Although decoquinate was used extensively as a coccidiostat for Eimeria protozoan infections in poultry and ruminant animals in the 60s and 70s, its use declined in the 80s. After the withdrawal of furazolidone from animal feeds, this trend reversed. This resurgence prompted the development of a rugged, reproducible HPLC method of analysis of animal feeds. Decoquinate has been approved for use in poultry, sheep, calf/cattle and goat feeds at 6% in the pre-mix and between 14 and 50 ppm in the commercial feeds. CVM formulated a poultry feed and a calf starter at 30 ppm for this study.
Decoquinate is extracted from feed matrices by homogenization with a solvent mixture of 1% MgCl2.6H2O in 1:1:5 CH3OH:CH2Cl2:CH3CN. The native fluorescence of decoquinate is enhanced by complexation with magnesium ion. The extract is injected onto a 5µ C18 column with a mobile phase of 5mM MgCl2.6H2O in 15:20:65 CH3OH:H2O:CH3CN at 40°C. Either UV (260nm) or fluorescence (Ex 270nm, Em 390nm) detection may be used. Recoveries at 23, 30, and 50ppm are 88±2% with RSDs <3.5%. Analyses of commercial calf starter samples found 58% (26ppm) to 130% (50ppm) with RSDs <4.5%, pre-mix, 109% with RSDs <3%.