SEPARATION OF METAL-IONS WITH SODIUM BIS(TRIFLUOROETHYL)DITHIOCARBAMATE CHELATION AND SUPERCRITICAL FLUID CHROMATOGRAPHY

Bis(trifluoroethyl)dithlocarbamate (FDDC) forms stable complexes with arsenic (As3+) and other metal ions (Bi3+, Co3+, Fe3+, Hg2+, Ni2+, Sb3+, and Zn2+) which can be separated by capilary supercritical fluid chromatography (SFC) using CO2 as a mobile phase. The fluorinated ligand is superior to its hydrogenated form, diethyldithlocarbamate (DDC), with respect to thermal stability and solubility in supercritical CO2. Substoichiometric solvent extraction studies showed that the stability constants of metal-FDDC complexes were greater than those of their nonfluorinated analogues. Using this FDDC extraction and SFC analysis, separation and detection of arsenic species in the presence of other metals can be achieved with the detection limit in the ppb range.