Glossary - Stellar MS - Stellar Mass Spectrometer Operating Manual - Glossary - Stellar MS

The sample interface between the liquid chromatograph (LC) and the mass spectrometer (MS).

A soft ionization technique operating at atmospheric pressure. Electrons from a corona discharge initiate the process by ionizing the mobile phase vapor molecules, forming a reagent gas. Charged species are generated in the gas phase.

Ionization performed at atmospheric pressure by using atmospheric pressure chemical ionization (APCI), heated-electrospray (H-ESI), or nanospray ionization (NSI).

A soft ionization technique that shows an ion generated from a molecule when it interacts with a photon from a light source.

Sets the ion injection time to maintain the optimum quantity of ions for each scan, based on the intensity of ions in a previous scan. The recorded spectral intensities are reported as the flux of ions per second passing through the gate by dividing the measured number of ions at the detector by the injection time.

The outer-coaxial gas (nitrogen) that assists the evaporation of the sample solution as it exits the ESI, APCI (optional), or APPI (optional) spray insert. The mass spectrometer heats this gas to the user-specified vaporizer temperature.

Data used to represent mass spectral peaks in terms of two parameters: the centroid (the weighted center of mass) and the intensity. The data is displayed as a bar graph. The normalized area of the peak provides the mass intensity data.

A neutral gas used in the collision cell to undergo collisions with ions.

A method of fragmentation where ions are accelerated to highkinetic energy and then allowed to collide with neutral gas molecules such as helium. The collisions break the bonds and fragment the ions into smaller charged product ions and neutral fragments.

Helium gas introduced into the ion trap mass analyzer that slows the motion of ions entering the mass analyzer so that the ions can be trapped by the RF voltage fields in the mass analyzer.

A valve on the mass spectrometer that can be plumbed as a divert valve or as a loop injector.

Converts ions in solution into ions in the gas phase by using electrospray (ESI) in combination with heated auxiliary gas.

HCD involves the use of high-energy collisions to induce dissociation of ions within the Ion Concentration Routing Multipole (ICRM). It is a form of Collision Induced Dissociation (CID), but we use the term HCD to differentiate between CID occurring in the 2D linear Ion Trap. HCD enables the generation of extensive fragmentation patterns, allowing for the structural elucidation of complex molecules.

A waveform applied to the linear ion trap that ejects all ions except the SIM ion or precursor ion.

Focuses and transmits ions from the API source to the mass analyzer.

The mass spectrometer can operate in either of two ion polarity modes: positive or negative.

A metal disk with a circular hole in the center that allows the ion beam to pass.

A process that produces a mixture of ionic species that is then separated according to the mass-to-charge ratios (m/z) of the ions to produce a mass spectrum.

An instrument that ionizes sample molecules and then measures and analyses the ions according to their mass-to-charge ratio (m/z). The resulting mass spectrum is a characteristic pattern for the identification of a molecule.

An abbreviation used to denote the quantity formed by dividing the mass of an ion (in Da) by the number of charges carried by the ion. For example, for the ion C7H72+, m/z = 45.5.

The scan power n in MSn, which expresses the number of stages of mass analysis. For example, a scan power of n = 1 corresponds to an MS1 (or MS) scan with one stage of mass analysis. A scan power of n = 2 corresponds to an MS2 (or MS/MS) scan with two stages of mass analysis. A scan power of n = 3 corresponds to an MS3 scan with three stages of mass analysis, and so on.

A type of electrospray (ESI) that accommodates very low flow rates of sample and solvent at 1–20 nL/min (for static nanoelectrospray) or 100–1,000 nL/min (for dynamic nanoelectrospray, which is also called nanoESI nanoLC gradient separation).

An electrically charged molecular species that can dissociate to form fragments. The fragments can be electrically charged or neutral species. A precursor ion can be a molecular ion or an electrically charged fragment of a molecular ion.

An electrically charged fragment of an isolated precursor ion.

Data representing mass spectral peaks as point-to-point plots, with each point having an associated intensity value.

A measure of the dispersion of a group of measurements relative to the mean of the group. Relative standard deviation is expressed as a percentage of the average value. The percent standard deviation is calculated as: %RSD = 100 × (S / X) where S is the standard deviation and X is the sample mean.

Each scan is one mass analysis (ion injection and storage/scan-out of ions) followed by ion detection. After the scans are summed, the scan data is sent to the data system for display, storage, or both. The process of ramping the amplitude of the RF and DC voltages on the multipole rods in the mass analyzer to transmit ions from the lowest mass to the highest mass of a specified scan range.

The scan power n in MSn, which expresses the number of stages of mass analysis. For example, a scan power of n = 1 corresponds to an MS1 (or MS) scan with one stage of mass analysis. A scan power of n = 2 corresponds to an MS2 (or MS/MS) scan with two stages of mass analysis. A scan power of n = 3 corresponds to an MS3 scan with three stages of mass analysis, and so on.

The inner coaxial gas (nitrogen), which is used in the API source to help nebulize the sample solution into a fine mist as the sample solution exits the ESI or APCI nozzle.

The ratio of the signal height (S) to the noise height (N). The signal height is the baseline corrected peak height. The noise height is the peak-to-peak height of the baseline noise.

Nitrogen gas that flows out from the gap between the sweep cone and the ion transfer tube into the API source. Sweep gas aids in solvent declustering and adduct reduction.

A device that delivers a solution from a syringe at a specified rate.

The sum of the ion current intensities across the scan range in a mass spectrum.

A vacuum pump that provides a high vacuum for the mass spectrometer and detector system.

A thick-walled, aluminum chamber, with various electrical feedthroughs and gas inlets, which encloses the API stack, ion optics, mass analyzers, and ion detection system.