Determination of Phytosterols in Marine Sediment by Liquid Chromatography-Dopant-assisted Atmospheric Pressure Photoionization Mass Spectrometry

Phytosterol biomarkers in marine sediments are often used to indicate the source of the sedimentary organics in the ocean, and to reflect the evolution of marine ecosystem and environment. In this study, a novel method 14 simultaneous determination of common phytosterols in marine sediments by non-aqueous reversed-phase liquid chromatography-atmospheric pressure photoionization mass spectrometry ( LC-APPI-MS ) was established. First, the APPI-MS characteristics of phytosterols were clarified. Under the positive APPI mode, phytosterols tended to produce stable characteristic ion peaks such as [ M + H - H2O ](+) , [ M + H - H-2 ](+) and [ M + H - 2H(2) ](+) . In the process of APPI-MS2, abundant fragment ion peaks were produced mainly through i-heterolysis. Second, LC-APPI-MS conditions were optimized, and a reversed-phase C-18 column was used to separate phytosterols with pure methanol as mobile phase and toluene as APPI ionization dopant , which could realize high sensitivity of detection for phytosterols in sediments. Furthermore, the method showed strong matrix interference resistance ability , good linear relationship ( R-2 >= 0. 9990 ) , high recovery rate ( 86. 4% - 94. 9% ) and good repeatability ( RSDs >= 8. 3% ). Finally, the proposed method was applied to detect common phytosterols in the surface sediment of Laizhou Bay in China, and several sterols, such as brassicasterol , fucosterol and sitosterol, etc. , were detected in every sediment sample. The total concentration of sterols was 4. 21-12. 91 mu g/g, among which the concentration of sitosterol was the highest. To sum up , the developed LC-APPI-MS method was a powerful tool 14 determination of common phytosterols in marine sediments , with easy-operation and high sensitivity.