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

This simple, rapid, sensitive spectrofluorometric method for the simul taneous determination of diflunisal and salicylic acid is based on the ir intrinsic fluorescence in chloroform-1% acetic acid solution. The b road-band overlapping conventional spectra of both compounds are resol ved by means of second-derivative synchronous fluorescence spectroscop y, obviating the need for pre-analysis sample separation techniques. T he 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. Se rum samples are treated with trichloroacetic acid to remove proteins a nd the two compounds are extracted into chloroform-1% acetic acid solu tion 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.