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.     

Direct injection of large sample volumes into capillary columns with packed column injector

A direct injection method for large volume samples which avoids severe tailing of the solvent peak has been developed using a packed column injector (up to 100 μl) leading into an ordinary capillary column (0.3 mm i.d.). Modifications are made to the cooler zones of the inlet port and on the carrier gas flow control system. This injection technique is based on the effective use of phase soaking and cold trapping using a retention gap. The large volume of solvent vapor is rapidly purged out of the injector with a higher flow of carrier gas while the solutes trapped at the head of the column are subsequently analyzed with another optimum flow rate. The proposed carrier gas flow regulation system is also compared with conventional split/splitless injection methods.     

Application of capillary gas chromatography to automated on-line quantitative analysis of solvent vapors

Solvent vapors in air may be measured with capillary gas chromatographic columns. By using large diameter columns and sample loops of approximately the same internal diameter, the column may be connected directly to the gas sampling valve. This approach eliminates the use of a splitter or cryogenic trapping and allows low levels to be measured. By operating the column at high velocity, column efficiency is sacrificed for increase in speed.     

毛细管色谱切割-反吹法归一化分析汽油中芳烃

发展了一种毛细管色谱切割 反吹方法分析汽油中的芳烃。利用OV 2 3 3 0强极性毛细管预柱将芳烃保留至n C1 0 之后 ,并反吹到非极性毛细管柱中按沸点详细分离分析。从预柱先流出的组分和从分析柱流出的组分都先后进入同一检测器中 ,因此可用响应因子校正的归一化方法定量分析汽油中的芳烃。该方法在15min内完成汽油中苯至C1 0 芳烃的分析 ,结果的重复精度误差≤ 3 % (RSD) ,切割误差± 5s时对分析结果的影响≤ 4% (RSD)。对该方法的装置和部分应用进行了讨论     

一种电色谱整体微柱的制备及其分离性能

毛细管电色谱具有很高的分离效率，但也存在一些缺点，如浓度检出限差、柱容量低和工作电压太高等。为了克服这些缺点，我们在2．7mm内径的石英管内用石英砂填充硅酸钾。甲酰胺聚合整体柱，并进行了电色谱分离的可行性研究。实验结果证明这种方法是可行的。它限制了热效应，可使用常规分析仪器检测，所需工作电压不超过1000V。     

Simultaneous Determination of Baicalin, Baicalein, Wogonin, Oxysophocarpine, Oxymatrine and Matrine in the Chinese Herbal Preparation of Sanwu-Huangqin-Tang by Ion-Paired HPLC

A sensitive and reliable ion-paired high-performance liquid chromatographic method has been established for the simultaneous quantification of six major active ingredients, namely baicalin, baicalein, wogonin, oxysophocarpine, oxymatrine and matrine in the Chinese herbal preparation, Sanwu-Huangqin-Tang. HPLC analyses were performed on a Phenomenex luna C₁₈ column with mobile phase of methanol–acetonitrile–aqueous phosphoric acid at a flow rate of 0.9 mL min⁻¹. The complete separation was achieved within 35 min for the six target constituents. A good linear regression relationship between peak-areas and concentrations was obtained over the range of 12.10–242.0 μg*mL⁻¹ for baicalin, 5.05–101.0 μg*mL⁻¹ for baicalein, 0.95–19.0 μg*mL⁻¹ for wogonin, 2.75–55.0 μg*mL⁻¹ for oxysophocarpin, 2.75–55.0 μg*mL⁻¹ for oxymatrine and 4.90–98.0 μg*mL⁻¹ for matrine, respectively. The repeatability was evaluated by intra- and inter-day assays with relative standard deviation (RSD) being less than 5.1%. The recoveries, measured at three concentration levels, varied from 93.8 to 102.1%. The assay was successfully applied for determination of six bioactive compounds in Sanwu-Huangqin-Tang. The interaction of chemical constituents was observed when the herbs were used in compatibility. The results indicated that the developed assay method was rapid, accurate and could be readily utilized as a quality control method for Sanwu-Huangqin-Tang.     

Two-dimensional liquid chromatography of peptides: An optimization strategy

Summary An optimization strategy for the separation of a small number of peptides from a complex biological sample by two-dimensional liquid chromatography is presented. Ion-exchange chromatography is followed by reversed-phase separation. The ion-exchange separation is performed with a step gradient which admits a high sample load and simplifies instrumentation. The reversed-phase separation complements the first dimension with a different retention mechanism and higher resolution by linear gradient elution.Chromatographic theory is combined with experimental design to find separation conditions, for both dimensions, that allow the fastest gradient in the second dimension, giving short separation time, low detection limits and high load capacity. This is illustrated by the separation of a peptide from rat brain tissue, with a simple off-line arrangement. The strategy presented is useful in both analytical and preparative applications, and is widely applicable as it does not rely on special instrumentation or extensive knowledge of the sample.Dedicated to Professor Leslie S. Ettre on the occasion of his 70th birthday.     

尸体脏器中敌百虫及其主要代谢物DDVP和水合氯醛的毛细柱GC/MS测定

本文应用Finnigan Mat 1020 GC/MS仪,以SE-54熔融硅毛细柱作分离柱,建立了尸体脏器中敌百虫及其主要代谢物DDVP和水合氯醛的分析方法。样品用CH_2Cl_2提取。敌百虫和DDVP的检测限均是15 ng,方法已成功用于刑事案件鉴定。