The objective of this lab was to consult for the FDA regarding a recently surfaced scandal involving false reporting of iron content in cereal as well as iron tablets. The makers of the cereal and the iron tablets, respectively, were allegedly reporting higher amounts of iron in their products than actually existed, as a way to save money but continue to provide products with “adequate” amounts of iron. The FDA needed consulting in order to analyze the products and use the data to determine the true amount of iron in each product, as well as confirm that the iron was usable by the human body. The methods used to analyze the products, data, and results will be provided in the sections below.
The entire experiment is based on the results from the calibration curve. The calibration curve is used to generate an equation that is then used to calculate molarity. This value is then converted to the desired unit, milligrams. So, to obtain the calibration curve data, two students began by preparing two solutions. The first was 100 mL of 1.0 x 10-3 M Fe(NO3)3, and the second was 100 mL of 0.10 M KSCN. Both solutions were made in 1.0 HNO3. The former solution was prepared using 0.0404 grams of Fe(NO3)3•9H2O on an analytical balance (calculations below). The latter solution was prepared using 0.97 grams of KSCN on a top loading balance (calculations below). Then, 1.0 mL of the iron nitrate solution was added to 100 mL of the KSCN solution and mixed. Being that the spectrophotometer (the instrument being used to measure absorbance) was already zeroed by the teaching assistant, the construction of the calibration curve could begin. To start, the cuvette was filled with the current mixture, placed into the spectrophotometer, and the absorbance was recorded. The cuvette was then emptied back into the beaker containing the entire solution, as not to skew the overall volume, and therefore the concentration.