1. The problem statement, all variables and given/known data Hi. I just did a lab where we are to determine the amount of iron present in a vitamin based on its absorbance (after reacting it with hydroquinon and o-phenanthroline) and I am having trouble making a conversion. At the beginning of lab, we prepared a " .04 mg/mL = 40 ppm " standard Fe solution. For our calibration curve, we made 1 sample using 10 mL of standard Fe mixed with some citrate (to adjust ph i think), 2mL of hydroquinone, and 3 mL of o-phenanthroline and then diluted with water to 100mL. Then, samples was made using 5, 2, 1 and 0 standard iron. I took absorbances and now need to construct my calibration curve, but I am to use concentration, not mL. Let's say, for the 10mL standard Fe sample. Am I supposed to just say that for every mL, there are .04 mg of iron and for every .04 mg of iron it is 40 ppm. So 10 mL is .04*10=.4mg of iron and .4 mg of iron is 400 ppm ? is this the correct way to convert? So I would have 1mL std Fe --> 40 ppm 2mL std Fe --> 80 ppm 5mL std Fe --> 200 ppm 10mL std Fe --> 400 ppm Is this right? I'm not sure if I need to account for the fact that it was diluted? I'm confused. Thank you!