Abstract: An ion source for a mass spectrometer operating at a low pressure has an atmospheric pressure sample ioniser which provides a sample flow containing desired sample ions. These ions are usually entrained with undesired gas and droplets. An interface chamber is held by a vacuum pump at a pressure between atmospheric and the operating pressure of the mass spectrometer. Sample ions with entrained gas are collected through an entrance orifice forming a stream of gas into the interface chamber. Sample ions exit the interface chamber through an exit orifice to the mass spectrometer. The interface chamber disrupts the stream of gas entering the interface chamber to provide a dead region having no net gas flow direction and the exit orifice is located in this dead region. The exit orifice should have no line of sight path to the entrance orifice or should be at least 30° off the flow axis of the stream entering the interface chamber through the entrance orifice.

Abstract: An ion source for a low pressure mass spectrometer has an atmospheric pressure sample ioniser operative at relatively higher pressure to provide a sample flow containing desired sample ions to the mass spectrometer via an inlet orifice. The sample flow invariably contains involatile components that are infused either as chromatographic buffers or which appear in the analyte as sample extraction byproducts. As the sample ions pass from the high pressure to the low pressure regions through the orifice, these involatile components are deposited on the peripheral regions of the inlet orifice. A conduit for the transportation of a cleaning fluid has an opening adjacent to the inlet orifice for dispensing the cleaning fluid onto at least a portion of a surface of the orifice member during operation of the ion source.