ABSTRACT
A new residue analytical method for the confirmation and quantification of avermectin residues in food is described in this article. This method allows a fast analysis for the determination of avermectin residues, abamectin (ABM), ivermectin (IVM), emamectin benzoate (EMA) and doramectin (DOR) by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Separation was performed using a short column of 1.8 microm particle size. The hybrid quadrupole/linear ion trap (QqQ(LIT)) system via the linearly accelerating (LINAC) high-pressure collision cell, allows the MS detection in multiple reaction monitoring (MRM) mode operating in fast scan acquisition times. The effect of reduced dwell times on mass spectral quality and sensitivity is evaluated in this study. For quantitative purposes, the influence of dwell time on S/N ratio and peak area was observed. ABM, IVM, EMA and DOR show an increased trend of peak area and S/N ratio, when dwell times are of 50 ms against 10-20 ms, suited when the number of compounds to be analyzed is higher. The sensitivity achieved by using the LC-MS/MS system is enough for the confirmation of avermectin residues in the selected commodities (salmon muscle and pepper) at trace concentration levels (sub-microg/kg and microg/kg) and therefore a sample pre-concentration step was not necessary. The instrumental limits of quantification (ILQ) are in the range of 0.15-5 ppb. Samples were extracted by solid-liquid extraction (SLE) procedure using acetonitrile, and cleaned-up using alumina. The average recoveries obtained were acceptable (80-95%). The calibration curves were linear over the working range from ILQs to 500 microg/kg. For the quantitative analysis, matrix-matched calibration and dilution of SLE extracts was proven as reliable alternative to compensate matrix-effects and for its feasible application in routine analysis.
