In the presentation Billy gave last friday he said that the calculation of the permutation rate was simply the slope of linear best fit of a plot of mass loss against time. However in the example spreadsheet you sent through you have also forced the linear regression line to pass through the origin. Is this correct? it certainly seems to make sense considering the data involved but I did just wanted to check as you had not mentioned this in .
Good spot. I had set the intercept to zero on the basis that you know the mass loss must be zero at time zero. You can do this if you have already allowed the tube to equilibrate for a reasonable period of time. If you just put the tube in directly from storage it is better to allow a non-zero intercept as there will be a non-linearity at the start as the analyte initially diffuses through. Make sense? Cheers – Billy