Evaluation of Mass Spectrometric Methods for Detection of the Anti-Protozoal Drug Imidocarb

Abstract

Imidocarb [N,N'-bis[3-(4,5-dihydro-1H-imidazol-2-yl)phenyl]urea, C(19)H(20)N(6)O(1), m.w. 348.41] is a symmetrical carbanilide derivative used to treat disease caused by protozoans of the Babesia genus. Imidocarb, however, is also considered capable of suppressing Babesia-specific immune responses, allowing Babesia-positive horses to pass a complement fixation test (CFT) without eliminating the infection. This scenario could enable Babesia-infected horses to pass CFT-based importation tests. It is imperative to unequivocally identify and quantify equine tissue residues of imidocarb by mass spectrometry to address this issue. As a pretext to development of sensitive tissue assays, we have investigated possibilities of mass spectrometric (MS) detection of imidocarb. Our analyses disclosed that an unequivocal mass spectral analysis of imidocarb is challenging because of its rapid fragmentation under standard gas chromatography (GC)-MS conditions. In contrast, solution chemistry of imidocarb is more stable but involves distribution into mono- and dicationic species, m/z 349 and 175, respectively, in acid owing to the compound's inherent symmetrical nature. Dicationic imidocarb was the preferred complex as viewed by either direct infusion-electrospray-MS or by liquid chromatography (LC)-MS. Dicationic imidocarb multiple reaction monitoring (MRM: m/z 175 → 162, 145, and 188) therefore offer the greatest opportunities for sensitive detection and LC-MS is more likely than GC-MS to yield a useful quantitative forensic analytical method for detecting imidocarb in horses.

Pharmacokinetics and bioequivalence of two imidocarb formulations in cattle after subcutaneous injection

“…In practical operation, but m/z 175 is more plentiful and stable for greater sensitivity. Therefore, the diprotonated m/z 175 [M+2H] 2+ was finally set to the parent ion in this study, which is consistent with Lehner 's study results [29].…”

Residue Depletion of Imidocarb in Bovine Tissues by UPLC-MS/MS

“…However, in our study, we found that when the ion (m/z 349.1) was used as the precursor ion, the intensity of the matrix effect was high, which seriously interfered with the detection of the sample. IMD is easily ionized in aqueous solution, and there are two main ionized forms (monoprotonated m/z 349.1 [M + H] + ; deprotonated m/z 175 [M + 2H] 2+ ) [27]. In practice, the abundance of IMD was stronger and more stable when m/z 175 was selected as the precursor ion.…”

Immunochromatographic assay based on high‐affine monoclonal antibody for the detection of imidocarb in milk

“…To detect IM residues in animal products, scientists have developed many analytical approach, for example, high performance liquid chromatography (HPLC) (Crescenzo, et al, 2002;Park et al, 2014;Tarbin & Shearer, 1992), LC mass spectrometry (LC-MS) (Inoue et al, 2011), mass spectrophotometry (Lehner et al, 2011), and electrochemical process (Atty et al, 2020;Nezammahalleh et al, 2018). Although these analytical methods are highly sensitive and accurate, they are time consuming, costly and requiring professional operators.…”