apci was applied to gc/ms and lc/ms also by horning's group in 1975. analyte in lc eluate was vaporized and ionized in a heated block. high sensitivity and simple mass spectra were obtained through this application. in the later decades, the coupling of apci with lc/ms became famous and caught a lot attention. the introduction of apci and lc-ms had expanded dramatically the role of mass spectrometry in the pharmaceutical industry in the area of drug development. the sensitivity of apci combined with the sensitivity and specificity of lc/ms and liquid chromatography-tandem mass spectrometry (lc-ms/ms) makes it the method of choice for the quantification of drugs and drug metabolites.