Lab Science Filtration: Applications-Grades-Classifications
Industrial and laboratory filtration are crucial in various processes and applications. Labs depend on appropriate, effective filtering to collect product residues and clean solvents that help to prepare samples for further purification or analysis. Labs must follow various protocols to account for purity, discoveries, or products they deliver, such as in the pharmaceutical or biopharmaceutical industry.
In addition, other industries such as food, beverage, chemical, and other various manufacturing processes. Filtration purifies a liquid or gas stream to remove unwanted contaminants, remove particulate that could damage equipment, or collect a desired product residue.
Applications
Because it clarifies products, samples, and testing materials, filtration is one of the most widely used applications in laboratory science and manufacturing. This staple application can be found in all of these industries.
Pharmaceutical
Chemical
Food & Beverage
Environmental Engineering
Water Filtration
Heating, Ventilation, and Air Conditioning
Filter Grade
The filter grade is determined using physical characteristics such as particle retention size, thickness, and weight.
General Purpose Filter Papers
| Retention µm | Flow Rate | Porosity | Grade No. |
|---|---|---|---|
| 11 | Medium | Medium | 1 |
| 8 | Medium | Medium | 2 |
| 5 | Medium | Medium | 413 |
Qualitative Filters
Qualitative filter papers are commonly referred to as “general purpose” and are used for the filtration of precipitates to determine the amount of constituents present in a sample in analytical separations or other general filtration applications.
| Retention µm | Flow Rate | Porosity | Grade No. |
|---|---|---|---|
| 40 | Fast | Coarse | 417 |
| 25 | Fast | Coarse | 415 |
| 25 | Fast | Coarse | 315 |
| 20-25 | Fast | Coarse | 4 |
| 11 | Medium | Medium | 1 |
| 8 | Medium | Medium | 2 |
| 6 | Medium | Medium | 3 |
| 5 | Medium | Medium | 413 |
| 5 | Medium | Medium Fine | 313 |
| 2.5 | Slow | Fine | 5 |
| 1 | Slow | Fine | 410 |
Quantitative Filter Papers
Quantitative filter paper has a reduced content with three variations commonly observed: ashless, hardened low ash, and hardened ashless. Ashless filter paper is used frequently for analytical techniques, such as gravimetric analysis or other general analytical applications, to determine and identify materials present in a sample.
Hardened low ash and hardened ashless filter papers are treated with acid to increase the wet strength and chemical resistance. However, hardened ashless filter paper has low ash content. In contrast, hardened low ash does not.
| Retention µm | Flow Rate | Porosity | Grade No. |
|---|---|---|---|
| 20-25 | Fast | Coarse | 41 |
| 20-25 | Fast | Coarse | 54 |
| 20-25 | Fast | Coarse | 541 |
| 16 | Fast | Medium/Coarse | 43 |
| 10 | Medium Fast | Medium | 454 |
| 5-10 | Medium | Medium Fine | 474 |
| 8 | Medium | Medium | 40 |
| 3 | Slow | Fine | 44 |
| 2.5 | Slow | Fine | 42 |
| 1 | Slow | Fine | 494 |
Glass Fiber Filters
Used in membrane-based instrumentation such as High-Pressure Liquid Chromatography (HPLC) or Gas Chromatography (GC) to remove particulate impurities from liquid and gas samples before analysis. Glass fiber filters are also used as pre-filters in conjunction with other syringe filters or other general applications.
| Retention | Flow Rate | Porosity | Grade No. |
|---|---|---|---|
| 2.7 | Fast | Coarse | GF/D |
| 1.6 | Fast | Fine | GF/A |
| 1.5 | Fast | Fine | 934-AH |
| 1.3 | Fast | Fine | 693 |
| 1.2 | Fast | Fine | GF/C |
| 1.2 | Fast | Fine | 696 |
| 1 | Medium-Fast | Fine | GF/B |
| 0.7 | Medium | Fine | 151 |
| 0.7 | Medium | Fine | GF/F |
Filtration Classifications
Mechanical, chemical, and biological filtration are the primary classifications of filtration. Mechanical filtration functions on the particulate size being filtered by utilizing filters with designated pores sizes. Mechanical filtration is most commonly used for removing larger media, such as sediments, silt, and organic matter from colloidal liquids like sediment-ridden water. In addition, mechanical filtration can be used for microscopic matter such as yeast, algae, or other media.
Chemical filtration separates samples using the molecular properties of a chemical, such as its polarity, to remove it from a solution. For example, activated carbon is commonly used to remove suspended solids and volatile organic compounds. This type of filtration occurs in the fuel industry’s application of biodegradation, crude oil assays, or biomass and biofuel assays. These applications require multiple chemical filtration steps to clarify samples and products.
Biological filtration helps remove contaminants before analytical analysis, like liquid chromatography or mass spectrometry. The process accomplishes filtration by using beneficial bacteria to clean the sample on a molecular level. This type of filtration can also be used for purifying and concentrating macromolecules in applications such as gel filtration chromatography.
The success of your laboratory’s filtration and purification arrangements depends on using the highest quality products available in conjunction with technical knowledge.
Methods of Filtration
Vacuum Filtration
Vacuum filtration creates a lower pressure inside the receiving flask that pulls the solution through the filter paper and leaves the suspended particles deposited as a residue on the filter paper.
Centrifugal Filtration
Centrifugal filtration is done via rotational movement of the filter body, and a filter is unnecessary. A defined rotational speed is set, and the solids or liquids are separated due to differences in density.
Gravity Filtration
Gravity filtration is when the suspended particulate is removed from the liquid by allowing gravity to pull it through filter paper and allows the particulate to deposit as a residue slowly. Gravity filtration is carried out at atmospheric pressure.
Force Filtration
Force filtration functions similarly to vacuum filtration, but instead, higher pressure is applied to a solution. This forces the solution through a filter faster, leaving the particulate as a residue on the filter paper.
Membrane Filtration
Membrane filtration is used for manufacturing various food and beverage products, such as low-fat/no-fat dairy products and whey proteins. A liquid is separated into its components when fed through a membrane filtration system. Many membrane materials are used for filtration that allows for microfiltration, ultrafiltration, nanofiltration, and reverse osmosis.
Cold Filtration
Cold filtration helps separate available fatty acids, proteins, or other molecules with a lower solubility at colder temperatures in a particular solvent. The reduced temperature causes the less soluble particulate to precipitate out of the solution, allowing it to be filtered.
Hot Filtration
Hot filtration helps to remove a small number of impurities from crystalline compounds. A crystalline compound is dissolved in a suitable solvent, and the temperature is raised until everything is dissolved. The solution is removed from heat and allowed to cool slowly, allowing the crystalline compound to crystallize. The slower the crystallization process, the more pure the crystalline compound will be, and impurities will be left behind in the solution.