Paraquat monoene

Reduced Paraquat (monoene diene) in ethyl acetate... 

Test a portion of the previously retained aqueous extract for the presence of paraquat and/or diquat, using the Sodium Dithionite test (see p. 144). If tiiis test gives a positive result, adjust the remaining aqueous extract to pH 10 by the addition of dilute ammonia solution, add 50 mg of sodium borohydride, allow to stand at room temperature for 30 minutes, and extract with an equal volume of redistilled ether. The ether extract contains the monoene and diene reduction products which can then be confirmed by GC and/or GC-MS. 

An alternative method, based on gas chromatography, involves the initial reduction of paraquat or diquat by sodium borohydride to produce the diene or monoene, as shown in Fig. 12. These products. 

Note. Unless otherwise stated, the analytical information given below refers to paraquat dichloride. For information on the monoene and diene reduction products for GC-MS analysis, see under Quaternary Ammonium Herbicides, p. 80. 

The standard method for analyzing paraquat is by ion-exchange cleanup followed by reduction to the radical cation, which is colored and read spect rophotometrically(5). The labor requirements and somewhat limited detectability of this method led us to develop a GC method based upon reduction with sodium borohydride to a mixture of the monoene and diene tertiary amines - both of which are amenable to GC on a deactivated column using an N-selective detector( ). The chromatogram shows both peaks (ratios may vary somewhat) which provides built-in confirmation of paraquat because of this dual response pattern. But the reduction-GC method is still a laborious one with a throughput of perhaps 8-10 samples/day under good conditions. It took nearly one man-year to develop and fully Validate. 

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