Validation of Linearity of an analytical method HPLC

[montana]

Hi,
In order to validate the linearity of an anlytical method for determination of tyrosine in human plasma, i used spike-and-recovery experiment .
My question is : after injection in hplc of standards solutions ( range of 1 to 20 mg/l) . i check the linearity of the curve , R2=0,999 and the equation of regression line : y=1.9 x+ 0.3.

Should i calculate the concentration of spiked plasma using the equation of standard solutions .

Thank You.

[tom jupille]

Should i calculate the concentration of spiked plasma using the equation of standard solutions .

How else would you do it?

If this were my problem, I would be somewhat concerned about what looks to be a significant y-intercept. What was the standard error?