Determination of Avermectin Residues in Food Matrices with Liquid Chromatography/Electrospray Ionization Mass Spectrometry

Dayue Shang, Angelo Di Cicco, Monica Dyck, Jagroop Dahiya, Nicole Gibbons, and Helen Nicolidakis
Health Canada, Health Products and Food Branch, Organic Residues Laboratory, Burnaby, B.C., V5G 4P2

Abstract

Avermectins are a class of compounds used as acaricides or parasiticides for animals or plants. In the aquaculture industry, ivermectin is used to control sea lice in salmon and trout. This family of drugs has relatively low water solubility and apparently has a relatively long persistence in food matrices. Therefore, there are concerns regarding the impact of the residues of these veterinary drugs on human health. Although there are LC/fluorescence based methods available, these require derivatization in the sample preparation process, which compromises sample stability. In addition, the LC/fluorescence methods do not offer the specificity required for trace analysis in food. The aim of this study was to develop a rapid LC/MS method which could be used to examine a large number of samples from a variety of food matrices. A systematic approach was adopted in the development of the method. Taking advantage of the superior specificity of SIM mode in mass spectrometry, a simple extraction process with no SPE clean-up was developed, which significantly reduced the sample preparation time and yielded good recoveries. Spike recovery was over 80 % for all four avermectins, i.e. abamectin, ivermectin, eprinomectin, and moxidectin, with relative standard deviations of 4 to16% for the compounds. The low quantitation limits for the avermectins was compound dependent and were as follows: 0.5 ppb (ng/g) for eprinomectin, 2.5 ppb for ivermectin and abamectin, and 25 ppb for moxidectin. The high limit of quantitation for all compounds was 100 ppb. A mini-survey was conducted using the newly developed method. Some results will be presented which indicate that the compounds can be found on a wide variety of food matrices.