Chromatography Glossary


Sample Matrix

The crude solution or material that contains the target analyte(s) which is to be analyzed or extracted, or more specifically, the actual composition of the sample.

Sample Preparation

A broad and diverse group of laboratory techniques used to clean up or conentrate analytes in a sample matrix.

Sample Valve

Is used to introduce (inject) the sample into the HPLC or GC for separation. The sample valve may be operated manually or automatically, providing very reproducible injection volumes. A syringe is used to introduce th sample into the injection port, which then fills an injection loop (injection loop volumes range from typically 5 to 200uL in analytical HPLC; 200 to 10,000µL in prep LC). A rotor is moved manually or pneumatically and the sample is swept out of the loop and onto the head of the column to begin the separation.

Saturator Column

Also called a Silica - saturator column. A chromatographic column packed with coarse silica particles and placed ahead of the injector. The purpose of the saturator column is to saturate the eluent with silica to keep the (silica - based) packing material in the separation column from dissolving.


Abbreviation of strong anion exchanger. Also known as Strong Base, SB or quaternary amine phase. Commonly used for separating nucleosides, nucleotides and organic acids. The surface of the SAX material is positively charged.


A mode of identification that sets the quadrupole to select all ions produced by the fragmentation of a sample molecule. The mass filter is swept across a range and all ions are measured. Scan mode is used to collect data suitable for a spectral library search.

Scan Line

Used in Mass Spectrometry for the line representing the RF/dc ratio on a stability diagram.


A substance that emits light when bombarded with nuclear radiation, (alpha, beta or gamma rays).


Abbreviation of strong cation exchange. Also known as Strong Acid, Sulphonic acid or SA. Bonded phase used in Ion Exchange Chromatography. Useful for separating Organic Bases. The surface of the SCX material is negatively charged.

Selected Ion Chromatogram

Refers to an output mode of the mass spectrometer detector, where the chromatogram is plotted using the ion intensity at a single mass versus time. Sometimes referred to as Selected Ion Monitoring (SIM).

Selected Ion Monitoring

A term used in Mass Spectrometry for an acquisition mode where the mass filter is set to allow one (or a small group) of ion(s) to pass. This typically results in higher sensitivity because the measurement is only of the ions of interest and the measurements last for longer periods of time. A sample must have been previously characterized before performing SIM.

Selective Detector

A detector which responds to a related group of sample components in the column effluent.


The degree of chromatographic discrimination obtained between one chemical species (usually the target analyte) and others (usually contaminants). The selectivity of the sorbent can refer to the ability to retain only the target analyte(s), or the degree of purity achieved as a result of the extraction.


Generally refers to Detector Sensitivity, the ability of the detector to give larger bands (other factors equal) and a better signal-to-noise ratio. This provides more precise analysis of very small concentrations.


The process of achieving two distinct elution times for two solutes.

Separation Factor

The ratio (alpha) of retention factors (k') for adjacent peaks. Also called Selectivity Factor or Relative Retention Ratio.

Separation In Space

A mass spectrometer where different mass ions are directed to different location.


Abbreviation of Supercritical Fluid Chromatography, this technique involves the use of an HPLC column (usually a small-bore ID column) with supercritical fluid as the mobile phase (usually CO2, modified with methanol). SFC is used to separate substances that cannot be dealt with effectively by LC, because of detector difficulties, or in gas chromatography, because of the lack of volatility.


The electrical output from the detector, usually in millivolts, which is sent to a chart recorder or equivalent device to graph the chromatogram.

Signal-to-Noise Ratio

A measure of the level of signal above the background noise. The minimum acceptable ratio is typically set to 3 or 10 to ensure sufficient signal for quantitation.


The Si-OH group found in silica gel. There are different strengths of silanol, depending upon their location on the surface of the gel and their relationship to each other. The strongest silanols are acidic and can sometimes react with basic compounds during chromatography by hydrogen bonding. Primary amines will interact very strongly with silanol groups.

Silica Gel

The most commonly used column packing material in liquid chromatography. It is porous and contains siloxane and silanol groups. It is used as a bare packing in adsorption, as a support in liquid-liquid chromatography or for chemically bonded phases. Also in SEC, as a packing material with various pore sizes.


Is the Si-O-Si bond, the main bond found in silica gel. It is a stable bond except at a high pH, usually breaking above pH 8.


Refers to the process used to make chemically modified stationary phases (bonded phases) for HPLC.

Silylation Reagent

Is a reagent which converts the free hydroxyl groups on the chromatographic support into inactive silyl groups, thus reducing polarity of the support.

Simulated Moving Bed

A process-scale chromatographic technique that uses a complicated system of valving to allow for a continuous feed of sample to be introduced onto the separation "bed" and purified sample to be collected.

Simulated Moving Bed Chromatography

A process technique in chromatography which uses a complicated system of valving to allow for a continuous feed of sample to be introduced onto the separation "bed" and purified sample to be collected.


A fritted metal or plastic filter that fits on the inlet end of the eluent delivery tube within the eluent reservoir. Serves to both filter the eluent and to weight down the inlet tube.

Size Exclusion

Refers to chromatography with column packings which separate compounds based on their molecular size, or more accurately, their hydrodynamic volume in a porous stationary phase.

Size Exclusion Chromatography (SEC)

Also known as gel filtration, gel chromatography or gel permeation. One of the most important LC methods where samples are separated by their size, or more accurately, their hydrodynamic volume in a porous stationary phase (silica or polmer). Includes both aqueous-soluble (GFC) and organic-soluble (GPC) separation techniques.


In mass spectrometry, this refers to the slope of the scan line on a stability chart. Changing the slope of the scan line adjusts the peak widths.

Slope Sensitivity Parameter

Selected integrator or data system parameter which sets the rate of change of the detector signal which will trigger the start of peak integration.

Slurry Packing

Is the way most often used to pack HPLC columns with microparticles. The packing is typically suspended in an iso-density slurry of 10% weight/vol. and is quickly pumped into an empty column, using a high pressure pump.

Solid Phase Extraction (SPE)

A sample preparation technique based on the separation mechanisms of liquid-solid chromatography. The intermolecular interactions between sample components, sorbent and solvent are optimized to effect retention of analytes on the solid phase extraction cartridge, followed by elution in a minimal volume of solvent.

Solenoid Valve

Solenoid Valve used for HPLC pumps is a valve which proportions solvents in isocratic and gradient mobile phase systems.


The quantity of a substance to dissolve in some liquid, whether aqueous or organic based.


The solute is the dissolved part of a mixture that is to be separated in a column using chromatographic techniques.


Preparation of the column to receive the sample.


A liquid that can dissolve other substances. In LC, solvent often refers to the organic component of the "mobile phase".

Solvent Degassing

Solvent degassing is the process of removing dissolved gases, especially oxygen, from HPLC solvents. Three methods are typically used: helium sparging, sonication and on-line vacuum degassing via oxygen exchange through a Teflon membrane.

Solvent Programming

Solvent programming refers to gradient elution or the changing solvent concentration over time.

Solvent Strength

The solvent strength refers to the ability of the solvent to elute a solute from the column. In comparing solvents, with all other conditions constant, the solvent causing the shortest retention time is the strongest solvent. Solvents are quantitatively rated in an eluotropic series.


Abbreviation of Standard Operating Procedure, an SOP is a detailed set of instructions for carrying out a procedure or method. SOPs are intended to improve consistency and standardize performance by eliminating variations in the interpretation of how a method is carried out.


Refers to the adsorption packing material used in liquid chromatography. The most common is silica gel.


A method of degassing solvents for HPLC. Inert gas, usually helium is bubbled continuously through the solvent resevoir, The helium displaces dissolved gases such as oxygen, which can cause bubbles to form in the chromatograph.

Specific Binding

The propensity of one molecule to bind only one other type of compound.

Specific Detector

A detector which responds to a single sample component or to a limited number of components having similar chemical characteristics.


Selective interactions between a specific analyte and the sorbent, or the differential retention behavior provided by different sorbents of the same class.

Spectral Inerpretation

In mass spectrometry for an identification method using rules based on chemical stability and reaction mechanisms to deduce the structure of a molecule.