|
Flavorings |
|
|
Limonene Limonene is an oily compound often found in citrus fruit, such as lemons and oranges but also naturally occurs in caraway, dill and bergamot. It is used in a variety of manufacturing processes as a resin, a solvent or as a wetting and dispersing agent. Limonene naturally occurs in both d and l forms.
Triplicate samples of 8.3 mg of each limonene enantiomer were injected into a flow injection analysis (FIA) system using laser-based polarimetry detection. The two chromatograms above show the detector’s response for the d -(+) limonene enantiomer in the top graph and the l -(-) limonene in the bottom graph. The baseline offset, indicated as (a), is the signal from an internal rotational standard corresponding to +29 microdegrees. The sensitivity of the laser-based polarimetric detection system is evident in these results. Detection limits of 10 - 100 ng are possible for most optically active compounds. Further, the selectivity of polarimetric detection is evident in the sign of the response obtained for the two enantiomers. Although the magnitude of the response is similar for both, the sign of the rotation differs for the two species. This large difference in signal obtained with polarimetric detection is a result of a subtle change in the arrangement of atoms about a single chiral center. The analysis of these enantiomers would be very difficult by other methods since they do not contain a chromophore with high molar absorptivity, and their physical properties (boiling point, vapor pressure, solubility, etc.) are identical.
|
