Interferences contributed by leaching from filters on measurements of collective organic constituents

Membrane and glass fiber filters are widely used in laboratory water and wastewater analyses. During sample filtration, some filters release organic compounds, which may interfere with organic analyses. This research investigated the interferences due to organic leaching in the determinations of dissolved organic carbon (DOC), biodegradable dissolved organic carbon (BDOC), soluble biochemical oxygen demand (BOD), and soluble chemical oxygen demand (COD) and the appropriate cleaning method for the filters. Nineteen filters studied included 16 membrane filters and 3 glass fiber filters. A wide variation was observed on the amount and characteristics of organics leaching from the filters. Some filters showed no organic leaching while some others had very high organic leaching. Soaking the filters in deionized distilled water (DDW) resulted in more leachable organics from the filters compared with filtering DDW through them. Certain filters should be avoided for use in the above analyses and soaking in DDW is a more suitable cleaning method than discarding initial filtration volumes for most filters.