Increasing selectivity in comprehensive three-dimensional gas chromatography via an ionic liquid stationary phase column in one dimension

Abstract

Recent advances in improving the selectivity and performance for a comprehensive, three-dimensional (3D) gas chromatograph (GC(3)) instrument are described. With GC(3), two six-port diaphragm valves are utilized as the interfaces between three, in-series capillary columns housed in a standard GC instrument fitted with a high data acquisition rate flame ionization detector (FID). Modulation periods for sampling from one column to the next are set so that sufficient slices (i.e., modulations) are acquired by the subsequent dimension resulting in comprehensive data. We present GC(3) instrumentation with significantly higher 3D peak capacity than previously reported. An average peak capacity production (i.e., per time) of 180 resolved peaks per minute was experimentally achieved for three representative analytes in a 3D diesel sample separation. This peak capacity production is about 4 times higher than our previous report. We also demonstrate the significant benefit of the added chemical selectivity of the three column GC(3) instrument relative to a two column GC x GC instrument, in which one of the three columns is a triflate ionic liquid stationary phase column with a high selectivity for phosphonated compounds (i.e., di-methyl-methyl phosphonate, di-ethyl-methyl phosphonate and di-isopropyl-methyl phosphonate). Using all three separation dimensions, the 2D separation fingerprint of a diesel sample is simultaneously obtained along with selective information regarding the phosphonated compounds in the diesel samples in the additional dimension.