High-performance liquid chromatographic assay for N2-[5-(hypoxanthin-9-yl)pentyloxycarbonyl]-L-arginine (ST 789) in plasma by cyclization with benzoin and fluorimetric detection.
This paper describes a new highly sensitive assay for N2-[5-(hypoxanthin-9-yl)pentyloxycarbonyl]-L-arginine, an immunomodulatory agent, required for clinical pharmacokinetic investigation. A pre-column derivatization by cyclization with benzoin in aqueous medium produces the fluorescent 2-substituted amino-4,5-diphenylimidazole fluorescing at 450 nm (excitation wavelength 310 nm). L-Arginine-acetyl-L-carnitinamide chloride (ST 857, II), another arginine derivative, was used as an internal standard. A C18 DB column (5 microns, 250 mm x 4.6 mm I.D.) and a 45:55 (v/v) mixture of 0.05 M ammonium phosphate at pH 7.2 and methanol as mobile phase were used. Linearity was ascertained in the range 5-100 ng. Extraction recovery from plasma proved to be higher than 90% in the range 5-50 ng/ml. Intra-day precision, expressed as coefficient of variation, was in the range 4.7-6.0%. The limit of quantification proved to be 5 ng/ml and the limit of detection 2 ng/ml at a signal-to-noise ratio of 5. The method is specific.
New Method for the Fluorimetric Determination of Guanidino Compounds with Benzoin
A new fluorimetric method for the precise and rapid determination of guanidino compounds with benzoin is described. This is based on their reaction in an aqueous potassium hydroxide solution with benzoin (dissolved in methylcellosolve), in the presence of β-mercaptoethanol and sodium sulfite, while the pH of the reaction mixture is maintained at 9.2 after the reaction. This method requires heating at 100° for only 10 min. The excitation and emission maximum wavelengths of the fluorescence from these compounds are at around 325 and 435 nm, respectively. The method is simple, selective for guanidine and monosubstituted guanidino compounds (including peptides with one or two arginyl residues) and sensitive ; almost all the compounds can be determined at concentrations as low as 40-170 pmol/ml.
Dünnschichtchromatographische bestimmung von kreatinin und kreatin im harn
Zusammenfassung Es wird eine dunnschichtchromatographische Trennung auf Zellulose fur Guanidinderivate beschrieben, die es ermoglicht, sowohl Kreatinin als auch Kreatin von storenden Harninhaltsstoffen sicher abzutrennen. Die isolierten Stoffe konnen mit guter Reproduzierbarkeit quantitativ ermittelt werden. Kreatinin wird nach einer modifizierten Methode nach Folin mit einer Genauigkeit von ± 3% bestimmt. Fur die Kreatinbestimmung wurde die Diacetylreaktion nach Kanig den Erfordernissen der Dunnschicht-Chromatographie entsprechend abgeandert. Hier betragt die Genauigkeit ± I .3%.