S. Panadero et al., KINETIC DETERMINATION OF SALICYLIC-ACID, DIFLUNISAL AND THEIR MIXTUREBASED ON LANTHANIDE-SENSITIZED LUMINESCENCE, Analytica chimica acta, 329(1-2), 1996, pp. 135-141
The combined use of kinetic and equilibrium measurements, obtained wit
h the aid of the stopped-flow mixing technique, allowed the developmen
t of a simple, fast direct method for the simultaneous determination o
f salicylic acid and diflunisal in untreated serum samples that can be
readily applied to routine analyses. The method is based on the forma
tion of ion-association complexes between the cationic surfactant cety
ltrimethylammonium bromide and the ternary anionic chelates formed by
salicylate and diflunisal with terbium(III) and EDTA in a basic medium
. The intramolecular energy transfer from salicylate or diflunisal to
terbium(III) gives rise to luminescence emission by the lanthanide ion
. The calibration graphs thus obtained are linear over a wide concentr
ation range and the detection limits are in the nanogram per millilitr
e region. Within-assay and between-assay relative standard deviation r
anged from 2.6% to 3.6% and from 1.3% to 8.5%, respectively. Mixtures
of salicylic acid and diflunisal in ratios between 6:1 and 1:12 can be
satisfactorily resolved. The proposed method was applied to the direc
t determination of these compounds in serum with recoveries of 92.7-10
9.0% for salicylic acid and 86.4-110.9% for diflunisal.