Vegetable oil as an alternative solvent in a simple green colorimetric liquid-liquid partitioning extraction for diphenhydramine hydrochloride determination

An investigation was made to use some vegetable oils, namely, extra virgin coconut oil, tea seed oil, soybean oil, and extra light olive oil, as alternative solvents for the simple green colorimetric liquid-liquid partitioning extraction determination of diphenhydramine hydrochloride (DPHH). The ion pair of DPHH and bromocresol green (BCG) in an aqueous phase is extracted into the organic phase. Microliter scale operation was performed. After extraction, the color changes of the organic phase were monitored by a smartphone. With image processing, calibration equations in the range of up to 80 mg L−1 DPHH were obtained when using vegetable oils as extractants. Limits of detection (LODs) (3σ) were 14, 11, 9, and 16 mg L−1 DPHH when using extra virgin coconut oil, tea seed oil, soybean oil, and extra light olive oil, respectively. Application to real samples of pharmaceutical preparations was demonstrated. Accuracy was evaluated by comparing the results obtained by the developed procedures with a high performance liquid chromatography reference method and %Label and 10% RSDs were obtained.