In the presented work, Cr(III) and Cr(VI) species are determined with a dual-source time-of-flight mass spectrometer, which uses an inductively coupled plasma and a nano-electrospray ionization source to provide simultaneous elemental, isotopic, molecular, and structural information within the same spectrometer. Indicative ESI species are identified for chromium(III) acetate, chromium chloride, chromium picolinate, and potassium dichromate in methanol and ethanol matrices. Analyte characterization from skimmer-nozzle collisionally-induced dissociation fragments is examined in detail. An online dilution apparatus is described for use with ESI for the determination of analytes that react with the solvent.