Determination of Zinc in Cough Drops by Standard Addition with Flame Atomic Absorption Spectroscopy An Instrumental Analysis Laboratory Experiment

Zinc is an essential element that can be found in some foods, but is also available as a dietary supplement and is a constituent in many multi-vitamins. An experiment was developed for a senior level analytical laboratory course utilizing a Flame Atomic Absorption Spectrometer (FAAS) for the analysis of this element in cold lozenges. FAAS is a well-established single element spectrochemical technique and has proven to be a cost-effective and fairly simple way to analyze for various elements at trace and ultra-trace levels in a range of matrices. The objectives of this experimental laboratory were twofold. The first objective involved demonstrating the strengths and weaknesses of flame atomic absorption spectro scopy. Prior to the conduction of this experiment, students were asked to determine the amount of zinc in the same type of cold lozenge sample by titration with ethylenediaminetetraacetic acid (EDTA). The purpose of this dual analysis was to demonstrate the multiple techniques open to the analytical chemist. Further, choosing one method over another in the area of elemental analysis can depend on many factors, including cost (both initial and operating), level of employee skill, required limits of detection, specificity, requisite precision/accuracy and single/multiple element application. The second objective of this experimental procedure was to introduce the students to analyte quantitation by standard addition, a common method utilized with FAAS. While meeting these two objectives, this laboratory exercise provided a novel and engaging application of FAAS and allowed the students to use modern instrumentation and analytical techniques to investigate the amount of zinc in cold lozenges.