反相高效液相色谱梯度洗脱同时测定复方茶碱片中7组分的含量

建立了一种灵敏、快速的反相高效液相色谱梯度洗脱方法，用于同时测定复方茶碱片中7组分的含量。采用YWG C18柱，以甲醇-磷酸二氢钠为流动相，用二极管阵列检测器，检测波长为214nm,15min即可将7种组分分离测定。该方法快速淮确，线性范围广，用于实际样品的测定，结果满意。     

高效液相色谱法测定喘静片的3种主要成分

 采用高效液相色谱法同时测定喘静片中的3种主要成分：茶碱、异戊巴比妥和盐酸甲基麻黄碱。以ODS作固定相,通过均匀设计方法选择的最佳流动相为V（0.015 mol/L磷酸二氢钠缓冲液,含体积分数为0.3%的三乙胺,pH 4.9 )∶V（甲醇）=35∶65,检测波长为215 nm,用程序调节检测器的灵敏度,以咖啡因作内标物。茶碱、异戊巴比妥、盐酸甲基麻黄碱的回收率分别为99.7%～102.6%,98.5%～100.2%,98.0%～102.7%,日间RSD分别为0.23%～1.2%,0.35%～2.5%,0.33%～1.6%。该方法简便、快速、准确。     

正交投影分光光度法同时测定联磺甲氧苄啶片中的SMZ和TMP

采用正交投影分光光度法同时测定3组分复方药物联磺甲氧苄啶片中磺胺甲恶唑(SMZ)和甲氧苄啶(TMP)二组分的含量。SMZ和TMP的平均回收率分别为99,6％和99．4％,测定结果的相对标准差分别为0,75％和0．60％。讨论了波长区间和波长间隔对测定结果的影响。     

以马来松香丙烯酸乙二醇酯为交联剂的茶碱分子印迹膜电化学传感器的研究

利用分子印迹技术, 以马来松香丙烯酸乙二醇酯为交联剂, 丙烯酸为功能单体研制了测定茶碱的新型电化学传感器. 以自由基热聚合的方式于玻碳电极表面制备茶碱分子印迹聚合物膜. 通过循环伏安法、电化学交流阻抗法及计时电流法研究了传感器对茶碱的响应特性. 结果表明, 在最佳的实验条件下, 传感器的峰电流与茶碱浓度在2.00×10^-7～3.45×10^-4 mol/L 范围内呈现出良好的线性关系(线性相关系数为0.9961), 检出限(S/N＝3)为1.00×10^-7 mol/L;该传感器的选择性高, 稳定性和重现性好, 将此传感器用于茶碱缓释片中茶碱的含量测定, 回收率为95.6%～103.8%.关键词 马来松香丙烯酸乙二醇酯; 茶碱; 分子印迹聚合物; 电化学传感器     

紫外光谱净信号法测定酸性环境下复方磺胺甲噁唑片两个有效组分

被分析组分的光谱净信号将正交于其它药物组分和辅料光谱所张成的光谱子空间,从而消除其它组分对被分析组分的光谱干扰,此净信号将与被分析组分的浓度成正比,据此建立了药物制剂分析的净信号方法。本文利用该方法研究了在酸性条件下紫外光谱测定复方磺胺甲噁唑片的两种有效成分磺胺甲噁唑(SMZ)和甲氧苄啶(TMP)。SMZ和TMP的线性范围分别为0.48~7.84μg/mL(r=0.9981)和0.12~1.5μg/mL(r=0.9986),平均回收率分别为99.5%和101.0%,RSD分别为1.87%和3.60%。本法简便、快速和准确,可用于酸性条件下复方磺胺甲噁唑片中SMZ和TMP含量的快速、同时准确测定。     

BP网络光度法测定去痛片中的四组分

应用Levenberg-Marquardt优化算法的BP网络,采用紫外分光光度法测定去痛片中四组分的含量。测定低含量组分咖啡因和苯巴比妥时,结合吸光度减法技术。氨基比林、非那西丁、咖啡因和苯巴比妥的平均回收率和RSD分别为99.3%,1.2%：;100.0%,1.1%;100.3%,1.5%;100.1%,1.3%。     

胶束电动毛细管色谱分离测定嘌呤衍生物

用胶束电动毛细管色谱(MECC)分离测定了咖啡因、茶碱、次黄嘌呤、黄嘌呤及尿酸五种嘌呤衍生物。研究了背景缓冲液浓度、pH值、十二烷基硫酸钠(SDS)浓度、分离电压、温度及进样时间等因素对五种嘌吟衍生物分离的影响。在选定的实验条件下,五种化合物在8min内达到基线分离。该方法具有快速、准确、重现性好等优点,已用于尿样、茶叶及复方茶碱片等样品的测定,结果满意。     

气相色谱法直接测定茶叶中的咖啡因和茶碱

采用超声提取 ,大口径毛细管气相色谱法 ,对茶叶中的咖啡因和茶碱进行了直接测定 ,结果表明 ,咖啡因和茶碱的检出限分别为 2 .0 0 mg/L和 2 .0 5 mg/L,平均回收率为 96 .7%和 1 0 0 .5 %相对标准偏差均小于 2 .0 %。     

近红外光谱快速测定复方磺胺甲噁唑药效成分

基于近红外漫反射光谱技术,利用偏最小二乘多元校正方法建立了复方磺胺甲噁唑片中的两个有效成分磺胺甲噁唑(SMZ)和甲氧苄啶(TMP)含量的快速同时测定方法。对于SMZ和TMP定量分析模型,相关系数分别为99.969%与99.938%,校正集残差分别为0.217与0.159,而预测根均方差分别为0.310和0.418。该方法具有简单、快捷、两组分同时准确测定以及样品不经任何预处理等特点。     

可可碱、咖啡因、茶碱的滤纸基质室温燐光测定

以快速定量滤纸为基质 ,用KI NaAc为重原子微扰剂 ,建立了测定痕量可可碱、咖啡因、茶碱的滤纸基质室温磷光 (PS RTP)分析法。该法取样量少 ,线性范围宽 ,可可碱、咖啡因、茶碱的线性范围分别为 14 4～5 76 ;5 .4 4～ 6 99;7.2 1～ 36 0ng/斑点 ;检出限分别为 1 14、0 78、1 80ng/斑点。该方法用于巧克力中可可碱、茶叶中咖啡因、氨茶碱药片中茶碱的测定 ,操作简便快速 ,选择性好。标准回收率在 92 8%～ 10 6 %之间 ;相对标准偏差RSD <5 %     

Caffeine and theobromine in coffee, tea and cola-beverages

Summary A new method based on reversed-phase ion-interaction HPLC is described for the identification and quantitation of theobromine, theophylline and caffeine in beverages. The interaction reagent used is octylamine orto-phosphate which also constitutes the mobile phase. The stationary phase is a microparticulate reversed-phase C-18 packing. With spectrophotometric detection at 274 nm, detection levels of 0.15, 0.30 and 0.40 ppm were achieved for theobromine, theophylline and caffeine, respectively.Quantitative analysis was performed by the standard addition method for theobromine and caffeine contents in tea, espresso-coffee, decaffeinated coffee, decaffeinated tea and cola-beverages.     

Coulometric Determination of Purine Alkaloid Series with Electrogenerated Chlorine

In acid solution, caffeine, theobromine, and theophylline are rapidly and quantitatively oxidized with electrogenerated chlorine in a stoichiometric ratio of 2 : 5 to give alloxan and urea. Procedures for the coulometric determination of microgram amounts of caffeine, theophylline, and theobromine in model solutions, caffeine in tea and coffee samples, and caffeine and theophylline in some pharmaceutical preparations were developed.     

Quantitative on‐line concentration for capillary electrophoresis with inkjet sample introduction technique

A quantitative sample introduction method based upon inkjet injection was applied to capillary electrophoresis coupled with stacking and sweeping on‐line concentration techniques. Methylxanthines were used as model compounds for the proof‐of‐concept of the method. The volume of injected sample could be easily manipulated by controlling the number of ejected droplets in the injection procedure. Under optimized conditions, a linear relationship between the ejected droplet number and peak area was obtained when the droplet number introduced into the capillary was less than 100. Under optimized quantitative on‐line concentration conditions, the limits of detection for theobromine, caffeine, and theophylline were 1.0, 2.0, and 1.0 μM, respectively. The inkjet injection system was evaluated by comparing it with conventional injection methods. The electropherogram of the inkjet injection mode was the same as that for hydrodynamic injection mode, and no sample discrimination was observed compared with the electrokinetic injection mode. The established method was applied to the determination of methylxanthines in bottled green tea. The recoveries of theobromine, caffeine, and theophylline were 94.1, 110.6, and 86.8%, respectively. We conclude that proposed method can be used for quantitative concentration for capillary electrophoresis, thus resulting in an improved accuracy.     

Liquid Chromatography of Adenine,Caffeine, Theobromine,Theophylline, Tannic Acid,Xanthine and its Application to Tea Analysis

A polystyrenesulfonic acid resin in the hydrogen form is a useful stationary phase for chromatographic separation of adenine, caffeine, theobromine, theophylline, tannic acid, xanthine and tea components with aqueous ethanol as eluent. The results indicated that caffeine, theophylline, theobromine, adenine, xanthine and tannic acid could be separated on a column of Dowex-50W-X8(H)⁺ by elution with 25% ethanol as eluent.     

Determination of adenine,caffeine, theophylline and theobromine by HPLC with amperometric detection

A relatively simple method for quantifying caffeine, theobromine, theophylline and adenine by HPLC with amperometric detection was developed. A C₁₈-column and an isocratic elution with phosphate buffer pH 3.5/methanol (90 : 10) were employed for the chromatographic separation of the investigated compounds. The optimal detection potential was +1.4 V. The limits of detection were 0.4 ng for adenine, 1 ng for theophylline and 2.5 ng for caffeine and theobromine. The method was applied to the determination of these purine alkaloids in beverages, tea, coffee and cacao. The determination was carried out directly or after solid-phase extraction.     

Simultaneous determination of methylxanthines in coffees and teas by UV-Vis spectrophotometry and partial least squares

This work describes a method to simultaneously determine caffeine (CF) and theobromine (TB) in coffee and tea samples using partial least squares (PLS-1). Sample preparation was required to eliminate strong interfering components. High-performance liquid chromatography (HPLC)-found concentrations of caffeine and theobromine (theophylline was not found in any analyzed sample) were used to construct universal calibration matrixes for coffee and tea. Due to the low levels of theobromine when compared to caffeine (up to 1000:1), theobromine addition standard was required to dramatically improve method performance. The method developed did not show statistically significant differences with an HPLC standard technique.     

Study on inclusion complex of cyclodextrin with methyl xanthine derivatives by fluorimetry

The inclusion complexes of beta-cyclodextrin (beta-CD) and HP-beta-cyclodextrin (HP-beta-CD) with caffeine, theophylline and theobromine were investigated by fluorimetry. Various factors affecting the formation of inclusion complexes were discussed in detail including forming time, pH effect and temperature. The results indicate that inclusion process was affected seriously by laying time and pH. The forming time of beta-CD inclusion complexes is much longer than that of HP-beta-CD. The optimum pH range is about 7-12 for caffeine, 8-10 for TP, 10.5-12 for TB. The intensities of their fluorescence increase with the decreasing of temperature. Their maximum excitation wavelengths are all in the range of 280-290 nm. The emission wavelength of caffeine and theophylline are both in the range of 340-360 nm, and that of theobromine is about 325 nm. The fluorescence signals are intensified with the increasing concentration of CD. The stoichiometry of the inclusion complexes of CD with these three methyl xanthine derivatives are all 1:1 and the formation constant are all calculated.     

Multivariate optimisation of the experimental conditions for determination of three methylxanthines by reversed-phase high-performance liquid chromatography

Caffeine (1,3,7-trimethylxanthine), theobromine (3,7-dimethylxanthine) and theophylline (1,3-dimethylxanthine) are the most important naturally occurring methylxanthines. Caffeine is a constituent of coffee and other beverage and included in many medicines. Theobromine and theophylline are formed as metabolites of caffeine in humans, and are also present in tea, cocoa and chocolate products.

In order to improve the chromatographic resolution (R_s) with a good analysis time, experimental designs were applied for multivariate optimisation of the experimental conditions of an isocratic reversed-phase high-performance liquid chromatographic (RP-HPLC) method used for the simultaneous determination of caffeine, theobromine and theophylline. The optimisation process was carried out in two steps using full three-level factorial designs. The factors optimised were: flow rate and mobile phase composition. Optimal conditions for the separation of the three methylxanthines were obtained using a mixture of water/ethanol/acetic acid (75:24:1%, v/v/v) as mobile phase and a flow rate of 1.0 mL min⁻¹. The RP-HPLC/UV method was validated in terms of limit of detection (LOD), limit of quantitation (LOQ), linearity, recovery and the precision, calculated as relative standard deviation (R.S.D.). In these conditions, the LOD was 0.10 μg L⁻¹ for caffeine, 0.07 μg L⁻¹ for theobromine and 0.06 μg L⁻¹ for theophylline. The proposed method is fast, requires no extraction step or derivatization and was suitable for quantification of these methylxanthines in coffee, tea and human urine samples.     

Determination of caffeine and caffeine-related metabolites in ephedra-containing standard reference materials using liquid chromatography with absorbance detection and tandem mass spectrometry

The concentrations of caffeine and caffeine-related compounds in 2 ephedra-containing reference materials have been determined by 3 independent methods with measurements performed by the National Institute of Standards and Technology (NIST) and a collaborating laboratory. Results from the 3 methods were used for value assignment of caffeine, theobromine, and theophylline in these Standard Reference Materials (SRMs). The methods used at NIST to determine the concentration levels of caffeine, theobromine, and theophylline in SRM 3243 Ephedra-Containing Solid Oral Dosage Form and SRM 3244 Ephedra-Containing Protein Powder used reversed-phase liquid chromatography with absorbance detection and tandem mass spectrometry. These reference materials are part of the first suite in a series of NIST SRMs that provide concentration values for multiple components in dietary supplements. These SRMs are primarily intended for method validation and for use as control materials to support the analysis of dietary supplements and similar materials.     

Simultaneous determination of caffeine and its primary demethylated metabolites in human plasma by high-performance liquid chromatography.

An improved high-performance liquid chromatographic method for the simultaneous determination of caffeine and its three primary metabolites (theophylline, theobromine and paraxanthine) in human plasma is described. The four substances were separated on a reversed-phase column (5 microns TSK gel ODS-80TM, 150 mm x 4.6 mm I.D.) by use of the mobile phase methanol-0.1 M NaH2PO4 (30:70, v/v) with a flow-rate of 0.8 ml/min. Absorbance was monitored at 274 nm. The detection limit was 5 ng/ml for theobromine and caffeine and 10 ng/ml for paraxanthine and theophylline. The linearity and reproducibility were sufficient for drug monitoring of caffeine and its primary methylxanthines.