a study of the quality of a local herbal tea and volatiles of parinari ...

(1958) as a parameter for identifying solutes from chromatograms (Skoog et al., 1998).
Retention indices calculated from a series of n-alkanes are used to identify the presence
of volatile constituents (Gazim et al., 2008). The retention index (RI) for any given
compound can be derived from a chromatogram of a mixture of that solute with at least
two normal alkanes having retention times that bracket that of the solute (Skoog et al.,
1998). A mass spectrometer (MS) separates rapidly moving ions on the basis of their
mass to charge ratios, m/z (Skoog et al.,1998). Mass spectrometer data and RI are
compared to confirm the identity of a compound (Viljoen et al.,2008). Identifications
made from mass spectral data alone could be inconclusive as those made from retention
index libraries. In an extensive retention index library several components can have
identical retention index values, therefore mass spectral data is needed to confirm
tentative identification by retention indices (Steward and Pitzer, 1988). To illustrate this
for the compound ethyl butyrate, using retention indices calculated from a series of C6-
C24 alkanes the retention index is 1051. This is considered to be tentative identification
and if after mass spectrometry the compound is also identified to be ethyl butyrate then
confirmation has been obtained from these two identification methods.
In conclusion, the choice of method of extraction will determine the type of volatile
constituents to be obtained from the food material studied. Each method has its own
strengths and limitations, a combination of these methods in extraction will provide a
better understanding of the type of volatiles in the food material.
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