Fig. 2. Chromatogram of pharmaceutical/cosmetic formulations (o/w emulsion and aqueous gel) analyte-free at 254 nm. Mobile phase was 0.2% metaphosphoric acid/methanol/acetonitrile (90:8:2, v/v/v).
5. Limits of detection (LOD) and quantification (LOQ)
The LOD is defined as the lowest active substance concentration which can be determined by the method, however not calculated precise and accurately. LOQ is the concentration of the sample in analysis that is obtained with adequate precision and accuracy . An estimation of the limits can be achieved by the determination of the signal/noise ratios of 3:1 (LOD) and 10:1 (LOQ). For this HPLC stabilityindicating method, the LOD and LOQ values were found to ≈0.05 and ≈0.17_gmL−1, respectively. Table 2 summarized the experimental data for the HPLC stability-indicating method parameters.