The accuracy of the method was determined by recovery experiments and was performed in triplicate by standard addition method at 80%

The accuracy of the method was determined by recovery experiments and was performed in triplicate by standard addition method at 80%, 100% and 120% of test concentration and analysis precision was expressed as % RSD. A known amount of measuring analyte was added to placebo preparations and was subjected to the proposed UPLC method. Results of recovery studies are shown in Table 3. The mean percentage recovery was 101.7% for Erythromycin estolate and % RSD was found to be less than 1.0%. The slope of Erythromycin estolate was 1.02 from 10% to 150% of Accuracy levels and the confidence level 95% of Accuracy of the method was 0.32.The results are shown in Table 3
Method repeatability (intra-day precision) was evaluated by assaying six injections of sample preparation of the same batch. The mean % assay was 104.78% and was within the acceptance criteria. The% RSD was found to be 0.41%.The results are shown in table 4. The difference in the assay of Erythromycin estolate in Erythromycin 250mg capsules between the preparations is less than 2.0% of %RSD.
Robustness of the method was established by determining the assay of a sample under small but deliberately modified chromatographic conditions specified under the method like flow rate, column temperature, pH of buffer or buffer strength in % v/v, mobile phase composition and wavelength on lower and higher side of the actual values. The drug concentration was analyzed under these changed experimental conditions. There was no significant change in the retention time and assay of the drug when the flow rate and composition of the mobile phase were changed. The results are illustrated in Table 5.