Whatman Filters

Whatman Syringe Filters

We carry the entire line of Whatman syringe filters. Here you will find an overview of the most common syringe filters:

Glass Microfiber Filters

The properties of borosilicate glass micro fibers from Cytiva provide retention levels down to the submicron range. These depth filters offer a combination of fast flow rate with high loading capacity and retention of very fine particles. Due to the high pore volume of glass microfiber filters, the loading capacity is much higher compared to a cellulose filter with similar retention.

Glass microfiber filters must be used flat and should not be folded. Whatman glass microfiber filters are made of 100% borosilicate glass and are usually completely binder-free. Binder-free glass microfiber filters can withstand temperatures up to 550 °C and can therefore be used for gravimetric analyses where ignition is required.

Filters are tested for weight per unit area, thickness, airflow, and mechanical strength. In addition, other parameters such as pore size, suction capacity, filtration efficiency, and surface properties are measured as required.

Cellulose Filters

Most qualitative and quantitative filter papers from Whatman are made from high-quality cotton linters that have been treated to achieve a minimum alpha cellulose content of 98%. These cellulose filter papers are used for general filtration and have a particle retention of up to 2.5 μm. A wide range of retention and flow rate combinations are available to meet the requirements of numerous laboratory applications. The various groups of filter papers offer increasing levels of purity, hardness and chemical resistance. The quantitative Whatman filter papers have extremely high purity and are suitable for analytical and gravimetric work.

These cellulose filters are used in qualitative analytical procedures for the determination and identification of substances. Pre-pleated qualitative filters are also available, offering improved flow rates and increased dirt-holding capacity compared to conventional compartment filters.

Whatman also offers a range of wet-strength qualitative filter papers which contain a small amount of chemically stable resins to improve their wet strength. This ensures that no significant contaminants are introduced into the filtrate. As the resin contains nitrogen, these grades should not be used for Kjedldahl determinations and similar procedures. All wet strength grades are available in prefolded form.

Qualitative Filter Papers

Grade 1: 11 µm

Grade 1 is the most commonly used filter paper for routine medium retention, medium flow applications. The expanded size range now includes filters from 10 mm to 500 mm in diameter and 460 mm x 570 mm in sheet size. This filter paper is also available in the Whatman FilterCup. This is a handy, serviceable 70mm polypropylene filter funnel with a capacity of 250ml and an integral filter.

This grade covers a wide range of laboratory applications and is often used for clarifying liquids. Traditionally, this grade is used for qualitative, analytical purification of precipitates such as lead sulfate, calcium oxalate (hot) and calcium carbonate.

In the agricultural industry, this grade is used for soil analysis and seed control. In the food industry, Grade 1 is used for many routine procedures to separate solid foods from liquids or to extract liquids, and is often used for training purposes to demonstrate simple qualitative analytical separations.

For the measurement of airborne contaminants using circles or rolls, atmospheric dust is collected from the air stream and the stain intensity is measured photometrically. For gas detection, the paper is impregnated with a chromogenic reagent and the color development is measured by optical reflection.

Grade 2: 8 µm

Grade 2 has slightly better particle retention than Grade 1, but with a correspondingly longer filtration time and higher absorption rate than Grade 1. Also available as a pre-pleated Grade 2V filter. In addition to the usual filtration in the 8 µm particle range, the additional absorption capacity is used, for example, to absorb soil nutrients in plant growth trials. Grade 2 is also used to measure specific contaminants in the atmosphere and for soil analysis.

Grade 3: 6 µm

Whatmann's Grade 3 is twice as thick as Grade 1, but with finer particle retention and excellent dirt holding capacity, allowing more precipitates to be retained without clogging. This extra thickness results in greater wet strength, making it ideal for use in Büchner funnels. The high absorption rate is particularly useful when the paper is used as a sample carrier. This filter paper is also available in the Whatman FilterCup. This is a handy, serviceable 70mm polypropylene filter cup with a 250ml capacity and an integral filter.

Grade 4: 20-25 µm

Grade 4 has an extremely fast filtration rate with excellent retention of coarse particles and gelatinous precipitates such as ferric and aluminous hydroxides. Very useful as a fast filter for routine purification of biological fluids or organic extracts during analysis. Grade 4 is used when high flow rates are required for measurements of air pollution and fine particle collection is not critical.

Grade 5: 2.5 µm

Grade 5 has the highest retention of very small particles in the qualitative filter paper range. Particularly suitable for the retention of very fine precipitates in chemical analysis. Slow flow rate. Grade 5 is an excellent clarifying filter for cloudy suspensions as well as for water and soil analyses.

Grade 6: 3 µm

Grade 6 is twice as fast as Grade 5, with similar fine particle retention. Often specified for water analysis applications in heating boilers.

Grade 520 a: 15-18 µm

Grade 520 a is a high wet strength filter paper with very high flow rates. It is often used for technical applications such as filtration of viscous liquids and emulsions, e.g. sweetened juices, spirits, resin solutions, oils or plant extracts. Also available fluted as Grade 520 1/2.

Grade 591: 7-12 µm

Grade 591 is a thick, high dirt-loading capacity filter paper for rapid filtration of medium to coarse precipitates. Offers high absorption rate and wet strength. Also available fluted as Grade 591 1/2.

Grade 595: 4-7 µm

Grade 595 is a thin, medium speed filtration paper for retention of medium and fine particles. Used in many routine analytical applications in various industries, e.g. particle separation of feed extracts or sample preparation for filtration of solids from digested environmental samples, e.g. for ICP/AAS analysis. Also available fluted as Grade 595 1/2.

Grade 597: 4-7µm

Grade 595 is a thin, medium speed filtration paper for retention of medium and fine particles. Used in many routine analytical applications in various industries, e.g. particle separation of feed extracts or sample preparation for filtration of solids from digested environmental samples, e.g. for ICP/AAS analysis. Also available fluted as Grade 595 1/2.

Grade 598: 8-10 µm

Grade 598 is a thick, high loading capacity filter paper. It combines medium particle retention with medium to fast filtration speed. Also available fluted as Grade 598 1/2.

Grade 0048

Grade 0048 is a cellulose/synthetic fiber nonwoven used for milk analysis and infant formula testing for fiber residues.

Grade 602 h: 2 µm

Grade 602 h is a dense filter paper for the collection of very small particles and the separation of fine precipitates. It is used for sample preparation, e.g. in the beverage industry for the determination of microfine ultrapure crystalline components, for acid spectra and for refractometric and HPLC analyses. Also available fluted as Grade 602 1/2.

Membrane Filters

Unlike cellulose and glass microfiber depth filters, membrane filters are conventionally classified as surface filters because the filter matrix acts as a screen and retains particulates almost entirely on the smooth membrane surface. The retention levels for these filters extend down to 0.02 μm and allow the efficient retention of sub-micron particulates and organisms. Water microbiology and air pollution monitoring are major applications for membranes.

Whatman offers a wide range of membrane filters which, due to their advanced technical specifications, are now the filters of choice for a wide range of applications. The membrane filters have a precisely controlled pore size distribution, greater resistance and flexibility, ensuring reproducibility and continuity. The Whatman Membrane Filter range includes a wide selection of membrane filters with pore sizes from 0.02 to 12 µm. Sterile and autoclaved packages are available for special applications. Coloured or gridded membranes are also available at Analytics-Shop.