Provided herein are systems and method for using unit mass library searches for sample identification in accurate mass spectrometry. In general, the systems and methods described herein: (a) obtain an accurate mass spectrum of a sample; (b) calculate a unit mass spectrum based on the accurate mass spectrum; and (c) conduct a unit mass library search, based on the calculated unit masses, to obtain at least one candidate species to thereby identify the sample. The systems and methods may further: (d) calculate exact masses for each of a plurality of candidate species; and (e) eliminate candidate species due to ions that are outside a mass error window. The mass error window may be less than 500 ppm. The system and methods presented may be used in, for example, gas chromatography mass spectrometry and/or liquid chromatography mass spectrometry systems.
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