Absorbance-based detection of arsenic in a microfluidic system with push-and-pull pumping

Rapid and portable analysis of arsenic (As) contamination in drinking water is very important due to its adverse health effects on humans. Available commercial detection kits have shown low sensitivity and selectivity in analysis, and also they can generate harmful by-products. Microfluidic-based approaches allow portable analysis with gold nanoparticles (AuNPs) as labels. However, they need complex surface modification steps that complicate detection protocols. Due to the lack of precise sensing and affordable solution, we focused on developing a microfluidic platform that uses a push-and-pull pumping method for sensitive detection of As. In this detection principle, a sample is introduced in the microfluidic channel modified with -SH functional groups where As can bind. Then, AuNPs are given in the channel and AuNPs bind on free -SH functional groups which are not allocated with As. Absorbance measurements are conducted to detect AuNPs absorbed on the surfaces and the resulting absorbance value is inversely proportional with As concentration. The method enables detection of As down to 2.2 mu g/L concentration levels in drinking water, which is well-below the allowed maximum As concentration of 10 mu g/L in the drinking waters by the World Health Organization (WHO). The paper reveals that multiple push-and-pull pumping of fixed volume of sample and AuNPs with a syringe pump can improve the binding efficiency in the microfluidic channel. With this technique, low amounts of sample (1 mL) and short total assay time (25 min) are sufficient to detect As.