Effect of additives on the flow-analysis determination of weak-acid-dissociable and total cyanide

The effect of reductants, complexants, and nitrite eliminators on the flow- analysis determination of weak-acid-dissociable and total cyanide has been studied for: 1. cyanide recovery from copper, nickel, and iron complexes; 2. cyanide generation from the reagents in the presence of common interfere nts; and 3. cyanide consumption by the reagents in the presence of those interferent s. In the absence of additives the U-V-assisted recovery of (total) cyanide fr om the iron complexes (using a succinate buffer) was insufficient. Arsenite and hypophosphite had no measurable effect on the recovery, ascorbic acid resulted in total recovery but under these conditions nitrite and sulfite s eemed to destroy cyanide. Phenanthroline promoted the recovery of cyanide f rom iron complexes but led to formation of cyanide from thiocyanate. Citrat e resulted in good recovery but in the presence of nitrite cyanide was form ed; the recovery with EDTA was also good. It proved necessary to destroy ni trite by use of sulfamic acid. If a combination of EDTA, citrate, and sulfa mic acid is used rather high concentrations of thiocyanate, nitrite, thiosu lfate, and sulfite can be tolerated in the samples. It is strongly advisabl e to test modifications of the cyanide determination comprehensively, becau se some surprising results have been obtained.