Caffeinated caffeine: Spotting the synthetic

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  • Published: Mar 15, 2012
  • Author: David Bradley
  • Channels: Chemometrics & Informatics
thumbnail image: Caffeinated caffeine: Spotting the synthetic

Synthetic versus artificial

Spectroscopic information from samples of caffeine-containing drinks has provided researchers in Germany with the necessary data to determine whether a new test beverage contains natural or synthetic caffeine. The technique could let regulators check how well manufacturers of added-caffeine products are adhering to the rules regarding labelling products as "natural" with respect to the drink's caffeine content.

Caffeine is a xanthine alkaloid found in the seeds, leaves and fruit of various plants; its natural role is as a pesticide defence against insects that would otherwise feed on the plant or its seeds. Many people consume infusions of these plants for the stimulating effects of caffeine. Most commonly in the west, the seeds of the coffee plant and the leaves of the tea plant are used as a source of caffeine However, products derived from the kola nut, yerba maté, guarana berries, guayusa, and yaupon holly are also sources of the stimulant.

Caffeine is, according to some sources, the world's most widely consumed psychoactive drug although it is not regulated in the same way as other psychoactive substances. Indeed, regulation of caffeine does not generally refer to its psychoactive properties but is there to ensure that products labelled as containing natural or organic caffeine are not adulterated with synthetic caffeine. Of course, strictly speaking there is no difference between a caffeine molecule derived from a natural source or synthesised in a chemical plant. Caffeine is organic whether it's natural or synthetic. But, that will not stop marketers labelling their products as "all-natural" or even more ironically when it comes to caffeine, "organic".

Nevertheless, in work funded by the German Federal Ministry of Economics and Technology and the German Research Foundation, Maik Jochmann and colleagues Lijun Zhang, Dorothea Kujawinski, Eugen Federherr, Torsten Schmidt in the department of Instrumental Analytical Chemistry, at the University of Duisburg-Essen, in Essen, have successfully tested an isotopic analysis technique that is a simpler and faster method for distinguishing between naturally sourced and synthetic caffeine.

Caffeine's isotopic fingerprints

The team built a model using stable-isotope analysis to provide a fingerprint for differentiating between synthetic and naturally sourced caffeine. The test exploits the subtle difference in carbon isotope profile present in an organic compound derived from contemporary plant sources and ones derived from much older sources in the form of petroleum-derived building blocks. The test itself takes just 15 minutes to carry out.

"On the basis of the carbon isotope analysis of 42 natural caffeine samples including coffee beans, tea leaves, guaraná powder, and maté leaves, and 20 synthetic caffeine samples from different sources by high-temperature reversed-phase liquid chromatography coupled to isotope ratio mass spectrometry, it is concluded that there are two distinguishable groups of caffeine delta 13C-values: one between -25 and -32 per-mille for natural caffeine, and the other between -33 and -38 per-mille for synthetic caffeine," the team explains.

The same approach might be used in a forensic sense to reveal adulteration of products based on ingredients from specific regions where the claimed substances have been substituted. Details of the study appear in the journal Analytical Chemistry. "This work is the first application of HT-RPLC/IRMS to real-world food samples, which showed several advantages: simple sample preparation (only dilution), high throughput, long-term column stability, and high precision of delta 13C-value," the team says. The technique could become a useful tool for stable isotope analysis of non-volatile compounds, the researchers add.

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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