Square-wave quantification of lead in rainwater with disposable gold electrodes without removal of dissolved oxygen

摘要

Only a few authors describe the use of gold electrodes for trace levels of lead quantification. In this work a sensitive and reliable procedure to the quantification of lead at trace levels by stripping analysis utilizing gold electrodes was developed. It was observed that the presence of chloride ions plays an essential role for lead deposition. Under this condition, the content of lead in rainwater was quantified utilizing disposable gold electrodes (CDtrodes), without removal of the dissolved oxygen. CDtrodes possess very flat surface, high crystalline homogeneity, very clean surface and present great performance for lead quantification in presence of hydrochloric acid. A special cell was designed to work with small volumes of samples (0.5 to 1.0 mL), an important condition to analyze small amounts of rain. Finally, the rapid scanning propitiated by the use of square-wave stripping voltammetry, coupled with blank subtraction eliminates the effect of the dissolved oxygen on the final result. Various experimental parameters were optimized to allow convenient monitoring of lead concentrations (in trace levels) with relatively short deposition times. Linear calibration plots were obtained for different concentration ranges (using different deposition times). A detection limit of 80 ng L-1 (or 80 ppt) of lead was estimated when a deposition period of 300 s was used. During this work, a reliable procedure for electrochemical cleanup of gold surfaces was also developed. The proposed method was tested for certified samples and employed for lead analysis in rainwater samples in Sao Paulo City. [References: 27]