Teaching Sample Preparation in the Undergraduate Laboratory

Abstract

Teaching sample preparation in an undergraduate analytical chemistry laboratory provides many challenges. For example, the time required to properly digest a sample means that sample preparation and method development are often deliberately overlooked in the undergraduate laboratory. To teach sample preparation, we have developed an experiment for the acid digestion of an iron ore sample in a microwave oven. From a pedagogical perspective, the microwave oven has the advantage of allowing easy control of experimental parameters such as heating power and time. This experiment requires two 3-hour lab periods. One lab period is required for determining the optimum conditions to achieve maximum extraction of Fe from an iron ore sample. The digestion parameters used for this experiment are choice of acid, digestion time at a fixed microwave power, and microwave power at a fixed time. A second lab period is required for the preparation of calibration standards and the analysis of the ore samples for Fe using flame atomic absorption spectroscopy. Using the optimum digestion parameters, Fe was measured in a known ore sample and was within 2% of the expected concentration.