Internal Standard
1. The terpene composition of an essential oil can be determined using gas chromatography-mass spectrometry.
A 5.00 ml sample of essential oils is spiked with 500.0 mL of 100.0 ppm n-decane as an internal standard and diluted to the mark in a 10.0 mL volumetric flask. A 10.0 mL portion of the mixture is injected into the GC-MS and the peak areas recorded to determine the concentration of limonene. A series of standards containing n-decane and limonene were also analyzed by the same method. The following results were obtained:
Concentration of Limonene (ppm) peak area limonene peak area n-decane
1.0 ppm 540 5,566
5.0 ppm 2,791 5,570
10.0 ppm 5,570 5,542
15.0 ppm 8,112 5,564
20.0 ppm 10,786 5,558
Essential Oil Unknown 1,055 5,549
Determine the concentration (in ppm) of limonene in the essential oil.