High sensitivity and specificity simultaneous determination of lead, cadmium and copper using μPAD with dual electrochemical and colorimetric detection

Abstract

A bismuth-modified electrode can increase the sensitivity of lead and cadmium detection. However, use of a bismuth-modified electrode in the detection of copper remains limited because the bismuth signal overlaps with the signal for copper. In this study, we developed a new microfluidic paper-based analytical device (μPAD) coupled with dual electrochemical and colorimetric detection to obtain high sensitivity and specificity for the simultaneous determination of lead, cadmium and copper. The μPAD is divided into two parts. The first part is electrochemical detection for the determination of lead and cadmium using a bismuth-modified, boron-doped diamond electrode (Bi-BDDE). The limit of detection was 0.1 ng mL−1 (for both metals). The second part is colorimetric detection for the determination of copper based on the catalytic etching of silver nanoplates (AgNPls) by thiosulfate (S2O32−). The color of AgNPls on μPAD changed from pinkish violet to colorless after the addition of copper; this change can be monitored by naked eyes and its detection limit was5.0 ng mL−1 by the Image J analysis. The proposed method was applied for the simultaneous determination of these three metals in real samples and no significant differences in accuracy and precision were observed compared to the standard method.