Hello. I decided to try and find caffeine concentration in coffee for my chem lab, and the concentrations seem very wrong and that I diluted it, but I am not sure where I did or if I did. I put 5 ml of the sample into a 125 ml separatory funnel with 1 ml sodium carbonate, 10 ml water, 20 ml methylene chloride. After collecting the organic layer, 20 ml of methylene chloride was added to the aqueous layer that was left and I repeated the extraction. I did this twice for each sample. After finding the absorbance through UV/Vis, I found that the concentrations were 9.88 ppm for decaf, 79.12 ppm for espresso, 13.30 ppm for cold brew, and 28.23 ppm for regular coffee. I'm sure that I messed up a little with the separatory funnel as I was unsure during that (there was emulsion and had to discard the first layer because it wasn't fully separating), but I do not think I lost THAT much caffeine. By looking at labels and things, my concentrations should have been way higher and in the hundreds. I was hoping someone could give me some idea on what went wrong or if there was a dilution somewhere. Thank you.