Solutions and calibrations
Standard stock solutions of CPL and PA (each, 1 mg/mL) were prepared separately by dissolving the compounds in ethanol then completing in 100-mL volumetric flasks. Ten mLs of each of the prepared stock solutions were further diluted with ethanol to LGX818 final volume of 100-mL. The diluted solutions were used as the working solutions for CPL and PA (each, 100 μg/mL). Standard solutions containing 5–60 μg/mL of CPL and 5–50 μg/mL of PA were prepared separately in ethanol. The absorption spectra of the prepared solutions were scanned in the range 200–400 nm and saved in the computer.
Dual wavelength method (DW)
Calibration graphs were constructed between the difference in absorbance at 231–255 nm 222–260 nm against the corresponding concentrations 10–50 μg/mL CPL and 10–40 μg/mL PA, respectively. The regression equations for both drugs were formulated.
Advanced absorbance subtraction (AAS)