ONLINE PRETREATMENT AND DETERMINATION OF PB, CU AND CD AT THE MU-G-L(-1) LEVEL IN DRINKING-WATER BY CHELATION ION-CHROMATOGRAPHY

A novel, highly sensitive method for the simultaneous separation and d etermination of lead, copper, cadmium and other transition metals in d rinking water was achieved by on-line sample pretreatment of chelation ion chromatography. Manganese, which coeluted with cadmium, was oxidi zed to permanganate by ammonium persulfate before injection. Permangan ate, with bulk quantity of alkali, alkaline earth metals, iron and alu minum, was eliminated by pyrophosphoric acid-ammonium acetate buffer s olution (pH 5.5), while retaining heavy and transition metals on a sel ective chelating resin (MetPac CC-1 column). Then, they were disabsorb ed and transferred to a sulfonated cation exchanger (TMC-1 column). Fi nally, the concentrated trace metals were separated on a bifunctional ion-exchange column (CS5A) by a concentration gradient of oxalic acid and sodium nitrate eluents, coupled with post-column spectrophotometri c detection with 2-[(5-bromo-2-pyridyl)azo]-5-diethylaminophenol (5-Br -PADAP) at 560 nm. The separation and color-development conditions wer e optimized. The detection limits for the method (signal-to-noise rati o=3:1) were at or below the mu g l(-1) level. The results of drinking water analyses were satisfactory. (C) 1998 Elsevier Science B.V.