Determination of Copper in Vitamin Tablets with Flame Atomic Absorption Spectroscopy

Multivitamin tablets containing copper, an essential micronutrient, are commonly available and are consumed by many people in the US and worldwide. An analytical chemistry laboratory experiment for determination of copper in vitamin tablets with flame atomic absorption sepectroscopy (FAAS) is described. The sample preparation methodology involves dry-ashing the vitamin sample in a silica crucible in a high temperature muffle furnace followed by acid treatment. The multiple-increment standard addition method is used to create calibration curves and absorbance measurements are made using the copper resonance line at 324.8 nm with air/acetylene FAAS. Results obtained for five commercial vitamin tablets analyzed by 39 students enrolled in a multi-section analytical chemistry course are presented. This experiment provides a venue for undergraduate students to learn the principles of FAAS, to have hands-on experience using FAAS instrumentation and to ascertain the fundamentals and the applications of the multiple-increment standard addition method. Additionally, since this experiment involves the analysis of real world samples, the analytical laboratory experience is made relevant and interesting.