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The fluorimetric characteristics of pipemidic acid (PIPE) have been investigated. It has been proven that the fluorescence emission band of pipemidic acid at 439 nm is significantly intensified in the presence of γ-cyclodextrin. The inclusional complexation between the antibacterial pipemidic acid and γ-cyclodextrin (γ-CD) has been studied. A 1:1 stoichiometry of the complex was established and its association constant was calculated by a nonlinear regression method, monitoring the changes in the fluorescence signal of pipemidic acid in the presence of γ-CD. According to the results obtained, a spectrofluorimetric method for the determination of PIPE has been proposed. The best limits of detection and quantification were obtained in presence of γ-CD, in acidic media. The dynamic range of the method was comprised between 0.18 and 1.40 μg/ml.

Binary mixtures of methotrexate (MTX) and leucovorin (LV) have been resolved by application of first-derivative spectrophotometry and partial least squares calibration (PLS-1). By measuring the first-derivative signals of MTX and LV at 354 and 300 nm, respectively, simultaneous determination was possible. The mean recoveries for urine samples were 91 and 96% for MTX and LV, respectively. Partial least squares (PLS-1) multivariate calibration has been applied to the determination of these compounds in serum and in urine without pretreatment of the samples. The absorption spectra of serum or urine samples spiked with methotrexate and/or leucovorin, were used to optimize the calibration matrixes by the PLS-1 method. The sensitivity and selectivity of the proposed procedures were calculated. Mean recoveries were 101 and 97% for MTX and LV, respectively, for serum samples, and 101 and 98% for MTX and LV, respectively, for urine samples.

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 C18 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.