2.1. Instrumentation
A double beam UV–vis spectrophotometer, model UV-2401 PC (Japan) with 10 mm matched quartz cell was used.
The HPLC instrument consisted of thermo separation product quaternary gradient equipped with a pump spectra system P-4000 having an inline membrane degasser, detector was a UV–vis detector belonging to spectra system UV 1000 and Rheodyne 9725 injector with 20 loop. All the data were processed using Data Ace software. Separation was achieved using a Prontosil C18 stationary phase(150 * 4.6 mm i.d. 5lm particle size) and the analytical column was protected by a Phenomenex C18 guard column (4*2.0 mm, i.d.).