Interfacing Hplc with Mass Spectrometry:

As it has been emphasized earlier, mass spectrometer is the most sensitive and ideal detector for liquid chromatography. It can provide both structural information and quantitative analysis for the separated compounds. When it is coupled with HPLC, it becomes a hyphenated technique similar to GC-MS. Unlike in GC where separated compounds are more or less in pure state, in case of HPLC inherent difficulty was in removing the liquid mobile phase while allowing the analytes to pass into the mass spectrometer. Therefore, the main problem encountered is the mismatch between the mass flows involved in HPLC (about 1g/min) which is two or three order of magnitude larger than can be accommodated by conventional mass spectrometer vacuum systems. Another problem is the difficulty in vaporizing nonvolatile and thermally labile molecules without degrading them. Several designs of interface have been developed, the main difference between them being the means of separating analytes from the mobile phase and the method of ionization employed. Many compromises have been suggested in the operating conditions of either the chromatograph or the mass spectrometer.