Using Classical EDTA Titrations To Measure Calcium and Magnesium in Intravenous Fluid Bags

Potency assays of pharmaceutical products are designed to measure the amount of an active ingredient in a sample. They are important quality control tools for all medications, including intravenous (IV) admixture fluid bags which are commonly prepared by pharmacists in healthcare facilities via extemporaneous compounding. An interdisciplinary laboratory module was created by combining the learning outcomes of a pharmacy compounding course with the classic undergraduate chemistry quantitative analysis course. The pharmacy students prepared the IV bags of calcium gluconate or magnesium sulfate in isotonic saline vehicle based on given prescriptions. The analytical chemistry students applied United States Pharmacopeia complexometric titration methods to determine the concentration of calcium or magnesium in the IV fluid and convert it to mass for each bag. The analytical results allowed the pharmacy students to confirm whether their IV bags met the passing criteria for the labeled claimed mass. This transformative learning experience provides an interesting real-life application for a quantitative analysis laboratory course and highlights the importance of quality control in the pharmacy compounding course.