Open/close configurable microfluidic pretreatment device with one-drop anodic stripping voltammetry for on-site heavy metal detection

Heavy metal pollution in foods and water is a serious problem in developing countries and poses serious risks to public health. To meet the high analytical demands, on-site and low-cost analytical methods are required. The electrochemical detection method is one of the portable and low-cost detection methods for heavy metals, and anodic stripping voltammetry (ASV) shows a superior limit of detection compared with other voltammetry techniques. Screen-printed electrodes can provide a cost-effective detection platform. However, the ASV detection with the low-cost electrodes cannot meet the requirement for ppb-level detection. In addition, environmental samples contain many impurities, which affect the ASV detection. Therefore, a pretreatment device is required for the ASV detection in environmental water analysis. In this study, a microfluidic pretreatment device is proposed as an on-site pretreatment device targeting small-volume pretreatment. To improve the detection limit of the ASV detection, a 1.0 ml sample volume is converted to 20 μl (one drop) by solid-phase extraction with chelating particles, which allows a ∼50 times preconcentration at maximum. The small volume of 20 μl also realizes the low cost by reducing the amount of expensive chelating particles. This procedure can convert the environmental water with many impurities to a clean and ideal solution for ASV detection. This study reports the basic microfluidic platform for this pretreatment procedure, utilizing Pb2+ ions as an analyte and a proof-of-concept of the working principle.