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A thin-layer chromatographic procedure utilising fluorescamine detection is described for the quantitation of cephradine, cefaclor, cephalexin and cefadroxil. The repeatability, sensitivity and detectability of the method are compared with those for o-phthalaldehyde fluorescence emission and UV absorption measurements on the plate. The applicability of the fluorescamine method to the determination of these cephalosporins in serum, urine and pharmaceutical formulations is discussed.

The determination of diclofenac sodium in tablets is presented as an example of an assay validation using spectrophotometry. The experimental design and different statistical approaches are given.

A procedure is proposed for the quantitative determination of both benzoic and sorbic acids in fruit beverages. This method is carried out by direct ultraviolet spectrophotometric measurements in silica chromatoplates after development with chloroform-methanol-water (65+35+7) and makes use of an internal standard. Applied to samples spiked with benzoic and sorbic acids, this technique gives accurate and reliable results with good recoveries. The sensitivity (about 1 ppm) is particularly convenient for trace level determination.