New spectrophotometric and smartphone-based colorimetric methods for determination of atenolol in pharmaceutical formulations

[Display omitted] •Novel spectrophotometric and smartphone-based colorimetric methods developed for atenolol estimation.•Inhibitory effect of atenolol on diazotization reaction used for determining ATE concentration.•Reactant concentrations are optimized using a central composite design and response surface methodology.•Developed methods validated by analyzing atenolol in pharmaceutical tablets and comparing them with HPLC.•Potential use of methods in quality control laboratories valuable for the pharmaceutical sector. Novel spectrophotometric and smartphone-based colorimetric methods were developed and validated for the estimation of atenolol (ATE) in pharmaceutical formulations. The measurement procedure is based on the de-diazotization reaction, in which ATE is able to inhibit the diazotized sulfanilic acid from reacting with 8-hydroxy quinoline (8-HQ) in a basic medium. As a result, the formation of red–orange color azo-dye is hindered, and the color intensity is decreased proportionally to concentration of ATE. In spectrophotometric method the azo-dye color fate was monitored at 495 nm. While in smartphone-based colorimetric (SBC) method the captured image in the design processed by RGB App and transferred to the absorbance. The reactant concentrations were optimized using a central composite design (CCD) and response surface method. The methods exhibit good linearity in the 8.0 to 60.0 µg mL−1 range with no significant effect of interferences. The spectrophotometric method yields a linear equation with a slope of 0.0187 (R2 = 0.9993), a limit of detection (LOD) of 1.28 µg mL−1, and a limit of quantification (LOQ) of 4.28 µg mL−1. On the other hand, the smartphone-based colorimetric (SBC) method demonstrates a linear equation with a slope of 0.0127 (R2 = 0.9965), an LOD of 2.13 µg mL−1, and an LOQ of 7.09 µg mL−1. Analyzing ATE in pharmaceutical tablets was utilized to validate the applicability of the developed methods, and the results were statistically compared with those obtained by the HPLC method using the t-test and F-test.