Determination of the Acid-Neutralizing Capacity of Different Antacid Tablet Samples Available on the Libyan Market in Ajdabiya Using Complementary Analytical Techniques

Abstract

Antacid preparations are widely used to manage the symptoms of gastric hyperacidity by chemically neutralising hydrochloric acid (HCl). The acid-neutralising capacity (ANC) of an antacid is an important analytical parameter because it quantitatively measures the amount of acid a defined quantity of the formulation can neutralise. However, ANC alone does not provide complete information about the physicochemical characteristics or chemical composition of a commercial pharmaceutical product. The present study therefore employed a complementary analytical approach involving acid–base back titration, pH measurement, and attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy to evaluate four commercial antacid formulations available in pharmacies in Ajdabia, Libya. The investigated products were Eno, Gaviscon, Gastavit, and Rennie. Samples were collected between November 2023 and February 2024. For ANC determination, 1.3 g of each powdered formulation was reacted with 30 mL of 1 N HCl, and the residual acid was back-titrated using 0.5 N NaOH. The measured ANC values were 8.0, 10.846, 10.769, and 19.3 mEq/g for Eno, Gaviscon, Gastavit, and Rennie, respectively. The measured final pH values were 9.26, 8.16, 8.67, and 11.25, respectively. ATR-FTIR analysis revealed absorption bands attributable to hydroxyl, C–O, C–H, and carbonyl-containing functional groups, with additional bands observed for C–N and C–H₂/C–H₃ groups in selected formulations. The results demonstrate substantial differences in acid-neutralising capacity among the examined products despite their common therapeutic purpose. The findings also demonstrate the value of combining titrimetric analysis with pH and spectroscopic characterisation when evaluating commercial antacid formulations.