Bisphenol A (BPA) was widely used in the manufacture of polycarbonate plastics and epoxy resins, and the risks associated with BPA remain highly controversial. As a result, numerous determinations of trace BPA are now carried out, creating the need for robust analytical processes. High-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) offers extremely high sensitivity for BPA detection, often with a detection limit of below 2 ppt, making it essential to use ultrapure water throughout the analytical process. A range of ELGA® pure water systems have been tested for this application, and offer effective removal of BPA to below the detection limit of HPLC-MS/MS.