negative intercept with my calibration curve

[oceanist]

Hi guys,

I met a significant negative intercept (~ 3 times the slope) with my calibration curve. I think it may come from the unsolved peak of my compound. There is a large interfering peaks just behind of the peak of my compound. I feel confident with the concentrations of my standard solutions.

My question is whether this big negative intercept is from the unresolved peaks which caused the loss of peak area? BTW, i plotted concentrations vs peak area.

Welcome to share thoughts regarding this issue...

Thanks...

[LabProARW]

Visually assuming a linear and not curvelinear response.... can you delete one standard which visually seems to skew the line negative at the intercept? Eyeballing it imagining the origin as a standard, many times I have seem one standard throw a calibration line negative. Usually the chromatography picked the wrong peak or integration was wrong for the standard which throws the line negative.

[carlo.annaratone]

are you sure a linear regression is fit for the job? did you try to plot the datapoints just to see how they look like?

[Peter Apps]

Hi guys,

I met a significant negative intercept (~ 3 times the slope) with my calibration curve. I think it may come from the unsolved peak of my compound. There is a large interfering peaks just behind of the peak of my compound. I feel confident with the concentrations of my standard solutions.

My question is whether this big negative intercept is from the unresolved peaks which caused the loss of peak area? BTW, i plotted concentrations vs peak area.

Welcome to share thoughts regarding this issue...

Thanks...

Where does the integration put the baseline of the peak of interest, if it is skimming the peak off the tail of the large interference then a loss of area is possible, and that will give you a negative intercept. If it drops to baseline the area will be systematically too large, and you will have a positive intercept.

The only satisfactory solutions are to improve the chromatography, or to use a selective detector.

Peter