A selective ion monitoring assay for probenecid.

A selective ion monitoring assay for probenecid (p-(dipropylsulfamyl)benzoic acid) using m-(di-isobutylsulfamyl)benzoic acid as an internal standard is described. The method has been applied to the determination of probenecid concentrations in human cerebrospinal fluid and lends itself to incorporation into the selective ion monitoring procedures used to quantitate other acidic and neutral compounds in such samples.