Capillary gas chromatography of pesticide residues in foods: Application of a split/splitless inlet system

Residue mixtures of pesticides in foods which were difficult to separate by packed-column gas chromatography were determined by capillary gas chromatography and electron capture detection. Manual injections of sample and reference standard were made with a 10 μL syringe on a septum-enclosed, split/ splitless inlet system. Optimal peak height repeatability (± 3%( was achieved with three-μL injections which were made within time periods of four hours or less. The average linearity coefficient (slope( obtained for detector response as a function of solution concentration was 1.1.     

Rapid and high-resolution analysis of geometric polyprenol homologues by connected octadecylsilylated monolithic silica columns in high-performance liquid chromatography

A Chromolith Performance octadecylsilyl (ODS) monolithic silica column (Merck) was compared with a conventional microparticulate ODS-bonded silica column in the high-performance liquid chromatography separation of natural polyprenols. A system comprising two connected monolithic columns afforded an equivalent separation at half the analysis time of the conventional method. Furthermore, ten connected columns achieved a tremendously high-resolution separation, in which the complicated series of homologous polyprenols with geometric isomerism were fully separated.     

Separation and sensitive determination of arsenic species (As/As) using the yeast-immobilized column and hydride generation in ICP–AES

Inorganic arsenic was separated using the yeast-immobilized column. Saccharomyces cerevisiae was covalently bonded unto the controlled pore glass, which showed selective preconcentration of As⁵⁺ over As³⁺. The effluent was directly connected to hydride generation (HG) to increase sensitivity. The optimum pH condition for the retainment of arsenic at the column was 7. As⁵⁺ and As³⁺ were completely separated in a few minutes with the flow rate of 1.5 ml min⁻¹. Three molars of nitric acid was adequate both for the elution of As⁵⁺ and hydride generation. The accuracy of the technique was tested with NIST SRMs. Quantitative analysis of arsenic species for herbicide, pesticide, and cigarette were performed, and the results showed good agreements with the suggested values. Yeast-immobilized column-HG-ICP showed a promising future for the arsenic speciation study.     

Quantitative analysis of nicotinic acid, nicotinamide and 3-cyanopyridine in industrial effluent by high performance liquid chromatography

A rapid and reliable high performance liquid chromatographic (HPLC) method for the simultaneous determination of heterocyclic compounds, namely nicotinic acid, nicotinamide, and 3-cyanopyridine, in industrial effluent is described. A Φ4.6 mm × 150 mm, 5 μm C-18 reversed phase stationery phase, and a methanol-acetonitrile-water tertiary mobile phase (20:20:60 v/v) were used for separation. The detection wavelength of a diode array (DAD) was set at 216 nm with a bandwidth of 16 nm. Phenol was used as an internal standard. The regression equations revealed a linear relationship between the concentration of the analytes injected and the peak area detected by DAD. The limits of detection (S/N = 3) ranged from 0.70 to 1.18 mg L⁻¹, the recoveries ranged from 87% to 102% and the precision expressed as % RSD intra-day and inter-day varied from 0.9 to 3.9 and 1.2 to 5.6, respectively. This method is rapid, sensitive and suitable for the monitoring of nicotinic acid, nicotinamide, and 3-cyanopyridine in effluent of related pharmaceutical manufacturing plants.     

大口径厚液膜毛细管柱的制备

制备出了内径从0.46～0.74mm、液膜厚度从0.9～5.6μm的SE-54大口径厚液膜玻璃毛细管柱,并对它们的性能进行了评价。对低沸点的C_1-C_4烃进行了初步分离。     

Advances in two-dimensional GC with glass capillary columns

A versatile two-dimensional gas chromatograph is described, consisting of 2 separate ovens, one intermediate trap, an auxiliary inlet, and the necessary hardware to effect off-line switching according to the principle of Deans. The unit has been designed for use with high resolution glass capillary columns. The performance of individual instrumental components was critically evaluated. Results showed that low dead volume glass to metal connections were required in the manifold and detector lines to minimize extra-column effects. The mass of the intermediate trap must be low to allow rapid heating. Operational parameters are discussed and examples of some applications are shown.     

Copper ring-disk microelectrodes: fabrication, characterization, and application as an amperometric detector for capillary columns

A novel approach to the fabrication of metal ring-disk (RD) microelectrodes is presented that employs flexible chemical vapor deposition (CVD) and electrode modification techniques. Specifically, the development of a copper ring-disk microelectrode is described utilizing a combination of CVD coating, electroetching, and electroplating. Initially, a 25 μm diameter tungsten wire is concentrically coated by CVD with an insulating layer of silica, a layer of tungsten metal, and finally, a second outer layer of silica. The copper surface was prepared by first creating micrometer cavities by electrochemical etching the tungsten in hydroxide solutions followed by electrodeposition of copper from aqueous solutions of Cu(II). Each step of the process was characterized by scanning electron microscopy, optical microscopy, and cyclic voltammetry, demonstrating the preparation of a viable metal-based dual ring-disk microelectrode system. For the purpose of demonstrating the concept of introducing specific selectivity into the device, amperometric detection of galactose in 0.1 M NaOH was performed at +0.60 V in bulk solution and after flow injection analysis in a capillary column.     

有机聚合物整体柱及其在生物大分子色谱分离中的应用

整体柱是近年发展起来的一种新型的色谱分离分析技术，与传统的色谱柱相比，具有制作简单、背压低、分辨率高、柱容量大等优点。本文介绍了有机聚合物整体柱及其在生物大分子色谱分离领域的应用，分析了其存在的问题，并展望了其应用前景。     

以万古霉素为流动相添加剂的高效液相色谱法手性分析系统的建立

以丹酰化苯甘氨酸、丹酰化苯丙氨酸、丹酰化丝氨酸、丹酯化丙氨酸为模型化合物，通过对色谱柱类型、缓冲液类型、pH和盐浓度、万古霉素用量、甲醇用量、柱温等色谱参数进行考察，建立了以万古霉素为手性流动相添加剂在普通色谱柱上进行手性分析的色谱系统，并在该系统中成功地拆分了酮洛芬对映体。     

Direct determination of estriol 3- and 16-glucuronides in pregnancy urine by column-switching liquid chromatography with electrospray tandem mass spectrometry

Using column-switching liquid chromatography/tandem mass spectrometry (LC-MS/MS), we developed an improved analytical method of urinary estriol glucuronides. This new method is derived predominantly from maternal and fetal precursors in pregnancy. We used in the following procedure: first, we filtered urine samples with a membrane filter. Next, we directly injected the 50 microL aliquot of urine samples onto a pre-column. Then, after activating the column-switching valve, we backflushed the loaded samples onto the C(18) analytical column. Urine samples can be assayed within 20 min without any sample preparation steps. We monitored separated estriol glucuronides by negative electrospray ionization (ESI) and selected-reaction monitoring (SRM). The calibration range of estriol-3-glucuronide (E3-3G) and estriol-16-glucuronide (E3-16G) was 0.1-20 microg/mL and the linearity of the method was 0.9984 for E3-3G and 0.9987 for E3-16G. The limits of detection at a signal-to-noise (S/N) ratio of 3 were 10 ng/mL (E3-3G) and 5 ng/mL (E3-16G). The analytical recovery was over 85% and, in general, inter-day and intra-day variability for precision and accuracy were less than 10%. When applied to a pregnancy urine sample to biomedical monitoring of the function of the maternal/fetal unit, the proposed method allowed rapid and sensitive screening for the detection of E3-3G and E3-16G.