Hey everyone,

I'm working on an experiment involving the analysis of total phenol content in coffee samples. To ensure accuracy, I created a calibration curve using different concentrations of gallic acid and UV-Vis spectrophotometry at 765 nm. I prepared several concentrations of gallic acid and obtained a calibration curve with a coefficient of 0.96, which seems great.

However, the regression line equation I got was 0.0515*x -19.9. This result is quite different from the standard equations I found online. I’m confused as to why my regression line is so far off.

Has anyone experienced something similar or have any insights into what might be causing this discrepancy?

Thanks!

You can find a calibration curve I found from the internet below which has a regression line of:

y = 0.0016x + 0.0192