Photochemical analysis studies-III A fluorimetric and ultraviolet spectrophotometric study of the photolysis of chloroquine on silica-gel thin layers, and its analytical application.

The photolysis of chloroquine on silica-gel thin layers has been studied by ultraviolet spectrophotometry and fluorimetry. It has been shown that a reversible photoisomerization of chloroquine takes place and yields a fluorescent photoproduct. The effect of pH, alkali-metal halides, and the eluent system on the fluorescence intensity of chloroquine and its photoproduct was investigated. The fluorescence on silica-gel thin layers is quenched by high concentrations of sodium hydroxide; this is explained in terms of interference of sodium ions in the hydrogen-bonded adsorption of chloroquine on the silica gel. The results have been used to develop a method for determination and separation of chloroquine at the nanogram level. Linear calibration plots are obtained, covering the range between 4 and 10(4) ng.