Showing papers in "Journal of Chromatographic Science in 1985"

Calculation of Flame Ionization Detector Relative Response Factors Using the Effective Carbon Number Concept

Abstract: Equations are given for relating flame ionization detector relative response factors to the effective carbon number (ECN) of neat and derivatized components. The ECN ap­ proach can be used for calculating relative response fac­ tors in cases where pure materials are not available for detector calibration. Examples of this approach are given for the analysis of polycyclic aromatic hydrocarbons and oxygenated organics in neat form, alcohols and acids as the trimethylsilylated derivatives, and carbohydrates as the trimethylsilyl-oxime derivatives.

Rapid and high resolution capillary supercritical fluid chromatography (SFC) and SFC/MS of trichothecene mycotoxins

Abstract: The potential application of capillary column supercritical fluid chromatography (SFC) and SFC/mass spectrometry (SFC/MS) for the separation and analysis of mycotoxins of the trichothecene group was examined. Trichothecenes present significant analytical problems for both gas and liquid chromatography with a major difficulty for the latter being the lack of sufficiently sensitive and selective detectors. Supercritical carbon dioxide mobile phases at temperatures up to 100 degrees C were used with deactivated fused silica columns coated with crosslinked stationary phases. Separations were obtained under pressure ramped conditions using long (15 m) 50-micron i.d. columns for several trichothecenes (diacetoxyscirpenol, deoxynivalenol, and T-2 toxin) and related higher molecular weight macrocyclic (roridin and verrucarin) trichothecenes. In addition, new rapid pressure programming techniques with short (less than 2m) 25- to 50-micron i.d. capillary columns were used to obtain fast separations in as little as 1 min. SFC/MS with ammonia chemical ionization provided high selectivity and sensitive detection (with approximately 1-pg detection limits) for trichothecene mixtures. The extension to complex sample matrices is discussed and the application of selective MS/MS detection is demonstrated.

Characterization of an on-column electrochemical detector for open-tubular liquid chromatography

Abstract: Description d'un processus de nettoyage electrochimique de l'electrode pour enlever les adsorbats parasites. Utilisation d'une technique amperometrique differentielle pulsee par la detection, dans le cas de l'oxydation d'acetaminophene

Capillary gas chromatographic analysis of volatile and non-volatile organic acids from biological samples as the t-butyldimethylsilyl derivatives.

Abstract: A quantitative procedure for the analysis of volatile organic acids and lactic acid in silage is described. The samples were extracted with diethyl ether, derivatized by t-butyldimethylsilylation, and then separated by capillary gas chromatography. The same procedure was useful for the identification by gas chromatography/mass spectrometry of organic acids in samples such as the metabolic fermentation products of anaerobic bacteria.

Differences in Chromatographic Properties of Fused Silica Capillary Columns, Coated, Crosslinked, Bonded, or Crosslinked and Bonded with Polyethylene Glycols (Carbowax 20M) Using Complex Fatty Acid Methyl Ester Mixtures

Abstract: Les phases liees ou liees et reticulees donnent de meilleures separations et sont plus stables. La polarite des phases varie avec leur traitement

Separation of Underivatised Amino Acid Enantiomers by Means of a Chiral Solvent-Generated Phase

Abstract: L'eluant contient de petites concentrations de Cu(II)-L-phenylalanine, N-methyl ou N,N-dimethyl-L-phenylalanine

Improvements in glass capillary gas chromatographic polychlorobiphenyl analysis.

Abstract: 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.

GC/Matrix Isolation/FTIR Applications: Analysis of PCBs

Abstract: High resolution capillary gas chromatography, coupled with the superior infrared spectra produced by matrix isolation FTIR, yields a powerful analytical tool which is applied to the analysis of polychlorinated biphenyls (PCBs). PCB congeners are identified in a commercially produced mixture (Aroclor 1221) using the matrix-isolated infrared spectra obtained by this method. The gas chromatograph/matrix isolation/Fourier transform infrared (GC/MI/FTIR) instrument utilized was developed at Argonne National Laboratory. GC/MI/FTIR is especially useful in the determination of PCBs in samples where the Aroclor pattern is not present.

Comparison of state-of-the-art column switching techniques in high resolution gas chromatography

Abstract: Comparaison de trois systemes du commerce: SGE (dans un four de Hewlett-Packard 5880), Valco (avec un CG IBM 9630), et Siemens (Si Chromat 2). Les systemes a deux fours sont a preferer pour des raisons pratiques (piegeage, mise en place de la colonne), sinon les performances sont equivalentes

Micro-Liquid Chromatography/Mass Spectrometry with Direct Liquid Introduction

Abstract: Travaux du laboratoire, en particulier sur le plan du materiel, c'est un injecteur a diaphragme qui est utilise comme interface chromatographe-spectrometre. Nombreux exemples de separations

Photolytic Derivatization for Improved LCEC Determinations of Pharmaceuticals in Biological Fluids

Abstract: Although electrochemical (EC) methods have been demonstrated to be sensitive and selective, wide use of EC detection in high performance liquid chromatographic (HPLC) assays in forensic and clinical toxicology laboratories has not been forthcoming. This fact is due to the general difficulty involved with the use of reductive EC detection methods, as well as to the lack of EC response in either the oxidative or reductive mode, for a number of classes of drugs having substantial clinical and forensic importance. The use of an on-line, post-column, continuous photolytic derivatization step, followed by conventional oxidative amperometric detection, alleviates many of these problems. In this report, the use of HPLC-photolysis-EC (HPLC-h nu-EC) for the trace determination of a number of controlled substances in biological fluids is presented. Following system optimization, the determination of phenobarbital, cocaine, methylphenidate, and several 1,4-benzodiazepines (and metabolites) is linear over three orders of magnitude. In addition, HPLC-h nu-EC offers a sensitive approach for these compounds, in that limits of detection (LODs) are all below 1 microgram/ml, ranging from 1 ng/ml to 750 ng/ml. The validity of this newer method is demonstrated in collaborative studies involving the trace determinations of phenobarbital in human serum, and chlordiazepoxide and its major metabolite, norchlordiazepoxide, in human urine. Finally, the authors' view of the role of HPLC-h nu-EC in the clinical and forensic toxicology laboratory is presented.

Reversed-phase chromatography of triglycerides--theoretical and practical aspects of the influence of injection solvents.

Abstract: The reversed-phase chromatography of triglycerides is very sensitive to both changes in the properties of the injection solvent relative to those of the mobile phase and to the volume injected. These well-established phenomena are rationalised in terms of solvent parameters and suggestions are made as to how optimum conditions can be derived. The practical consequences of this are illustrated with chromatograms of olive oil samples.

An Introduction to Small-Bore Columns

Abstract: On examine en particulier l'interet de ces colonnes par rapport a la sensibilite massique, et a l'economie de solvant. L'accent est aussi mis sur la notion de diametre optimal pour un systeme chromatographique donne

A gas chromatographic micromethod for trace determinations of phenols

Abstract: La methode convient a l'analyse de tres petits echantillons (0,5 a 1 ml). La detection se fait par ionisation de flamme et capture electronique. La limite de detection pour le phenol, les chlorophenols, le p-cresol, les dimethyl- et nitrophenols varie de 0,01 a 0,2 ng/ml a l'exception du phenol (dinitro-«2,4»)

Dynamic headspace analyses of residual volatiles in pharmaceuticals.

Abstract: Pharmaceutical preparations may be assayed for volatile organic compounds by purging them with a stream of inert carrier gas and collecting the organics onto a suitable sorbent material, from which they may be backflushed to a gas chromatograph. Compared to solvent extraction, the process offers advantages of increased sensitivity, ease of automation, and elimination of the solvent peak. Examples are given of three major sources of volatiles in pharmaceuticals, with the development of a method for quantitating the volatiles using an internal standard.

Peak Variance as a Function of HPLC Column Length and Diameter

Abstract: La variance decroit avec la longueur pour des colonnes de 22 a 10 cm. On observe des anomalies pour 3 cm et 4,6 mm de diametre interne, mais ce dernier diminuant jusqu'a 2,1 mm on retrouve la variation theorique prevue

Liquid Chromatographic Determination of the Enantiomeric Composition of Amphetamine and Related Drugs by Diastereomeric Derivatization

Abstract: A procedure is described for the derivatization of amphetamine and methamphetamine enantiomers with 4-nitrophenylsulfonyl-(S)-prolyl chloride. The resulting diastereomeric amphetamine derivatives were resolved by a reversed-phase procedure. The derivatization yield was maximized in the 95% range using a five-fold molar excess of the chiral derivatizing agent and an approximate 18 to 1 ratio of base (NaHCO3) to total acid generated in the reaction.

Comparison of Dynamic and Static Mixing Devices for Gradient Micro-HPLC

Abstract: Recherche des parametres optimisants, qui sont nombreux: type de pompe, melange initial, nature des solvants, debits, geometrie de la cellule de melange, etc...

Determination of polycyclic aromatic hydrocarbons in environmental samples by high performance thin-layer chromatography and fluorescence scanning densitometry.

Abstract: High performance thin-layer chromatography (HPTLC) with fluorescence scanning densitometry was used for the quantitative determination of polycyclic aromatic hydrocarbons in the soluble organic fraction of air particulate samples. A method using normalized emission response ratios was developed to determine sample identity and to test for peak homogeneity. To preserve the high sample throughput of HPTLC, the two-point calibration method was used for quantitation. The principal advantages of HPTLC as a screening technique for environmental samples are its low cost, methodological simplicity, high sample throughput, and the ability to analyze crude samples with a minimum amount of sample cleanup.