Chemistry Reference
In-Depth Information
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Figure 9.7
Concentration of caffeine extract as a function of the extraction time.
Caffeine concentration determined at different solid/liquid extraction
time periods. Separation conditions as those given in Figure 9.2. The
analyzed dietary product: tea product G.
using a standard curve consisting of at least five points. The concentration of
the reference standards was selected on the basis of the extract concentration.
The caffeine content of thirteen different dietary products, including nine tea
and two coffee products, was determined. The results showed that the
concentration of caffeine increased continuously with time during the solid/
liquid extraction to reach its maximum concentration after about 20 minutes.
It indicates that all the caffeine content may be extracted during this time
period.
Summary Points
N
This chapter describes the quantitative analysis of caffeine in dietary
products, such as tea, coffee and chocolate, by multiple-injection capillary
electrophoresis.
N
Multiple-injection capillary electrophoresis improves the precision of the
assays since the samples to be determined are analyzed under the same
conditions.
N
With the method developed it was possible to analyse up to five samples
within a single electrophoretic run.
N
A calibration curve was constructed by analysing simultaneously five
standard solutions of caffeine at different concentrations within a single
run. Acetaminophen as an injection marker was added to the standard and
to the analyte samples to compensate for injection volume fluctuations.
N
Caffeine was extracted from ground coffee, chocolate, as well as tea leaves
with hot water through solid/liquid extraction.
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