The Fate of Chlorpropham With Particular Reference to Its Use as a Potato Sprout Suppressant

[摘要] This thesis examines the fate of chlorpropham when applied to stored potatoes to suppress sprouting. Throughout this project the work concentrated on the use of chlorpropham in potato processors' stores and in particular crisp manufacturers' stores since these are operated in a consistent manner and the largest proportion of the sprout suppressant formulation of chlorpropham is used in these stores. The fate of chlorpropham was investigated in two distinct areas. The portion of the applied chlorpropham that ends up in the crisps as a residue is the first area, while investigation of the possible biotransformation products of chlorpropham produced by three potato pathogens is the second. A sensitive analytical method for the determination of chlorpropham residues in crisps was developed using acetonitrile as extracting solvent followed by an oil reducing step which was essentially a counter-current separation of chlorpropham and co-extracted oil with final quantification by gas chromatography (GC) or high performance liquid chromatography (HPLC). Recovery from crisp samples spiked with chlorpropham was 93.2%+/-6.37 and the minimum detectable amount was 0.035 mug/g when the GC was used. When the HPLC was the instrument used to quantify the residues then a minimum of 0.02 mug/g could be detected and quantified. A chlorpropham residue of 0.45 mug/g was detected in crisps produced from slices originally containing a 0.18 mug/g residue. Chlorpropham contamination of untreated material resulted after frying in friers which had been previously processing chlorpropham treated material. The existing literature concerning the transformation of chlorpropham is reviewed in Chapter 2, with particular reference to potatoes and potato storage situations although little information was available on the fate of chlorpropham that is applied to this staple food. Radiolabelled chlorpropham that had been synthesised by Isabel Boyd in this department was purified using an alumina clean-up column and made ready for use in the biotransformation studies. Erwinia carotovora var. atroseptica (bacterial soft rot), Polyscytalum pustulans (skin spot) and Phoma exigua var. foveata (gangrene) were grown on standard growth media apart from the fact that labelled chlorpropham had been incorporated into the media. The E. carotovora var. atroseptica, a facultative anaerobe, was cultured under both aerobic and anaerobic conditions. Complete recovery of the medium incorporated radiolabel as unaltered chlorpropham was observed. In the P. pustulans study complete recovery of the radiolabel was not achieved. Unaltered chlorpropham contained all of the label that was extracted, but since only incomplete recovery of the applied radiolabel was achieved then it is invalid to state that no metabolites were produced. In the metabolism study of the P. exigua var. foveata, more complete recoveries of the radiolabel from the cultures were accomplished and a water soluble metabolite was detected. Characterisation of this metabolite was not possible but some solvent partitioning characteristics were identified as were its chromatographic behaviour on HPLC.

[发布机构] University:University of Glasgow

[关键词] Plant sciences, Organic chemistry