Stopped-flow determination of dipyridamole in pharmaceutical preparations by micellar-stabilized room temperature phosphorescence.

The stopped flow mixing technique has been used to study the kinetic determination of dipyridamole by means of micellar-stabilized room temperature phosphorescence (RTP). This mixing system diminishes the time required for the deoxygenation of the micellar medium by sodium sulfite. The phosphorescence enhancers thallium (I) nitrate, sodium dodecyl sulfate (SDS), and sodium sulfite were optimized to obtain maximum sensitivity and selectivity. A pH value of 10.6 was selected as adequate for phosphorescence development. The kinetic curve of dipyridamole phosphorescence was scanned at lambda(ex)=303 nm and lambda(em)=616 nm. Then, the intensity at 10 s, and the maximum slope of phosphorescence development, for an interval time of 1 s, were measured. Two determination approaches: intensity and rate methods, were proposed. The calibration graphs were linear for the concentration range from 50 to 400 ng ml(-1). The detection limits, according to Clayton et al., Anal. Chem. 59 (1987) 2506, were 21.5 and 37.5 ng ml(-1), for intensity and initial rate measurements, respectively. By applying the error propagation theory, the detection limits were 19.0 and 33.0 ng ml(-1), for intensity and initial rate measurements, respectively. Two commercial formulations (persantin and asasantin) were analyzed by both proposed methodologies. Adequate recovery values were obtained in both cases.