Estimation Of LOD And LOQ Lab Analysis

3.2. Estimation of LOD and LOQ using LMS and IRLS Limit of detection (LOD) according to Miller [51] is equal to YB+3 SB where YB is the value of the calculated intercept and SB is the Sy/x while limit of quantitation LOQ will be equal to YB+10 SB LOD and LOQ for each compound at each case were calculated. The LOD and LOQ after the robust regression line fitting of data were lower than those obtained before the treatment of data in both cases of linearity. As seen in Table 23, the LOD and LOQ were decreased from microgram range; 11.45 and 34.36 µg/mL to become in the nanogram range; 0.70 and 2.10 ng/mL, respectively, upon applying LMS for ∆F method in the ideal case of linearity. The effect is much more pronounced in non-ideal case of linearity. This indicated that the linearity ranges for
The data of fluorimetric method, ∆F and F-ratio, treatment was done using OLS, LMS and IRLS in both cases of linearity. The values of recovery % were in the accepted ranges (98-102%) indicating the good accuracy of the method obtained after treatment of data, such effect is highly significant in the non-ideal case as they came closer to 100%. For example in Table 24, in non-ideal case, for ∆F-method, upon using LMS regression, the values of mean recovery% of concentration levels 20, 40 and 60 µg/mL increased from 91.20 % to 100.23%. In the same time, the RSD% for the different concentration levels used in the study showed a great decrease in their values upon applying both LMS and IRLS robust regression methods. This indicates that the proposed robust, non-parametric methods are superior and totally valid for the estimation of the unknown drug concentrations in the whole linearity range with acceptable accuracy and