Simultaneous determination of p-aminohippuric acid, acetyl-p-aminohippuric acid and iothalamate in human plasma and urine by high-performance liquid chromatography

A sensitive and specific high-performance liquid chromatographic assay was developed for the simultaneous determination of p-aminohippuric acid (PAB), acetyl-p-aminohippuric acid (aPAH), and iothalamate in human plasma and urine. Plasma samples were prepared by protein precipitation with acetonitrile followed by evaporation, reconstitution in mobile phase, and injection onto a C-18 reversed-phase column. Urine samples were diluted with 3 volumes of mobile phase prior to injection. Column effluent was monitored by UV detection at 254 nm. The lower limits of quantification in plasma were 0.5 mg/l for PAH and aPAH, and 1.0 mg/l for iothalamate. The within-day and between-day coefficients of variation in plasma and urine were less than or equal to 7.8% for all analytes. This method is well suited for renal function studies using iothalamate and PAH, whether administered as a bolus dose or by continuous infusion, to measure glomerular filtration rate and effective renal plasma flow, respectively. (C) 1998 Elsevier Science B.V. All rights reserved.