Towards the rapid analysis of total glucosinolate in oilseed and vegetable crops
AbstractThis work describes approaches to the development of an analytical method for the determination of glucosinolates -important plant metabolites that affect the commercial value of both vegetable and oilseed crops. One approach was to modify an established myrosinase/glucose oxidase bi-enzyme biosenscr so as reduce the previously reported by-product interference of the sensor signal. Covalent immobilisation of glucose oxidase on nylon nets replaced direct immobilisation on the electrode surface, and oxygen consumption replaced hydrogen peroxide formation as the measurand. Myrosinase was dissolved in the background solution. The sensor responded rapidly (< 10 min) to the presence of isolated glucosinolates in solution although the magnitude of response varied between classes of glucosinolates. By-product interference was greatly reduced even following continuous exposure.. However, there was insufficient time to explore the full potential of this biosensor approach to the rapid determination of glucosinolates. Another approach exploited the general observation that under certain conditions glucosinolates can reduce ferricyanide. Whilst no reaction was observed between glucosinolates and ferricyanide neutral pH, the incubation with glucosinolates in alkaline solutions resulted in reduction of ferricyanide to ferrocyanide. Both electrochemical and spectrophotometric techniques could be used to monitor the reaction progress. The reaction mechanism of the process was elucidated and lthioglucose, an alkaline degradation product of glucosinolates, identified as the species that reacted with ferricyanide. A method was further developed so as to enable the analysis of glucosinolates in rapeseed extracts. Given sample pre-treatment to reduce interference from phenolics, the spectrophotometric technique was shown to allow determinations of total glucosinolates in rape seeds that were in close agreement with independent analyses using official ISO methods. The procedure recommended in this work could be further improved by developing more effective methods of eliminating interference from residual phenolics. Nevertheless, the procedure already has some advantages both over ISO methods and over other existing methods for total glucosinolate determination. Furthermore, given recent advances in thick-film fabrication of miniature fluidic devices, it could be possible to adapt the procedure so that it could be carried out using a simple convenient single-use sensor format.
CitationJezek, J. (1999) 'Towards the rapid analysis of total glucosinolate in oilseed and vegetable crops'. PhD thesis. University of Bedfordshire.
PublisherUniversity of Bedfordshire
TypeThesis or dissertation
DescriptionA thesis submitted to the University of Luton, Faculty of Creative Arts Technology & Science for the degree of Doctor of Philosophy, August 1999
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