Preparing the Food Samples
3. Weigh out about 2.5 g of the solid food and place in a crucible.
4. Heat the crucible with a hot burner flame until the food sample has turned to ash. This should take approximately 5-20 minutes depending on the food sample used.
5. Remove the burner and allow the ash to cool. When cool, transfer to a small beaker.
6. Add 10 mL of 2.0 M HCl and carefully stir for one minute. Add 10 mL of distilled water. Stir.
7. Filter the mixture; collect the filtrate. Add 2.5 mL of 0.1 M KSCN. Mix well.
Finding the Absorbance
8. Use a spectrophotometer at a wavelength of 458 nm or use the fixed wavelength (458 nm) on the UV-VIS.
9. Place each standard solution and food solution into a separate cuvette.
10. Measure and record the absorbance of each solution.