A method of assessing the linearity and dynamic range of a mass spectrometer is described comprising analyzing two or more test standards containing positional isomers, for example, using a series of N isomeric analytes with or without an internal standard where N is an integer from 2 to 6 inclusive. The concentrations of the N isomeric analytes may or may not be interleaved between two or more standards. The method allows for repeated instrument characterization without having many of the problems associated with using only a single standard such as octafluoronaphthalene (OFN), for example, persistence, and it may lessen sample carryover issues between adjacent samples. Methods are described using positional isomers of dibromodifluorobenzene in various configurations that show an improved means for qualitative and quantitative analysis of one or more analytes by GC-MS.