Glossary of Lab Terms

When the micron rating of a membrane filter is 100% accurate, without exception.

The soaking up of a liquid into a porous substance such as a sponge.

Activated carbon filters are created under high temperatures to increase absorption. Activated carbon filters can remove colors, odors and tastes from liquids and gases.

The adherence of a liquid to the surface of a solid to form a thin film coating.

Affinity purification, also called affinity chromatography, is a chromatographic method used to separate a specific molecule from a complex mixture. It is based on highly specific biological interactions between two molecules, such as interactions between enzyme and substrate, receptor and ligand, or antibody and antigen. These interactions, which are typically reversible, are used for purification by placing one of the interacting molecules, referred to as affinity ligand, onto a solid matrix to create a stationary phase, while the target molecule is in the mobile phase.

Fluid entering a filter or filter system.

Multiple particles gathering together to make a mass.

The air surrounding a subject.

The temperature surrounding a subject.

In an aqueous solution, one or more substances (solutes) are dissolved in water (solvent). Water dissolves only hydrophilic substances such as acids, bases and many salts. In a chemical equation, the symbol (aq) indicates that a certain substance is dissolved in water, e.g. NaCl(s) → Na+(aq) + Cl-(aq)

Analytical procedure to determine purity or concentration of a specific substance in a mixture.

A vessel for heating materials under high steam pressure. Used for sterilization and other applications.

To reverse the flow of fluid through a filter media, in an effort to remove solids.

Bacterial culture refers to the process of growing bacteria in or on a medium in a lab environment. The culturing parameters vary between the different bacterial species. One of the most important factors is oxygen. Depending on whether your bacteria need oxygen or not, you have to grow the bacterial cells in an aerobic or anaerobic culture.

A unit of pressure. One (1) bar equals 14.5 PSI.

Biochemistry explores the chemical processes within and related to living organisms, focusing on processes happening at a molecular level. This covers a range of scientific disciplines, including genetics, microbiology, forensics and medicine.

The surface area on a filter that has not been utilized during filtration.

Drastically reduced or restricted fluid flow due to the pore opening of a filter media being blocked by contaminate.

The method used for pore size determination. It is based on the fact that, for a given fluid and pore size with constant wetting, the pressure required to force an air bubble through the pore is in inverse proportion to the hole size.

A buffer is an aqueous solution consisting either of a mixture of a weak acid and its conjugate base, or a weak base and its conjugate acid, which is resistant to changes in pH. Buffers are used to maintain a stable pH in a solution, as they can neutralize small quantities of additional acid or base.

The point at which the pressure against a membrane exceeds its ability to resist breaking open.

The ability of a fluid to flow around the filter unintentionally allows particles to flow downstream.

Solids retained by a filter in the form of a thick mixture.

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During centrifugation, the contents of a sample tube are spun at a defined speed to separate the contents based on their relative densities.

The separation of substances in a mixture based on their affinity for certain solvents and solid surfaces.

The initial pressure drop across the filter when it is clean and new.

Tube or cylinder containing the chromatographic bed or stationary phase, usually in the form of beads.

The gas, liquid, or particulate to be retained by a filter.

A filtration system in which the feed stream flows across the filter media and exits as a retentate stream. The retentate stream is recycled to merge into the feed stream, while a portion of it passes through the filter media, resulting in concentration of the feed stream (referred to as concentrate).

Feed stream flows in one direction only, perpendicular to and through the filter medium to emerge as product or filtrate.

Liquids pass through a tortuous maze of filter fibers that gradually become more compact. As the fluid passes further through this filter bed, smaller and smaller sizes of particulate contamination are removed by a filtration mechanism known as direct interception (or mechanical sieving). Commonly these are manufactured in polypropylene or glass fiber.

Differential pressure is essentially the difference in pressure between two given points. For a filter it is measured between the inlet and outlet of the filter housing that the filter is housed in.

Deoxyribonucleic acid (DNA) stores the hereditary material in all organisms. It consists of a double helix formed by two single strands made from the nucleobases (adenine, guanine, cytosine and thymine) and a sugar-phosphate (deoxyribose and a phosphate group) backbone.

Drug screening is the process of identifying and optimizing potential drugs before selecting a compound for clinical trials. It can involve screening vast compound libraries for a particular biological activity in high throughput assays.

The top and bottom components of the filter cartridge that hold the filtration media in place.

The casing or vessel that holds the filter cartridge.

The clear liquid that remains after filtration.

The process of separating particles from a liquid or gas using a filter.

The ability of the filter to remove particles of a specified size.

Flow cytometry is a method for the qualitative and quantitative measurement of biological and physical properties of cells and other particles. Particles are suspended in a high-velocity fluid stream, and passed through a laser beam one at a time.

Fluorometry is a technique used to identify and quantify analytes in a sample by adding fluorophores that bind to the analyte of interest to the sample, exciting them with a beam of UV light and detecting and measuring the emitted wavelength. By comparing the sample fluorescence to known standards, the analyte can be quantified.

Gene expression is the process by which information encoded in DNA is converted into a protein molecule. It consists of two steps, transcription and translation. During transcription, the information stored in DNA is converted into messenger RNA (mRNA), a sort of ‘instruction for making proteins’. The mRNA then leaves the cell nucleus, and the ribosome translates it into a protein, reading codon by codon and adding the corresponding amino acid for each sequence to the protein.

A fibrous material made from borosilicate glass, commonly used as a filter and separator medium. Glass Fiber filters are hydrophilic (water wettable) and perform the function of coalescing immiscible liquids for separation. May be used effectively on compressed air, gas, or liquids that are acidic but only slightly caustic. Also referred to as fiberglass.

Also called Retention Volume. Volume of fluid retained in a filter and/or housing after purging the assemble with air or suitable gas.

Having an affinity for water; a membrane which will wet with aqueous solutions.

Literally, fearing water; a membrane which cannot be wetted by and repels aqueous and other high surface tension fluids; when pre-wetted with low surface tension fluid, such as alcohol, the filter will then wet with water.

The technique of using an antibody that binds to a particular protein to precipitate it out of a solution is called immunoprecipitation (IP). IP requires that the antibody is coupled to a solid substrate at some point in the procedure, and can be used to isolate and concentrate a specific protein from a sample containing thousands of different proteins.

Chemical inactivity; unable to move; totally unreactive.

Vessels filled with ion exchange resin (anion, cation, or mixed) for producing conditioned or DI Water. Also, type of column used for Ion Exchange Chromatography (IEC).

A laboratory centrifuge is a device with a central motor that spins a rotor containing sample tubes. The resulting centrifugal force speeds up the sedimentation process, and centrifuges are commonly used to separate particles with different sizes and densities suspended in a liquid.

Centrifuges designed to accommodate tubes with a capacity of 2 ml and less are called microcentrifuges, and instruments optimized for very high speed – generating forces of up to 1,000,000 g – are called ultracentrifuges.

Liquid handling means transferring liquid from one location to another. As there are often countless samples of only a few microliters in volume that need to be transferred, accuracy, precision and throughput are key.

Manual pipettes (or mechanical pipettes) require manual operation of the piston by pushing the plunger down with the thumb. Pipette tips also need to be ejected manually via the tip ejector and the volume is usually adjusted by twisting the plunger.

Media preparation refers to the process of mixing nutrients and other substances to produce a culture medium for the growth of microorganisms, such as bacteria or fungi.

A semi-permeable material used in microfiltration that allows certain substances to pass through while blocking others based on size and characteristics.

A microporous synthetic semi permeable structure manufactured from PES, Nylon, PTFE, and Cellulose that is used to reduce or completely remove microorganisms or bacteria from a fluid. Typically, these are 100 microns thick.

Methods used to assess the effectiveness and integrity of the membrane, ensuring proper filtration. Testing include bubble point, pressure decay and forward flow tests.

Microbiome is a term that describes the genome of all the microorganisms, symbiotic and pathogenic, living in a particular habitat, e.g. the human gut. The human microbiome has extensive functions in development of immunity, defense against pathogens, synthesis of vitamins and fat storage, as well as an influence on human behavior.

Microfiltration is a filtration process using a microporous medias, membrane and depth filters, that retains the suspended solids of a fluid. Sometimes also called Process Filtration this dead-end filtration technology works in a range between 0.1 micron to 40 microns.

1 micron is 0.001mm (1/1000 of a millimetre). A pencil point is about 40 microns or 0.040mm (40/1000 of a millimetre) and one of the smallest things an unaided eye can see. Often represented by the symbol "µ".

Synthetic materials derived from naturally occurring cellulose. First materials used in the manufacture of membrane filters. Mixed cellulose esters membranes are used in a wide variety of applications, e.g., concentration of bacteria in water analysis (GN-6) and sampling of air.

An arbitrary micron value assigned by the filter manufacturer, based upon removal of some percentage of all particles of a given size or larger. It is rarely well defined and typically not reproducible.

A thermoplastic, polymeric material that has high mechanical strength & compatibility with many different kinds of chemicals. When used as a membrane it is hydrophilic.

The amount of particles a filter can hold before requiring replacement or cleaning.

The specified size of particles that a filter is designed to capture and prevent from passing through. Particle Retention Rating indicates the filter's ability to remove particles of a certain size or larger, typically measured in microns (µm) and expressed as a nominal or absolute rating depending on the filter type and testing method used.

The filtered liquid that passes through the membrane, leaving behind impurities and particles in the retentate.

The degree to which a fluid will pass through a permeable substance under specified conditions. The space or void volume between molecules allowing fluid flow.

The inverse (negative) logarithm to the base 10 of hydrogen ion concentration. Measure of a substance’s acidity or alkalinity with 7 being neutral. Measure of hydrogen ion concentration.

Polyether sulfone(PES) is primarily composed of benzene rings, ether bonds, and sulfone groups in its sructural formula. The ether bonds make the molecular chains highly fluid in the molten state, making it easy to mold. The sulfone groups can enhance heat resistance. The sulfone groups on voth sides are conjugated benzene rings, which increase the thermal stability of the molecular chain. Compared with other polymers, PES has excellent mechanical, chemical, and thermal stability, and is easy to process, making it an excellent material for the preparation of filter membranes.

A thermoplastic polymeric material which is resistant to a broad range of chemicals. When used as a membrane, polypropylene is hydrophobic.

More commonly known as Teflon. Highly durable and resistant to a broad range of temperatures and chemicals. PTFE is hydrophobic.

The diameter of the microscopic pores in a membrane, determining the size of particles or microorganisms that can pass through.

The percentage of void space in a filter media or cartridge, also known as voids volume.

A method of analysis using a filter paper to determine the presence or absence of a substance in a sample, without measuring the exact quantity, essentially providing a "yes or no" result based on whether particles are caught by the filter, rather than how much is caught; this is typically done with a qualitative filter paper, which is designed for general purpose filtration and identifying components of a mixture rather than precise quantitative analysis.

A method where the exact amount or quantity of a substance captured by a filter is measured, typically through weighing the filtered residue on a filter paper with minimal ash content, allowing for precise analysis of the substance's concentration in a sample, often used in techniques like gravimetric analysis; in contrast to qualitative testing which only identifies the presence or absence of a substance without measuring its amount.

A reagent is a compound or mixture added to a system to cause a chemical reaction or test if a reaction occurs. A reagent may be used to find out whether or not a specific chemical substance is present, by causing a reaction to occur with it.

The concentrated solution or suspension containing particles, microorganisms, or substances that are retained by the membrane during filtration.

A filtration separation method (usually crossflow or stirred cell type) operating at 200-1500 psi to overcome osmotic pressure. Pore sizes are typically in the order of 10-10meters (107mm). Efficiency is usually described in terms of percent salt rejection with 90% being common.

Solid-phase extraction is a sample preparation method used to separate dissolved or suspended compounds in a liquid mixture depending on their physical and chemical properties. The sample is usually passed through a cartridge containing a solid adsorbent that either retains the analyte or the impurities.

Final or sterile air filtration removes microorganisms from air or other gases, to protect contacted food and beverage products, ingredients, packaging and equipment surfaces from airborne microbial contamination.

Sterility is the state of being free from living organisms. Sterile products, such as pipette tips, are needed to prevent contamination in cell culture assays. For very sensitive applications, products should not only be sterile, but also free from DNase, RNase, PCR inhibitors and endotoxins.

The total area available for filtration within the cartridge.

Titration is a chemical analysis method used to determine the concentration of an unknown solution. To calculate its concentration, a solution of a known concentration that reacts in a definite, known proportion with the unknown solution is progressively added until the reaction neutralizes.

A separation method operating at 50-200 psi in crossflow filtration mode. Efficiency is approximately 90%. Used to separate large molecules according to their molecular weight.

A surfactant added to a membrane to assure complete intrusion (wetting) by a high surface tension fluid such as water.