DETERMINATION OF COPPER SPECIATION IN FRESH-WATER SAMPLES THROUGH SPE-SPECTROPHOTOMETRY

The Cu(I)-bathocuproine complex was separated by solid phase extractio n (SPE) on octadecyl (C-18) bonded silica cartridges or disks followed by elution and spectrophotometric detection (SPE-spectrophotometry) a nd applied as a detection and speciation method for Cu in water sample s. For a PTFE-supported C-18 disk, the bathocuproine-available copper detection limit of 0.4 mu g l(-1) for ultrapure water (500 ml sample) was raised to 3.8 mu g l(-1) in polluted water due to filter blockage by colloids. UV irradiation gave total copper analysis, no filter bloc kage and a lower detection limit. Repeated analysis of drinking water gave a standard deviation of +/- 1%, correct concentration was determi ned in certified riverine water and a satisfactory result was obtained in an interlaboratory calibration for Cu in freshwater. A comparison of C-18 cartridges and disks for direct analysis of water samples show ed long filtration times for a C-18 cartridge and high blanks for a gl ass fibre-supported C-18 disk; PTFE-supported C-18 disks gave rapid fi ltration and low blanks in both filtered and unfiltered water samples. A significant difference was noted for Cu determination in the presen ce of NTA (nitrilotriacetic acid) when bathocuproine was immobilised o n the disk rather than pre-equilibrated with Cu, and interpreted in te rms of lability of the Cu-NTA complex and short contact time with bath ocuproine on the disk. In speciation analysis, SPE-spectrophotometry i s sensitive, precise and convenient for freshwater samples and has the advantage over electrochemical analysis at a Hg electrode of being a Hg-free method.