HPLC is well established as an analytical technique. Why is HPLC the most popular technique in analytical laboratories today? highlights the reasons that justify this claim. The wealth of information made available by commonly used HPLC detectors can be enriched further by mass sensitive detectors.
The idea behind writing this article is not to undermine the contributions of conventional HPLC detectors but to highlight the additional benefits offered by mass sensitive detectors.A review the article on Essentials of mass spectroscopy will help you appreciate the capabilities and potential of mass sensitive detectors.
LC – MS has established itself as one of the most sensitive techniques for separation and identification of organic compounds. Liquid chromatography offers a wide scope for separation of mixtures of compounds through selection of mobile phase mixtures, column dimensions, choice of stationary phase options and different detectors. Conventional LC detectors differentiate between different sample components on the basis of retention time and quantify them on the basis of peak height or area. This works absolutely fine for components which yield well separated peaks but quantification becomes difficult when several components elute closely or even co-elute.
LC – MS is of extreme help in such demanding separations as the mass spectra reflects intensities of individual mass fragments that get ionized and separated on the basis of the mass to charge ratios. In a nutshell LC – MS offers the best of both liquid chromatography and mass spectroscopic techniques which proves to be highly beneficial in resolving closely eluting sample components. In addition the other benefits offered by combining LC with mass detection are:
Separation on the basis of mass to charge ratios of ionized species supplements compound separation by chromatographic column separations
Finger Printing of Compounds
Reliable peak assignment in presence of complex sample matrices is possible due to fingerprinting of molecules on account of precise molecular fragmentations under controlled operating conditions
Molecular Mass Determination
The technique offers precise values of molecular weights of parent as well as ionized molecular mass fragments.
Controlled fragmentation conditions permit structural elucidation of parent or ionized molecules
High levels of accuracy are possible using LC- MS analysis.
It can be seen that LC- MS is capable of providing several additional samples details than is possible when using only conventional detectors. The limiting factor is higher cost of MS detector coupled with additional cost of operation. The advantages offered far outweigh the additional costs when demanding separations and quantification become necessary.