Electrophoresis\nand Quartz Crystal Microbalance Instrumentation\nto Sense Nanoplastics in Water

We report a Technical Note on detecting nanoplastics\nin water samples\nthrough electrophoresis and quartz crystal microbalance (QCM) instrumentation.\nWe conducted electrophoresis experiments by immersing a QCM in a sample\nof ultrapure water containing polyethylene (PE) nanoplastics. It was\ninteresting to observe that nanoplastics were attracted toward the\nQCM and adhered to one side of the QCM electrode. The attached particles\nintroduced mass loading to the QCM and were characterized by a decrease\nin resonance frequency of the crystal. Furthermore, when a small region\naround the center of electrode was alone exposed for direct contact\nin water and the rest of the electrode was masked using photoresist,\nthe nanoplastics were concentrated only in the exposed electrode region,\nsignificantly enhancing detection sensitivity. To further investigate\nthe applicability for real-life water samples, we experimented with\nthe technique with readily available bottled drinking water and mineral\nwater, where we spiked these water samples with nanoplastics. It was\nobserved that the resonance frequency shifts were significantly larger\nfor samples with nanoplastics compared to samples without nanoplastics.\nIn addition, Raman spectroscopy and microscopy imaging were used to\nfurther confirm the presence and locations of nanoplastics on the\nelectrode surface. This study highlights the combination of electrophoresis\nand QCM effectiveness in detecting nanoplastics across different water\ntypes and their potential for broader applications in environmental\nmonitoring.