The high sensitivity and rapid analysis times of mass spectrometry have led to its importance as an analytical technique; however, low signal-to-background ratios and isomeric/isobaric interferences can be problematic during the analysis of complex mixtures. Separation techniques such as chromatography and electrophoresis are often coupled to mass spectrometry prior to ionization to reduce the complexity of the subsequent mass analysis but these separations are often the speed limiting step. Post-ionization separation techniques such as ion mobility spectrometry are much more rapid and can also be used prior to mass analysis, either as a stand-alone separation method or as a complementary separation step after a liquid phase separation. At the low electric field strengths used in many ion mobility techniques the mobility of the ions is independent of the electric field strength used, and ions of the same charge state are separated based their collision cross-section. The work described herein couples differential ion mobility spectrometry (DIMS) separations to mass spectrometry. DIMS devices take advantage of the fact that ion mobility becomes dependent on electric field strength at high electric fields strengths (>10.0 kV/cm). By alternating between low and high electric field strengths, DIMS devices separate ions based on the difference between their mobilities in low and high electric field strengths. Many factors influence the separation achieved with DIMS devices. This work begins by examining the role of the mass spectrometer desolvation gas in keeping solvent vapors from entering the DIMS devices and affecting the DIMS separation. Work characterizing the intra‑DIMS fragmentation of peptides is then described, including how the DIMS carrier gas temperature and composition affect the fragmentation of ions as they travel through a DIMS device. The improvement of DIMS separations via two distinct methods are then explained. The first is the use of a newly developed technique wherein the compensation field applied to the DIMS device and the amount of helium present in the DIMS carrier gas are scanned simultaneously. The second is the intentional addition of solvent vapors to the DIMS carrier gas, which is applied to the separation of four glucose isomers and also the separation of three phosphorylated hexoses.