Analytical Notes

Precision

closeness of agreement btw independent test results and stipulation conclusion

Accuracy

Closeness btw results with true value

Repeatability

method completed in single session with same solutions, equipment, and instruments

Reproducibility

precisions under any other set of conditions

determinate error

affects the accuracy

indeterminate error

does not affect the accuracy

Molarity

Molality

Weight % composition

k_eq

for aA + bB → cC + dD

Johnson noise (thermal noise)

random fluctuations of electrons in an electronic device

How do you reduce Johnson noise

lower operating temperature

Shot noise

random variation is small number of photons reaching a detector or small number of electrons and holes in a semiconductor

how can you reduce affects of shot noise

increase signal and integration time, use beam splitter

Flicker noise

random fluctuations in current, power is inversely proportional to frequency

how to reduce flicker noise

signal modulation

What is the UV wavelength range

10-200 nm

what is the near-UV wavelength range

200-400 nm

what is the visible light wavelength range

400-750 nm

Transmittance

where I = intensity of the beam

Absorbance is proportional to

the amount of analyte

what is the IR wavelength range

30-3000 cm^-1

In IR, the higher the frequency, the higher the BLANK, and greater BLANK

bond order, mass difference of atoms

In Raman spec, what can be used as a solvent

water

what happens to a sample in Mass spec

first ionized, then bombarded with a beam of electrons/charged particles

what happens in the magnetic sector of a mass spectrometer

a magnetic field separates ions based on momentum and m/z ratio

What does a quadrupole do in mass spec

only allows ions of a particular m/z show stable trajectory via parallel metal rods

what does an ion trap do in mass spec

isolates charged particales (ions) via m/z so they are detected by their m/z

inductively coupled plasma requires what Ar

high temp

ICP (inductively coupled plasma) is

generated via electromagnetic induction

Direct current plasma requires what Ar

high temp

DCP (direct current plasma)

an electrical arc is struck between two anodes and a cathode to vaporize and ionize samples

microwave induced plasma requires what Ar (or nitrogen)

high temp

MIP (microwave induced plasma)

microwaves are coupled in a discharge tube and ionizes the sample

spark source mass spec

high voltage pulsed spark applied between two electrodes in vacuum

glow discharge

high voltage discharge applied to solid sample under vacuum

electronic transitions are associated with

large dipole changes

steps of atomic spectroscopy

atomization, excitation/absorption, isolation, detection

What does a flame atomizer do

nebulizes sample (creates aersol mist), mist is atomized in high-temp flame

electrothermal atomization (graphite furnace)

sample is evaporated, second heating ashes to solid, third heating atomizes samples

Hollow cathode lamp

puts out wavelength for individual elements

electric discharge lamp

generates light passing electric current through gas/metal vapor

deuterium arc lamp

controlled electric discharge causes D2 to dissociate and emit UV radiation

fluorescence

process in which a molecule emits a photon 10^-8 to 10^-4 s after absorbing a photon (transition between states of the same spin multiplicity)

phosphorescence

emission of a photon during a transition between states with different spin quantum numbers

UHPLC

smaller particle, higher pressure, faster separation

Monochromatic light

single uniform wavelength

directional light

parallel rays in a specific direction

coherent light (laser)

beam of EM waves where photons maintain a constant, predictable phase relationship with one another over time and space

high spectral purity

extreme stability, narrow linewidth (essentially one frequency), and minimal noise

what are components of a michelson interferrometer

beam splitter, fixed mirror, moving mirror, recombination point, detector (interferrogram)

In HPLC, the longer the column, the better the

seperation

surface plasmon resonance

monitors real-time molecular interactions by detecting changes in refractive index

Electrospray ionization is compatible with

LC

resolving power/mass resolution

m/Δm

time of flight

a low m/z ratio will be fastest to detector

selectivity factor alpha =

k₂/k₁

if the selectivity factor is = 1,

poor seperation as k’s are the same

partition coefficient

k= c_s/c_m

lowest parition coefficient k will elute

first

electron capture detector in gas chrom

responds to higher electron affinity (responds to halogenated organics like dicarbondiphenyl)

Flame ionization detector in gas chrom

measures concentration of organics, relies of combustion of carbon atoms

thermal conductivity detector

measures ability of gas to conduct heat (not as sensitive)

Refractive index detector in LC

detects compounds lacking UV absorption (sugars, alcohols, lipids, polymers)

as column temperature increases, retention time

decreases

as column length increases, retention time

increases

as stationary phase film thickness increases, retention time

increases

as intermolecular interactions increase, retention time

increases

what is axial diffusion

solute molecules diffuse from highly concentrated center of sample bands to more dilute regions along and against direction of flow

intersystem crossing

radiationless, excited electron transitions between two states with different spin mulitplicity

internal conversion

molecule enters highly excited vibrational level in an electronic state with the same energy as original vibrational level in the previous electronic state