Lab-on-a-chip rises to cola challenge


Can you tell the difference between them? © Jeffrey Blackler/Alamy

The great taste of fluorescence has allowed researchers in Finland to develop a microfluidics device that can analyse complex unknowns in a liquid using microfluidics. The electronic tongue is able to tell the difference between colas, as well as vodkas, red wines and mineral water.

This latest electronic tongue can rise to the challenge of the cola taste test. It quickly spotted the difference between the two main rival brands, but what remains to be seen is whether or not it can taste the secret ingredients purported to be in those products.

Pekka Hänninen, at the University of Turku, and colleagues developed a technique they refer to as liquid fingerprinting. They created a lab-on-a-chip based on an array with various surface modulators, such as detergents, polymers, metal salts and proteins. These modulators interact to different degrees with components of the liquid and then alter the long-lived luminescence of a non-specific europium label in the system. The device thus responds to non-specific interactions with components in the liquid sample but produces a characteristic fingerprint of fluorescence, depending on which chemicals are present in the liquid.

liquid fingerprinting

Liquid fingerprinting can tell the difference between colas by measuring how they alter the luminescence of a europium label © ACS

The researchers suggest that their system differs from other electronic noses or tongues as it has high sensitivity because of the properties of the europium label. Moreover, all the components of a given sample together produce a unique fingerprint so that identification of specific ions or molecules is not required to differentiate between two cola or vodka brands, for instance, or bottled water from different sources.

Their fingerprinting protocol is simple as the sample is diluted and the europium label added in solution and dispensed by microfluidics to the array of wells. A few minutes of incubation is enough to produce a result, which is then read by a low-cost fluorescence plate reader. The team say that their liquid fingerprinting approach could be used for quality control on food and drink production lines and checking for adulteration and counterfeit products.

‘This is an interesting study and I certainly think that the advance has merit since it is a universally applicable technique and could allow not only a compositional analysis but also lead to fingerprinting of different liquids which could be invaluable for tracing the history of a given batch of liquids,’ says Lee Cronin of the University of Glasgow, UK. ‘It will be interesting to see how this technique takes off and how it compares with other techniques that are used as competitors in the liquid fingerprinting field.’


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