Development of high performance liquid chromatographic methods for the determination of cyadox and its metabolites in plasma and tissues of chicken

Cyadox (CYX) is an antimicrobial growth-promoter of the quinoxalines. It is highly effective on improving growth and feed conversion of chicken with little toxicity. For food safety concerns, HPLC-UV methods were developed for the sequential determination of CYX and its major metabolites, 1,4-bisdesoxycyadox (BDCYX) and quinoxaline-2-carboxylic acid (QCA), in plasma, muscle, liver, kidney and fat of chicken. For CYX and BDCYX, samples were subjected to a deproteinisation, a degrease and a liquid–liquid extraction. For QCA, samples were subjected to an alkali hydrolysis, a liquid–liquid extraction and a cation exchange column (AG MP-50 resin) clean-up. Analysis was performed on a RP-C18 column by UV detection with a gradient program of wavelength. Gradient elution was performed at a flow of 1 mL/min. The limits of quantification for CYX, BDCYX and QCA in plasma and tissues were 0.025 μg/g, and 0.002 μg/g for QCA in muscle. The recoveries of three compounds in plasma and tissues were 70–87% with inter-day relative standard deviation (R.S.D.) less than 10%. An animal experiment was performed to show the applicability of the present methods in real biological samples, which demonstrated a satisfactory applicability since all compounds could be detected nearly in all tissues. The present methods were highly sensitive and accurate, and could therefore be useful in pharmacokinetic and residue studies for cyadox in chicken. The developed methods will be further applied in the residue screening of cyadox and its metabolites in chicken.