APPLICATION OF THERMAL LENS SPECTROMETRIC DETECTION TO THE DETERMINATION OF HEAVY-METALS BY ION CHROMATOGRAPHY

Dual-beam thermal lens spectrometry (TLS) was tested as a potential de tection technique after the ion chromatographic separation of some hea vy metals. Before detection, heavy metal ions of interest (Cu2+, Ni2+, Co2+, Zn2+, Cd2+, Pb2+, Fe2+ and Fe3+) were separated on a Dionex HPI C-CSS separation column. For the Separation of Cu2+, Ni2+, Co2+, Zn2+, Pb2+ and Cd2+, oxalic acid was added to form anionic and cationic met al complexes, which were then separated on the same column. For the se paration of Fe2+ and Fe3+, pyridine-2,6-dicarboxylic acid was added to the eluent and iron species were separated as anions. 4-(2-Pyridylazo )resorcinol was used as a postcolumn reagent to form absorbing metal c omplexes characterized by an absorption maximum at 520 nm. For Cu2+ an d Co2+ ions, TLS detection at 514.5 nm was found to be advantageous co mpared with UV-Vis detection at 520 nm (lambda(max) = 520 nm), whereas for Zn2+ and Ni2+ the detection limits of the two techniques were com parable.