Multi-residue analysis of avermectins and moxidectin by ion-trap LC-MSn© Crown copyright.
Abstract
A multi-residue method was developed and validated for the
quantitation and confirmation of avermectins and moxidectin residues in
bovine liver. Target analytes were extracted from liver homogenate using C8
solid phase cartridges, chromatographed under basic pH conditions in order
to promote the formation of analyte anions, and detected by ion-trap mass
spectrometry (MS) in negative ion mode using an atmospheric pressure
chemical ionization interface (APCI). The method provided detection
capabilities (CCβ, where β = 0.05)
for eprinomectin, abamectin, doramectin, moxidectin and ivermectin of 3.1,
3.2, 2.2, 4.0 and 3.2 ng g−1 liver respectively, well
below their respective maximum residue limits (MRLs). The critical
concentrations for MRL compliance (CCα, where
α = 0.01) were 840, 28, 130, 130 and 130 ng
g−1 respectively. Analysis of liver fortified at the
appropriate MRLs gave recoveries (% ± RSD) of 70.9 ± 11.6
(n = 14), 69.1 ± 3.9 (n = 13), 65.9 ± 6.4
(n = 19), 69.7 ± 9.3 (n = 19) and 73.2 ±
10.5 (n = 19), respectively, for each analyte. Calibration curves
fitted a second order polynomial function (R2
0.9978) over a wide range of concentrations (0 to 10000 ng
ml−1). The detection of two daughter-ions for each analyte
allowed for quantitation and the confirmation of identity. The method is
suitable for application in European Union statutory veterinary drug
residue surveillance programmes, since it fulfils appropriate analytical
criteria, and has the particular advantage of enabling high throughput
multi-residue quantitation and confirmation of the target analytes.