Development and validation of a liquid chromatography-tandem mass spectrometry method for comprehensive detection of organophosphate esters and their degradation products in sediment

The present work aimed at the development of a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for comprehensive determination of twelve organophosphate (OP) triesters, five OP diesters and two hydroxylated degradation products in sediment. As the target compound possess a wide range of physicochemical properties, different LC-MS/MS conditions and sample preparation strategies were tested. The optimal condition is based on the extraction of 2 g of dried sediment by ultrasonic-assisted extraction and clean-up by solid phase extraction, and then the extract was separated using a ZORBAX C18 column (4.6 mm × 100 mm, 1.8 μm) and analyzed by MS in multiple reaction monitoring mode. The overall method was validated in terms of linearity, matrix effect, and limits of quantification (LOQs), recoveries and precision. All targets had wide concentration ranges and the correlation coefficients (r) were higher than 0.99. LOQs of all analytes were 0.01-5.0 ng g^-1 dw, most of which are lower than those previously reported. In most cases, the recoveries were from 68.56 to 140.22% at three spiked levels (low, medium and high), with RSDs lower than 22.38%, and the reproducibility obtained in five nonconsecutive days was lower than 26.18%. This method was successfully applied to nineteen marine sediment samples. Tri-n-butyl phosphate (TNBP) and tris (phenyl) phosphate (TPHP) were detected in over 84% of samples and the concentration levels were the highest among all OP triesters. For OP diesters, DPHP was 100% detected in all samples with the highest amount. The total concentrations for OP triesters and their degradation products were n.d.-107.2 ng g^-1 dw and n.d.-101.7 ng g^-1 dw, respectively. This is the first study reporting contamination of both OP triesters and their degradation products, especially hydroxylated degradation products, in sediment. Considering the ubiquitous existence of targets as well as their toxicity to biota, study on the OPEs and their degradation products in marine environment deserves a special attention.