Advantages And Disadvantages Of Chromatography

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that of a three-dimensional spherical ion trap, which translates to more accurate measurements for trace analysis.
Mobile phase
The liquid phase being pumped through an HPLC column to act as a carrier for the sample, to establish equilibration with the stationary phase, and eventually to elute the separated compound peaks.
Molecular weight
Summation of the weights of all the elements in a molecule, expressed in amu or dalton. In mass spectral analysis, the weight of the molecular ion produced in a soft chemical ionization such as ion spray or electrospray.
MS/MS system
A tandem, triple quad or hybrid dual mass spectrometer system used to study MS fragmentation mechanisms. The second analyzer is used to further fragment ions separated in the
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Only precursor ions that form this neutral compound will show in the product ion scan that is produced.

Normal-phase chromatography
Partition separation on unbounded polar silica columns. Mobile phase is usually a nonpolar solvent but can be an acidic polar solvent.
Washing a system with 6 N nitric acid after removing the HPLC column. Cleans the pump heads, check valves, and the injection loop and protects them against salt corrosion for a period of time.
Plunger and seal
Solvent flow in an HPLC pump is created by a sapphire plunger driven by a reciprocating cam-and-spring mechanism through a Teflon seal into a pumping chamber. Check valves in the pump’s inlet and outlet fitting prevent reverse solvent flow and allow pressure buildup to overcome flow resistance in the column.
Precursor ion
The target ion submitted for fragmentation studies in a MS/MS system. A precursor scan is a mass scan of the fragmentation ions produced by thermal collision with a heavy gas molecule.
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Changes in this factor result in shifting of relative peak positions. See also Alpha factor and Resolution equation.
SIC (single-ion chromatogram)
A chromatogram produced by displaying the ion current produced versus time for a given mass (m/z). It can be produced by operating in single-ion mode or extracted from a scanned fragment database.
SIM (single-ion monitoring)
The mass spectrometer measures one or only a few specific m/z points. Since fewer mass measurements are made than in scan, they are made more often, with a proportional increase in sensitivity. Also an acronym for selective ion monitoring.
Size-separation chromatography
Chromatography in which separation is made on the size of the molecules on controlled-pore-size columns. Also referred to as gel filtration.
Bar plots of signal intensity in volts versus ion fragment mass/charge, measured in amu, for a given MS scan or range of scans. The data are usually summed around unit mass and presented as a bar graph of intensities relative to the base