Question

Is a calibration curve of limonene peaks or comparison to an internal standard such as anisole a better method for quantifying limonene content of a sample? Why?

The data output for your GC trace only displays time from 3-8 minutes. What is happening in the first 3 minutes?

Answer 1

The monoterpene d-limonene, (4R)-(+)-limonene , is the major component of all citrus essential oils.

The GC columns is inexpensive and present minimal safety concerns. The experiment must demonstrate proper GC quantitation using the internal standardization method.

For a “real” mixture, this requires finding a compound that (i) is not present in the sample, (ii) does not react with the sample,and (iii) does not co-elute with a component in the sample.

The components of citrus oils include a wide variety of hydrocarbons, aldehydes, alcohols, esters, ketones, and some miscellaneous compounds. However, there are very few ethers, and in particular, anisole has not been detected.This compound was chosen as the internal standard for the experiment because it can be separated from both d-limonene and n-hexane on stationary phase. Although some co-elution undoubtedly occurs, the minor components are buried in the baseline with the integrator setting that keeps the limonene and anisole on scale. Anisole also has the advantage of limited toxicity .

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The data output for your GC trace only displays time from 3-8 minutes. What is happening in the first 3 minutes?

Ans. This represents dead time; dead time in chromatography usually signifies the unretained peak time in GC, or the time for one column's worth of mobile phase.