Comparison by capillary SFC and SFC-MS of soxhlet and supercritical fluid extraction of hamster feces

Components of hamster feces ranging from low molecular weight fatty acids through the expected range of triglycerides have been eluted in a single SFC run with simultaneous pressure and temperature programming. Temperature programming from 140°C to 240°C was required to provide optimum conditions for separation of the fatty acids and to move the elution region of the sterol esters away from that of the triglycerides. Data from chemical ionization and electron impact mass spectrometry of compounds separated by SFC were used to confirm identities suggested by retention measurements and to provide tentative identities of unknown compounds. SFC with flame ionization detection was used to compare Soxhlet extraction, off-line supercritical fluid extraction (SFE), and on-line SFE of the feces. Although samples obtained by Soxhlet extraction and SFE produced very similar chromatograms, SFE required far less time and consumed much smaller quantities of organic solvent.     

Modelling and prediction of retention in high-performance liquid chromatography by using neural networks

Summary Multi-layer feed-forward neural networks trained with an error back-propagation algorithm have been used to model retention behaviour of liquid chromatography as a function of the composition of the mobile phases. Conventional hydro-organic and micellar mobile phases were considered. Accurate retention modelling and prediction have been achieved using mobile phases defined by two, three and four parameters. With micellar mobile phases, the parameters involved included the concentrations of surfactant and organic modifier, pH and temperature. It is shown that neural networks provide a competitive tool to model varied inherent nonlinear relationships of retention behaviour with respect to the mobile phase parameters. The soft models defined by the weights of the networks are capable of accommodating all types of linear and nonlinear relationships, neural networks being specially useful when the relationships between retention behaviour and the mobile phase parameters are unknown. However, to train neural networks more experimental points than with hard-modelling methods are required, hence the use of the networks is recommended only for those cases where adequate theoretical or empirical models do not exist.     

Sample capacity in open tubular and micro-packed columns for GC

Equations have been derived from which the maximum sample size which may be loaded on a column without significantly affecting the performance may be calculated. It is shown that micro-packed columns can handle a sample which is as much as forty times larger than that which can be loaded onto wall-coated open tubular columns with comparable conditions.     

氨基酸分析方法的研究进展

对目前应用于氨基酸分析的主要方法作了较详细评述。这些方法包括柱后衍生高效阳离子交换色谱法、柱前衍生反相高效液相色谱法、高效阴离子交换色谱-积分脉冲安培检测法等。引用文献73篇。     

单柱离子色谱法测定茶叶中草酸根和硫酸根的研究

本文研究单柱离子色谱分离测定茶叶中微量草酸根和硫酸根的方法。样品水浸泡，酸化液。上ＳｈｉｍＰａｒｓｋＩＣ－Ａ＿２柱分离，用２．０ｍｍｏｌ·Ｌ￣（－１）Ｈ－２Ｃ＿８Ｏ＿４／１．９ｍｍｏｌ·Ｌ￣（－１）Ｔｒｉ淋洗液洗脱，电导检测器检测，检测灵敏度为１．６Ｓ／ｃｍ，最低检出限０．０５μｇ／ｍＬ；线性范围Ｌ；相对标准偏差１．０６％；平均回收车９８．７２％９７．８８／。该法简便、快速、准确、灵敏、选择性好。     

Surface Energy of Silica-TEOS-PDMS Ormosils

Inverse gas chromatography (IGC) was applied to characterize the surface energy of organically modified silicates (ormosils) by measuring the interaction of molecular organic probes with the ormosil surface. Ormosils were prepared by the sol-gel method by the reaction of TEOS (tetraethoxysilane), PDMS (polydimethylsiloxane) and different types of silica (Aerosil 130, Aerosil 200 and Aerosil 380). The isosteric heat of adsorption, q _st, and the dispersive component of the surface energy, _s ^D, were estimated by using the retention volume of different nonpolar and polar probes at infinite dilution. The dispersive component shows an increase as the specific surface area of the silica is increased from 29.6 mJ/m² to 51.4 mJ/m² at 60°C. Such values are lower than that obtained for aerosil particles meaning that PDMS chains impede the interaction with silanol groups located on the silica surface. The specific interaction parameter, I^SP, and the enthalpy of specific adsorption, H _a ^SP, of polar probes on the ormosil surface were also measured in order to obtain the acid-base character of ormosil surface. The H _a ^SP, was correlated with the donor, DN, and the acceptor, AN, numbers of the probes to quantify the acidic, K _A, and the basic, K _B, parameters of the substrate surface. The obtained results suggest that the silica particles were covered by PDMS chains in a different way depending on the type of silica used. The values of K _A and K _B suggest that the ormosil surface is amphoteric, with predominantly acceptor electron sites.     

Separation of ortho-substituted tetraphenylporphyrins by preparative HPLC

Summary A method for the separation of substituted tetraphenylporphyrins by preparative liquid chromatography is reported. The quality of the columns formed by axial compression of various stationary phases is tested.     

Determination of 19-norandrosterone in CCQM-P68. NIST results using an isotope dilution liquid chromatography/tandem mass spectrometry method

The US National Institute of Standards and Technology (NIST) participated in an international interlaboratory study under the auspices of the Consultative Committee for Amount of Substance (CCQM) for the determination of 19-norandrosterone (19-NA) in urine, the principal metabolite of nandrolone and certain other synthetic testosterone substitutes banned for use by the World Antidoping Agency (WADA). Prior to this study, NIST developed a candidate reference measurement procedure based upon isotope dilution liquid chromatography/tandem mass spectrometry. This method was applied to a urine sample distributed to the participants in the study by the Australian National Measurement Institute, Pymble, Australia (NMIA). The NIST results were in very good agreement with those from the other participants, all of whom used methods based upon gas chromatography/mass spectrometry. All known significant sources of uncertainty were evaluated, resulting in a relative expanded uncertainty of less than 5% (coverage factor k = 2).     

Application of the Hall™ electrolytic conductivity detector for the analysis of chloroanilines and chloronitroanilines in POTW sludges

Simultaneous detection with a 700-A Hall? and an NPD detector is an effective technique for characterizing chloro-and chloronitroanilines in highly complex Publicly Owned Water Treatment Works (POTW) sludges. The utilization of a modified Varian effluent splitter and a SE-54 fused silica capillary column permitted the detection of mid-picogram quantities of the polar chloroanilines without sacrificing peak shape. The response of the Hall? detector in the halogen mode was roughly proportional to the number of chlorine atoms present, while the response of the Hall? in the nitrogen mode and the NPD was less predictably influenced by the presence of one or more nitro groups. When combined with retention time data, the ratio of the NPD response to the Hall? response has been found to substantiate the presence of chloro- and chloronitroanilines in sludge extracts.     

Analysis of high-performance liquid chromatography bonded stationary phases using thermogravimetry

A thermogravimetric method was developed for determining the C-18 bonded phase content of reversed phase high performance liquid Chromatographic stationary phases. The method yielded data that were comparable to the sum of carbon and hydrogen content. Excellent agreement between the two methods was achieved by heating the stationary phase samples to 150°C in order to remove adsorbed species prior to elemental analysis.This research stemmed from the author's Master's degree research undertaken at California State Polytechnic University Pomona, and conducted at the Getty Conservation Institute (GCI).The author is greatly indebted to the following colleagues at the GCI for their advice during the course of this project: Neville Agnew, Charles Selwitz, Dusan Stulik and David Scott. The HPLC bonded stationary phase samples were prepared by John Streng, California State Polytechnic University, Pomona.