Use of shift gradient in the second dimension to improve the separation space in comprehensive two-dimensional liquid chromatography
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Comprehensive two-dimensional liquid chromatography (LC × LC) has received much attention because it offers much higher peak capacities than separation in a single dimension. The advantageous peak capacity makes it attractive for the separation of complex samples. Various gradient methods have been used in LC × LC systems. The use of continuous shift gradient is advantageous because it combines the peak compression effect of full gradient mode and the tailed gradient program in parallel gradient mode. Here, a comparison of LC × LC analysis of Chinese herbal medicine with full gradient mode and shift gradient mode in the second dimension was performed. A correlation between the first and second dimensions was found in full gradient mode, and this was significantly reduced with shift gradient mode. The orthogonality increased by 43.7 %. The effective peak distribution area increased significantly, which produced better separation.
KeywordsComprehensive two-dimensional liquid chromatography Shift gradient Peak distribution Chinese herbal medicine
The authors thank the China Scholarship Council (CSC) and the German Academic Exchange Service (DAAD) for funding. We also thank Agilent Technologies and SIM for providing some equipment and software and Phenomenex for the columns.
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