The present invention relates to improving the ability of a hyphenated instrument to analyze a sample benefiting from having the first instrument's analysis of the same sample. A fast switching machenism can be used as the interface between an ion mobility spectrometer (IMS) and a mass spectrometer (MS) such that the obtained IMS spectrum is converted into a timing diagram that controls the vacuum inlet's size dynamically during analysis of a neutral and/or charged chemical and/or biological species such that a smaller pumping system can be used.