An apparatus for detecting a substance comprising a direct analysis in real time apparatus; a neutral excluder; a mass spectrometer; and a vessel in. The apparatus may also comprise a separator, a gas, an alcohol, a filter, and a pump. The apparatus may also comprise electrodes in communication with the direct analysis in real time apparatus and the neutral excluder. A method for detecting a substance comprising contacting the substance with a direct analysis in real time apparatus ion stream; forming an ion and a neutral particle; flowing the ion and the neutral particle into a neutral excluder; contacting the ion and the neutral particle with a gas; and flowing the ion into a mass spectrometer.