LC-MS is an example of a “hyphenated” technique combining two analytical techniques.  The Liquid Chromatograph (HPLC or UHPLC) is used to separate mixtures of compounds which then elute into to a Mass Spectrometer (MS) for detection. The neutral molecules are first ionised, the molecular ions and their fragments are then separated by their mass to charge ratio before being detected. MS enables identification of the compounds as well as increasing confidence in the results.