Whatman Grade 40 high-purity filters from GE Healthcare's Life Sciences business are general-purpose papers for quantitative analysis. Grade 40 filters are suitable for a variety of analytical filtration applications. High-purity filters contain 0.007% maximum ash content Medium nominal particle retention rating of 8 µm Medium filtration speed (Herzberg 340 s) Particularly useful for gravimetric analysis GE offers a range of Whatman ashless filter paper for your gravimetric analysis needs. See our other ashless grades to find the right filter for your sample, or use our hardened ashless grades if your analysis involves strong acid/alkali suspensions. High-purity filters support accurate analysis in applications sensitive to very low levels of background contamination and in gravimetric analysis where ash content might affect weight measurements of combusted samples. GE's high-purity Whatman Grade 40 ashless paper is suited to: Soil analysis, when separating solid matter from aqueous extracts Quantitative determination of milk sediment Use as a clean-up filter for solutions prior to atomic absorption (AA) spectrometry Analysis of constituent components in cements, clays, iron, and steel products Collection of trace elements and radionuclides from the atmosphere.