Ion-pair Reversed-phase HPLC Research Articles

High pressure liquid chromatographic determination of thioglycolic acid in cold wave fluids and depilating creams

Synopsis A high pressure liquid chromatographic method is described for the determination of thioglycolic acid in hair waving fluids and depilatories. Prior to chromatography the acid is converted into a yellow-coloured nitrobenzooxadioazole (NBD) derivative to permit HPLC detection at 464 nm. Optimum derivatization conditions could be obtained when 0.01% aqueous solutions of thioglycolic acid were heated with NBD-C1 at pH 7. Hair waving fluids and depilatories are simply diluted with an aqueous buffer of pH 7 and, if necessary, clarified and filtered, before the derivatization procedure. To the mixture an internal standard Sunset Yellow FCF, Colour Index nr. 15985, is added before performing ion-pair reverse phase HPLC. A reverse phase C18 column is used. The mobile phase is aqueous methanol, to which the counter ion, tetrabutyl-ammonium phosphate, is added. Recoveries ranged from 97.8 to 100.7%. The proposed method permits a resolution of other possible mercaptocompounds such as thiolactic acid and thioglycerol. Sixty market samples of cold wave fluids and depilatories have been analysed by the proposed method, and the results compared with data obtained by iodometric titration.

High performance liquid chromatographic determination of clavulanic acid in human urine.

An ion pair reversed phase HPLC method for the determination of clavulanic acid has been developed. Since clavulanic acid had poor absorption (lambda max 201 nm in water) in a UV-region suitable for HPLC detection, the detectability was enhanced by bathochromic shift of lambda max due to solvent effect. The shifts of lambda max were measured with the solutions containing clavulanic acid, tetrabutylammonium bromide, and phosphate buffer salts in aqueous methanol. The magnitudes of the observed shifts were investigated with respect to pH, ionic strength, methanol content, and TBAB concentration. The results indicated that TBAB concentration was the predominant factor responsible for the bathochromic shifts. Taking account of the results together with solvent effects on the retention of clavulanic acid on hydrophobic stationary phase, HPLC condition suitable for detection and separation of clavulanic acid in urine was established as follows; mobile phase: 10 mM TBAB + 0.6 mM NaH2PO4 + 0.4 mM Na2HPO4 in H2O - MeOH, 10:1 (v/v)(pH 7.02), flow rate: 1.5 ml/minute, stationary phase: LiChrosorb RP-18 (25 cm x 4.6 mm i.d.), detection: UV 220 nm. The applicability of the present method is demonstrated by determining the time course of urinary excretion of clavulanic acid after oral administration of a conjugated tablet of clavulanic acid and amoxicillin to human subject.

Rapid assay of adenine nucleotides or creatine compounds in extracts of cardiac tissue by paired-ion reverse-phase high-performance liquid chromatography

The developed method of ion-pair reverse-phase high-pressure liquid chromatography (hplc) enables one to separate adenine nucleotides in cardiac tissue extract within 10 min with recovery of about 98% and lowest detection limit of 10 −6 m. Separation of creatine and phosphocreatine is performed by ion-pair reverse-phase hplc (recovery about 98%) using detector wavelengths of 210 nm; the lowest detection limit is in the range of 3 × 10 −6 m.

Daily fluctuation (circadian and ultradian) in biogenic amines of the rat brain.

Daily fluctuation (circadian and ultradian) in biogenic amines of the rat brain.