ONE-DROP FLAME ATOMIC-ABSORPTION SPECTROMETRY OF METALS USING DIRECT NEBULIZATION OF CHLORINATED-HYDROCARBON EXTRACTS OF METAL-CHELATES

The flame atomic absorption spectrometric behaviour of metals extracted into non-flammable chlorinated hydrocarbon solvents (dichloromethane, chloroform and carbon tetrachloride) as their neutral chelates or as ion-paired complexes was studied by a one-drop method with direct nebulization of small volumes of organic extracts and with deuterium background correction. Direct nebulization of organic extracts into a fuel-lean air-acetylene flame gave interesting background-corrected signal profiles, depending on the metals and not depending on extraction agents and solvents. The signal profiles were roughly correlated with the charring and atomizing temperatures of the metals in electrothermal atomic absorption spectrometry and with the dissociation energies of the metal monoxides. Direct nebulization into a dinitrogen oxide-acetylene flame gave a simple signal profile, not depending on the metals. Direct injection of 20-40 mul aliquots of organic extracts of Co, Cu, Fe, Mg, Mn and Ni chelates into an air-acetylene flame gave the maximum, constant and reproducible spike-like signals. Direct nebulization of about 50 mul of organic extracts of Ag, Cd, Pb and Zn chelates also gave very sensitive spike-like signals, compared with those obtained by nebulization of aqueous metal solutions. With the combined use of extraction concentration, this small injection volume of less than about 60 mul resulted in a very sensitive and reproducible flame atomic absorption spectrometric determination of trace amounts of Ag, Cd, Pb and Zn in solid samples without deuterium background correction.