Development and Validation of Purple Sweet Potato (Ipomea batatas L.) Pigment as a Titrimetric Indicator for Hydrochloric Acid Quantification

Abstract

An analytical method development requires a validation procedure. The method is valid if it meets certain performance criteria. The purpose of this study was to validate purple sweet potato (PSP) pigment (PSPP) as titration indicator (TI) for hydrochloric acid quantification. PSPP was extracted using analytical-grade (AG) and medical-grade (MG) ethanol. PSPP extracted by AG and MG ethanol were designated PSPP-AG and PSPP-MG, respectively. PSPP-AG and PSPP-MG were used as indicators in the titration of HCl with NaOH, and the method was validated by assessing the following parameters; precision, accuracy, linearity, limit of quantification (LoQ), limit of detection (LoD), robustness, and uncertainty. Results demonstrated that PSPP-AG and PSPP-MG have high linearity with R² values of 0.9990 and 0.9991, respectively. They also have high accuracy with recovery of 102.4%, and high precision with coefficient of variation (CV) ranging from 0.1609% to 0.8773%. PSPP-AG and PSPP-MG gave LoD of 0.0220 M and 0.0213 M, and LoQ of 0.0734 M and 0.0709 M, respectively. PSPP-AG and PSPP-MG had excellent reproducibility, with CV ranging from 0.199% to 0.518%, and low uncertainty (0.000262 M and 0.000905 M). PSPP-AG and PSPP-MG are robust indicators; they were insensitive to changes in treatment conditions, with t-stat < t-table of 3.475 < 4.303 for variations in sample volume, and 1.380 < 12.706 for variations in NaOH concentration. The HCl content quantified by PSPP-AG and PSPP-MG was 0.041 M, the same as that obtained with methyl red and phenolphthalein. Therefore, PSPP-MG and PSPP-AG are valid indicators for HCl quantification in pharmaceutical dosage forms.