Determination of cyanuric acid residues in catfish, trout, tilapia, salmon and shrimp by liquid chromatography–tandem mass spectrometry

Abstract

In May 2007, investigators discovered that waste material from the pet food manufacturing process contaminated with melamine (MEL) and/or cyanuric acid (CYA) had been added to hog and chicken feeds. At this time, investigators also learned that adulterated wheat gluten had been used in the manufacture of aquaculture feeds. Concern that the contaminated feed had been used in aquaculture and could enter the human food supply prompted the development of a method for the determination of CYA residues in the edible tissues of fish and shrimp. Liquid chromatography–tandem mass spectrometry (LC–MS/MS) was employed as a sensitive technique for the analysis of CYA in catfish, tilapia, salmon, trout and shrimp tissue. CYA was extracted from ground fish or shrimp with an acetic acid solution, defatted with hexane, and isolated with a graphitic carbon black solid-phase extraction column. Residues were separated from matrix components using a porous graphitic carbon LC column, and then analyzed with electrospray ionization in negative ion mode on a triple quadrupole mass spectrometer. Selective reaction monitoring was performed on the [M−H] − m/ z 128 ion resulting in the product ions m/ z 85 and 42. Recoveries from catfish, tilapia and trout fortified with 10–100 μg kg −1 of CYA averaged 67% with a relative standard deviation (R.S.D.) of 18% ( n = 107). The average method detection limit (MDL) for catfish, tilapia and trout is 3.5 μg kg −1. An internal standard, 13C 3-labeled CYA, was used in the salmon and shrimp extractions. Average recovery of CYA from salmon was 91% (R.S.D. = 15%, n = 18) with an MDL of 7.4 μg kg −1. Average recovery of CYA from shrimp was 85% (R.S.D. = 10%, n = 13) with an MDL of 3.5 μg kg −1.