Development of the spectrophotometric method for the determination of metoprolol tartrate in tablets by using bromocresol green

The aim of the work was to develop and validate a spectrophotometric method for determining metoprolol tartrate in tablets based on the reaction with bromocresol green (BCG). Material and methods. Analytical equipment: two-beam UV-visible spectrophotometer Shimadzu model -UV 1800 (Japan), software UV-Probe 2.62, laboratory electronic balance RAD WAG AS 200/C, pH-meter И-160МИ. The following APIs, dosage forms, reagents and solvents were used in the work: pharmacopoeial standard sample (CRS) of metoprolol tartrate (Sigma-Aldrich, (≥ 98 %, HPLC)), BCG (Sigma-Aldrich, (≥ 98 %, HPLC)), "Metoprolol" tablets 50 mg (Kyivmedpreparat, series 0035415), "Metoprolol" 100 mg (Farmak, series 30421), methanol (Honeywell, (≥ 99.9 %, GC)), ethanol (Honeywell, (≥ 99.9 %, GC)), chloroform (Honeywell, (≥ 99.9 %, GC)), acetonitrile (Honeywell, (≥ 99.9 %, GC)), and ethyl acetate (Honeywell, (≥ 99.7 %, GC)). Results and discussion. A spectrophotometric method was developed for determining metoprolol tartrate by reaction with BCG in a methanol solution using the absorption maximum at a wavelength of 624 nm. Stoichiometric ratios of reactive components were established, which were 1:1. The developed method for the quantitative determination of metoprolol tartrate was validated following the requirements of the SPhU. The analytical method was linear in the concentration range of 5.47-38.30 μg/mL. The limit of detection and quantification were 0.41 μg/mL and 1.24 μg/mL, respectively. According to the «greenness» pictogram of the analytical method using the AGREE method, the score was 0.79, which indicates that the proposed spectrophotometric method for the determination of metoprolol was developed in compliance with the principles of «green» chemistry. Conclusions. A spectrophotometric method for determining metoprolol tartrate in tablets based on the reaction with BCG in compliance with the principles of «green» chemistry has been developed and validated. Furthermore, the developed method for the quantitative determination of metoprolol tartrate was validated following the requirements of the SPhU. In summary, the developed method has a low negative impact on the environment and can be applied for routine pharmaceutical analysi