Mass Spectrometry and Spectroscopy Terminology

A comprehensive set of flashcards covering key terms and definitions in mass spectrometry and spectroscopy.

70 eV electrons (MS)

The standard electron energy used in electron ionization mass spectrometry, providing reproducible ionization patterns.

90° pulsed excitation (NMR)

A radiofrequency pulse that tips magnetization from the z-axis into the xy-plane, maximizing NMR signal.

Absorbance

A logarithmic measure of light loss by a sample; A=−log10T=log10(P0/P).

Aerosol

A suspension of fine liquid or solid droplets in a gas, produced in processes like nebulization.

Air/acetylene flame

A combustion flame used in atomic absorption and emission spectrometry as an atomization source.

Argon plasma (ICP)

A highly ionized argon gas sustained by RF power, providing high temperatures for atomizing analytes.

Atomization

Conversion of analyte species into free atoms in the gas phase, typically done via flame or plasma.

Base peak (MS)

The most intense peak in a mass spectrum, with its intensity set to 100%.

Beam chopping

Interruption of a light beam to convert a steady signal into an AC signal.

Beer’s Law

The relationship A=εbc describes absorbance's dependence on molar absorptivity, path length, and concentration.

Blackbody radiator

An idealized object that emits radiation based solely on its temperature.

Boltzmann distribution

The statistical distribution of particles among energy levels at thermal equilibrium.

Chemical interference

Error in spectroscopy signals caused by reactions that alter analyte atomization.

Chemical ionization (CI)

A soft gas-phase ionization technique that forms protonated or adduct ions.

Chromophore

The part of a molecule responsible for light absorption during UV-Vis spectroscopy.

Derivatization

Chemical modification of analytes to enhance their detectability or stability.

Detection limits

The lowest concentration of analyte that can be reliably distinguished from the blank.

Deuterated internal standards

Isotopically labeled chemicals used to correct for matrix effects in mass spectrometry.

Deuterium arc lamp

A UV light source used for measurements in the ultraviolet region.

Dispersion

The separation of light into its component wavelengths using a prism or grating.

Double beam

Spectrophotometer design that measures sample and reference beams simultaneously.

Dynodes

Electrodes in a photomultiplier tube that amplify the number of electrons generated from a photon.

Electron ionization (EI)

A mass spectrometry ionization method producing radical cations via high-energy electrons.

Electron multiplier detector

A detector that amplifies ions by converting them to electrons and cascading them.

Electronic transition

Promotion of an electron between energy levels, responsible for UV-Vis absorption/emission.

Emission monochromator

Device isolating a specific emission wavelength in fluorescence or ICP-OES.

Emission spectrum

A plot of emitted intensity versus wavelength from excited atoms or molecules.

Excitation monochromator

Monochromator that selects the excitation wavelength in fluorescence spectroscopy.

Exponential decay waveform

Signal characterized by exponential decrease, relevant in NMR and fluorescence decay.

Flame atomic absorption

Technique measuring absorption of radiation by ground-state atoms atomized in a flame.

Flame atomic emission

Technique measuring emitted light from excited atoms returning to lower energy states.

Fluorescence

Prompt light emission from an excited singlet state to a lower singlet state.

Fluorophores

Molecules or groups that emit fluorescence after absorbing light.

Fourier series

Representation of periodic waveforms as sums of sine and cosine terms.

Fourier transform

Mathematical operation converting time-domain signals into frequency spectra.

Fragmentation (MS)

Breakdown of molecular ions into smaller ions and neutrals in mass spectrometry.

Free induction decay (NMR)

Time-domain NMR signal observed after an RF pulse.

Frequency

Number of oscillation cycles per second of a wave, measured in hertz.

Frequency domain spectrum

Plot of signal intensity versus frequency obtained by Fourier transforming a time-domain signal.

FTICR

Fourier Transform Ion Cyclotron Resonance mass spectrometry with ultra-high-resolution spectra.

Gaussian waveform (FT)

Time-domain signal with a Gaussian shape, used to control line shape.

Glass cuvette

Rectangular glass cell for liquid samples in visible absorbance measurements.

Graphite furnace

Electrothermal atomization device for AAS increasing sensitivity.

Grating

Optical component with grooves that diffracts light into component wavelengths.

Grooves (gratings)

Finely spaced lines on a diffraction grating determining dispersion and resolving power.

Hard ionization

Methods that impart high energy, causing extensive fragmentation.

High vacuum

Very low pressure required in mass spectrometers to reduce collisions.

Hollow cathode lamp

A line source in AAS emitting sharp lines characteristic of the analyte metal.

Induction coil

Coil used to couple RF power into gases like argon in ICP.

Inductively coupled plasma (ICP)

High-temperature plasma created by RF induction used in atomization.

Infrared radiation

Electromagnetic radiation associated with molecular vibrational transitions.

Interference pattern

Constructive and destructive intensity patterns produced by coherent waves.

Interferogram

Signal recorded in an interferometer transformed to obtain a spectrum.

Internal conversion

Non-radiative relaxation between electronic states of the same spin multiplicity.

Internal standards

Known compounds added to correct for variations in measurements.

Intersystem crossing

Non-radiative transition between electronic states of different spin multiplicity.

Ion source

Region in mass spectrometers where neutral species are converted into gas-phase ions.

Ionization

Process of forming ions from atoms or molecules by gaining or losing electrons.

Ionization interference

Error arising when analyte ionization is affected by easily ionized species.

Ionization suppressor

Species added to minimize ionization interference in atomic spectroscopy.

Isobaric

Referring to species with the same nominal mass but different composition.

Isobaric interference

Interference in MS when species with the same nominal mass overlap in peaks.

Luminescence

Emission of light from excited states not due to high temperature.

Matrix effects (Atomic)

Changes in analyte signals due to other components affecting efficiency.

Mercury Cadmium Telluride (MCT)

High sensitivity semiconductor IR detector used in FT-IR spectrometers.

Microwaves

Electromagnetic radiation with longer wavelengths used in NMR and heating.

Molecular ion (MS)

Ion corresponding to the intact analyte molecule before fragmentation.

Monochromator

Optical device that isolates a narrow wavelength band from a broader spectrum.

Multichannel detection

Simultaneous measurement at multiple wavelengths or masses using detector arrays.

Multiplex detection (FT)

In FT techniques, measuring all wavelengths at once and separating them mathematically.

Nebulization

Conversion of a liquid sample into a fine aerosol for analytical techniques.

Non-radiative

Relaxation processes where energy is lost without light emission.

Non-volatile

Describes substances that do not readily vaporize, unsuitable for GC.

Phosphorescence

Delayed light emission from a triplet state back to a singlet ground state.

Photodiode array (PDA)

Linear array of photodiodes used to record entire spectra simultaneously.

Photoelectric effect

Emission of electrons from materials upon photon absorption.

Photomultiplier tube

Sensitive vacuum light detector converting photons to amplified electrons.

Plasma temperature

Effective temperature characterizing energy distribution in a plasma source.

pn Junction (PDA)

Interface between p-type and n-type semiconductor regions in photodiodes.

Quartz cell

Cuvette made of fused silica for UV and visible light measurements.

Radiative

Relaxation processes releasing energy as emitted photons.

Radio waves

Long-wavelength electromagnetic radiation used for NMR excitation.

Reference sample

Blank or standard used to correct for sample signal variations.

Relaxation

Return of an excited system to equilibrium involving various processes.

Releasing agents (atomic)

Chemicals that bind interfering species, freeing analyte atoms for atomization.

Resolution

Ability to distinguish closely spaced spectral features or signals.

Resolution enhancement

Techniques used to sharpen spectral peaks and separate overlapping features.

Resolving power (m/Δm)

In MS, the ratio of measured mass to the smallest distinguishable mass difference.

Rotational modes

Motions corresponding to molecular rotation; observed in microwave/IR spectra.

Rotational transition

Change between rotational energy levels producing spectral lines.

Scattering

Redirection of light by particles, contributing to background and analytical use.

Sensitivity enhancement

Strategies that increase signal relative to noise in measurements.

Signal averaging

Summing repeated measurements to reduce noise and improve S/N.

Signal processing

Mathematical manipulation to enhance signal quality in data.

Single beam

Spectrophotometer design measuring only the sample beam sequentially.

Singlet state

Electronic state with all paired electron spins; ground or initial states for fluorescence.

Slit width

Width of entrance/exit slits in a monochromator affecting resolution and throughput.

Soft ionization

Methods minimizing fragmentation while preserving molecular ions.

Spectral interference

Overlap of spectral features complicating quantitative analysis.

Spectrometry

Measurement of spectra focusing on quantitative determination.