Comparison of different methods for the determination of several quinolonic and cinolonic antibiotics in trout muscle tissue by HPLC with fluorescence detection

Quinolonic and cinolonic derivatives are mainly used as antibacterials in fish-farms. In this paper we describe a careful revision of the treatment procedures of samples and a prodedure for the determination of residues of these compounds. Because of the complexity and duration of these procedures, several studies have been carried out and these have lead to a simpler and shorter method. Three approaches have been examined: lyophilization followed by extraction with chloroform, solid-liquid extraction with chloroform and solid-liquid extraction with sodium hydroxide solution, followed by liquid-liquid partition in chloroform. Some previous studies into the partition equilibrium are also included. As a result of our studies we propose a procedure with a lower number of steps than those previously described in the literature. This method has been applied to the analysis of nalidixic, 7-hydroxymethylnalidixic and oxolinic acids and cinoxacin in trout muscle. These analysis have been carried out using an HPLC system equipped with a C-18 column and fluorimetric detection. The mobile phase was acetonitrile:oxalic acid. The recoveries obtained were: 70-97 % for 7-hydroxymethylnalidixic acid, 75-78 % for nalidixic acid, 71-95 % for oxolinic acid and 72-85 % for cinoxacin.