ISSN:0935-6304    

DOI:10.1002/jhrc.1240180402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractA novel chiral stationary phase (CSP) derived from the atropisomeric enantiomerS‐3,3′‐dicarboxy‐2,2′‐dihydroxy‐1,1′‐binaphthyl (S‐DDBN) has been synthesized and its use for the separation of enantiomers demonstrated. The chiral selector is covalently bonded to amino‐functionalized silica gel, thus enabling the use of alcohols as mobile phases. Good chiral discrimination was obtained for the pharmacologically interesting class of benzergoline derivatives which act as selective dopamine D1receptor agonists. This paper reports the successful separtion of fifteen structurally related benzergoline racemates with separation factors up to 3.5. The influence of small differences in molecular structure on chiral discri

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractIn order to investigate the relationship between terpenoid content and black bear foraging preference, an analytical method was required to quantify mono‐ and sesquiterpenoids present in Douglas‐fir sapwood. Sapwood samples were scraped from trees, immediately frozen in liquid nitrogen, and then homogenized. A simple extraction requiring no clean‐up step was performed with ethyl acetate. Extracts were analyzed by gas chromatography with mass selective detection versus external standards. The recoveries of 22 terpenoids from fortified controls were approximately 90% with good precision (relative standard deviations of approximately

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe characteristic kinetic and retention properties of a silica‐based cyanopropylsiloxane‐bonded sorbent for solid‐phase extraction are described. Abraham′s solvation parameter model is used to characterize the contribution of individual intermolecular interactions to retention under liquid chromatographic and sample processing conditions with aqueous methanol mixtures as the mobile phase. The main features governing retention by the sorbent are the solute's size and hydrogen‐bond basicity; interactions of a dipole type are not significant when aqueous methanol solutions are employed as the mobile phase. Compared to typical silica‐based octadecylsioxane‐bonded sorbents the greater difficulty of forming a cavity in the solvated cyanopropylsiloxane‐bonded sorbent more than offsets the more favorable dipole‐type and solute hydrogenbond base interactions of the cyanopropylsiloxane‐bonded sorbent. It is shown that there are no practical circumstances for which a cyanopropylsiloxane‐bonded sorbent would be more useful than a typical ODS sorbent for the isolation of organic non‐electrolytes from water by

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractAn in‐line collector assembly designed for use in supercritical fluid extraction (SFE) vessels is described. This assembly enables solutes extracted by supercritical fluids (SF) to be retained in‐line on standard solid phase extraction (SPE) columns. The assembly consists of a standard 1 mL or 3 mL SPE column fitted into a specially fabricated Teflon© sleeve. The SPE column‐Teflon sleeve assembly is inserted into the SFE vessel followed by the sample matrix. This unit forms a leak‐tight seal with the vessel's end‐cap up to pressures of 680 bar. The choice of sorbents used in the in‐line SPE columns is dependent upon the properties of the solute in the supercritical state. After SFE is completed, the SPE column is removed and the solutes are recovered in 1–2 mL of the eluting solvent. No further clean‐up is normally required prior to chromatographic analysis of the analyte. A comparison was made of recoveries by in‐line and off‐line (after SF decompression) techniques for the SFE of three anabolic steroids in fortified chicken liver. The HPLC chromatograms of the steroids from the off‐line SPE columns were too complex for quantitation, because of coeluting artifacts, whereas chromatograms obtained from in‐line SPE columns were free from UV‐absorbing interferences

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe concentration sensitivity of a thermal conductivity detector (TCD) depends, among other factors, on the amount of sample mixture in the detector's sensing cell. Since the cell volume has to be appropriately matched with column diameter, it makes the concentration sensitivity of a TCD dependent on column diameter and, therefore, on the speed of gas chromatography. Through reduction of column diameter, higher speed tends to lead to a reduction in the concentration sensitivity of the cell. The factor which the most directly affects the concentration sensitivity of a TCD cell is the heat power conducted through the cell. The higher the power, the greater the sensitivity. The limit of detection of a TCD depends on the concentration‐sensitivity of its cell and on the level of statistical errors in the measurement. The errors increase with increasing analysis speed. As the column diameter is reduced, the errors cause additional worsening (on top of the decrease in concentration sensitivity) of the detection limit, dynamic range, and other performance characteristics of the TC

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractA new HPLC method for the fully automatic determination of aromatic sulfonates in aqueous samples is presented. The analytical procedure consists of an on‐line combination of ion‐pair extraction (IPE) and ion‐pair chromatography (IPC), both using RP‐C18 solid‐phase material and a tetrabutylammonium salt as ion pairing reagent. Experimental details and performance data are given. This method is suited for the trace‐level determination of a wide variety of benzene, naphthalene, anthraquinone and stilbene sulfonates. Detection limits for surface water using a diode‐array detector are in the sub‐ppb range. For naphthalene sulfonates a very good selectivity and minimal detectable limits of 0.02 μg/L or even lower can be achieved. So far, this method has been successfully applied to waste water, river water, bank filtrate, and water from different steps of drinking water production. The fate of several aromatic sulfonates has been studied beginning at the effluents of industrial waste water treatment plants and ending after activated carbon filtration in a water works. Napthalene‐1,5‐disulfonate (NDS, Armstrong acid) andcis‐4,4′‐dinitrostilbene‐2,2′‐disulfonate (DNS) appear in the raw water of the investigated water works and therefore have to be termed as relevant to water works. In contrast to other disulfonates NDS is extremely stable to biodegradation and ozonation and it is even desorbed from a highl

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractA method has been developed to enable thermal desorption of airborne substances from solid adsorbents based on active charcoal by means of microwave energy, followed by on‐line GC‐FID analysis. Ceramic traps were filled with 50 mg of commercially available graphitized carbon black. Adsorption efficiency and desorption conditions for three substances covering a broad range of vapor pressure were investigated. The recovery rate, breakthrough, and linearity of the system were determined by direct fortification with standard solutions, followed by microwave thermal desorption and gas chromatographic separation. The recovery efficiencies were 80–84 %, with a standard deviation of 3–6 %. The correlation coefficient of the linear range between 1 (10 for one of the compounds) and 1000 ng was>0.999. Initial experiments were performed to investigate the enrichment of the standards from the gaseous state. The recovery rates of the most volatile compound was increased by optimizing the density of the

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractFlumecinol and related compounds can, without derivatization, be separated into their enantiomers by gas chromatography on cyclodextrin phases; permethylated β‐cyclodextrin dissolved in OV‐1701 can be particularly recommended. Thermodynamic data describing the different intensities of interaction of the individual enantiomers with the stationary phases were determined. The values measured imply different separation mechanisms for the compounds investig

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180410

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractAn automatic sampling device has been developed for capillary zone electrophoresis. The sample is introduced to the column electrokinetically by rapidly exchanging buffer for sample in a narrow channel drilled in a plexiglass block. The autosampler is capable, under computer control, of performing multiple sample injections from a large volume sample source (such as a reaction vessel) as the sample concentration changes, and thus presents the possibility of analyzing time‐varying processes by CZE. Peak area reproducibility in electropherograms obtained after use of the sampler is less than 1% and efficiency is more than 2.2 × 105theoretical plat

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180411

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY