A Rapid Method for the Analysis of Diquat and Paraquat in Potatoes

Publisher Website
Google Scholar
Abstract
A rapid method was developed for the analysis of paraquat dication (I) and diquat dication (II) as their diene reduction products (ID and IID, respectively), in potatoes. Macerated potato tissue was spiked with various levels of the dications, 0.05, 0.5 and 5.0 ppm. The dications were reduced using a sodium borohydride/ethanol reduction procedure with reduction and simultaneous extraction in a single 50 ml glass-stoppered centrifuge tube. The diene reduction products were extracted into hexane and analyzed by GLC and a N/P-thermionic detector. Quantification by external standard method or internal standard method resulted in recoveries of 35, 38, 48 and 39, 42, 64% for diquat and paraquat, respectively. When a spiked macerate was well-mixed, recoveries were low due to adsorption; precision was within .+-. 5.4% (S-D). The importance of spiking technique was also illustrated. Upon thorough mixing equilibration of diquat spiked potatoes, recoveries were reduced dramatically. Adsorption of the dications and diene reduction products to glassware reduced recoveries and accounted for poorer precision; this latter effect was overcome by prior silanization of the glassware. Modification of existing NaBH4 methods resulted in a procedure for I and II analysis requiring only 30 min/sample for complete analysis. Use of NaBH4 reduction and analysis of I in potatoes had not been previously reported.