Determination of Nonylphenol and Octylphenol in Fish and Shellfish by High-Performance Liquid Chromatography/Electrospray Mass Spectrometry

A simple and reliable method using liquid chromatography-electrospray ionization-mass spectrometry (LC/ESI-MS) has been developed for the determination of 4-nonylphenol (4-NP) and 4-octylphenol (4-OP) in seafood and meat. LC separation was performed on a Cadenza CD-C18 column (100 x 2 mm i.d.) with a gradient system of 50% acetonitrile (containing 1 mM ammonium acetate and 0.005% acetic acid)-acetonitrile as the mobile phase at a flow rate of 0.2 mL/min. The negative ionization produced molecular related ions: (M - H)(-), at m/z 205.1 and 219.1 for 4-OP and 4-NP, respectively. The calibration graphs for 4-NP and 4-OP were rectilinear from 0.5 to 50 ng/mL with selected ion monitoring (SIM). The compounds were extracted with methanol, and the extracts were cleaned up on a Isolute Multimode cartridge (500 mg). The method involves enzymatic deconjugation by beta-glucuronidase and correction of the stable isotopically labeled internal standard, 4-octylphenol-d type. The recoveries of the compounds from seafood fortified at a level 10 ng/g was 72.1 similar to 89.6%, with high precision. The limits of detection of the compounds in seafood were 0.5 similar to 2 ng/g.