About the Classifications of Quantitative and Qualitative Filter Papers

What makes the filter paper different from the normal paper?
The filter paper is made of fiber with numerous holes on its surface, and the particles will pass through, leaving the larger solid particles on it to achieve the filtration function. So it can separate the mixing of liquid and solid substances. HAWACH filter paper is using only high-quality raw materials, ensuring high repeatability and uniformity.

In the market, there are different kinds of filter papers available for applications in the laboratory. Due to the wide variety of sizes, materials, types, and grades, filter papers are used in a wide variety of applications. It’s of great importance to get the right one for your work and experiments. Generally, the most commonly used filter papers are two types quantitative and qualitative. Both have three filtration speeds ranging from very slow to very fast, which is affected by these specifications. The choice of filter paper must be used strictly in accordance with its physical properties for the proper application

Qualitative filter paper

For the qualitative filter paper, with the amount of ash produced after ashing no more than 0.13%, its main application is to determine and identify materials in routine separation. Qualitative filter papers can be classified into filter paper grades based on different attributes such as thickness, weight, and particle retention. Commonly used qualitative filter paper grades include 1-6, 91, and 113, which are used in several industries.

BIO 1: 11μm (medium retention capacity and flow rate)
Suitable for routine filtration, with discs of 10mm to 500mm discs, and rectangles of 460*570MM.

BIO 2: 8 μm (longer filtration time and lower filtration speed)
With slightly stronger retention than BIO 1.
Besides the ordinary particle filtration, it is also applied in monitoring air and soil special pollutants and intercepting soil nutrients in plant growth experiments, and so on.

BIO 4: 20-25μm (very fast filtration speed)
It retains both coarse particles and deep colloidal substances well, such as ferric hydroxide and aluminum hydroxide, making it ideal for fast biological or organic extractions in everyday analytical filters.
BIO-4 qualitative filter paper is ideal for rapid filtration of routine biological fluids and organic leachates in analysis. The only high-speed collection is required, but the collection of fine particles is not strict in air pollution monitoring.

BIO-5: 2.5μm (slow retention and flow rate)
It is often used to clarify liquids, converting wide laboratory applications.
In chemical analysis, BIO 5 scientific filter paper can collect small, deep objects encountered. Not only are the paper and disc available, but also it can be customized. It is the most effective qualitative filter paper for collecting small particles, suitable for suspended solids clarification, water, and soil analysis as well as chemical analysis.

BIO 6: 3 μm, (medium to slow filter paper)
With similar fine particle retention, BIO-6’s filtration speed is doubled compared with BIO-5. We often use it in boiler water analysis.

Quantitative filter paper
The quantitative filter papers with the amount of ash produced after ashing in a furnace, not more than 0.0009%, which is often called hardened filter papers, it is frequently used in quantitative and gravimetric analyses for pressure or vacuum filtration, with precipitate to be recovered. The qualitative analytical techniques are able to separate, determine and identify materials.

During the production process, producers use pickling to make the paper ash-free to a high degree of purity. Ashless filter paper is also available with ash content below 0.1 mg. This weight is so small that it can be ignored on analytical balances. Quantitative filter papers typically have high wet strength to withstand pressure and vacuum filtration. In the case of qualitative filter papers, the wet strength is usually lower. However, wet-strengthened filter papers are available for qualitative analysis and can be used for pressure filtration and vacuum filtration.

Ashless Filter Papers: Grades 40 to 44 have a nominal ash content of 0.007%, while Grade 589 is typically 0.01%; these very pure filter papers are suitable for a wide range of critical analytical filtration processes.
Hardened low ash filter paper: 0.015% standard ash content; strong acid treatment to remove trace metals and high wet strength and chemical resistance; especially suitable for Buchner filtration (hard and smooth surface of filter paper, easy to recover sediment).
Hardened Ashless Filter Paper: Standard 0.005% ash content; acid hardened for high wet strength and chemical resistance with extremely low ash content; hard surface for a wide range of critical filtration processes.

Conclusion
In conclusion, ask yourself 6 questions when purchasing filter paper:
Do I need qualitative or quantitative analysis?
What particle retention/nominal pore size is required?
Do I need high-wet strength paper?
What diameter do I need?
Does this paper need to be burnt to ashes?
Do I need to get a sample to do a test?