Automated calibrant system for use in a liquid separation/mass spectrometry apparatus

A method of calibrating a mass spectrometer in a liquid separation/mass spectrometer apparatus during processing of a liquid sample, wherein the apparatus includes a mass spectrometer, a liquid separation system which processes a liquid sample to yield an effluent, a calibrant system for providing a volume of a pneumatically pressurized reference liquid, an ion source in fluid communication with the mass spectrometer, and a switching valve in fluid communication with the liquid separation system, the calibrant system and the ion source, the switching valve having a first position which provides fluid communication between the liquid separation system and the ion source, and a second position which simultaneously provides fluid communication of the reference liquid from the calibrant system to the ion source and effluent from the liquid separation system to waste, the method comprising:

• (a) initiating processing of a liquid sample by the liquid separation system to provide an effluent;
• (b) actuating the switching valve to the first position to communicate the effluent from the liquid separation system to the ion source for conversion therein to an ionized aerosol and for delivery therefrom to the mass spectrometer to initiate analysis of the liquid sample;
• (c) actuating the switching valve to the second position to communicate the reference liquid from the calibrant system to the ion source for conversion therein to an ionized aerosol and for delivery therefrom to the mass spectrometer while communicating the effluent from the liquid separation system to waste;
• (d) obtaining a mass spectrum of the ionized reference liquid molecules from the mass spectrometer;
• and
• (e) actuating the switching valve back to the first position to communicate the effluent from the liquid separation system to the mass spectrometer to resume analysis of the liquid sample.