fast separation of five Ecstasy derivatives was achieved in 1 min.     

Simultaneous Determination of Guaifenesin and Theophylline by Chemometrics Methods

In this study, simultaneous spectrophotometry determination of guaifenesin and theophylline in pharmaceuticals by chemometric approaches has been reported. Spectra of mixtures of these drugs were recorded and corresponding first derivatives were calculated. Partial least squares regression (PLS) alone and ant colony optimization (ACO) coupled with PLS were used in analysis of the data. Ant colony system (ACS) as an efficient ACO algorithm was used. In addition, ACS was combined to genetic algorithm (GA) to produce better results. The analytical performances of these chemometric methods were characterized by relative prediction errors. These methods were successfully applied to pharmaceutical formulation.