Isolation and Multiresidue Detection of Macrolide Endectocides Present in Animal Matrices

Abstract

A simple, rapid, and sensitive method for isolation and detection of macrolide endectocides (moxidectin, doramectin, selamectin, ivermectin, and eprinomectin) in animal sera and liver is described. Fortified sera or homogenized liver samples were treated with sodium chloride followed by organic solvent extraction. No additional steps were required prior to analysis. Separation of analytes and collection of mass information was achieved by liquid chromatography/mass spectrometry with positive atmospheric pressure chemical ionization set in selected ion monitoring mode with each sample analysis complete in 15 minutes. Presence of each compound was confirmed based on 2 separate extracted ion profiles. Detection of avermectins and moxidectin in a range of working standards was achieved at 10, 50, and 100 ppb. Quantitation of these compounds in fortified samples was based on standard calibration curves with R2 > 0.99. Detection limits of 10 ppb for ivermectin, moxidectin, and doramectin, 50 ppb for selamectin, and 100 ppb for eprinomectin were achieved in spiked sera. Recoveries of avermectins and moxidectin in 500 ppb fortified sera fell between 61 and 89% (+/-5.7-15.7). Analysis of fortified liver gave comparable results with recovery of selamectin of 83-91% +/- 18.3. A complete mass spectral fragmentation pattern of selamectin and affordable screening method for 6 macrolide endectocides are reported. Method comparison for salt treatment and solid-phase extraction of fortified samples is discussed.

Positive and negative electrospray LC–MS–MS methods for quantitation of the antiparasitic endectocide drugs, abamectin, doramectin, emamectin, eprinomectin, ivermectin, moxidectin and selamectin in milk

“…The residual plots, however, indicated a slightly negative curvature. Although many reports in which electrospray or atmospheric pressure chemical (APCI) ionization list linear calibration functions [17,13,15], others report the use of second order polynomials gave the better results [19]. A variety of theoretical models have been developed to explain the electrospray process.…”

“…However, this method was limited to only one analyte, and presumed the absence of abamectin in the samples. To overcome the sodium adduct and linearity problems, several methods have been reported using LC-MS with atmospheric pressure chemical ionization (APCI) with positive ion detection in which either the [M + H] + [12], the [M + NH 4 ] + [16], or fragment [17] ions were monitored. Linear calibration curves were obtained using APCI with negative ion [M − H] − monitoring [15,18,19].…”

Review of methodology for the determination of macrocyclic lactone residues in biological matrices

“…However, gradient elution has been used by a number of researchers [54,70,119,126,131,138,143,169]. Gradient elution may be used to separate the residues or to remove late eluting interferences from the column that may interfere with subsequent determination [131,132,138,143,169]. In the case of LC-MS, gradients are quite frequently used because late eluting interferences can interfere with MS ionisation processes.…”

“…Coles et al extracted emamectin, doramectin and ivermectin residues from liver and salmon muscle using acetonitrile and purified the extracts on deactivated alumina and C 18 [132]. Samples were extracted using acetonitrile and sodium chloride was added to allow separation of the acetonitrile and aqueous layers.…”

“…More recently, multi-residue methods, capable of determining two or more residues, have been reported [120][121][122][123][124][125][126][127][128][129][130][131][132][133][134]. Samples are typically extracted using organic solvent [83,88,92] and cleaned up by liquid-liquid partitioning [95], solid phase extraction [96,97,100] or immunoaffinity chromatography [116,128].…”