3.2.2. Linearity and LLOQ
RA and A1 calibration curves showed good linearity over the concentration range of 5-750 ng/ml. The typical calibration plot equations and their correlation coefficients were calculated as follows: RA: y = 2.01 × 10−3 x + 1.12 × 10−1 (r2 = 0.9987); A1:y = 2.99 × 10−4 x + 3.80 × 10−3 (r2 = 0.9995). In the equation y = ax + b , x is the concentration of the analyte in the serum, and y is the peak area ratio of the analytes to the IS. The lower limit of quantitation (LLOQ) of RA and A1 is 5 ng/ml, and the coefficients are 8.14% and 7.32%, respectively. The signal-to-noise ratios of RA and A1 (SN) are 97 and 102, respectively.