Sonically Assisted Electroanalytical Detection of Ultratrace Arsenic

Abstract

A simple portable handheld electrochemical sensor with an integrated sound source for the detection of ultratrace quantities of arsenic using square wave anodic stripping voltammetry is described. The sensor uses low-frequency sound (250 Hz) during the arsenic deposition step to enhance the sensitivity of the arsenic stripping response. It is found that under quiescent (silent) conditions a detection limit of 2.1 x 10(-7) M with a sensitivity of 0.51 M(-1) A is achievable using a 120-s accumulation period, while applying low-frequency sound using a "sonotrode" reduced this detection limit to 3.7 x 10(-9) M with an increased sensitivity of 27.2 M(-1) A. Thus, the low-frequency sonotrode is shown to increase the sensitivity by ca. 50 times while reducing the limit of detection by 2 orders of magnitude. A study of the effect of copper contamination is carried out as well as analysis in real samples; it is found that although as expected copper detrimentally effects the arsenic limit of detection, it does not rise significantly above 10(-8) M levels.