SIMULTANEOUS DETERMINATION OF DIFLUNISAL AND SALICYLIC-ACID IN HUMAN SERUM BY 2ND-DERIVATIVE SYNCHRONOUS FLUORESCENCE SPECTROSCOPY

This simple, rapid, sensitive spectrofluorometric method for the simultaneous determination of diflunisal and salicylic acid is based on their intrinsic fluorescence in chloroform-1% acetic acid solution. The broad-band overlapping conventional spectra of both compounds are resolved by means of second-derivative synchronous fluorescence spectroscopy, obviating the need for pre-analysis sample separation techniques. The range of application is 0-25 mg/l for diflunisal and 0-13 mg/l for salicylic acid. The detection limits for diflunisal and salicylic acid are 0.01 and 0.03 mg/l, respectively. The method has been applied for the determination of diflunisal and salicylic acid in human serum. Serum samples are treated with trichloroacetic acid to remove proteins and the two compounds are extracted into chloroform-1% acetic acid solution prior to instrumental determination. Analytical recoveries range from 97 to 105% (mean 99%) for diflunisal and from 91 to 107% (mean 96%) for salicylic acid, respectively. Within-run CVs for the method for three diflunisal-salicylic acid mixtures varied from 2.6 to 4.8% for mass ratios 1/5 to 5/1. Day-to-day CVs for mixtures varied from 2.7 to 6.8%, respectively.