Modified brucine method

New modifiers have traditionally been discovered by the trial-and-error method. Many naturally occurring chiral compounds (the chiral pool38) have been screened as possible modifiers. Thus, the hydrogenation product of the synthetic drug vinpocetine was discovered to be a moderately effective modifier of Pt and Pd for the enantioselective hydrogenation of ethyl pyruvate and isophorone.39 Likewise, ephedrine, emetine, strychnine, brucine, sparteine, various amino acids and hydroxy acids, have been identified as chiral modifiers of heterogeneous catalysts.38... 

All three samples contained the same amount of nitrate (1.0 mg./liter) but increasing concentrations of chloride namely, 10, 200 and 400 mg./liter. The best results were obtained with the modified brucine (21) method (Table X), although nearly equal precision and accuracy were obtained by the chromotropic acid (26) method. All nitrate methods, however, failed to produce accurate results in the presence of a moderately high chloride concentration. 

Contrary to the statement in Standard Methods (1), it has been found that high concentrations of chloride ion produce a decrease in brucine-nitrate color in the standard brucine technique. The modified technique only gives a constant response with chloride concentrations between 27 to 50 grams Cl"/liter. In our modification the effect of variable chloride concentrations is masked out by adding a large amount of sodium chloride to the reaction mixture before color development (Table III). 

Behpour M, Ghoreishi SM, Khayatkashani M, Motaghedifard M (2012) A new method for the simultaneous analysis of strychnine and brucine in Strychnos nux-vomica unprocessed and processed seeds using a carbon-paste electrode modified with multi-walled carbon nanotubes. Phytochem Anal 23 95-102... 

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