Key components in HPLC analysis

2 Refractive-index detectors. These detectors are used when the analyte of interest cannot be detected by UV. Their use, however, is somewhat limited as they lack both sensitivity and stability and their very design makes them impossible to use with gradient elution and difficult to use with mixed (isocratic) solvents. 

The use of mass spectroscopy and HPLC offers great potential for the quantification and identification of polymer additives. However, its adoption has been fraught with practical problems, created by the very nature of the eluent from the chromatograph. One possible solution to this problem is the moving-belt interface, in which the eluent is sprayed on to a circulating belt and the solvent evaporated in stages, so that finally only the analyte is carried into the mass spectrometer. This approach has been successful in the separation and identification of some polymer additives [60]. However, it can only be used for Cl and El mass spectroscopy, and the interface can only be operated with mobile phases containing less than 50% water. Newer interfaces such as thermospray and particle beam offer potential in this area. 

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