Question- I am trying to write up a lab report where I used colorimetry to check the absorbance of a reagent with different concentration of solution but I'm having a tough time using my calibration curve to determine the concentrations of unknown solutions. The issue is that my absorbance vs. concentration graph has a negative slope and thus when trying to determine the concentration of the unknown solution, it ends up being negative.
I am utilizing a special reagent that at higher concentrations has a lower absorbance than it has at low concentrations. I need help for above question.