Determination of bopindolol by sequential injection technique with spectrophotometric detection.

In the proposed procedure, the determination of bopindolol using a sequential injection technique (SIA) with spectrophotometric detection at 560 nm is described. The new method of determination is based on the color reaction of the indole group in the molecule of bopindolol with 4-dimethylaminobenzaldehyde (Ehrlich's reagent) in acidic medium with production of a violet water-soluble complex. Due to the kinetic standpoint of reaction, the "stopped flow" technique with mixing coil between the valve and detector was tested and optimized. The proposed SIA system was used for the direct determination of bopindolol in tablets, negative effects of interfering substances (excipients of tablets) were not observed. The selectivity of the proposed method of determination was tested in the presence of seven interfering substances from the group of beta-blockers with good results. The interference effect was observed only in the presence of pindolol. The sample throughput with stopped flow technique was 40 samples per hour. Bopindolol was determined in the linear range from 1 to 10 microg ml(-1), RSD was less than 1% (n=10), with limit of detection (3sigma) 0.1 microg ml(-1) and limit of quantification 0.5 microg ml(-1). Obtained results were compared with conventional HPLC method, both analytical techniques were in good agreement.