Direct determination of dipyridamole in serum

A new method for the determination of dipyridamole in serum for concentrations between 10 and 100 ng ml-1 by means of matrix isopotential synchronous fluorescence spectrometry and derivative techniques is proposed. This new method is useful for the determination of compounds in samples with unknown background fluorescence, such as dipyridamole in serum, without the need for tedious preseparation. The determination was performed in an ethanol/water medium (15% v/v) at a pH value of 10.0, provided by adding an ammonium chloride/ammonia buffer solution. Since dipyridamole is a stimulant which is very much used like a doping substance in sport, the method was successfully applied to the determination of dipyridamole in serum. Better sensitivity and repeatability are achieved for these matrices than with the fluorometric ones described in the literature. An exhaustive statistical analysis has been developed for all calibration graphs. This treatment includes robust regression such as least median of squares which also detects outliers and leverage points. The overall least-squares regression has been applied to find the more exact straight line which fits the experimental data. The error propagation has been considered to calculate the detection limit, determination limit, and the repeatability of the method.