[Analysis of 5-pyrazolinone derivatives in pharmaceutical products. I. Spectrophotometric analysis of two-component drugs containing propyphenazone].

Two new methods for the determination of active components in the preparations Gardan P (propyphenazone + noramidopyrine) and Pabialgin P (propyphenazone + allobarbital) have been elaborated. The first one is a direct spectrophotometric method based on measurements of absorption at two wave lengths; at lambda = 218 and 270 nm for Pabialgin P, and at lambda = 232 and 260 nm for Gardan P. The second method, the chromatographic-spectrophotometric method has been based on separation of individual components by thin-layer chromatography followed by their spectrophotometric determination. The results obtained by the above two methods were compared with the results given by the titrimetric method according to the producer's standard. Statistic analysis by the Student's and F-Snecodor's tests has shown that all these methods are equally precise but differ in accuracy, sensitivity and selectivity. The spectrophotometric determination of allobarbital has proved to show the highest accuracy (Wz = 1.4), while the acidimetric determination of propyphenazone in the non-aqueous medium has appeared least accurate (Wz = 3.7). Sensitivity of the tested methods was found to range from 3 x 10(-4) g/cm3 for the titrimetric methods to 6 x 10(-6) g/cm3 for direct spectrophotometric measurements. In respect of selectivity, only the chromatographic-spectrophotometric method has proved to be enough selective and to give quite correct results.