Phosphorimetric determination of nafronyl in pharmaceutical preparations

Room temperature phosphorescence was applied to determine nafronyl in pharm aceutical preparations. The linear range of concentration was between 20 an d 1000 ng ml(-1). The use of phosphorescence enhancers such as thallium(I) nitrate (external heavy atom), sodium dodecyl sulfate (micellar agent) and sodium sulfite (deoxygenation agent) were studied and optimized to obtain m aximum sensitivity and adequate selectivity. Determination was performed in sodium dodecyl sulfate 1.32x10(-2) M, thalli um nitrate 1.78x10(-2) M and sodium sulfite 1.0x10(-2) M. The pH value was 10.5, attained by adding sodium hydrogen carbonate/sodium carbonate 2.0x10( -2) M at a measurement temperature 20 degrees C, Phosphorescence was fully developed in 20 min. Intensity was then measured at lambda(ex)=288 nm and l ambda(em)=491 nm. Recovery was tested in Praxilene 100 mg (commercial formu lation containing nafronyl). Recovery was 104.2% with 2.4% standard deviati on. Overall least squares regression was used to find the straight line that fi tted the experimental data. The detection limit according to the error prop agation theory was 6.1 ng ml(-1) and the detection limit proposed by Clayto n was 10.0 ng ml(-1). Repeatability and relative standard deviation were al so determined according to this theory, with satisfactory results. (C) 1999 Elsevier Science B.V. All rights reserved.