Fluorimetric determination of salsalate in urine, serum and pharmaceutical preparations

A method for the determination of salsalate at concentrations between 0.10 and 1.00 mug ml(-1) by means of fluorescence spectrometry technique is proposed. Salsalate, lightly soluble in water, is totally extracted into chloroform. In this organic phase, the drug shows low fluorescence but when an alkaline medium is provided, salsalate undergoes a substantial increase of the fluorescent intensity. Thus, the determination is performed in a chloroformic medium, where pyrrolidine chloroformic solution is added to give the basic character. The fluorescence measurements to quantify salsalate are carried out in its fluorescent band centered at lambda(ex)=299 nm and lambda(em)=410 nm. The method was successfully applied to the determination of salsalate in authentic pharmaceutical preparations, urine and serum. Samples of these latter two matrices, urine and serum, are extracted into chloroform, using in the aqueous phase a pH 4.8, provided by adding acetic acid/sodium acetate buffer solution. Owing to matrix interference, the method of standard additions was used to determine salsalate in the serum. The sensitivity and repeatability achieved with the proposed method are adequate for the determination of salsalate in these matrices.