Determination of trace elements in raw material for polyurethane production using direct sampling graphite furnace atomic absorption spectrometry

The concentration of Fe, Mg, Mn and Na at ultra-trace levels was determined in polymeric diphenylmethane dianiline, a raw material for polyurethane production, by direct sampling graphite furnace atomic absorption spectrometry (DS-GFAAS). A Zeeman-effect background correction system operated in 2-field or 3-field dynamic modes was used. Calibration was carried out using aqueous reference solutions and a sample mass between 0.5 and 35 mg was used. The relative standard deviation was calculated after successive measurements (number of replicates was 14 to 23 throughout the range of sample mass) and was below 15%. Blank values obtained using DS-GFAAS were lower than those obtained with other evaluated procedures. The accuracy was evaluated by comparison of the results with those obtained by inductively coupled plasma optical emission spectrometry (ICP-OES) after microwave assisted digestion (MAD) in closed vessels and microwave-induced combustion (MIC). There were no statistical differences (confidence level 95%) between the results obtained for the analysis of all the analytes by DS-GFAAS and those obtained by ICP-OES after MAD and MIC. The limits of detection were considerably lower (0.06 to 0.27 ng g(-1)) in comparison with those obtained by ICP-OES after MAD (35 to 5443 ng g(-1)) and MIC (12 to 4890 ng g(-1)).