In this study, we develop the technique of using a liquid particle counter to measure the retention of polymer membrane filters and apply that technique to two use cases. In the first use case, we look at the performance of two membranes in 30% hydrogen peroxide and compare the results with the retention performance measured by single nanoparticle ICP-MS and the more traditional standardized particle techniques. In the second use case, we investigate several different polymer membranes in hydrochloric acid and study the impact of pore size and surface modification on the native particle removal efficiency and compare this with traditional techniques. These two use cases demonstrate the utility of this technique and its ability to provide insight into the performance of polymer membrane filters where existing methods do not.