Pyrolysis of reversed-phase high-performance liquid chromatographic packing materials

Pyrolysis coupled with gas chromatography and or mass spectrometry, allows the identification of the bonded chain in reversed-phase high-performance liquid chromatographic stationary phases. It is possible to distinguish whether an octadecylated reversed-phase was prepared with a trifunctional(e.g., trichloro or monofunctional dimethyl, e.g., dimethyl-ethoxy) octadecylsilane from the relative heights of the heptadecene and octadecene peaks. The nature of the pyrolysis products was investigated. No carbon chains are formed with more carbon atoms than in the bonded chain. The peak area ratio of methane to that of the combined C₄ products allows one to deduce whether the reversed-phase was deactivated as not by reaction with a trimethylsilylating reagent (end-capping).     

Rapid, high-resolution high-performance liquid chromatographic analysis of antibiotics

A HPLC column devised for high separation speed combined with highly practical operating features has been found useful for separating antibiotics. Important characteristics involve compromises in packing particle size, column configuration and support-stationary phase combinations. We determined that these columns are useful for rapid, high-resolution separations with unmodified state-of-the-art HPLC equipment without the extra-column band-broadening effects typical of so-called “fast” HPLC columns. The proposed columns feature efficient sterically-protected monofunctional silane stationary phases that provide good separation reproducibility and high column stability. The combination of these unique bonded silanes and a highly purified, less-acidic silica support give superior peak shapes for antibiotic compounds. The proposed column configuration can halve separation times and double peak heights without loss in resolution, compared to widely used analytical columns. Increased mobile phase flow-rates permit even faster separations of antibiotics with only modest loss in resolution and peak heights for trace analyses in biological systems.     

New materials for solid-phase extraction and multiclass high-performance liquid chromatographic analysis of pesticides in grapes

Sample preparation procedures which included the use of new aminopropyl (NH2) and octadecyl (C18) solid-phase extraction (SPE) sorbents are proposed for the simultaneous multiclass determination of the fungicide benomyl and of the herbicides tebuthiuron, diuron, simazine, atrazine, and ametryn in grapes, using single wavelength high-performance liquid chromatography. Sorbent preparation uses a fast, easy, and effective procedure to obtain silica-based materials, made by depositing polysiloxanes on a silica support followed by thermal immobilization. Recovery results of the compounds, after elution from the SPE cartridges, indicate that the most efficient system employed silica loaded with 40% of an aminofunctional polydimethylsiloxane as sorbent, using dichloromethane:methanol (95:5, v/v) as eluent. Method validation, carried out in agreement with International Conference on Harmonization directives, was performed at three fortification levels (100, 200, and 1000 microg kg(-1)). Limits of detection and quantification show that the method developed can be used to detect the pesticides at concentrations below the maximum residue levels established by Codex Alimentarius, the US Environmental Protection Agency, the European Union, and Brazilian legislation.     

Group-selective prefractionation and analysis of nucleosides and catecholamines by high-performance liquid chromatographic techniques

Conclusions The use of borate as ligand in conventional affinity chromatography has found numerous applications in biochemical research [6], as for example for the clean-up of ribonucleosides and catecholamines in physiological fluids, the separation of DNA and RNA, the isolation of glycosidated hemoglobins, separation of aminoacylated RNA from free RNA, ligand mediated (piggyback) chromatographic enrichment of enzymes or the separation of base Q containing tRNA from base Q free tRNA. With the development of borate functionalized silica borate affinity chromatography has also been turned out to work under HPLAC conditions.By use of a column switching technique we could introduce a combined HPLAC/HPLC method particularly suitable for the on-line clean-up and analysis of ribonucleosides in complex matrices. We now have expanded the application of our on-line system for the clean-up and analysis of the adrenergic amines from spiked physiological matrix which means a powerful improvement compared to the system introduced by [7] for the on-line analysis just of one of the dopamine catabolites. The method described should be the method of choice for the majority of applications mentioned above as it greatly decreases the analysis time, is suitable for automation and in conjunction with a data-processing system, is applicable to routine clinical analysis.

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Gruppenselektive Vortrennung und Analyse von Nucleosiden und Catecholaminen mittels hochleistungs-chromatographischer Techniken

     

Ion-pair high-performance liquid chromatographic analysis of aspartame and related products

A simple and accurate quantitative determination of aspartame (L-alpha-aspartyl-L-phenylalanine methyl ester), a new artificial sweetener, is described. The method, which is based on ion-pair high-performance liquid chromatography, allows the determination of aspartame in finished bulk and dosage forms, and the detection of a few related products at levels down to 0.1%.     

Determination of coumermycin A1 in plasma by reversed-phase high-performance liquid chromatographic analysis

Coumermycin A1 is an antibiotic isolated from Streptomyces hazeliensis var. hazeliensis nov. sp. as a sodium salt which exhibits antistaphylococcal activity. A sensitive and selective high-performance liquid chromatographic method was developed for the determination of the compound and three known homologues which are extracted from plasma buffered to pH 6.5 into methyl-tert.-butyl ether-2-propanol (97.5:2.5), the residue of which is dissolved in the mobile phase and analyzed by automated reversed-phase high-performance liquid chromatography using UV detection at 330 nm for quantitation. Novobiocin is used as the internal standard. The method was used to determine the plasma concentration--time profile of coumermycin A1 in the dog following a single intravenous administration of a 12 mg/kg dose of a solubilized dosage form of the bulk drug substance.     

Enantiospecific high-performance liquid chromatographic analysis of 2-phenylpropionic acid, ketoprofen and fenoprofen

A high-performance liquid chromatographic method has been developed for the quantitation of the R- and S-enantiomers of 2-phenylpropionic acid, ketoprofen and fenoprofen. The assay consists of extracting the arylpropionic acid with an internal standard and measuring the total (R + S) concentration of enantiomers by reversed-phase chromatography, derivatising the chromatographic fraction corresponding to the enantiomers to form R- and S, R-2-phenylethylamide distereoisomers which are resolved by normal-phase chromatography in order to calculate the fraction of each enantiomer. The limits of sensitivity of the assay for 2-phenylpropionic acid, ketoprofen and fenoprofen are 6, 0.2 and 2.5 mg/l, respectively.     

Gel filtration and high-performance liquid chromatographic analysis of phosphotungstic acid soluble peptides from blue cheeses

Summary The nitrogen fraction from cheese, soluble in phosphotungstic acid has been analyzed by gel permeation and high performance liquid chromatography. Elution profiles of this fraction on Sephadex G-10 show that there are no peptides of molecular weight higher than 700 daltons. Six fractions have been obtained. The first one has the peptides and some amino acids. Fractions II to VI contains mostly free amino acids. Fraction I has been separated into many peaks by HPLC. Six or seven of these peaks are presumed to correspond to peptides. A part of this work has been presented in XXI Reunión Bienal de la Socieded Espa?ola de Química. Sept. 1986. Santiago de Compostela. Espa?a.     

Residue analysis of triazine herbicides in soil: Comparison of a capillary gas chromatographic and a high-performance liquid chromatographic method

Summary Two methods for the determination of triazines in soil were developed and compared. After extraction of the residues with methanol and clean-up by gel permeation chromatography, the samples evaporated were analysed for triazines by splitless capillary gas-chromatography with NP-detector (GC-NPD) and microbore high performance liquid chromatography with UV detector (HPLC-UV) at 222 nm. Both methods gave similar results. The microbore HPLC method was suitable for the analysis of a number of triazines at 10 ppb whereas capillary GC method was used for the analysis of triazines at 5 ppb. Satisfactory average recoveries for the two methods were obtained at 80 ppb and 20 ppb, respectively.

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Rückstandsanalytik von Triazin-Herbiciden im Boden: Vergleich zwischen einer capillar-gas-chromatographischen und einer hochleistungs-flüssig-chromatographischen Methode

Zusammenfassung Zwei Methoden zur Bestimmung von Triazinen im Boden wurden entwickelt und miteinander verglichen. Nach der Extraktion der Rückstände mit Methanol und clean-up durch Gelpermeations-Chromatographie wurden die Proben eingeengt und auf Triazin-Rückstände hin untersucht. Zur Detektion wurden die splitlose Capillar-Gas-Chromatographie mit NP-Detektor (GC-NPD) und die Microbore-Hochdruckflüssig-Chromatographie mit UV-Detektor (HPLC-UV) bei 222 nm verwendet. Beide Methoden ergaben vergleichbare Ergebnisse bei einem Minimum an Zeit- und Materialaufwand und der Möglichkeit der Automatisation der Rückstandsanalytik. Die Microbore-HPLC-Methode erreichte nach einfachem GPC clean-up eine Nachweisgrenze von 10 ppb im Vergleich zu 5 ppb bei der Capillar-GC-Methode. Zufriedenstellende Wiederfindungsraten wurden für beide Methoden bei 80 ppb und 20 ppb ermittelt.

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On leave from: Institute of Hydrobiology, Academia Sinica, Wuhan, P. R. China     

Correlation of urokinase activity from biopotency and high-performance liquid chromatographic assays

A simpler, less expensive, and faster high-performance liquid chromatographic method was shown to be an alternative to urokinase potency determinations by the Ploug method. Post-elution recovery of the low-molecular-weight form was 104 +/- 2.4% as determined by the Ploug method. Two analysts reported relative standard deviations of 1.6% and 1.1% based on peak height determination of eight replicate injections of a single sample of low-molecular-weight material. Linearity at the same wavelength for low- and high-molecular-weight forms was 0.9999 and 0.9992, respectively, for peak height versus potency.