Understanding the effects of potassium ferricyanide on lead hydride formation in tetrahydroborate system and its application for determination of lead in milk using hydride generation inductively coupled plasma optical emission spectrometry.

ABSTRACT

To understand the formation of plumbane in the Pb(II)-NaBH4-K3Fe(CN)6 system, the intermediate products produced in the reaction of lead(II) and NaBH4 in the presence of K3Fe(CN)6 were studied. The produced plumbane and elemental lead were measured through continuous flow hydride generation (HG)-inductively coupled plasma optical emission spectrometry (ICP OES) and X-ray diffraction spectrometry techniques, respectively. Based on the experimental results, the explanations can be depicted in the following steps: (1) plumbane and black lead sediment (black Pb) are formed in the reaction of lead(II) and NaBH4; (2) the black Pb is oxidized by K3Fe(CN)6 to form Pb2[Fe(CN)6], which further reacts with NaBH4 to form more plumbane and black Pb; and (3) another round starts in which the produced black Pb from the step 2 is then oxidized continuously by K3Fe(CN)6 to form more Pb2[Fe(CN)6] complex, which would produce more plumbane. In short, the black Pb and Pb2[Fe(CN)6] complex are the key intermediate products for the formation of plumbane in the Pb(II)-NaBH4-K3Fe(CN)6 system. Based on the enhancement effect of potassium ferricyanide and potassium ferrocyanide, a method was developed to analyze lead in milk with HG-ICP OES technique. The detection limit of the method was observed as 0.081 µg L(-1). The linearity range of lead was found between 0.3 and 50,000 µg L(-1) with correlation coefficient of 0.9993. The recovery of lead was determined as 97.6% (n=5) for adding 10 µg L(-1) lead into the milk sample.