Rapid Characterization of Spices and Herbs by Direct Heating
Sample Introduction Using a Curie-Point Pyrolyzer
K. Nashimoto, T. Inoue. K. Nagaoka, Y. Sumida, and S. TeradaKyoto College of Pharmacy, Yamashina Kyoto. Japan
C. Watanabe
Dow Chemical Japan Ltd., Gotenba Shizuoka Japan
Key Words:
1 Introduction
Analysis of the components of spices and herbs is very important
for research into their composition and for quality evaluation. andalso for their identification. A promising method for this purpose iscapillary gas chromatography. However, gas chromatographic
analysis of the volatile components of spices and herbs usuallyrequires appropriate sample preparation procedures. such as
solvent extraction, steam distillation. efc. These procedures are
tedious and difficult with small amounts of sample. On the otherhand. pyrolysis GC is one of the most useful auxiliary techniques inpolymer characterization [1 -3], and has been used for examination of complicated biological materials [4-6]. It is well known thatthese techniques can be applied directly to solid materials and wehave already discussed their application to crude drugs [7]. The
pyrolysis temperature has a great effect on the product distribution. At relatively low temperature. thermal desorption can beachieved in the pyrolyzer. but no pyrolysis occurs. The chromatograms may then be fairly similar to patterns obtained from solvent
extracts or steam distilled fractions by conventional injection. A
similar technique has been used for the thermal desorption ofvolatile compounds from insects [8-9]. At higher. temperature.
the evaporated volatile components together with the pyrolysis
products of volatile and non-volatile components give a characteristic pattern as an analytical fingerprint for a given a characteristic pattern as an analytical fingerprint for a given spice or herb.
A suitable pyrolyzer for this purpose is of the high frequency
induction heating type (Curie-point pyrolyzer), because of a highly
repeatable pyrolysis temperature ad rapid temperature risetime. This paper describes the analysis of spices and herbs bydirect heating using a Curie-point pyrolyser and comparision of
the conventional method.
2Experimental

A laboratory-made Curie -point pyrolyzer was directly coupledwith a Hewlett Packard 9880A gas chromatograph (or Shimadzu
GC-7A) equipped with a name ionization detector(FlD). Two FSCC
were used which were coated with immobilized methylpolysiloxane (0.25 mm x 25 m) and PEG-20M (0.25 mm X 25m). Nitrogen carrier gas flow rate (40 ml/min) at the pyrolyzer was reduced

to 0.8 ml/mn at the capillary column through a splitter. The otheranalytical conditions were described in the figure captions. A
given ground (or chopped) spice or herb was placed h rolled ferrymagnetic foils. and direct heating was performed in various ferromagnetic foils. each having a different Curie-point temperature byhigh frequency induction. These ferromagnetic foils with Curie
point of 349℃ 358℃. 385℃. 423℃. 500℃. 650℃, 747℃, and
920℃ were purchased from Japan Analytical Industry Co Ltd.
(Tokyo Japan ). The vaporized gases from the pyrolyzer wereintroduced into the injector at 270℃ through a heated 5 cm length
0.5 mm i.d. glass-lined stainless tube. The samples of spices andherbs (commercial origin in Japan) were ground (or cut) and1-10 mg aliquots were analyzed respectively.

3 Results and Discussion
Direct heating of the spices is achieveed on ferromagnetic foils in
the pyrolyzer. Typical chromatograms of sage obtained by direct
heating at 358℃ and 650℃ for 3 s are illustrated in Figures 1 and 2.
The reproducibility of the retention times obtained by this method
is very good. also at other temperatures [7]. The reproducibility ofquantitation by this method was evaluated by measurements ofabsolute peak area of anethol in fennel. star anise. and aniseed(see Table 1 and Figure 5). and was found to be highly reliable.
At relatively low temperature (349℃. 358℃. and 385℃). thechromatograms resemble the GC pattern obtained for the solvent
extracts introduced by conventional injection, although someslight pyrolysis seems to occur. The chromatograms of cloves
obtained by both methods are illustrated in Figures 3 and 4. After
heating at 349℃ for 3 s in the pyrolyzer. the residual simple isanalyzed again and again. The area of the major peak(eugenol) of
the second run chromatogram is just one fifteenth of that of thefirst run. and in the third run it is negligible. For vaporization of all
the volatile components. Such as the essential oil. a temperatureof 349℃ proves to be adequate with a heating time of 7s,while at385℃ heating for 3 s is sufficient. It thus becomes possible
evaluate the volatile components in a small sample of a spicewithout tedious sample preparation procedures. This is especiallyvalid with aromatic spices and herbs which contain much essentialoil.

When used at relatively low temperature this method is applicable
to determination of anethol in fennel, star anise. and aniseed.
Quantitative determination of anethol in various spices is perfomed by the method of standard addition (addition of a weighedamount of anethol) to avoid discrimination at the sample inlet
system. A plot of the peak area of anethol vs. sample weight gives
a straight line. also after addition of anethol (0.01012 mg) to thesamples containing anethol. The calibration curves for fennel are
shown in Figure 5. The anethol contents (%) of various spices
determined by this method are summarized in Table 1. The resultscompare favorably with those obtained by the conventional
method..
The chromatograms obtained at higher temperature (650. 757.
and 920℃ for 3 s) show numerous peaks differing from those of
the solvent extracts. The evaporated volatile components
together with the pyrolysis products of the volatile and nonvolatile components give a characteristic pattern. or analyticalfingerprint. for a given spice or herb. However. the identification ofeach peak becomes increasingly difficult.
Consequently. this simple. rapid method using small sample sizeand giving good reproducibilities. is applicable to the evaluationand identification of spices and herbs.