Complexation of Hg(II) by humic acid studied by square wave stripping voltammetry at screen-printed gold electrodes

Author(s)

do Nascimento, Fernando Henrique ^[1] ; Masini, Jorge Cesar ^[1]

Affiliation

^[1] Inst Quim, BR-05513970 Sao Paulo - Brazil

• Document type: Journal article
• Source: Talanta; v. 100, p. 57-63, OCT 15 2012.
• Web of Science Citations: 16

Abstract

This paper reports the development of a sequential injection (SI) method to study the complexation of Hg(II) by humic acid (HA) using square wave anodic stripping voltammetry at a screen-printed gold electrode (SPGE). The SI system injected samples (in 0.020 mol L-1 NaNO3 and pH 6.0) to the flow cell during the deposition step and exchanged the medium to 0.050 mol L-1 HCI to perform the stripping step under stopped flow conditions. For sample volume = 750 mu L flow rate = 15 mu L s(-1) (deposition step), and square wave frequency = 100 Hz, the detection limit was 20 nmol L-1 and the sampling throughput was 17 analyses per hour. Complexation of Hg(II) was studied using a 25.0 mg L-1 suspension of HA (72.5 mu mol L-1 of ionizable sites), and total Hg(II) concentrations from 1 to 20 wool L-1. The diffusion coefficient of the complex was (1.3 +/- 0.2) x 10(-7) cm(2) s(-1). A complexing capacity of 537 mu mol g(-1) was found. The log of the differential stability constant (log K-DEF) decreased from 7.0 to 5.3 as the log of the degree of site occupation (log 0) increased from -1.6 to -0.5. The values of log K-DEF were consistent with complexation of Hg(II) by carboxylic and phenolic groups. (C) 2012 Elsevier B.V. All rights reserved. (AU)

• FAPESP's process: 10/04372-1 - Study of interactions of Hg(II) with heterogeneous ligands of natural occurrence by voltammetric techniques
• Grantee: Fernando Henrique Do Nascimento
• Support Opportunities: Scholarships in Brazil - Master