Development and Validation of a Stability Indicating RP-HPLC Method for the Determination of Two Sun Protection Factors (Koptrizon and Tinosorb S) in Topical Pharmaceutical Formulations Using Experimental Designs

Table 3

Method precision, intermediate precision result, LOD, LOQ evaluations, and linearity data for KPT and TIN.

Parameter	Koptrizon	Tinosorb S
Precision Day-1/repeatability (𝑛=6)	101.3 ± 0.39; 0.38; 0.31	100.2 ± 0.51; 0.51; 0.41
(% Assay ± SD; % RSD; 95% C.L.)
Intermediate precision/reproducibility (𝑛=6)	100.2 ± 0.53; 0.53; 0.42	99.9 ± 0.29; 0.29; 0.24
(% Assay ± SD; % RSD; 95% C.L.)
LOD (μg mL^−1)	0.024	0.048
LOQ (μg mL^−1)	0.08	0.16
Linearity range (μg mL^−1)	0.08–225.8	0.16–225.1
Correlation coefficient	0.99999	0.99999
Intercept (a)	2103.15	2032.08
Slope (b)	27767.747	13163.737
Bias at 100% response	0.050	0.102

95% C.L.: 95% confidence interval.