A Brief Introduction to HAWACH Qualitative Filter Paper

Qualitative filter paper is made of cellulose fiber material processed into filter paper, which works on the principle that the fibers combine to form a porous matrix with different pore sizes, which can capture solid particles while allowing liquids to pass. It’s generally used to filter solutions and do qualitative tests such as chloride and sulfate. Qualitative analysis filter paper is generally more residual ash, and can’t be used for quality analysis.

Qualitative filter paper is divided into fast, medium-speed qualitative filter paper, slow qualitative filter paper and ultra-slow qualitative filter paper, the shape could be round and square, usually used in combination with the filter funnel, with good filtration, absorption, a certain mechanical strength, wet strength, paper laxity and other characteristics. Commonly used for routine qualitative analysis applications in laboratories that do not require precise measurement or strict control of particle retention (e.g., clarifying liquids, filtering samples, removing particulate matter from solutions).

HAWACH offers qualitative filter papers made from high-quality cellulose fiber materials that have been chemically treated to enhance their filtration performance. When folded, these filter papers have unique advantages over their counterparts in terms of faster flow and increased negative weight, and are widely used in applications such as chemical characterization, filtration and separation of solutions, and the manufacture of test papers of corresponding purity. The company offers six types of qualitative filter papers in fast (20μm-25μm), medium (8μm-11μm), slow (6μm) and super slow (2μm-4μm), with Qualitative Filter Paper Disc Grade: BIO-1, BIO-2, Qualitative 20 Micron Filter Paper Grade: BIO-4, BIO-5, Qualitative Filter Paper Biology Grade: BIO-6 ,Wet Strengthened 10 Micron Filter Paper Grade: BIO-91 and BIO-113 available.
chemical filter paper filter paper roll suppliers filter paper used in laboratory

Features of qualitative filter paper

1. Ash <0.15%
2. Stable PH value: 0-12
3. High temperature resistance: 120℃
4. High porosity: can filter out particles of various sizes
5. Durable: qualitative filter paper is thicker and can withstand handling and operation during filtration
6. High absorbency: can absorb and retain large amounts of liquid
7. Non-clogging: Progressive flow rate allows liquid to pass through at a reasonable speed without clogging.

Typical applications of qualitative filter paper

Qualitative filter papers have different characteristics such as pore size, filtration speed, paper thickness, etc. Different characteristics are suitable for different applications (specific applications depend on experimental needs). HAWACH has summarized some typical applications.
1. Air monitoring: for air pollution monitoring, collection and analysis of airborne particulate matter.
2. Soil analysis: for separating solid particles in soil samples to help determine the nutrient content, pH and other properties of the soil.
3. Water quality testing. Used for water quality testing, filtering particles from samples, helping to determine the purity of water and detecting any contaminants.
4. Bioassays: for various bioassays (e.g. protein purification and enzyme assays), removal of unwanted solids or debris from samples, separation of proteins of different molecular weights.
5. Pharmaceutical industry: for filtration of liquid and solid materials in drug development and quality control processes, removal of impurities and particulate matter from pharmaceutical preparations.
6. Chemical manufacturing: for removal of solid particles from chemical solutions, separation of liquid and solid phases in chemical reactions.
7. Food and beverage testing: it’s used in food and beverage testing to filter out particles or contaminants from samples

Frequently asked questions about qualitative filter paper

Q1: Is the glossy side of qualitative filter paper facing up or down?
a: Qualitative filter paper usually has no obvious front side (glossy side) or back side (gross side), it is a symmetrical film made of cellulose fiber, both front and back sides are used with the same effect, so it does not matter which side faces up or down during use, some manufacturers will print a watermark or logo on one side of the filter paper, in this case the side with the watermark or logo can face up.

Q2: How long does it take to slow down the qualitative filter paper?
a: Qualitative filter paper is designed to remove solid particles from liquids. The speed of the filter paper is the time it takes for the liquid to pass through the filter paper and is determined by the porosity and thickness of the filter paper. Typically, fast qualitative filter paper is with 20μm-25μm pore size and 25-30s filtration speed; Medium-speed qualitative filter paper pore size is 8μm-11μm, filtration speed 35s-70s; Slow qualitative filter paper pore size is 2μm-6μm, filtration speed 100s-140s.

Q3: Does qualitative filter paper contain calcium impurities and phosphorus?
a: Qualitative filter papers are usually made of natural cellulose fibers, where calcium and phosphorus are naturally present. HAWACH filter papers are made of highly pure cellulose fiber material and processed by a special process, so the content of calcium and phosphorus impurities is very, very low and does not affect the performance in filtration applications.

Q4: Is qualitative filter paper resistant to nitric acid? Is it soluble in acetone?
a: Qualitative filter paper is usually made of cellulose fibers, which are resistant to weak acids and bases and insoluble in acetone, but not to strong acids (nitric acid is a strong acid), while prolonged exposure to acetone will cause the filter paper to weaken or dissolve.

Q5：Does qualitative filter paper test engine oil with fast or slow speed?
a: When testing motor oil, it is recommended to use fast qualitative filter paper, not chronic qualitative filter paper (because motor oil usually contains small particles of dirt, metal chips and other contaminants, which will not only clog the qualitative filter paper and slow down the filtration process, but also affect the accuracy of the test results).

For your reference:
Fast qualitative filter paper: used for fast filtration of liquids with low suspended matter content, usually for applications where speed is more important than accuracy.
Medium-speed qualitative papers: used for general purpose filtration (e.g., clarification of liquids, filtration of particulate matter).
Slow-speed qualitative filter paper: suitable for filtration of liquids with high suspended matter content, samples with large particulate matter, usually for applications where high accuracy is required.
Ultra-slow-speed filter paper: suitable for very fine filtration, usually for applications where the sample contains very fine particulate matter.

HAWACH also provides OEM customization. If you have special size or aperture requirements, please contact us by phone: +86-29-89284429 or by email (info@hawach.com).