Direct determination of lead in sweet fruit-flavored powder drinks by electrothermal atomic absorption spectrometry

摘要

A simplified method for direct determination of lead in sweet fruit-flavored powder drinks, syrups and honeys by electrothermal atomic absorption spectrometry without sample digestion is proposed. Samples were dissolved in water, acidified to 0.2% (v/v) HNO3, and directly injected into an end-capped transversely heated graphite atomizer (THGA). Building up of carbonaceous residue inside the atomizer was effectively precluded for sugar solutions not exceeding 8.0% (m/v) when a heating program with two pyrolysis steps (600 and 1000 degrees C) was carried out without air-ashing. Under these conditions one atomizer supported about 250 firings. Among various chemical modifiers tested, better recovery and repeatability results were obtained with a 5 mu g Pd + 3 mu g Mg(NO3)(2) mixture. Tests carried out with individual concomitants containing up to 1.0 mu g Na, K, Ca or Cl, and up to 10.0 mu g phosphate or sulphate, and several mixtures of these six concomitants, did not reveal significant interferences on lead atomization. Characteristic mass and detection limit based on integrated absorbance were 15 and 11 mu g Pb, respectively. The relative standard deviation based on 10 measurements for typical samples (20-60 mu g g(-1) Pb) was always lower than 5.5%. The detection limit of 7.0 ng g(-1) Pb attained the Coder recommendation for the maximum allowed lead contents in the sugar samples. Application of t-test to the results obtained by the proposed direct analysis, and the official method adopted by Food Chemical Coder, demonstrated that there were no significant differences at the 5% probability level. (C) 1998 Elsevier Science B.V. [References: 18]