Determination of zinc in vegetal tissue microsamples by platinum-wire loop in flame atomization atomic absorption spectrometry.

The zinc content of 3 microL of vegetal samples (tree leaves, lichens and grape sap) atomized from a Pt-wire in the methane-air flame has been determined by atomic absorption spectrometry. The effect of gas flow rates and the atomization height in the flame on the absorption of zinc was evaluated at 213.9 nm. The best results were obtained at a height of 5 mm and gas flow rates of 200 L/h air and 26 L/h methane, respectively. The effect of Na, K, Ca, Mg, SO4(2-), and PO4(3-) on the absorption of zinc was studied too. The detection limit of 0.40+/-0.21 ng was obtained at a significance level of 0.05, using the two-step Neyman-Pearson criterion. The zinc content of the samples has been determined with continuous nebulization and by atomization from the Pt-wire, using both the standard calibration curve and the standard addition method. The results of the two procedures agree within the determination errors.