Development of a capillary gas chromatographic procedure

A simple and fast capillary gas chromatographic method with flame ionisation detection (FID) has been developed for the analysis of fluoxetine, fluvoxamine, citalopram, sertraline and paroxetine in their pharmaceutical preparations, using clomipramine as internal standard in order to achieve quantification. The reported method is the first screening one that allows the determination of the five selective serotonin reuptake inhibitors by GC, permitting also to avoid prederivatization for the first time and it is even a pioneering work including an extensive analytical validation and robustness treatment on placebo pharmaceutical formulations too. Optimal conditions for the quantitative gas capillary separation were investigated: column head pressure (100 kPa), injector and detector (FID) temperatures (210 and 260 °C), time and temperature for the splitless step (0.80 min and 80 °C, respectively), volume injected (2 μL) and oven temperature program, providing analysis times shorter than 7 min. Aspects such as stability of solutions, linearity, accuracy, precision, detection and quantitation limits are examined on a selected placebo in order to validate this method. Peak purity is assessed using mass-selective detection (DMS). The robustness of this method was evaluated using the Plackett-Burman fractional factorial experimental design with a matrix of 15 experiments and the statistical treatment proposed by Youden and Steinner. The scope of the validated method is proved in the analysis of almost existing pharmaceutical preparations, with recoveries between 98.5% and 102.4% with regard to their nominal contents. Finally, the proposed method could be also a very successfully option for the analysis of these SSRIs in real urine samples introducing a previous solid phase extraction-preconcentration step.     

Development of an impurity test for 3-tropanyl-3,5-dichlorobenzoate using capillary gas chromatography

Summary A simple, accurate and sensitive capillary gas chromatographic test procedure was developed for the detection and quantification of impurities in bulk 3-tropanyl-3,5-dichlorobenzoate, a drug which is a neural serotonin 5HT₃ receptor antagonist. The drug substance was dissolved in acetonitrile and chromatographed on a 30 m×0.32 mm 0.25 μm film DB-5 column operated with a temperature program of 80 to 230°C. A flame ionization detector was used, and the impurities detected in the drug were estimated from peak areas on a percent basis compared to the parent peak. Validation of this procedure included a recovery study of spiked impurities from 0.1 to 1.2% (w/w) and a repeatability study using two different synthesized batch lots of the drug.     

Quantitative capillary gas chromatographic analysis

Summary The attainment of precise quatitative analytical data using open-tubular (capillary) columns in standard, commercially available gas chromatographic instrumentation is demonstrated. Key elements in the design and proper utilization of the instrumentation are discussed. The function of the various sample introduction systems is elaborated and their quantitative performance demonstrated. The extra-column contribution to band-spreading is determined and the resultant data is used assessing the suitability of commercial instrumentation for highspeed capillary gas chromatography. The quantitative analysis of a sample containing some eleven components in less than thirty seconds is shown.Dedicated to Dr. L. S. Ettre on his sixtieth birthday.     

Analysis of aspartic acid racemization. Evaluation of a chiral capillary gas chromatographic and a diastereomeric high-performance liquid chromatographic method

A recently developed chiral gas chromatographic method and a diastereomeric high-performance liquid chromatographic method for the analysis of aspartic acid enantiomers in protein hydrolyzates have been evaluated. Although both techniques are fast and convenient, the latter is preferred because of its higher reproducibility and shorter analysis time. Furthermore, this method offers the possibility of on-line derivatization and analysis.     

聚合离子液体毛细管气相色谱固定相的性能评价

离子液体作为毛细管气相色谱固定相的选择性和热稳定性是近年人们关注的课题。本文合成了1-烯基-3-苄基咪唑-二(三氟甲基磺酰)亚胺盐(VBIm-NTf2)离子液体并经毛细管柱内聚合制得了聚合离子液体PVBIm-NTf2色谱柱。与VBIm-NTf2色谱柱相比,PVBIm-NTf2色谱柱具有良好的色谱选择性和热稳定性。PVBIm-NTf2色谱柱对Grob试剂、醇混合物、酯混合物和苯系物等都表现了很好的分离能力,并且色谱峰峰形窄且对称。该聚合色谱柱在250 ℃下老化6 h后仍具有良好的分离能力和选择性。本文还测定了PVBIm-NTf2的Abraham溶剂化参数,解析了该固定相与溶质间的相互作用,相关研究国内尚未见报道。研究表明,对常规离子液体进行柱内聚合是改善常规离子液体气相色谱固定相的热稳定性和选择性的有效途径。     

气相色谱毛细管柱操作参数最优化探索

本文对气相色谱毛细管柱如何选择合适的柱温与载气线速进行了探讨,提出了一种在最短时间内使一种难分离物质达到预期分离的最优化方法,本法数学模型简单.实验工作量小,最优操作参数范围的估计较可靠,改变了凭经验与直觉选择分析件的传统方法,可适用于现代具有微机控制的色谱仪。     

Evaluation of two commercial capillary columns for the enantioselective gas chromatographic separation of organophosphorus pesticides

The separation of the enantiomers of 13 organophosphorus pesticides (OPPs) has been investigated by gas chromatography (GC) with flame ionisation detection (FID) using two different commercially available chiral columns, Chirasil-Val (l-valine-tert-butylamide) and CP-Chirasil-Dex CB (heptakis (2,3,6-tri-O-metil)-β-cyclodextrin). Using the Chirasil-Val column no chiral resolution was obtained for the OPPs investigated under any tested experimental condition. The use of the CP-Chirasil-Dex CB stationary phase enabled good individual enantiomeric separation of two OPPs, ruelene and trichlorfon and partial separation of naled, chloretoxyphos, isophenphos and metamidophos. Also, the obtained chromatographic results showed that Chirasil-Dex could resolve enantiomers through the combination of different mechanism (e.g. formation of inclusion complexes and/or interactions outside the cyclodextrin cavity).

Under optimised conditions, precision, linearity range and detection limits were evaluated for the enantiomers of ruelene and trichlorfon using CP-Chirasil-Dex CB column and electron capture detection (ECD). By using the GC-ECD method the enantiomers of these OPPs could be satisfactorily detected at very low concentration levels. The detection limits observed were 1.5 ng mL⁻¹ and 11.5 ng mL⁻¹ for the enantiomers of trichlorfon and ruelene, respectively.     

Simplex optimization of a programmed temperature capillary gas chromatographic separation

The modified simplex algorithm proposed by Nelder and Mead has been used to optimize the separation by temperature programmed capillary GC, of volatile compounds present in alcoholic beverages. An adequate objective function, CRF, based on the separation factor of Kaiser has been used for the optimization process. A factorial design was initially performed to verify the relationship between the several parameters of interest. Following this, the optimization was executed and a surface adjusted within the set of experimental data.     

On-line introduction of high-pressure gas-liquid sample for capillary gas chromatographic analysis

An on-line sample introduction technique in capillary gas chromatograph (CGC) for the analysis of high-pressure gas-liquid mixtures has been designed and evaluated. A sample loop of 0.05 microL and a washing solvent loop of 0.5 microL are mounted on a 10-port switching valve, which serves as the injection valve. A capillary resistor was connected to the vent of sample loop in order to maintain the pressure of the sample. Both the sample and the washing solvent are transferred into the split-injection port through a narrow bore fused silica capillary inserted into the injection liner through a septum. The volume of the liner is used both as the pressure-release damper and evaporation chamber of the sample. On-line analysis of both reactants and resultants in ethylene olimer reaction mixture at 5 MPa was carried out, which demonstrated the applicability of the technique.     

Improvements in glass capillary gas chromatographic polychlorobiphenyl analysis

Separation of a 1:1:1:1 calibration mixture of Aroclors 1221, 1016, 1254, and 1260 on soda glass capillaries coated with Apolane (C-87) or Apiezon L is described. Polychlorobiphenyl congener structures are assigned to 112 separated and partially separated zones. The quantitative composition of Aroclor 1221 is reported. The performance of the two stationary phases on different lengths of laboratory and commercially prepared capillaries is compared and found to be very similar. Aroclors 1221, 1016, 1254, and 1260 are employed (1:1:1:1) for the primary calibration mixture because they contain all components of the commercial materials which pollute the environment; they are also easily obtained from the U.S. EPA Repository so that the method can be used in any laboratory by employing the calibration data given here.     

Insoluble beta-cyclodextrin polymer for capillary gas chromatographic separation of enantiomers and isomers

An insoluble beta-cyclodextrin polymer cross-linked with identified epichiorohydrin has been prepared; its structure was identified by means of infrared and 13C NMR spectra. Three capillary columns have been coated with the polymer treated by ultrasonication by three coating methods. Chromatographic characteristics such as column efficiency, thermal stability and polarity, have been studied, and two kinds of disubstituted benzene isomers and eight pairs of enantiomers have been separated on the three capillary columns. The results show that the beta-cyclodextrin polymer is suitable for use as a capillary gas chromatographic stationary phase, and that the column, prepared by loading beta-cyclodextrin polymer stationary phase with 50% methyl-50% phenylsilicone (OV-17), shows good chromatographic properties in separating enantiomers and positional isomers.     

A fast derivatization procedure for gas chromatographic analysis of perfluorinated organic acids

A rapid and simple derivatization procedure has been developed for gas chromatographic determination of perfluorinated organic acids (PFCAs, C₆–C₁₂), using isobutyl chloroformate (IBCF) to convert the acids into the more volatile isobutyl esters, under catalysis by pyridine. The procedure was optimized in an acetonitrile medium and applied to GC techniques with electron-capture detection (GC-ECD) and mass spectrometry with electron-impact ionization (GC-EI-MS); for the sake of comparison, HPLC with electrospray-ionization MS (HPLC-ESI(−)-MS) was also tested. The LOD and LOQ values obtained for these three techniques were compared, and the lowest LODs were obtained with GC-ECD (0.06–1.80 μg mL⁻¹). The procedure was further optimized in an aqueous medium, obtaining the best results in a phosphate buffer (pH 2.5, 50 mmol L⁻¹), in which the LOD and LOQ values were measured for GC-ECD a GC-EI-MS. The lowest LODs were found for GC-EI-MS (0.030–0.314 μg mL⁻¹). The practical applicability was tested on Vltava river water samples.     

Electron-capture gas chromatographic procedure for simultaneous determination of amphetamine and N-methylamphetamine.

An electron-capture gas chromatographic procedure for the simultaneous determination of amphetamine and N-methylamphetamine in biological samples is described. The method employs extraction with the ion-pairing reagent bis(2-ethylhexyl)phosphoric acid, and back-extraction with 0.5 M hydrochloric acid. The hydrochloric acid phase is basified, and the amphetamines and the internal standard benzylamine are derivatized with pentafluorobenzenesulfonyl chloride prior to analysis on a gas chromatograph equipped with a capillary column. Levels of amphetamine and N-methylamphetamine have been determined in the urine and liver of rats treated chronically with (-)-deprenyl.     

Preparation and chromatographic characteristics of calix[4]arene polysiloxane as stationary phases for capillary gas chromatography

Summary Two new kinds of calix[4]arene derivatives, 5, 11, 17, 23-tetra-tert-butyl-25,27-bis(isopropylcarbamoyl-methoxy)-26,28-diundecenyloxy calix[4]arene (C[4]A) and 25,27-dibutoxy-5, 11, 17, 23-tetra-tert-butyl-26,28-diundecenyloxy calix[4]arene (C[4]B0, are prepared and then are polymized by two different processes. Three calix[4]arene polysiloxane stationary phases for capillary gas chromatography are obtained. Their chromatographic characteristics, including column efficiency, polarity, selectivity, glass-transition temperature and thermal stability are studied. Retention mechanisms are also discussed.