PHOTODISSOCIATION GAS-DIFFUSION ION CHROMATOGRAPHY SYSTEM FOR DETERMINATION OF TOTAL AND LABILE CYANIDE IN WATERS

An automated system for determination of total and labile cyanide In water samples has been developed. The stable metal-cyanide complexes such as Fe(CN)63‒ are photodls-soclated In an acidic medium with an on-line Pyrex glass reaction coll irradiated by an Intense Hg lamp. The released cyanide (HCN) is separated from most Interferences In the sample matrix and Is collected in a dilute NaOH solution by gas diffusion using a hydrophobic porous membrane separator. The cyanide Ion is then separated from remaining interferences such as sulfide by Ion exchange chromatography and is detected by an amperometric detector. The characteristics of the automated system were studied with solutions of free cyanide and metal-cyanide complexes. The results of cyanide determination for a number of wastewater samples obtained with the new method were compared with those obtained with the standard method. The sample throughput of the system Is eight samples per hour and the detection limit for total cyanide is 0.1 µg/L. © 1990, American Chemical Society. All rights reserved.