Testing Effectiveness of Common Antacids Danielle Friedman – Background & Hypothesis David Hwang – Methods & Protocol Ankur Patel – Deliverables & Pitfalls Victoria Tsai – Equipment & Budget

Hypothesis(es) & Aim(s) or Objective(s): Background: Resistance of partly neutralized weak acids or bases present in aqueous solution to change in pH is known as “buffering.” In various systems of the body that require constant pH, buffers are used to control acidic or basic conditions and keep enzymes and organs working at their pH optimum. Antacids are over-the-counter drugs in tablet or liquid form that neutralize acid and act as a buffer in the stomach. Most commercial antacids contain calcium carbonate, magnesium hydroxide, or a combination of the two. Hypothesis(es) & Aim(s) or Objective(s): The buffer index of the active ingredients of three antacids, calcium carbonate, magnesium hydroxide, and calcium carbonate + magnesium hydroxide, will be compared to determine which is the most effective buffer under physiological conditions. The combination of calcium carbonate + magnesium hydroxide will be the most effective buffer and therefore have the greatest buffering capacity. Danielle Friedman

Methods & Protocol: Derive titration curve for both CaCO3 and Mg(OH)2 Compare equal amounts equimolar solutions of both antacids Titrate with standardized HCl solution Measure pH every .25 mL HCl added to generate large sample count Analyze titration curve Calculate buffer index within stomach pH (1-3) Find effective pH range of buffer Find amount of acid antacid can neutralize David Hwang

Neutralizing Capacity (pH) Proposed Deliverables/Findings: The Thymol Blue should cause the solution to change from yellow to red at a pH of 1.2-2.8. From the titration curve determine the buffer index (volume of acid neutralized) within the pH range of the stomach (1-3). The flat portion of the titration curve corresponds to the effective range of the buffer. The inflection points of the titration curve correspond to the pKa. CaCO3 should have 2 pKas due to CO3 having a charge of -2. Mg(OH)2 should have 1 pKa due to OH having a charge of -1. Active Ingredient Neutralizing Capacity (pH) CaCO3 1.0-4.5 Mg(OH)2 CaCO3 + Mg(OH)2 Effective buffer range http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=6858409&dopt=Abstract Equivalence Point Halter 1983 Ankur Patel

Potential Pitfalls: If the titration does not produce a smooth curve and regions of the curve are missing, too much HCl was added between measurements. If the samples are not pure, the titration curves will not reflect the true behavior of the antacids. If the molarity of the solutions are not accurate, then the buffer index will be an inaccurate representation of the effectiveness. However, the pH range of the flat portions of the curve would not be affected by variability in molarity and could be used as an alternative method of analysis. Ankur Patel

Equipment/Materials and Budget & Justification: Equipment - Needed to perform the titration of the two active ingredients being tested. Two 50 mL burettes and burette stand, Balance, Magnetic stirrer and stirrer bar, pH meter with combination glass-silver/silver chloride electrode and holder Supplies - The following supplies include the two active ingredients being tested and hydrogen chloride which will be used to titrate calcium carbonate and magnesium hydroxide. Calcium Carbonate (CaCO3), Supplier: Sigma-Aldrich (CAS Number: 471-34-1 ), $91.50/500g; Magnesium Hydroxide (Mg(OH)2), Supplier: Sigma-Aldrich (CAS Number: 1309-42-8), $41.80/250g; Hydrogen Chloride (HCl), Supplier: Sigma-Aldrich (CAS Number: 7647-01-0), $218.50/227g; Indicator: Thymol Blue, Supplier: Sigma-Aldrich (CAS Number 76-61-9), 24.10/5g. Total:$375.90 Newly Purchased Equipment - No new equipment will be necessary. All the equipment that is needed for this experiment is already present in the lab. Victoria Tsai