Abstract

A procedure for the quantitative determination of hydrogen cyanide (HCN) released by plants has been developed based on the UV-vis spectrum of the sodium picrate-cyanide complex. Fresh plant tissue mixed with toluene was placed in a gas flow system designed to carry the evolved HCN through 2,4- dinitrophenylhydrazine solution in acidic water:ethanol to trap interfering volatile carbonyl derivatives, and then into an alkaline solution of sodium picrate. After 18 h of gas flow at a rate of 6 mL/min, the absorbance of the solution was measured at 500 nm and the concentration of HCN was determined by calibration in the range 10-3 - 10-5 M. The molar absorptivity coefficient (1.385 L/cm M) yielded a detection limit of 2.6 x 10-6 mol/L and a 92.6 ± 2.6% recovery yield of HCN. The method was applied to determine the cyanide release capacity of Passiflora capsularis (up to 3.34 mg of HCN/g fresh plant tissue), and of croziers of Pteridium aquilinum var arachnoideum (10.4-61.3 mg of prunasin/g fresh plant tissue), and its rate of HCN production (K = 2.20 ± 0.01 x 10-4/s). Cymbopogon citratum, known to release large quantities of volatile, potentially interfering, monoterpene ketones and aldehydes, gave a negative reaction.
Copyright © 2000 John Wiley & Sons, Ltd.

This article was published on Phytochemical Analysis
Phytochem. Anal. 11, 309-316 (2000)