Phosphorimetric determination of nafronyl in pharmaceutical preparations Original Research Article

Room temperature phosphorescence was applied to determine nafronyl in pharmaceutical preparations. The linear range of concentration was between 20 and 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 maximum sensitivity and adequate selectivity. Determination was performed in sodium dodecyl sulfate 1.32×10−2 M, thallium nitrate 1.78×10−2 M and sodium sulfite 1.0×10−2 M. The pH value was 10.5, attained by adding sodium hydrogen carbonate/sodium carbonate 2.0×10−2 M at a measurement temperature 20°C. Phosphorescence was fully developed in 20 min. Intensity was then measured at λex=288 nm and λem=491 nm. Recovery was tested in Praxilene 100 mg (commercial formulation containing nafronyl). Recovery was 104.2% with 2.4% standard deviation. Overall least squares regression was used to find the straight line that fitted the experimental data. The detection limit according to the error propagation theory was 6.1 ng ml−1 and the detection limit proposed by Clayton was 10.0 ng ml−1. Repeatability and relative standard deviation were also determined according to this theory, with satisfactory results.