The procedure for measuring the solubility of artemisinin included suspension of excess amount of artemisinin in 1 ml of n-hexane-ethyl acetate mixture and maintaining the suspension under stirring at constant temperature for 6 h until the equilibrium was reached. Equilibration time of 6 h was confirmed from previously measured dissolution kinetics of artemisinin in n-hexane-ethyl acetate mixtures. Dissolution kinetics experiment consisted of suspension of excess amount of artemisinin in 5 ml of n-hexane-ethyl acetate mixture (75:25, v/v) at 25 °C under constant agitation for 24 h (Beauchamp, 2001). Concentration of artemisinin in solution determined after every hour confirmed that Z-DQMD-FMK the
equilibrium was reached in 6 h. After equilibration, saturated solution was separated from undissolved artemisinin by syringe filters (precooled to 15 and 5 °C in case of measurements at those temperatures, respectively). The liquid
phase was analyzed with high performance liquid chromatography (HPLC) using UV detection at 220 nm, as previously described (Malwade et al., 2013a), to determine the artemisinin concentration in End-product inhibition
phase. Alternatively, the concentration of artemisinin in the liquid phase can also be determined by using simple gravimetric method in case of unavailability of HPLC. All solubility measurements were repeated thrice. The solubility of artemisinin measured in n-hexane-ethyl acetate solvent mixtures of varying composition at 25, 15 and 5 °C is shown in Fig. 4. It is clear from the standard deviation shown in Fig. 4 that the solubility data is fairly reproducible, clearly demonstrating the reliability of the proposed apparatus for solubility measurements.