EFFECT OF ACIDS, MODIFIERS AND CHLORIDE ON THE ATOMIZATION OF ALUMINUM IN ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY

The effect of HNO3, HCl and H2SO4, as well as various modifiers, Mg(NO 3)(2), Pd(NO3)(2), Ca(NO3)(2) and NH4H2PO4, on the atomization of alum inium from a L'vov platform in electrothermal atomic absorption spectr ometry was investigated. No interference was observed on the integrate d absorbance of Al from any acid studied. The m(0) observed for 10 mu g l(-1) (200 pg) Al aqueous solution, prepared by diluting a commercia l Al stock solution with doubly de-ionized water, was much poorer than expected, owing to a failure to transfer Al to the furnace, it could be corrected by adding as little as 0.25% v/v of a mineral acid. The e xpected m, for Al was unaffected by modifiers such as Mg(NO3)(2), Pd(N O3)(2), Ca(NO3)(2) and NH4H2PO4. Addition of either calcium, magnesium , or palladium nitrates produced a sharper absorbance peak, and Al was delayed in appearance. Either Ca(NO3)(2) or Mg(NO3)(2) can stabilize Al during pyrolysis, allowing a very high (>1700 degrees C) thermal pr etreatment temperature to be used. However, multiple atomization peaks were observed when using Mg(NO3)(2). The multiple peaks became more t roublesome as the tube aged. Calcium nitrate is recommended as a bette r modifier for those samples (e.g., bone) in which Ca is a large compo nent of the matrix. A serious interference from chloride salts varied with chloride concentration, pH and pyrolysis temperature. This 'suppr essive' interference from chloride was overcome by using Ca(NO3)(2) as a modifier in HNO3, and a pyrolysis temperature in excess of 1400 deg rees C.