Abstract: A mass spectrometer utilizing an inlet nozzle having multiple atmospheric pressure inlets to provide multiple streams of different fluid samples such that their chemical contents can be analyzed simultaneously within a single mass spectrometer with limited or no interaction between the individual streams of sample. This capability is made possible by positioning the nozzle within a nozzle housing wherein the nozzle defines a plurality of orifices extending therethrough from the atmospheric pressure environment of the orifice inlets to the reduced air pressure environment of the nozzle outlets without allowing any mixing between the samples as they pass through the nozzle. Samples are provided to the nozzle by an electrospray ionization needle which simultaneously ionizes the fluid and supplies it to one individual nozzle orifice.