A highly sensitive method for analyzing marker phytoplankton pigments: Ultra-high-performance liquid chromatography-tandem triple quadrupole mass spectrometry

A sensitive and specific ultra-high-performance liquid chromatography-tandem triple quadrupole mass spectrometry (UHPLC-MS/MS) method was developed for the purpose of decreasing the detection limit of quantification (LOQ) and reducing sample analysis time. In total, 14 marker pigments were determined and validated using an internal standard (IS) method with trans-8'-Apo-beta-carotenal as the IS. Electrospray ionization in positive mode was applied for the detection of pigments. The 14 types of pigments were separated in less than 15 min and presented good linearity, with the coefficients ranging from 0.9915 to 0.9991 using a UHPLC C8 column. The LOQ attained for 14 pigments were from 0.005 ng mL^-1 to 0.500 ng mL^-1, which enabled quantification of the pigments in seawater at ppt level. Both intra-day and inter-day precisions were less than 15%. The method was validated using seawater samples and the recovery of the analytes ranged from 62.8% to 120.2% at two spiked concentrations. Compared with previous methods, UHPLC-MS/MS method improved the efficiency of qualitative analysis and significantly decreased the detection LOQ for analyzing marker phytoplankton pigments at trace/ultra-trace levels in complex matrices.