Development and performance of an automated HPLC-analyzer for catecholamines

Summary An automated, dual-column HPLC method has been developed that can be used routinely to quantify the parent catecholamines in body fluids. The method is based on a new, laboratory-prepared column material with size exclusion and high performance affinity chromatography properties. A microprocessor controlled column-switching technique is used with an optional integrated reaction-system for postcolumn derivatization for fluorescence detection. Natural fluorescence can be used for higher concentration levels. The commercially available analyzer allows, for the first time, the direct injection (up to 0.5 ml) of an appropriate biological fluid. In its integrated sample-processing mode, it exhibits, chemoselectivity and -specificity, with a detection limit of 2 pg, high precision and speed of analysis.     

Analysis of light hydrocarbons (C2?C6) at PPT levels by high resolution gas chromatography

An analytical technique is described which allows the determination of C₂? C₆ hydrocarbons in the ppt-range from up to 21 air samples after removal of air humidity. Preconcentration is carried out on a two stage cryotrap system. The compounds are separ ated on a temperature-programmed capillary coated with Al₂ O₃. Detection limits (S/N 2:1) of 1.5 to 5 ppt were obtained for air samples from the Arctic. The reproducibility of the method was about 3% at the 50–100 ppt level. Practical problems are discussed in detail.     

Simultaneous determination of D- and L-serine in rat brain microdialysis sample using a column-switching HPLC with fluorimetric detection

Both D- and L-serine in rat brain microdialysis sample were simultaneously determined by pre-column fluorescence derivatization with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F), separation of the derivatives on ODS column, TSKgel ODS-80TsQA, followed by Pirkle type chiral columns, Sumichiral OA-2500 (S), which gave a sufficient enantiomeric separation of NBD-D-serine and NBD-L-serine, and fluorimetric detection at a wavelength of 540 nm with an excitation wavelength of 470 nm. The peaks of NBD-D-serine and NBD-L-serine in the rat brain microdialysis sample were clearly found, and the validation study showed satisfactory results; the precision and accuracy were within 5.14 and 109%, respectively. Using the proposed HPLC method, the time-course profile of D-serine concentration in rat prefrontal cortex following intraperitoneal administration of D-serine was investigated. As a consequence, D-serine appeared to be rapidly distributed in the brain, and then decreased gradually with time in the extracellular fluid of the rat prefrontal cortex. The proposed HPLC method will be useful for in vivo studies on D-serine, which acts as a coagonist for N-methyl-D-aspartate receptor, to the extracellular fluid of rat brain.     

Fast determination of nicotine and 3-ethenylpyridine in indoor environments

Summary Different sampling and analysis techniques for the determination of gas-phase nicotine and 3-ethenylpyridine in environmental tobacco smoke are reported. Graphitized carbon traps, annular diffusion denuders, and nebulizer collectors have been used as sampling devices in combination with either thermal desorption or with water extraction. Capillary gas chromatography and ion-pair reversed-phase chromatography were applied to desorbed and liquid samples obtained in an intercomparison indoor study. The methods developed here show some advantages over existing methods in terms of analysis time, sensitivity and loading capacity.     

烯烃气相色谱保留指数的QSRR研究

通过对184个烯烃类化合物在不同固定相不同柱温下的617个样本的气相色谱保留指数值(RI)与其部分参数:拓扑指数(mQ)、偶极矩(DPL)、固定液极性值(CP)及柱温(T)建立定量-色谱保留相关(QSRR)模型.分别利用多元线性回归(MLR)、偏最小二乘回归(PLSR)、人工神经网络(ANN)建模,同时采用内部及外部双重验证的办法对所得模型稳定性能进行深入分析和检验,建模计算值、留一法(LOO)交互检验(CV)预测值和外部样本的复相关系数Rcum,QLOO和Rext分别为0.999 2,0.998 4和0.999 2(MLR);0.999 0,0.998 0和0.999 1(PLSR);0.999 4,0.998 7和0.999 2(ANN).结果表明:所建定量结构保留关系(QSRR)模型具有良好的稳定性和预测能力,较好地揭示了烯烃类化合物在不同固定相不同柱温上气相色谱保留指数的变化规律.     

国产氢型阳离子交换(磺酸型)HPLC色谱柱在利巴韦林注射液分析中的应用-I

采用国产的氢型强阳离子交换(磺化苯乙烯-二乙烯基苯共聚物)色谱柱测定了利巴韦林注射液的含量。色谱柱为国产的氢型强阳离子麦科菲色谱柱(MKF-CIS),流动相为水(稀硫酸调至pH=2.5±0.1),检测波长207nm,流速1.0mL/min,温度65℃。结果表明,MKF-CIS色谱柱可以较准确的测定利巴韦林注射剂含量,在12.5μg/mL~500μg/mL浓度范围内,其浓度与峰面积的线性相关性良好(r=0.9999),平均回收率99.8%,RSD=0.558%。由此,国产麦科菲MKF-CIS色谱柱可以简便、准确、重复性好地用于利巴韦林测定,代替传统的C18硅胶柱及进口的同类型色谱柱。     

Practical applications of open tubes in liquid chromatography

The practical applications of open tubes in liquid chromatography as separation columns and as reactors for post column derivatization are discussed. With present technology, the potential efficiency of open tubular columns cannot be fully exploited. As reactors in post column derivatization, these tubes offer many advantages if knitted or stitched to enhance radial mass transfer. The application of open tubes with diameters between 0.12 mm and 0.6 mm as reactors in the selective and sensitive detection of amino acids is demonstrated.     

Capillary supercritical fluid chromatography with flame photometric detection using a large bore column SFC pumping system

A commercially available instrument with an SFC pumping system suitable for wide bore columns (4.6 mm i.d.) has been modified for capillary supercritical fluid chromatography (CSFC) by incorporating a double-stage flow splitter. The first flow splitter was installed in front of the sample injection valve in order to avoid a high solute split ratio. The second splitter was mounted in the column oven so that the injected sample (0.2 μL) would be split to the capillary column. In order to perform pressure programmed elution, a pressure regulating system equipped with a gradient programmer has been used. Flame photometric detection was optimized for the analysis of organosulfur compounds by CSFC. In this study, detection limits were found to be 6–14 ng and the experimentally determined exponent (n value) varied from 1.721 to 1.984 depending on the compounds tested. Sulfur- and phosphorus-containing thermally labile pesticides can be chromatographed and selectively detected by using CSFC/FPD in either sulfur- or phosphorus mode, respectively.