A complex of α-cyano-4-hydroxycinnamic acid (CHCA) and zeolite was used as the matrix for the analysis of drugs and their metabolites in urine by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). It was found that acetaminophen (AAP) and its metabolites could be detected in urine without any pretreatment or separation process. It was also found that the hydrolysis of one of the metabolites, glucuronide, was promoted when a mixture of urine and the developed matrix was heated at 343 K for 15 minutes. Because of the homogeneous distribution of CHCA on the zeolite surface, high reproducibility of the analyte peak intensity was achieved. By using isotope-labeled acetaminophen (D4-AAP) as the internal standard, quantitative analysis of AAP in urine from a donor who took 300 mg of AAP four hours before was performed, and 5.29 ± 0.19 mg of AAP was detected in 1.00 g of urine.

The ingredients of an antipyretic (acetaminophen, AAP) and their metabolites excreted into fingerprint were detected by surface-assisted laser desorption ionization (SALDI) mass spectrometry using zeolite. In the fingerprint taken 4 h after AAP ingestion, not only AAP but also the glucuronic acid conjugate of AAP (GAAP), caffeine (Caf), ethenzamide (Eth), salicylamide (Sala; a metabolite of Eth), and urea were detected. Fingerprints were collected over time to determine how the amounts of AAP and its metabolite changed with time, and the time dependence of the peak intensities of protonated AAP and GAAP was measured. It was found that the increase of [GAAP+H]+ peak started later than that of [AAP+H]+ peak, reflecting the metabolism of AAP. Both AAP and GAAP reached maximum concentrations approximately 3 h after ingestion, and were excreted from the body with a half-life of approximately 3.3 h. In addition, fingerprint preservation was confirmed by optical microscopy, and fingerprint shape was retained even after laser irradiation of the fingerprint. Our method may be used in fingerprint analysis.