I

ANNO 2 Numero 3
Milena Rancan, Anna Gloria Sabatini [1]
Determination of lead in honey by Stripping Chronopotentiometry (SCP)

[1] CRA - Istituto Nazionale di Apicoltura, Bologna (Italy)

Corresponding author: mrancan@inapicoltura.org

A procedure for the determination of lead content in honey was set up by means of stripping chronopotentiometry (PSA) using a mercury film-plated electrode. In the procedure the honey sample is only dissolved in ultrapure water without any step of pre-treatment save the addition of the oxidant solution for the stripping stage of the analysis. During electrolysis, Pb2+ is reduced by an applied voltage of –900 mV and amalgamated, Pb(Hg), at the working electrode. During stripping, voltage is turned off and the amalgamated lead is chemically reoxidised and stripped back into the solution in ionic form. Stirrer works (1500 rpm) for 300 seconds during the electrolysis step whereas it is switched off during the stripping time. Mercury(II) ions are used as oxidant: 2 ml of a Hg2+ (800 mg l-1 in HCl) solution should be added for 2 g of honey dissolved in 20 ml of ultrapure water. As long as lead is being stripped off the working electrode, the electrode potential remains stable.

The standard addition technique is employed to determine the relationship between the stripping time and the lead concentration. Afterwards the first acquisition in the sample, a known volume of lead standard solution is added and the stripping time is again recorded. As the relationship between the stripping time and concentration is linear, the increase in the stripping time permits calculation of the lead content in the sample solution.

The detection limit is 0.679 ng ml-1 corresponding to 7.5 ng g-1 on honey sample. The results obtained by the new proposed method were confronted to the results obtained analysing the same samples by electrothermal atomic adsorption spectrometry (ETAAS) and they resulted to be comparable. The range concentration found in honey samples was between 4.8 ng g-1 and 24 ng g-1 of lead.