Whatman Filter Paper Quantitative Grades

Qualitative vs. Quantitative Filter Paper

Both qualitative and quantitative filter paper grades are composed of a high percentage of alpha cellulose, a quality we maintain across all Whatman cellulose filter papers. The primary difference between them lies in ash content—the amount of non-volatile residue left after combustion. Qualitative papers may contain up to 0.06% ash, while quantitative papers undergo an acid treatment to reduce ash content, often to less than 0.01%.

This reduced ash content is crucial for quantitative analysis. After filtration or sample collection, the filter paper can be incinerated, leaving behind minimal, predictable residue, which simplifies subsequent measurements.

Quantitative filter papers are available in three main types: ‘ashless,’ ‘hardened low ash,’ and ‘hardened ashless.’ Let’s take a closer look at each.

Ashless Filter Paper

Grade 40 (8 μm)

Grade 40 is the standard choice for general-purpose ashless filter paper, offering medium filtration speed and particle retention. Common applications include:

• Gravimetric analysis of substances in cements, clays, iron, and steel.
• Separation of solid matter in soil analysis.
• Quantification of sediments in milk.
• Analytical-grade clean-up for atomic absorption spectroscopy.
• Collection of trace elements and radionuclides from the atmosphere.

Grade 41 (20 μm)

As the fastest ashless paper, Grade 41 is perfect for filtering coarse particles and gelatinous precipitates. It also excels in quantitative air pollution analysis.

Grade 42 (2.5 μm)

With the finest particle retention among Whatman cellulose filter papers, Grade 42 is ideal for critical gravimetric analysis. It is particularly effective for filtering precipitates such as:

• Barium sulfate
• Metastannic acid
• Finely precipitated calcium carbonate

Grade 43 (16 μm)

Grade 43 strikes a balance between Grades 40 and 41, offering good particle retention and twice the flow rate of Grade 40. It’s particularly useful for:

• Foodstuffs analysis
• Soil analysis
• Particle collection for XRF analysis (air pollution monitoring)
• Inorganic analysis in construction, mining, and steel industries

Grade 44 (3 μm)

This thinner version of Grade 42 minimizes ash weight per sample while still retaining very fine particles, with nearly twice the flow rate.

Hardened Low Ash Filter Paper

Hardened low ash filter paper grades are designed with high wet strength and enhanced chemical resistance, achieved through the addition of a small quantity of chemically stable resin. These properties make them ideal for Büchner funnel filtrations, allowing for straightforward recovery of precipitate from the filter surface.

Grade 50 (2.7 μm)

Grade 50’s small pore size and slow flow rate make it ideal for retaining very fine crystalline precipitates. Its hardened glazed surface resists fiber shedding and can withstand wet handling and scraping for precipitate removal, making it suitable for:

• Vacuum filtration on Büchner and 3-piece filter funnels
• Carrying integrated circuits

Grade 52 (7 μm)

Similar to Grade 50, Grade 52 offers high wet strength but with a medium pore size, providing balanced retention and flow rate through its very hard surface.

Grade 54 (22 μm)

Whatman Grade 54 hardened low ash quantitative filter paper is specially designed for Büchner funnel and Hirsch funnel filtration, enabling fast vacuum suction filtration ideal for recrystallization applications. This hard, smooth, high wet-strength filter paper efficiently collects coarse and gelatinous precipitates with minimal fiber shredding, even when wet.

Hardened Ashless Filter Paper

Hardened ashless filter papers are suited for a variety of precipitate sizes. Along with general filtration Grade 540, the range includes Grade 542 for retention of fine precipitates and Grade 541 for fast filtration. All three grades are designed for use in gravimetric analysis.
These filter papers exhibit high wet strength and chemical resistance and are acid hardened, which reduces ash to an extremely low level. Their tough surfaces make them suitable for a wide range of critical analytical filtration operations. Each grade offers a convenient combination of filtration speed and particle retention.

Grade 540 (8 μm)

A general purpose hardened ashless filter paper with medium retention and flow rate. Extremely pure and strong with a hard surface. High chemical resistance to strong acid and alkali. Frequently used in the gravimetric analysis of metals in acid/alkali solutions and in collecting hydroxides after precipitation by strong alkalis.

Grade 541 (22 μm)

The general purpose hardened filter paper with medium retention and flow rate. Very hard surface.

Grade 542 (2.7 μm)

High retention of fine particles under demanding conditions. Slow flow rate. Very hard and strong with excellent chemical resistance.
Often used in gravimetric metal determinations.