RESUMO
A liquid chromatographic (LC) method was developed and statistically validated for simultaneous determination of nitrofurazone, nitrofurantoin, furazolidone, and furaltadone residues in bovine muscle tissues. These antimicrobial residues in samples stabilized at pH 6.0 were extracted with acetonitrile and purified by liquid-liquid partition between dichloromethane-ethyl acetate and hexane saturated with acetonitrile. The acetonitrile-ethyl acetate extract was concentrated, and drug residues were dissolved in LC mobile phase, filtered, and determined by LC. A C18 reversed-phase (ODS Hypersil) column at 35 degrees C, a mobile phase of 0.01M sodium acetate buffer (pH 4.5)-acetonitrile (70 + 30), and a UV/visible diode array detector at 365 nm were used. The retention times and UV spectra of peaks in spiked samples were compared with those of known nitrofurans. Limits of detection (LD) and quantitation (LQ) were 1 and 2 micrograms/kg, respectively. Average recoveries were 76% (range, 60-110%). Relative standard deviations ranged from 6 to 18% at 5 fortification levels from 1.5 to 20 micrograms/kg). (Fortification levels for furaltadone were 3 to 40 micrograms/kg). The method was used to analyze 350 samples per year from 1993 to 1995.
