Determination of four forms of vitamin B_(12) and other B vitamins in seawater by liquid chromatography/tandem mass spectrometry

摘要

RATIONALE: Vitamin B_(12) is an essential nutrient for more than half of surveyed marine algae species, but methods for directly measuring this important cofactor in seawater are limited. Current mass spectrometry methods do not quantify all forms of B_(12), potentially missing a significant portion of the B_(12) pool. METHODS: We present a method to measure vitamins B_1, B_2, B_6, B_7 and four forms of B_(12) dissolved in seawater. The method entails solid-phase extraction, separation by ultra-performance liquid chromatography, and detection by triple-quadrupole tandem mass spectrometry using stable-isotope-labeled internal standards. We demonstrated the use of this method in the environment by analyzing B_(12) concentrations at different depths in the Hood Canal, part of the Puget Sound estuarine system in Washington State. RESULTS: Recovery of vitamin B_(12) forms during the preconcentration steps was >71% and the limits of detection were <0.275 pM in seawater. Standard addition calibration curves in three different seawater matrices were used to determine analytical response and to quantify samples from the environment. Hydroxocobalamin was the main form of B_(12) in seawater at our field site. CONCLUSIONS:We developed a method for quantifying four forms of B_(12) in seawater by liquid chromatography/mass spectrometry with the option of simultaneous analysis of vitamins B_1, B_2, B_6, and B_7. We validated the method and demonstrated its application in the field.