High-Throughput Fast-Scan Anodic Stripping Voltammetry in a Microflow System

Abstract

A flow-onto thin-layer electrochemical cell, incorporating Pt-based Hg microelectrodes, is used for fast-scan anodic stripping voltammetry (FS-ASV) at microbore flow rates. The slow flow rates are uniformly altered and controlled utilizing a gas displacement pump. Flow injection is carried out with a low-dead-volume six-port valve. In such a microflow system, the high precision that is observable in quiescent solutions is maintained. The detection limits (e.g., 0.17 nM for Cd 2+ with a 2-min preconcentration, or 0.19 pg of Cd 2+ at 4.9 μL/min) are remarkably lower than those previously reported in other flow systems utilizing Hg microelectrodes. Compared to ASV in quiescent solutions and in other flow systems, this setup has an excellent sample throughput and low sample consumption. For example, at moderately fast scan rates (e.g., 15 V/s), one analysis of a sample containing Pb 2+ or Cd 2+ at submicromolar levels takes about 10 s, with only 0.82 μL of sample consumed. Experimental conditions that govern the sensitivity, sample consumption, and throughput are discussed (i.e., scan rate, flow rate, Hg film thickness, and preconcentration time). Finally, potential use of this device for automatic analyses is demonstrated.