Determination of nonylphenol ethoxylate metabolites in vegetables and crops by high performance liquid chromatography–tandem mass spectrometry

A method has been developed for the simultaneous determination of the concentration of nonylphenol (4-NP), nonylphenol monoethoxylates (NP1EO) and nonylphenol diethoxylates (NP2EO) in vegetables and crops by liquid chromatography–tandem quadrupole mass spectrometry (HPLC–MS/MS). These target compounds were extracted from vegetable and crop samples with acetonitrile, and then the extracts were cleaned using solid phase extraction with graphitised carbon black tandem primary secondary amine (PSA) cartridges. The MS method enabled highly reliable identification by monitoring the corresponding ammonium adduct [M+NH4]+ in the positive mode for NP1EO and NP2EO, and the deprotonated molecule [M−H]− in the negative mode for 4-NP. Recoveries for the spiked samples ranged from 65% to 118%. The limit of detection (LOD) of 4-NP, NP1EO and NP2EO was 3, 5 and 0.1 μg kg−1, respectively. This method would be useful for the quick and routine detection of the residues of 4-NP, NP1EO and NP2EO in vegetables and crops.