Analysis of Caffeine by Liquid Chromatography-Mass Spectrometry - Caffeine: Chemistry, Analysis, Function and Effects - page 121

histamine like chlorpheniramine. Other pharmacological agents are also
commonly found in these medications, such as a decongestant like
pseudoephedrine, an antitussive like cloperastine and an antiviral like
amantadine. Caffeine is also commonly included as a mild stimulant and
vasodilator to counteract the sedative effects of the antihistamine and any
systemic vasoconstriction due to the decongestant.
Feng et al (2009) developed and validated a rapid, simple and sensitive LC-
MS-MS high performance liquid chromatography with positive ion electro-
spray ionization tandem mass spectrometry to simultaneously determine
paracetamol, amantadine hydrochloride, chlorpheniramine maleate and
caffeine in human plasma. Sample preparation entailed methanol-induced
protein precipitation and adding of tramadol hydrochloride as internal
standard. Analytes were separated using a mobile phase comprised of
methanol and water (80 : 20, v/v), containing 0.5% formic acid and on a
C18 column. A triple quadrupole MS fitted with an ESI source was employed
in the MRM mode. Quantification of caffeine was done by investigating the
m/z 195.1 A 138.3 transition.
In the following year, Li et al (2010) developed and validated a rapid and
sensitive method based on LC-MS-MS for the simultaneous quantification of
paracetamol, pseudoephedrine, chlorpheniramine, cloperastine and caffeine in
human plasma. Sample preparation involved liquid/liquid extraction and
addition of diphenhydramine as an internal standard. Chromatographic
separation was achieved in a run time of only 2.6 min, on a C18 column, using
a mixture of formic acid : 10 mM ammonium acetate : methanol (1 : 40 : 60, v/
v/v) for elution. Detection was carried out by a triple quadrupole MS fitted
with an ESI source operating in the positive mode using MRM mode for
quantification. The same m/z transition (195.1 A 138.3) used by Feng et al
(2009) was employed in this method.

d n 0 t 2 n g | 3

7.3 Concluding Remarks
The analysis of caffeine is usually fairly simple, although the complexity may
increase depending on the investigated matrix. In major food sources, such as
coffee and tea, caffeine analysis may be routinely and reliably performed by
colorimetric methods or HPLC with UV detection. In biological fluids, major
caffeine metabolites, such as paraxanthine and 1-methyl-uric acid, may also be
analyzed using HPLC-UV. LC-MS methods are preferred especially for
determining caffeine and metabolites at low levels and-or in very complex
matrices.

Summary Points

N

This chapter focuses on the different existing methods for analysis of
caffeine and other methylxanthines in food, water and biological matrixes.