Reversed-phase liquid chromatographic method for the determination of p-aminobenzoic acid and anthranilic acid in urine: application to the investigation of exocrine pancreatic function

Abstract

Exocrine pancreatic function can be assessed by determining the recovery in urine of p-aminobenzoic acid (PABA) following the oral administration of (N-benzoyl-L-tyrosylamino)benzoic acid (bentiromide). However, misleadingly abnormal results often occur in patients with abnormal intestinal, liver and renal function. Co-administration of ¹⁴C-PABA and the determination of the ratio of the recoveries of PABA to ¹⁴C-PABA, the PABA excretion index (PEI), has been used to eliminate these misleading results. Unfortunately, this has the disadvantage of exposing patients to radioactivity. We report the development and optimization of a modified test in which anthranilic acid, the ortho isomer of aminobenzoic acid, is substituted for the radiolabelled PABA. PABA and anthranilic acid in urine are determined by a C₁₈ reversed-phase HPLC method. Peak detection is carried out at 254 nm. The method is specific for PABA and anthranilic acid, precise and fairly rapid. The PABA excretion index values in patients with pancreatic steatorrhoea (0.18–0.43) determined using the new liquid chromatographic method were clearly separated from those in healthy controls (0.63–1.14).