MALDI-TOF MS quantification of coccidiostats in poultry feeds.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is a relatively new technique that is having a great impact on analyses. This study is the first to demonstrate the use of linear MALDI-TOF MS to identify and quantify coccidiostats in poultry feeds. 2,5-Dihydroxybenzoic acid (DHB) was found to be the best matrix. In MALDI-TOF MS, coccidiostats form predominantly [M + Na](+) ions, with additional small amounts of [M + K](+) and [M - H + 2Na](+) ions, and no obvious fragment ions. Salinomycin and narasin were unstable in the concentrated DHB matrix solution but were stable when dried on the MALDI-TOF MS probe. A simple fast Sep-pak C18 cartridge purification procedure was developed for the MALDI-TOF MS quantification of coccidiostats in poultry feeds. The MALDI-TOF MS limit of detection for lasalocid, monensin, salinomycin, and narasin standards was 251, 22, 24, and 24 fmol, respectively. The method detection limit for salinomycin and narasin in poultry feeds was 2.4 microgram/g.