Laboratory Filter Membranes May Release Organic Particles That Affect Water Analysis

Commercial filter membranes have been widely used in laboratory water filtration processes without any pretreatment. However, whether they will leach organics into the membrane filtrates that can potentially interfere with the subsequent water analysis has long been overlooked. In this study, we found that filtering deionized water through the five typical commercial filter membranes produced filtrates with the total organic carbon (TOC) ranging from 0.32 to 7.2 mg L–1. Scanning electron microscopy and dynamic light scattering results show that the organics are present as irregularly shaped particles with a wide size distribution. Raman spectroscopy demonstrates that the organic particles share the same vibrational and fluorescence signatures with the blue separator papers between the membranes, indicating that they originated from the separator papers. Soaking the membranes in deionized water for 24 h, washing membranes for 30 s, or using a water sample volume over 100 mL can reduce the TOC in the membrane filtrates to below 1 mg L–1. This study systematically and quantitatively evaluates the potential interferences introduced by the laboratory membrane filtration step on water analysis and guides future users to take the best practice to mitigate such interferences.