Chromatography Glossary


Flanged Fittings

A low pressure fitting that requires flanging, or spreading the end of the tube before use. Used in a 1/4.28 threaded flat bottom fitting for low or moderate pressure.

Flangeless Fittings

A low pressure fitting that does not require flanging the end of the tubing.

Flash Chromatography

A fast, simple and inexpensive technique for the rapid purification or separation of organic reaction mixtures. Separations take place at high flowrates under medium-pressure conditions (10-40psi) within either dry, self-packed glass columns or pre-packed disposable plastic cartridges.

Flash Point

The lowest temperature at which a solvent vapor above the solvent itself will ignite.


Florisil is a highly selective, high magnesia silica used for removing polar contamination from a nonpolar matrix. It is used in both column chromatography and also as a sample cleanup medium. Polar interferents from plant and animal homoginates are selectively removed before quantification of samples containing, eg., pesticides and dioxins.

Flow Cell

The small chamber in the detector in which sample eluent passes through. Response to component concentrations are measured as the eluent passes through. Micro LC requires smaller cell sizes (>5uL) in order to reduce extra-column effects.

Flow Rate

The volumetric rate of flow of mobile phase through a column. A typical flow rate for a normal column of 4.6mm id would be 1 to 2 mL/min.

Flow Rate Adjustment

When scaling up to preparative or down to narrow bore LC, it is often desirable to maintain the same retention times. This can be achieved by multiplying the normal flowrate by the factor X, where X = (r2/r1)² ; r2 is the new radius, r1 is the old radius.

Flow Resistance Parameter

This term is used to compare packing density and permeability of columns packed with different particles; it is dimensionless.

Flow Sensitivity

Refers to detectors which respond to small changes in the flow rate, eg., refractive index, amperometric, conductivity and mass spectrometer detectors.

Flow Stability

The long term ability of a pump to produce a constant flow rate.


Emission of electromagnetic radiation (usually visible light) resulting from the absorption of electromagnetic radiation of a different wavelength.

Fluorescence Detector

Fluorescence Detector measures the fluorescence of a sample compared to the mobile phase. Fluorescence can be inherent or chemically induced. Laser-induced Fluorescence is one of the most sensitve LC detection methods.


Abbreviation of the amino acid derivatizing agent 9-fluorenylmethylchloroformate. Reacts with primary and secondary amines and amino acids to form highly fluorescent derivatives to increase detection sensitivity.


In HPLC, focusing refers to concentrating the sample on the head of the column by injecting the sample in a very dilute solvent.

Food Safety Modernization Act (FSMA)

The Food Safety and Modernization Act (FSMA), passed by Congress in 2011, is the first major legislative reform of the Food and Drug Administration (FDA) in over 70 years. Owing to the ongoing globalization of the food supply, the Act has a strong focus on insuring supply chain safety and security.

Foreline Pressure

A term used in Mass Spectrometry for the measured pressure between the rough vacuum and the high vacuum pump.

Foreline Pump

In Mass Spectrometry, this is a mechanical pump, used in series with the diffusion pumps. Provides rough vacuum at the exhaust of the diffusion pump.

Foreline Vacuum

A term used in Mass Spectrometry for the measured pressure between the rough vacuum and the high vacuum pump.


Irreversible decline in chromatographic performance due to deposition and accumulation of submicron particles and solutes on the surface and in the pores of the packing bed. May be caused by crystallization and precipitation of small solutes or coating of larger molecules like proteins and plant pigments.

Fourier Transform Ion Cyclotron Resonance

In Mass Spectrometry, a mass filter that determines the mass-to-charge ratio of an ion in the presence of a magnetic field by measuring it's cyclotron frequency.


Fast Protein Liquid Chromatography, a trademark name of Pharmacia, for fast, highcapacity and high-resolution separations of biomolecules in various modes: reversed phase, gel filtration, hydrophobic interaction, ion exchange and affinitiy chromatography. FPLC is an HPLC technique which replaces stainless steel instrumentation with glass, plastics, and titanium.

Fraction Collection

Fraction Collection is the collection of purified sample or peak cuts after a chromatographic or electrophoretic separation. Collected fractions are used for further characterization or for purified product formulations.

Fraction Collector

A device that collects the effluent after it has passed through the detector. It can be programmed to take fixed time (i.e., fixed volume) samples or sometimes can be interfaced to the detector and triggered to start collecting when a peak starts to elute and stop collecting when the peak is eluted.

Fraction Range

Refers to the working range of a gel or packing material, in size exclusion chromatography (SEC). This is the range in which the packing is able to separate molecules according to their size. Molecules that are too large to spread into the pores, are excluded. However, molecules that can spread (diffuse) ? into the pores fill the packing material and elute, unseparated, at the permeation volume.

Fragment Ion

In Mass Spectrometry, this is an electrically charged dissociation product of an ion. The relative abundances of characteristic fragments are used to qualitatively identify molecules. Fragmentation may occur during or after ionization.

Free Silanols

Unreacted silanol groups that remain on the silica surface after the primary bonding reaction.


Porous ceramic, polymeric or metal material. Available in pore sizes from 0.5 micron and larger. It is used as a filter medium at various points along the flow path of the chromatograph, and in particular, at both ends of a column to hold the packing material within the column.

Frontal Chromatography

IUPAC Definition: A procedure in which the sample (liquid or gas) is fed continuously into the chromatographic bed. In frontal chromatography no additional mobile phase is used.


A characteristic of a peak that elutes from a column, such that the center of mass of the peak is before its maximum. An asymmetry factor <1 indicates fronting.

Functional Group

A group of atoms having the same properties when appearing in various molecules. Functional groups incorporated into a support matrix can provide a point of attachement for bonding, eg., amino propyl silica. Functional groups in solute molecules can often be utilized as a reactive site for derivatization to improve selectivity or detection sensitivity in HPLC.


An electronic control often found in strip chart recorders. Increasing the gain, increases the sensitivity of the recorder to react to changes in the signal.

In Mass Spectrometry, the multplication of electrons produced in the detector.

Also can be used to indicate the slope of the scan line in a stability diagram. The higher the gain, the narrower the peak widths at higher masses.

Gas Ballast

In Mass Spetrometry, a procedure used to reduce the condensation of condensable vapors within a rough pump. Mechanically, this is done by admitting a controlled amount of dry gas to the compression stage of the pumping cycle of a rotary-vane pump.

Gas Chromatography

A separation technique in which the mobile phase used is a gas.

Gaussian Curve

A standard error curve, based on a symmetrical bell - shaped band or peak. Most chromatographic theory assumes there will be a Gaussian peak.

GC Headspace

Headspace is most suited for analysis of very light volatiles in samples that can be partitioned into the head space gas volume from liquids or solids.


Gas chromatography-mass spectometry.


A gel is a solid packing used in eg., ion exclusion and size exclusion chromatography. A gel is made up of two parts, the dispersed medium which is solid and the dispersing medium which is the solvent.

Gel Filtration Chromatography

Gel filtration chromatography (GFC) is size exclusion chromatography (SEC) performed with aqueous mobile phases. It usually applies to separations using soft gels (eg polydextrans). Most gel filtrations involve biopolymers.

Gel Permeation Chromatography

Gel Permeation Chromatography is a technique used to separate organic-soluble polymers based upon molecular weight, or more accurately, their hydrodynamic volume in a porous stationary phase.

Geminal Silanol

Where one Si atom has two free silanols bound to it, creating a more reactive site.

Ghost Peak

Chromatographic peaks which do not come from the injected sample. These can come from a variety of sources, eg., plasticizers dissolved by solvents, contaminants or residue from previous samples in the injector, build up of contaminant in the column or recycled solvents.


Good Laboratory Practices. A set of quality assurance and quality control guidelines for the collection of laboratory data that is to be reported to government agencies.


Good Manufacturing Practices. A set of manufacturing guidelines and quality procedures.


Abbreviation of Gel Permeation Chromatography, an alternate name for size exclusion chromatography (SEC), particularly nonaqueous SEC, with organic mobile phases. It is used for the separation and characterization of polymers. The separation of polymers by GPC is based upon molecular weight, or more accurately, their hydrodynamic volume in a porous stationary phase.


In a gradient system, the mobile phase composition changes with time, usually from the weakest solvent to the strongest solvent.

Gradient Elution

The condition where chromatographic separation is obtained by changing the mobile phase composition. Gradient elution is useful to separate samples with multiple components that have a wide range of polarity.

Gradient Former

A device, including electronic and fluid handling components, that changes the composition of the eluent during a run. Comprises electronic pump control for high pressure mixing, with the addition of solvent proportioning valves in low pressure mixing systems.

Gradient Range

Refers to the difference between the highest and lowest concentrations of strong solvent used in a gradient.