Bioequivalence and Bioavailability Forum

Dear dharmanandh,

Usually concentrations are calculated by a weighted linear regression:

y = mx + b (here in France we rather write it y = ax + b)

where y is your peak area ratio (analyte to IS) and x is the concentration. Back-calculating the concentration of your calibration samples is done exactly the same way as for unknown samples:

x = y/m - b/m.

It becomes more complex if you are using a quadratic equation (y = ax² + bx + c). You can get two solutions to such a formula, only one of which will be relevant:

x = (-b ± squareroot(b²-4a(c-y)))/2a

Regards
Ohlbe