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 extracte d 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 neb ulization of small volumes of organic extracts and with deuterium back ground 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 age nts and solvents. The signal profiles were roughly correlated with the charring and atomizing temperatures of the metals in electrothermal a tomic absorption spectrometry and with the dissociation energies of th e metal monoxides. Direct nebulization into a dinitrogen oxide-acetyle ne flame gave a simple signal profile, not depending on the metals. Di rect 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 ga ve very sensitive spike-like signals, compared with those obtained by nebulization of aqueous metal solutions. With the combined use of extr action concentration, this small injection volume of less than about 6 0 mul resulted in a very sensitive and reproducible flame atomic absor ption spectrometric determination of trace amounts of Ag, Cd, Pb and Z n in solid samples without deuterium background correction.