DIRECT DETERMINATION OF LEAD IN SWEET FRUIT-FLAVORED POWDER DRINKS BYELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY

A simplified method for direct determination of lead in sweet fruit-fl avored powder drinks, syrups and honeys by electrothermal atomic absor ption spectrometry without sample digestion is proposed. Samples were dissolved in water, acidified to 0.2% (v/v) HNO3, and directly injecte d into an end-capped transversely heated graphite atomizer (THGA). Bui lding up of carbonaceous residue inside the atomizer was effectively p recluded for sugar solutions not exceeding 8.0% (m/v) when a heating p rogram with two pyrolysis steps (600 and 1000 degrees C) was carried o ut without air-ashing. Under these conditions one atomizer supported a bout 250 firings. Among various chemical modifiers tested, better reco very and repeatability results were obtained with a 5 mu g Pd + 3 mu g Mg(NO3)(2) mixture. Tests carried out with individual concomitants co ntaining 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 m ass and detection limit based on integrated absorbance were 15 and 11 mu g Pb, respectively. The relative standard deviation based on 10 mea surements for typical samples (20-60 mu g g(-1) Pb) was always lower t han 5.5%. The detection limit of 7.0 ng g(-1) Pb attained the Coder re commendation for the maximum allowed lead contents in the sugar sample s. Application of t-test to the results obtained by the proposed direc t analysis, and the official method adopted by Food Chemical Coder, de monstrated that there were no significant differences at the 5% probab ility level. (C) 1998 Elsevier Science B.V.