2.8. Statistical analysis
Results were given as mean ± standard deviation of three inde- pendent determinations. Significant differences between results were calculated by one-way analysis of variance (ANOVA). Differ- ences were considered to be significant at P < 0.05 (95% confidence level). All statistical analyses were performed with Statgraphics Plus 5.1 (Statistical Graphics Corporation, Inc., Rockville, MD, USA).