[intelibp1600]

I completed an AAS lab. It is an analysis of lead by standard addtion. I had a 0ppm solution with absorbance 0.018, 2ppm with 0.030nm, and 3ppm with 0.036.

I had to plot the absorbance and ppm. The x intercept of the line will be the concentration of the diluted sample with no standard addition.

After plotting, the number for the X-intercept comes out to be -3.0ppm. Is it possible to have negative ppm in this case?

[tamim83]

Do you mean y intercept? 

[intelibp1600]

No, it's x intercept. I have to find the concentration of the diluted sample with no standard addition.

[tamim83]

Oh yeah, I completely forgot  , I was trying to find my olf lab report on a similar experiment, but it was a no go.  I am very sure that your concentration would not be negative.  The answer should be larger than zero.  You would have either a concentration of zero ppm or above. 

[VeraGTi]

Hi,

In standard addition method, when your calibration curve intercepts de X gives you the value for your sample concentration but with a positive sign. Therefore, the concentration of lead in your sample is actually 3ppm. In standard addition methods your plot will always intercept X in a negative value.. You just have to take that value in module. -> |-3.0ppm|