An enzyme-linked immunosorbent assay for hippuric acid: its potential application for biological monitoring of toluene exposure

An enzyme-linked immunosorbent assay (ELISA) for hippuric acid (HA) was developed using polyclonal anti-HA antibodies. Anti-HA antibodies were obtained by immunizing rabbits with N-benzoyl-cysteine (B-Cys) or N--benzoyl-lysine (B-Lys). An antibody with highest reactivity to HA was obtained from anti-B-Lys antiserum by affinity chromatography with B-Cys-Sepharose. The ELISA system was composed of solid-phase B-Cys, anti-HA antibody, and horseradish peroxidase-conjugated anti-rabbit immunoglobulin antibody. The detection limit of the ELISA for HA was around 1 g/ml. The urinary HA concentration determined by the ELISA system correlated well with that obtained by high-performance liquid chromatography (HPLC). The ELISA system was considered to be useful in the biological monitoring of toluene exposure, and to be more advantageous than time-consuming HPLC, especially when measuring a large number of samples.