Drug Detection and Quantification Directly from Tissue Using Novel Ionization Methods for Mass Spectrometry

Solvent assisted ionization inlet (SAII) and matrix assisted ionization vacuum (MAIV) were used to quantify rapidly an antipsychotic drug, clozapine, directly from surfaces with minimal sample preparation. This simple surface analysis method based on SAII- and MAIV-mass spectrometry (MS) was developed to allow the detection of endogenous lipids, metabolites, and clozapine directly from sections of mouse brain tissue. A rapid surface assessment was achieved by SAII with the assistance of heat applied to the mass spectrometer inlet. MAIV provided an improved reproducibility without the need of a heated inlet. In addition, isotope dilution and standard addition were used without sample clean-up, and the results correlate well with liquid chromatography tandem MS using sample work-up. Using the simple surface methods, standard solutions containing clozapine and a deuterated internal standard (clozapine-d8) at different concentration ratios were used in the extraction and quantification of clozapine from brain tissue sections of a drug-treated mouse using different tissue thicknesses. The amount of clozapine extracted by these surface methods was independent of tissue thickness.