This paper describes the use of two separate electrosprays for introducing sample and reference for accurate mass liquid chromatography/mass spectrometry (LC/MS) on an orthogonal acceleration time-of-flight mass analyzer. This is carried out using an adaptation of the multiplexed electrospray ion source in which only two of the sprays are utilized. Results are shown for the positive ion detection of trace-level components in complex matrixes and good mass accuracies are obtained, even for very low level components. An example of accurate mass measurements obtained using negative ion LC/MS is also shown. To obtain additional structural information, an example of cone voltage fragmentation is included and shows that good mass accuracy can be obtained for both precursor and fragment ions.