Instrumental Methods Exam 3

vocab list

electronic transition

the movement of an electron from one energy level or orbital to another within an atom or molecule when absorbing UV-vis light

chromophore

a part of a molecule that is responsible for its color because it absorbs specific wavelengths of light causing an electron to get excited

auxochrome

substituent that alters wavelength or intensity of absorption

absorbance

the measure of how much light a substance absorbs as it passes through it

transmittance

the measure of the amount of light that passes through a material calculated as the ratio of radiant energy transmitted to the total radiant energy recieved

beer lambert law

states that a solution’s absorbance of light is directly proportional to its concentration and the path length the light travels through the solution

molar absorptivity

a measure of how strongly a chemical species absorbs light at a specific wavelength

bandwidth

range of wavelengths transmitted by a monochromator

stray light

unwanted light that interferes with an optical system degrading its performance by causing reduced image quality inaccurate measurements and color distortions

monochromator

an optical device that separates polychromatic light into its individual wavelengths and allows for the selection of a narrow band of this light

photomultiplier tube

a vacuum tube that detects very weak light signals by converting photons into electrons and then amplifying the electron signal to create a measurable electrical current

diode array detector

an electronic detector that simultaneously measures multiple wavelengths of light to create a full spectrum unlike traditional detectors that measure at a single wavelength

single beam spectrophotometer

a type of instrument that passes a single light beam through a sample to measure its light absorption

double beam spectrophotometer

a type of instrument that uses two separate beams of light to measure the absorbance or transmittance of a sample

baseline correction

a data processing technique used in spectroscopy and other field to remove unwanted background signal distortion or noise from a spectrum

gas chromatography

an analytical technique used to separate and analyze compounds in a sample that have been vaporized in a carrier gas

carrier gas

an inert gas used in analytical techniques to carry vaporized sample components through a system for separation and detection

injection port

an internal combustion engine fuel delivery methods that sprays fuel into the intake port just before the intake valve to mix with air before it enters the cylinder 

split injection

a gas chromatography technique for high concentration samples where only a fraction of the injected sample enters the column while the rest is vented

splitless injection

a gas chromatography technique used for trace analysis of low-concentration samples where all the vaporized sample is directed onto the column for maximum sensitivity

capillary column

a long narrow hollow tube with a stationary phase coated on its inner surface used to separate components of a mixture

stationary phase

the fixed substance in a chromatography system on which components of a mixture are separated

retention time

the time it takes for a specific substance to pass through a system

dead time

time taken by unrelated species

temperature programming

gradual oven temperature increasing to separate compounds with varying volatilities

flame ionization detector

measures organic compounds by burning them in a hydrogen flame

thermal conductivity detector

measures the concentration of gas by comparing the thermal conductivity of the sample gas to that of a reference gas

electron capture detector

a type of highly sensitive detector used in gas chromatography to detect compounds that have an affinity for electrons

GCMS interface

a crucial component that connects a gas chromatograph column to a mass spectrometer ion source allowing the transfer of separated compounds from the GC to the MS

electron ionization

hard ionization producing reproducible fragmentation

chemical ionization

soft ionization with less fragmentation

mass analyzer

a component in a mass spectrometer that separates ions based on their mass to charge ratio

quadrupole

a distribution of electric charge or magnetization consisting of four equal monopoles or two equal dipoles arranged close together with alternating polarity and operating as a unit

time of flight

analyzer separating ions based on velocity

mass spectrum

a graph that plots the relative abundance of ions in a sample against their mass to charge ratio

molecular ion

an ion formed by removing an electron without fragmentation

fragmentation pattern

the specific was a molecules breaks into smaller charged fragments during ionization

base peak

the tallest peak in a mass spectrum representing the most abundant ion formed during the analysis

library matching

method of identifying an unknown compound or substance using spectral databases

selected ion monitoring

a mass spectrometry technique that improves sensitivity and specificity by only detecting ions of specific predetermined mass to charge ratios rather than scanning the full spectrum

HPLC-high pressure liquid chromatography

an analytical technique used to separate identify and quantify the components within a mixture

mobile phase

a liquid or gas that moves through a chromatography system too carry a sample mixture through a stationary phase

reversed phase chromatography

a separartion technique that uses a non polar stationary phase and a polar mobile phase to separate compounds based on their hydrophobicity

normal phase chromatography

a separation technique where a polar stationary phase is used with a non polar mobile phase

gradient elution

a chromatography technique that gradually increases the eluent strength during a separation by systematically changing the mobile phase composition over time

isocratic elution

a chromatography technique where the mobile phase or solvent has a constant composition throughout the entire separation process

retention factor

a value use din chromatography to quantify how far a compound travels relative to the solvent front

resolution

a measure of how well two peaks are separated with a higher value indicating better separation

column efficiency

a measure of chromatographic column’s ability to produce sharp narrow peaks indicating minimal band broadening

UV-vis detector

measures the amount of UV and visible light absorbed by a sample as it passes through a flow cell

fluorescence detector

measure the light emitted by a sample after it has been excited by a specific wavelength of light

refractive index detector

measures the difference in the refractive index between the mobile phase and the eluent containing the analyte

LCMS-liquid chromatography mass spectrometry

a combined analytical technique that separates compounds in a liquid sample using liquid chromatography and then identifies and measures them based on their mass to charge ration using mass spectrometry

electrospray ionization

a soft ionization technique that creates charged ions from liquid phase analyzed allowing them to be analyzed by a mass spectrometer

atmospheric pressure chemical ionization

a mass spectrometry technique that uses gas phase ion molecules reaction at atmospheric pressure to convert neutral molecules into ions for detection

ion source

a device that generates ion which are charges atoms or molecules by adding or removing electrons

desolvation

the process of removing a solvent from a solute in a solution

mass to charge ratio

a physical quantity that represents a particle’s mass divided by its electric charge

tandem mass spectrometry

an analytical technique that combines two or more mass analyzers to provide more detailed molecular information than a single mass spectrum

collision induced dissociation

a technique used in mass spectrometry to fragment ions by colliding them with neutral gad molecules converting their kinetic energy into internal energy to break chemical bonds

selected reaction monitoring

a target mass spectrometry technique for accurately quantifying specific peptide and by extension proteins in complex mixtures

neutral loss scan

a technique in tandem mass spectrometry used to selectively detect compounds that lose a specific neutral fragment during fragmentation

ion trap

a device that uses electric and magnetic fields to confine ions in a specific space

orbitrap

a type of ion trap mass analyzer used in mass spectrometry that uses an electric field to trap ions and measure their mass to charge ration

high resolution mass spectrometry

an analytical technique that uses mass to charge ratio measurements with high precision to accurately determine the mass of molecules and their ions