Acid Labile Surfactants Containing Ketal-Linkage in Micellar Electrokinetic Chromatography and Electrospray Ionization Mass Spectrometry

Abstract

The combination of micellar electrokinetic chromatography (MEKC) with electrospray ionization mass spectrometry (ESI-MS) would yield a very powerful analytical technique. However, hyphenating both techniques is not easy. Sodium 4-[(2-methyl-2-undecyl-1,3-dioxolan-4-yl) methoxy]-1-propane sulfonate (ALS) and sodium 2,2-Bis(hexyloxy)propyl sulphate (OALS) are possible solutions to link MEKC with ESI-MS. They are surfactants that are hydrolyzable under acidic condition. Their hydrolysis products are compatible with ESI-MS. They can be utilized as pseudostationary phases to perform a separation and then acid-hydrolyzed before being introduced into the ESI-MS. Both surfactants are compared with sodium dodecyl sulphate (SDS). ALS and OALS offer different selectivity than SDS. In term of mobility, ALS has a slower mobility than SDS. OALS has a greater mobility than SDS. ALS contains a cyclic ketal while OALS contains an acyclic ketal. OALS hydrolyzes much faster than ALS. The hydrolysis can be slowed down by lowering the temperature and vice versa.