Monitoring particles below 20 nm in liquid chemicals is a key metrology gap identified by the IRDS. This presentation compares two approaches for sulfuric acid: in-situ aerosolization with condensation particle counting (A-CPC) and ex-situ on-wafer measurement by sequential spin coating with surface-enhanced particle sizing (SSC-SEPS). It covers method optimization, comparison with particle standards, and applications, showing that both techniques capture added contaminants and offer complementary strengths for online monitoring and detailed size analysis.