Monoterpene hydrocarbons from values

Figure 3. Modified Ir values of the monoterpene hydrocarbons from citrus...

The modified Ir data for monoterpene hydrocarbons from the three species of citrus oils were subjected to a multivariate analysis. According to principal component (PC) analysis, the citrus essential oils examined were clearly discriminated, with 93.3% of the accumulation contribution ratio of both PCI and PC2 (Fig. 4A). As shown in Fig. 4B, p-pinene (PCI, 0.530 PC2, -0.80), a-terpinene (0.685 0.062) and P-phellandrene (0.324 0.810) were large for the absolute value of the eigenvector of monoterpene system hydrocarbons, followed by terpinolene (0.367 -0.010). These compounds greatly contributed to the modified Ir discrimination of the citrus essential oils. 

The RI values of sesquiterpenes studied in our laboratory range from 1330 to 1533 (203 iu) on OV-101 and from 1464 to 1766 (302 iu) on PEG 20M (see Table 1). From these data it is evident that the polar PEG 20M is more selective for the separation of sesquiterpenes, but some sesquiterpene hydrocarbons do not separate on PEG 20M either (for example y- and 5-cadinenes). The ARI values of sesquiterpenes are somewhat higher (112 to 260 iu) than for monoterpenes and, like ARI values of monoterpenes, the values depend mainly on the number of double bonds in the molecule (see Table 2). 

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