LC/MS or HPLC/MS is the combination of liquid chromatography (LC, or HPLC) with mass spectrometry (MS). Chromatography is used for separation and mass spectrometry for identification and/or quantification of the substances. Usually, further detectors are interposed, such as UV, ELS or conductivity detectors. Mixtures of substances that cannot be analysed successfully with GC/MS can often be analysed more precisely with LC/MS (liquid chromatography). LC has the advantage that temperature-sensitive and/or high-molecular substances do not have to be evaporated, but also the disadvantage that the half-value width of the peaks is significantly larger, which means that the temporal resolution and thus the chromatographic separation of similar substances with comparable retention times is poorer (but here, too, newer developments from around 2003 have led to qualitative leaps).  

(Quelle: https://www.chemie.de/lexikon/LC/MS.html)