250 ��g. Precision Validation of the method for precision was measured by using standard solutions containing lumefantrine at concentrations covering the entire calibration range. Further the method was validated for instrumental precision, intraday precision, and interday precision. Instrumental precision was studied by repeated analysis (n = 10), of lumefantrine standard solution (6.250 ��g/ml) on the same day. The RSD for instrumental precision was 0.10 %. The precision of the method in terms of intraday variation (%CV) was determined by analyzing lumefantrine standard solutions in the range (1.250-12.500 ��g/ml) three times on the same day. Interday precision (%CV) was assessed by analyzing these solutions (1.250-12.500 ��g/ml) on three different days over a period of one week. The results of the precision studies are shown in Table 2. Table 2 Summary of precision and accuracy Accuracy The accuracy of the method was established by use of standard addition method i.e., measurement of recovery at three different concentration levels. 80%, 100%, and 120% of the standard drug solutions were added to the solution of known concentration and the percentage recovery was then determined. The results are summarized in Table 2. Specificity The optimized mobile phase gave a very good resolution of lumefantrine, indicating the specificity of the method. A typical absorbance spectrum of the drug is shown in [Figure 2]. The optimized solvent system yielded a symmetrical peak for the drug with RF 0.59 [Figure 3]. To achieve the best detection sensitivity, wavelength 266 nm was selected for detection. Figure 2 Absorption spectrum of lumefantrine scanned at 190-400 nm Figure 3 Representative chromatogram of standard lumefantrine at 266 nm Ruggedness and robustness Ruggedness is a measure of the reproducibility of a test result under normal, expected operating conditions from instrument to instrument and from analyst to analyst. Robustness is a measure of the capacity of a method to remain unaffected by small but deliberate variations in the method conditions. The %RSD was recorded less than 2%, thus indicating reliability of the method. Reproducibility The repeatability of sample application was assessed by spotting drug solution (10 ��l) seven times on an HPTLC plate then development of plate and recording the peak height and area for the spots. The %RSD for peak height and peak area values of lumefantrine were found to be 0.49% and 0.98%, respectively. Repeatability of measurement of peak height and area were determined by spotting 10-��l standard drug solution on the HPTLC plate and developing the plate. The separated spot was scanned seven times without changing the position of the plate. %RSD for measurement of peak height and peak area of lumefantrine was 0.53 and 1.05, respectively. Stability studies To test the stability of drugs on the HPTLC plates, analyte was tested against freshly prepared solutions.