Synchronous scanning second derivative spectrofluorimetry for the simultaneous determination of diflunisal and salicylic acid added to serum and urine as ternary complexes with terbium and EDTA

By using second derivative synchronous scanning fluorescence spectrometry the simple resolution of two nonsteroidal, antiinflammatory drugs diflunisal and salicylic acid, as ternary complexes with terbium and EDTA, is accomplished. The method developed is simple, sensitive and rapid, and has been successfully applied for the determination of both compounds in 10 μl of untreated human serum and urine samples. The detection limits for diflunisal were 0.9 and 1.8 mg l−1, and for salicylic acid 1.2 and 1.7 mg l−1, in serum and urine, respectively. The mean analytical recoveries from serum and urine samples spiked with diflunisal (25–100 mg l−1) and salicylic acid (28–138 mg l−1) were 99 ± 8% (serum) and 102 ± 8% (urine) for diflunisal and 102 ± 9% (serum) and 95 ± 8% (urine) for salicylic acid. The precision of all determinations varied from 2.5 to 10%.