Chromatography Glossary



This is a term used in size exclusion chromatography (SEC) to describe the process of where a solute can enter a mobile phase filled pore of the packing material.


An abbreviation for Perfluorotri-n-butylamine, a stable, non-toxic compound used for tuning and calibration of a mass spectrometer.


A numerical designation of relative acidity or alkalinity of a solution. A pH of 7.0 indicates precise neutrality. Progressively higher values indicate increasing alkalinity and lower values increasing acidity. The pH scale ranges from 0 to 14 and is logarithmic, ie., a change from one integer, from eg., 5 to 6, is a change of an order of magnitude (10x).

Phase Ratio

The ratio of the volume of the mobile phase to that of the stationary phase in a column.

Phenyl Phase

Phenyl bonded phase is used in the reversed phase mode. It has unique selectvity which is useful for analyzing aromatic compounds. It is produced by bonding dimethylphenyl chlorosilane to silica gel.

Physiological buffer

An aqueous buffer with a pH between 6.8 and 7.4.

Physiological fluids

Biological fluids which include urine, blood, serum, lymph fluid etc.


Abbreviation for inlet pressure


Abbreviation for isoelectric point

Pirani Gauge

In mass spectrometry, a thermal conductivity gauge used to measure pressures in low vacuum regions. This low vacuum gauge measures heat loss and pressure by changes in the resistance of the heated wire.

Pirkle Column

Chiral "brush-type" stationary phases, based on low-molecular weight bonded phases with one or more optically active chiral selector attached and, used in the separation of a wide variety of enantiomers. Named after the developer, Dr. William Pirkle, University of Illinois.


The pH at which fifty percent of the ionizable groups on a molecule are ionized and fifty percent are uncharged and neutralized. Adjustment of the pH of a solution containing an acid to two pH units above the pKa results in approximately 99% ionization.

Planar Chromatography

A separation technique in which the stationary phase is present as or on a plane. The plane can be a paper, serving as such or impregnated by a substance as the stationary bed (Paper Chromatography, PC) or a layer of solid particles spread on a support, e.g., a glass plate (Thin Layer Chromatography, TLC). Sometimes planar chromatography is also termed Open-Bed Chromatography.

Plate Count

Efficiency is measured in terms of the number of plates, N, the symbol for the number of theoretical plates. N is most commonly calculated as follows: N=16(tr/wb)², where tr is the retention time and wb is the width of the peak base.

Plate Height

Refers to the height equivalent to a theoretical plate.


Accumulation of debris in the fluid flow path, restricting or blocking flow.

Pneumatic Pump

Pumps which employ a gas to displace the liquid mobile phase either directly or via a piston.

Polar modifier

An ion pairing agent. An ionic organic compound added to the eluent in Ion Pair Chromatography which will ionically bind charged solutes. The agent usually (but not always) contains a hydrocarbon chain that makes the sample hydrophobic so that the ion pair can be retained on a reversed phase column. The agent is believed to form an ion pair with the sample ion via their respective ionizable groups. The resulting pair has a net charge, ie., the solute pair appears neutral, allowing for improved chromatography (eg., sharper peaks and better retention).

Polar Molecule

A molecule with an unsymmetric distribution of charge.

Polar-Bonded-Phase Chromatography

HPLC method, different from reversed-phased chromatography.Mobile phases that do not contain water are used with this method.

Polarimetric Detector

A detector that measures the ability of the solution in the cell to rotate a beam of polarized light. Used in the detection of chiral molecules.


Polarity is a measure of the separation of charges in a molecule; hydrocarbons are non-polar; alcohols are polar; more polar stationary phases interact more strongly with polar samples and usually provide a better separation.

Polarity Index

Arelative classification of a group of solvents according to their ability to solvate a select group of polar and nonpolar solutes. The index is an indication of a solvent's ability to act as a proton donor, a proton acceptor, or a dipole.The polarity index of a solvent is represented by p'.

Polyacrylamide Gel

Is a neutral hydrophilic polymeric packing material used in aqueous SEC. It is made by the copolymerization of acrylamide with (N,N,-methylene)bisacrylamide.

Polymeric Packing

Is a packing based on polymeric material, normally taking the form of spherical beads. Polymers used as stationary phases in HPLC fall into two general categories: hydrophilic and hydrophobic. Polymers can be either synthetic (eg., PS-DVB, PVA) or natural (eg., cellulose, agarose). Natural polymers used as packings do not come in the form of spherical beads; they are generally crystalline materials limited to low pressure applications.

Polymeric Phase

Polymeric phase refers to bonding of HPLC stationary phases using polyfunctional silylating reagents, yielding a branched typed bonded phase rather than monomeric type.


Polypropylene is abbreviated PP. Material Compatibility and Uses: Used for low pressure parts and tubing. Not recommended for use with most organic solvents.


Polypropylene is abbreviated PP. Material Compatibility and Uses: Used for low pressure parts and tubing. Not recommended for use with most organic solvents.

Polystyrene Divinylbenzene Resin

PS-DVB, is the most common polymer base used in ion exchange chromatography. Ionic groups are incorporated by chemical reactions. Neutral PS-DVB beads are used in reversed phase chromatography and size exclusion chromatography.


Polysulfone is abbreviated PS. Material Compatibility and Uses: Used to make filter membranes. Not recommended for use with most organic solvents. A hydrophilic low protein binding membrane with high flow characteristics.

Polyvinyl Alcohol

Polymerized and cross-linked polymer gel (based on ethanol homopolymer) used as a separation medium in biochromatography. It is used in bead form in gel permeation chromatography which have aqueous mobile phases such as gel filtration chromatography (GFC).

Polyvinyl Chloride

Polyvinyl Chlorideis abbreviated PVC. Material Compatibility and Uses: Used to make filter membranes. Not recommended for use with organic solvents.


Small opening in resins or support matrices that allow molecules to pass into and through. Pores increase the surface area and provide contact regions on the support where the chromatographic process takes place.

Pore Size

The average diameter of the porous openings on the surface of a sorbent particle. The smaller the pore size, the higher the overall surface area of the packing material.

Pore Volume

Refers to the total volume of pores in porous packing, in mL/g. This is measured by the BET method of nitrogen adsorption or by mercury intrusion, where mercury is pumped into the pores under high pressure.


Describes the ratio of the volume of the interstices to the volume of the solid particles, for a porous adsorbent. The pore volume is also used as a measure of the porosity.

Porous-Layer Bead

Refers to a small glass bead which is covered with a thin layer of stationary phase. This thin layer can vary from being an adsorbent, a resin or a phase chemically bonded onto an adsorbent.

Porous-Layer Open-Tubular (PLOT) Column

These columns there is a porous layer on the inner wall. Porosity can be achieved by either chemical means (e.g., etching) or by the deposition of porous particles on the wall from a suspension. The porous layer may serve as a support for a liquid stationary phase or as the stationary phase itself.

Positive Displacement Principle

A term used in mass spectrometry for a mechanical vacuum pump that transports gas with the aid of pistons, rotors, vanes, valves, and other devices. The gas is compressed and then expelled from the pump.

Post-Column Derivatization

A version of reaction chromatography in which the separated sample components eluting from the column are derivatized prior to entering the detector. The derivatization process is generally carried out "on-the-fly", i.e., during transfer of the sample components from the column to the detector.


Abbreviation of parts per billion. An expression for analyte concentration; one part of the substance per billion total parts. Commonly used in environmental analysis.


Abbreviation of parts per million. An expression for analyte concentration; one part of the substance per million total parts. Commonly used in environmental analysis.

Practical Quantitation Limit

The Practical Quantitation Limit is the lowest level that can be reliably achieved within specified limits of precision and accuracy during routine laboratory operation.


Process causing a solid to settle out of solution by the action of gravity or by chemical reaction, which forms a substance (precipitate) that separates as solid particles in the liquid.


A measure of the reproducibility of measurments of the same quantity. It is generally determined through the analysis of duplicate (syn = replicate) samples.


A precolumn is inserted into the system between the pump and injector. It is used when the solvent is very aggressive toward the packing material.

Precolumn Filter

A filter placed immediately ahead of the column. It removes particulate matter which may be in the mobile phase, can chemically sorb substances that could interfere with the separation, or as a saturator column, presaturates the mobile phase with stationary phase to prevent stripping of the column. Its volume has little effect on the isocratic elution but causes a delay to the gradient in gradient elution.

Precursor (Mass Spec.)

In mass spectrometry, irregularly shaped spike which can appear on the low mass side of a mass peak when displayed in a profile scan.

Preparative Chromatography

Is the process of using liquid chromatography to separate and then collect a sufficient amount of material for other purposes.