Quantification of total phosphate in aquatic products using acid hydrolysis combined with liquid chromatography-tandem mass spectrometry

ObjectiveA method for the quantification determination of total phosphate （calculated in PO43-） in aquatic products was established by using acid hydrolysis combined with liquid chromatography-tandem triple quadrupole mass spectrometer （LC-MS/MS）.MethodsThe sample were extracted with nitric acid hydrolysis at boiling water bath， that converted polyphosphates， including pyrophosphate （P2O74-）， trimetaphosphate ［（PO3）33-］ tripolyphosphate （P3O105-）， and hexametaphosphate （P6O186-）， into orthophosphate （PO43-）. The total phosphate （calculated in PO43-） in the resulting solution following extraction was determined by LC-MS/MS operated in selected reaction monitoring （SRM） mode with negative electrospray ionization. Quantitation was performed using the internal standard method. The chromatography， mass spectrometry， acid hydrolysis， and extraction conditions were optimized， and the established method was validated.ResultsGood linearity was observed for total phosphate in the concentration range of 0.1 mg/L to 20.0 mg/L， with correlation coefficient greater than 0.999. The limits of detection （LOD） and quantitation （LOQ） of orthophosphate in aquatic products were 0.03 g/kg and 0.10 g/kg， respectively， based on signal-to-noise ratio of 3 and 10. Recoveries ranged from 84.4% to 96.6% at spiked levels of 1.0， 5.0， and 10.0 g/kg， with intra-day and inter-day relative standard deviations （RSDs） both below 10.0%.ConclusionThe developed method features simple sample preparation， high resistance to matrix interference， good accuracy， and rapid analysis. It is therefore well-suited for determining total phosphate in aquatic products.