POSITIVE-ION AND NEGATIVE-ION MASS-SPECTROMETRY OF DIPHENYLMETHANE ANTIHISTAMINICS AND THEIR ANALOGS AND RAPID CLEANUP OF THEM FROM BIOLOGICAL SAMPLES

Positive-ion electron impact (PIEI), positive-ion chemical ionization (PICI) and negative-ion chemical ionization (NICI) mass spectra are pr esented for 15 compounds of diphenylmethane antihistaminics and their analogues, and each fragmentation pathway was analyzed. In the PIEI mo de, molecular peaks were very small or missing for most compounds. Pea ks at m/z 58, due to a dimethylaminomethyl group liberated, constitute d base peaks in five compounds. Peaks at m/z 165 and/or 167, due to di aromatic rings plus a methyl group, appeared in most compounds. In the PICI mode, peaks due to M + H and M + C2H5 appeared in all compounds. Peaks due to diaromatic rings plus a methyl or ethyl group constitute d base peaks in five compounds, which had an ether bond in their struc tures. In the NICI mode, anions at m/z M-H appeared in most compounds. Peaks at m/z 35 were observed for compounds having a chlorine group i n their structures. Detection limits for total ion monitoring of these compounds were 20-50 ng on column in the PIEI mode, 100-200 ng in the PICI mode and 500-1000 ng in the NICI mode. A rapid and simple clean- up procedure of these drugs with use of Sep-Pak C18 cartridges is also presented. The drugs could be detected by gas chromatography with DB- 1 and DB-17 capillary columns with satisfactory separation from impuri ties in their underivatized forms. The recovery of the drugs, which ha d been added to whole blood and urine, was more than 60% except for me clizine.