Precision
For a reproducibility study, a series of three
measurements on three consecutive days was performed,
and the precision of the area results calculated as relative
standard deviation (RSD %). The peak area precision for
thymol,
α
-methyl-trans-cinnamadehyde, capsaicin, and
piperidine was determined for the low level calibration
points up to 200 ppb. Thymol shows values in all cases
of 3% RSD and below. This compound is less affected
by potential active sites in the GC system. The active
compounds
α
-methyl-trans-cinnamaldehyde, capsaicin,
and piperidine also show excellent precision data ranging
from 0.5% to 8% RSD over the length of the study. This
excellent area precision of the other active analytes at low
concentration levels is achieved by the use of an analyte
protectant in the applied extracts.
A spiked real life spice sample has been measured
on three consecutive days, as well, to calculate the
precision of the measurements. The peak area data in
Table 3 indicate a low level spike below 10 ppb. The
reproducibility over three days for all compounds tested
is in the range of 1-3%.
5
Figure 9. Quantitative calibrations on low concentration side 10-200 ppb.
Conclusions
The described method using the TSQ 8000 GC-MS/MS
system provides a very sensitive and precise assay for
the trace analysis of receptor-sensitizing and active
compounds like capsaicin, piperine, and thymol. Excellent
symmetrical and stable peak shape can be achieved for
these polar spice components by using sorbitol as analyte
protectant.
Analyte protectants can reduce the phenomenon of
poor chromatographic peak shapes and keep the
chromatographic integrity over long sample series with
symmetrical peaks and very stable results with excellent
precision. Automatic peak integration is facilitated, peak
areas are increased, and the reproducibility improved
significantly.
All the investigated compounds, in particular capsaicin,
piperine, and thymol, can be detected with high signal-
to-noise ratio even at the low 10 ppb level. A matrix
sample with measured concentrations well below 10 ppb
demonstrated the excellent reproducibility of the TRACE
1310 GC system. The precision in all measured levels
including the low 10 ppb concentration was below 10%
RSD.
Table 3. Precision of a spiked spice sample analysis
Compound Name
Day 1
[area cts]
Day 2
[area cts]
Day 3
[area cts]
RSD%
Thymol
96.513
94.128
91.462
2.70%
alpha-Methyl-trans-cinnamadehyde
97.665
93.579
92.918
2.70%
Capsaicin
100.669
105.363
99.392
3.10%
Dihydrocapsacin
102.752
103.852
101.089
1.40%
Piperine
104.307
106.685
103.274
1.70%
