Absorption
The taking in of a substance by another. The absorber 'sucks in' the substance, as a sponge sucks in water.
Adsorption
The natural phenomenon of a gas, vapour or liquid being attracted to and held on the surface of a liquid or solid.
Atmospheric Pressure Chemical Ionisation (APcI)
APcI consists of an aerosol generator, a heat adding process and an efficient atmospheric ionisation process. An interface for LCMS techniques.
Atomic adsorption
A spectrophotometry method where a sample is heated to a high temperature and thereby decomposed into atoms and ions that absorb or emit electromagnetic radiation.
Carrier gas
Gas used to transport a sample through a chromatography column. Usually nitrogen, hydrogen, helium or oxygen.
Chromatography
A process by which the components of a mixture are separated. The process uses two phases. Stationary phase - a bed of inert material with a large surface area. Typical materials include silica, alumina and silica gel. Normally held in a column. Mobile phase - a gas or liquid that flows through the stationary phase, carrying the sample to be analysed. Inside the column, the sample components are separated by their different degrees of attraction to the stationary phase, which is coated or packed into the column. Some components are highly attracted to the stationary phase and take longer to exit (elute) from the column. Other components are less attracted and elute more quickly. A detector connected to the exit end of the column detects the sample components as they emerge.
Column
Columns are used in chromatography to hold the stationary phase. Packed columns normally require 30-50 cc/min per column of nitrogen at 30-40 psig (2-4 barg). Capillary columns are much smaller diameter than packed columns and require approx 1-2 cc/min nitrogen flow. However, the detector at the end of the column assembly usually requires a higher flow than this so the carrier gas is supplemented by make-up gas after passing through the column.
Detector
After a sample exits a chromatography column it flows through a detector which converts changes in the sample's composition into an electrical signal. A chromatogram is then produced, giving a visual representation of the composition.
Electron Capture Detector (ECD)
ECDs measure signal loss rather than signal gain. They are high sensitivity detectors which always use UHP nitrogen as the carrier gas.
Electrospray Ionisation (ESI)
A process which allows virtually any ion in solution to be transported into the gas phase intact for mass spectral analysis in LCMS.
Flame Ionisation Detector (FID)
A highly sensitive and accurate detector used to sample organic compounds using a hydrogen flame.
Fourier Transform Infrared (FTIR)
Gas Chromatography (GC)
A chromatography technique where gas is used to transport the sample through a chromatography column as a means of separating its volatile constituents. Gases used are usually nitrogen, hydrogen, helium or oxygen.
Gas Chromatography - Mass Spectrometer (GCMS)
An analytical technique combining Gas Chromatography for separation with Mass Spectrometry for sample analysis.
Gel Permeation Chromatography See Size Exclusion Chromatography.
High-performance liquid chromatography A technique employing liquids adsorbed on extremely small and uniform particles to provide very high sensitivity.
Inductively Coupled Plasma (ICP)
Ion Chromatography
A well established separation technology for separation of anionic and cationic species. Depends on ion exchange processes.
Ion Trap Mass Analyser
Ion traps (short for quadrupole ion traps) confine the motion of ions in three, rather than two dimensions.
Liquid Chromatography
A chromatography technique where liquid is used to transport the sample through a chromatography column.
Liquid Chromatography - Mass Spectrometer (LCMS)
An analytical technique combining liquid chromatography for separation with mass spectrometry for sample analysis.
Make-up gas Gas
used to supplement carrier gas when capillary columns are used in chromatography. The make-up gas does not need to be the same as the carrier gas, unless used on a TCD.
Mass Spectrometer
In a mass spectrometer, a sample of gas is ionised by an electron beam and the ions are accelerated toward a magnet which separates the ions according to their mass. All Mass Spectrometers have four features in common.
1. A system for introducing the sample to be analysed into the instrument.
2. A system for ionising the sample.
3. An accelerator that directs the ions into the measuring apparatus.
4. A system for separating the constituent ions and recording the mass spectrum of the sample.
Mass Spectroscopy
Where a sample of an organic compound is placed in a vacuum, vapourised, ionised and given extra energy, all of which cause individual molecules to fragment. These molecular fragments are then sorted according to their weight by the electric and magnetic fields in a mass analyser.
Nitrogen Phosphor Detector (NPD)
A detector similar to an FID but specifically designed to detect nitrogen and phosphor. Used commonly in the pharmaceutical industry as many drugs contain nitrogen.
Nuclear Magnetic Resonance (NMR)
A spectroscopy technique depending on transitions between nuclear-spin energy states by absorption of radio-frequency electromagnetic energy.
Quadrupole Mass Analyser
'Quads' have been the workhorse in mass analysis for decades. By varying voltages to four rods, a selected range of sample ions can be filtered from the ion source to the ion detector. Compatible with LC and GC.
Size Exclusion Chromatography (SEC)
Also called gel permeation chromatography. Relies on the size differences of analytes to affect separation.
Spectroscopy
The sudy of the interactions of electromagnetic radiation within substances.
Thermospray (TS)
Involves the spraying of heated Liquid Chromatography effluent into a vacuum evacuated region and generating ions. These ions are then sampled into the mass analyser through an aperture from this region.
Thin-layer Chromatography
A chromatography technique where adsorbent material is on a glass or plastic film rather than in a column.
Thermal Conductivity Detector (TCD)
In this detector an electrical current heats three filaments whose themal characteristics are then altered by the sample and carrier gas. Helium is usually the carrier gas but Hydrogen is a suitable alternative and can also prolong filament life.
Time of Flight Mass Analyser (TOF)
The simplest type of mass analyser. TOF systems require a pulsed ion source, a flight tube and an ion detector. The mass of an ion is related to the time it takes to travel through the flight tube.
