The Iranian researchers, who published their findings in the journal Talanta, report that the detection limit obtained by this technique, based on corona discharge ion mobility spectrometer (IMS), is comparable to other methods used to detect and determine OTA in crops like licorice root but that it is less expensive and less time-consuming.
“Due to complexity of the current available techniques, only a few laboratories, mainly in Europe and North America, are known to carry out such analysis.
Hence, it usually takes a few weeks for a sample to be sent to the credible lab and analyzed. Considering these facts, the application of IMS in measuring OTA could be regarded as a rather faster, more available method,” note the authors.
OTA is a mycotoxin produced by several fungal species of the genera Penicillium and Aspergillus. Animal studies have linked the toxin to renal tumours at high dosages.
EC regulation imposing 80 ppb max levels for OTA in pure and undiluted liquorice extracts (obtained whereby 1kg of extract is obtained from 3 to 4 kg liquorice root) came into force earlier this year.
The toxin can develop in the liquorice root and, as it is a mould, will grow where there is moisture. The regulation requires producers to dry root more intensively so that moisture evaporates effectively and quickly.
The authors explained that measurements were carried out in the inverse operation mode to enhance the separation power of ion mobility spectrometry: “This novel method was developed in our lab in which, rather than generating an ion packet, a dip was created in the ion beam, hence increased resolution by up to 60 per cent as compared to the conventional linear mode,” they added.
The authors said that they divided a licorice root sample into two halves, one sent to an accredited lab, Gesellschaft für Bioanalytik in Hamburg, Germany (GBA), and one was used for extraction using their IMS procedure.
“The amount of OTA in the real sample was calculated to be 88 ± 6 pg/g equivalent to 8.8 ± 0.6 ng/g licorice root after recovery corrections were affected. This was very close to the value (8.5 ng/g) reported by GBA Lab, Germany, for a similar sample.
To verify the results, a similar procedure was used for a second fresh sample of licorice root and the OTA content was found to be 0.6 ± 0.1 ng/g, which is comparable to 0.5 ng/g reported by GBA Lab,” found the researchers.
They concluded that their novel approach yields an acceptable detection limit, a good accuracy, and an appropriate recovery level: “Low detection limit, fast response, simplicity, portability, and relatively low cost are its main advantages.”
Used by manufacturers in confectionery products - notably Trebor Bassett's (Cadbury's) Liquorice Allsorts brand and by French sweet leader Haribo liquorice is a wild-growing plant native to southern Europe and parts of Asia, and is harvested in the autumn two to three years after planting.
The concentrated and purified extract of the liquorice roots Glycyrrhiza glabra is used in confectionery formulations - as a sweetener, flavouring agent and enhancer, and debittering agent, with the major European markets for liquorice confectionery being Netherlands, Germany, Scandinavia, Spain, France and Italy.
Published online ahead of print: doi: 10.1016/j.talanta.2010.11.004
Title: Determination of ochratoxin A in licorice root using inverse ion mobility spectrometry
Authors: M Khalesi, M. Sheikh-Zeinoddin, M. Tabrizchi