Optimization of GC-MS conditions based on resolution and stability of analytes for simultaneous determination of nine sesquiterpenoids in three species of Curcuma rhizomes.

GC-MS is a powerful tool for analysis of volatile oil, and resolutions of analytes were exclusively used as marker for optimization of the conditions. However, volatile oil usually contains heat labile components which may degrade and result in wrong results during GC analysis. In present study, based on both resolutions and stabilities of 11 sesquiterpenoids, GC-MS conditions were optimized for simultaneously quantitative determination of nine compounds including beta-elemene, curzerene, curcumol, isocurcumenol, germacrone, curdione, curcumenol, neocurdione and curcumenone in Ezhu. However, the other two compounds, i.e. furanodienone and furanodiene, were still thermal sensitive and not available for GC analysis. The results showed that both resolutions and stabilities of analytes should be considered for optimization of GC conditions because the properties of most components in volatile oil are unknown. Under optimum conditions, a capillary column (30 m x 0.25 mm i.d.) coated with 0.25 microm film 5% phenyl methyl siloxane was used for separation. Pulsed splitless inlet with temperature of 190 degrees C was selected for sample injection (0.2 microl). The calibration curves of nine sesquiterpenoids showed good linearity (r2>0.9989) within test ranges. The optimized method showed good repeatability for quantification of these nine components in Ezhu with intra- and inter-day variations of less than 1.42% and 2.79%, respectively. The validated method was successfully applied to quantify 9 sesquiterpenoids in 18 samples of 3 species of Curcuma used as Ezhu.