Page 6 - PERIODIC Magazine Issue 6

Electrochemical Sensors -

Hot off the press

The success of Professor Richard Compton and his group in using electrochemical
sensing to detect the spiciness of chillies has led to the recent new development
of sensors for garlic, turmeric and ginger. Having built up a successful commercial
partnership with Zimmer & Peacock (Z&P), they now have ambitious plans to use this
technology to solve further analytical challenges.

This science underpinning the ChilliPot was originally born
out of the group’s research into both carbon nanotubes and
disposable screen printed electrodes (the latter are used to
detect blood-glucose levels in diabetics) - they sought to find
a molecule that could adsorb onto carbon nanotubes readily
and capsaicin was one that fitted the bill. The large surface
area of the carbon nanotubes means that the detection is
sensitive and so faster, giving rise to the short detection
time of the ChilliPot sensor. Upon adsorption, capsaicin is
electrochemically oxidised to a species containing ortho-
quinone functionality through two irreversible steps. This
species then falls into a redox electrochemical loop with a
catechol (1,2-dihydroxybenzene) species. It is the redox
reaction between these two species which is detected at the
For years there was no accurate and convenient procedure carbon nanotube electrode, giving rise to a novel capsaicin
to measure the spiciness of chilli peppers, the only method detection method.
requiring the use of a panel of five ‘expert’ tasters. The
Scoville organoleptic test involved dissolving an exact
weight of dried pepper in alcohol to extract capsaicin, the
molecule responsible for the spice in chillies. Decreasing
concentrations of extracted capsaicin were then given to
the panel until a majority (at least three of the five) could no
longer detect the heat. This test has two main problems: it
is highly subjective to one’s perception of taste and it is also
extremely inconvenient to assemble a panel of chilli experts
every time a chilli’s heat needs to be tested.

Professor Compton’s group has recently developed a
method of measuring the spiciness of chilli products without
eating them. This resulted in the ChilliPot, a device produced A chance encounter between Professor Compton and Martin
in collaboration with Z&P, an electrochemical sensor Peacock, of Z&P, led to the collaboration and production
manufacturing company. Readings are given in less than a of the ChilliPot, as it is known today: “There was a rapid
minute, marking a distinct improvement in the amount of realisation of a strong synergy between myself and Martin,
time for a panel of tasters to assess the chilli spice. leading to a project of significant commercial and scientific
merit,” Professor Compton reflected. “We chose to license
Although high-performance liquid chromatography (HPLC) the ChilliPot sensors last year”, Martin continued. “I went
quantifies capsaicin concentrations, ChilliPot devices are to a chilli festival and took the device to the real people
handheld and present a much more accessible, efficient, that would be using it. As scientists we can be quite scared
cheaper and faster solution to the problem. about taking science out of the lab and showing it to people,

6
Periodic The Magazine of the Department of Chemistry