Integrated Aerodynamic/Electrochemical Microsystem for Collection and Detection of Nanogram-level Airborne Bioaccessible Metals

The soluble fraction of aerosol particulate matter containing trace metals has the potential to engender toxicity and exacerbate the adverse health effects of particulate matter. In this study, an inertial-impaction-based fluidic chip integrated with electrochemical detection was developed to achieve high collection efficiency and measurements of the bioaccessible metal fraction at the nanogram level. The average collection efficiency for ultrafine and fine particles larger than 50 nm, obtained at a flow rate of 2.5 L/min, was above 70%. The detection ranges of aerosol soluble copper depended on the collection duration and airflow rate. At a working flow rate of 3.1 L/min and collection efficiency of 70%, the microsystem was capable of detecting Cu concentrations above 53 ng/m3, 32 ng/m3 and 8 ng/m3 with 3 h, 5 h and 20 h collection periods, respectively, which were in the range of reported atmospheric concentrations. The detection ratio of real-world samples (i.e. PM10-like aerosol) was 100 ± 14%, indicating excellent aerodynamic collection and reliable electrochemical detection. The collection and sensing performance of the microsystem demonstrates a new step towards an online, mobile, low-cost, and miniaturized routine monitoring system for bioaccessible metals and possibly other soluble components in the aerosols.