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Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: exoem on November 17, 2017, 04:22:45 PM

Title: Good calibration?
Post by: exoem on November 17, 2017, 04:22:45 PM

Hi everyone  :) . Today I created a calibration curve in order to determine proteins concentration in a brain extract, by adding Biuret and Folin–Ciocalteu reagent to several standard albumin solutions and a blank solution, and measuring absorbance at 640 nm, but I am not sure if the R^2 coefficient (0.9464) is high enough to consider the curve as a valid one. What do you think? Thank you.
 
(https://i.imgur.com/kLtmeaF.jpg)

Title: Re: Good calibration?
Post by: Corribus on November 18, 2017, 12:37:51 AM

Based on the residuals there doesn't appear to be an obvious systematic error,  but ultimately there's no right answer.  Either it meets your criteria or it doesn't.  If in doubt,  do the experiment again, after considering potential sources of error.  How are you making solutions and solutions? Is your instrument calibrated? Have you verified that your spectral shape isn't changing? How many  times have you made each measurement?