Characteristics of ultrafiltration membranes with respect to the removal of nanoscale particles can be determined by surrogate challenge tests (SCTs). Key elements of a successful SCT are the selection of a suitable surrogate and a reliable quantification method. A major challenge when using nanoparticles as surrogates is their quantification in the filtrate, since commonly used particle detection methods are often lacking in sensitivity. The applicability of laser-induced breakdown-detection (LIBD) as a monitoring tool for SCTs has therefore been evaluated. The SCTs were carried out using polystyrene (PS) and silicate particles spiked into ultrapure water and into bank filtrate. Nanoparticles were detectable down to 10 nm and, depending on the material, down to a few ng/L. The nominal pore-size of the ultrafiltration membrane could be confirmed during the tests, demonstrating the suitability of LIBD as a highly sensitive monitoring technique for SCTs.

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