REALLY important NEED to know

Question 1

Matrix Matching

Answer 1

Used in analysis to compensate for matrix effects that influence analytical response.

Question 2

4 processes of laser

Answer 2

1. Pumping, a process by molecules in ground state of a laser is excited to E3 by means of an electrical discharge, passage of an electrical current, or
   exposure to an intense radiant source.
2. Spontaneous Emission, a species in an excited electronic state may lose all or part of its excess energy by spontaneous emission of radiation.
3. Stimulated emission, the excited
   laser species are struck by photons that have precisely the same energies. Collisions of this type cause the excited species to relax to the lower energy state and to simultaneously emit a photon. The stimulated emission is totally coherent with the incoming radiation.
4. Absorption, two photons with energies exactly equal are absorbed

Question 3

XRF

Answer 3

1. An incoming x-ray knocks out an electron from an inner atomic orbital
2. An unstable electron configuration is produced
3. An electron from a higher energy orbital fills the hole and excess energy is emitted as a fluorescence x-rays which can be measured

Question 4

ICP torch

Answer 4

very very hot and makes ions to use in MS. Analyte must be separated before entering ICP. Laser adsorption to produce ions. Plasma detected through cooling cone. Extraction lens attracts positive ions from plasma. Ions enter collision cell (with H2 or He). Ions guided to mass spec

Question 5

ESI

Answer 5

used for large molecules where fragmentation is avoided.
Dispersal of fine spray charges droplets followed by solvent evaporation and ion ejection. Sample is injected into high voltage capillary and comes out as a highly charges mist. Solvent evaporated with N2. Molecular ions then repel each other and charged analyte is ejected into mass analyzer.

Question 6

Matrix Assisted Laser Desorption ionization (MALDI)

Answer 6

Analyte is mixed in matrix solvent and applied to metal plate. A laser light hits causing energy absorption. The analyte is ionized and ejected into gas phase and is then accelerated into chosen MS.

Very expensive but has HIGHEST m/z ratio

Question 7

Multiple reaction monitoring (MRM) vs Selected “” (SRM) vs product ion scan (PIS

Answer 7

MRM/SRM monitors each precursor ion/product ion transition at a time.

SRM is monitoring only a single fixed mass window
MRM scans rapidly over multiple mass windows and thus acquires traces of multiple fragment ion masses

PIS used for qualitative applications to obtain structural information.
Q1 is set to allow only the transmission of one m/z. The parent ion collides with Argon gas in Q2 to create fragment or product ions. Product ions are scanned through Q3

All allow relative and absolute quantification of proteins, peptides and metabolites.

Question 8

Adsorption

Answer 8

Solute equilibrates between mobile phase and surface of stationary phase. Adsorbed on surface of stationary phase

Question 9

Ion- exchange

Answer 9

Ions in mobile phase are attracted to counterions covalently attached to stationary phase. Anion exchange resin

Question 10

Partition

Answer 10

Solute equilibrates between mobile phase and film of liquid attached to stationary phase. Bonded to surface of column

Question 11

Affinity

Answer 11

Solute in mobile phase is attracted to specific groups covalently attached to stationary phase. All other molecules wash through

Question 12

Van deemter equation!!
KNOW

Answer 12

Used to find the optimal flow rate for the best resolution!

Question 13

H of Van deemter equation

Answer 13

Plate height

Question 14

A of Van deemter equation

Answer 14

Multiple Flow Paths
The residence time in the column for molecules of the same species is variable. Some flow paths are longer than others.

Question 15

B/Ux of Van deemter equation

Answer 15

Longitudinal Diffusion
Diffusional broadening of a band. Takes place along axis of column and while band is moving along column by flow of solvent. Species migrate from a more concentrated part of medium to a more dilute. The faster the less diffusional broadening.

Question 16

Cux of Van deemter equation

Answer 16

Mass Transfer Coefficients
The finite time required for solute to equilibrate between mobile and stationary phases. Cs Rate of mas transfer through stationary phase. Cm is “ “ mobile phase

Question 17

Chromatography applications
Qualitative and Quantitative

Answer 17

Qualitative: gives either retention time or position on the stationary phase

Quantitative: Peak height (amount of analyte present), Peak area (Shows concentration

Question 18

Gas vs Liquid chromatography
what is it
mobile phase
stationary phase
cost
analytes
Separation
Van D
Detectors

Answer 18

Look at Image

Question 19

Open Tubular Column
Advantages and Disadvantages

Answer 19

Common in GC. Made of fused silica and plymides or support and protection.

Offers high resolution, short analysis time and greater sensitivity then packed columns.

has a less sample capacity

Question 20

Three types of open tubular columns?

Answer 20

Wall Coated: Has a thick film of stationary liquid on inner walls

Support coated: Has solid particles coated with stationary liquid. Can handle larger samples but performance isn’t as good

Porous Layer: Solid particles are the active stationary phase

Question 21

Making Liquid Stationary phase

Answer 21

The choice is base on “like dissolves like” non-polar columns are the best for non-polar solutes (strong for strong ect..). Surface silanol groups are exposed and strongly retain polar compounds by adsorption. To prevent stationary phase bleed silanol is bonded to silica surface.
Column surface deactivated by silanization.

Question 22

Column Bleeding?

Answer 22

Occurs at high temperatures where the stationary phase decomposes and the products elevate background signal and increase interference.

Question 23

How to reduce column bleeding?

Answer 23

To reduce this use the thinnest stationary phase on the narrowest and shortest column

Question 24

Temperature programming?

Answer 24

Temperature of column is raised during separation to increase analyte vapour pressure and decrease retention time.

Question 25

white powder?

Answer 25

test to see if the compound is organic or inorganic
1) Burn it → if it burns it is organic, it it doesn’t it is inorganic
2) Do an XRF → if the result is mainly silica it is organic, but if significant amounts of metals are present, it is inorganic

inorganic:
o Do an acid digestion to dissolve the insoluble powder
o Perform atomic absorption spectroscopy to test for metals (ex. Fe, Mn, etc.) and their percent by weight

organic:
o Perform an FT-IR (ATR since insoluble)
o The vibrational spectra gives a very good detailed fingerprint region which will tell us very quickly what the unknown white powder is once compared to reference spectra

Question 26

priceless painting?

Answer 26

o XRF - X-ray Fluorescence
it is non-destructive and therefore will not ruin or alter this priceless painting
Through XRF, I would obtain a good idea of the sorts of metals present in the pigments the artist used
However, for this information to even mean anything, a known authentic painting from this artist would also need to be analyzed under XRF to obtain a “standard reference” of how much metals are present in the pigments this author is known for using

o FT-IR (ATR)
Can provide information on the bonds in the pigments, canvas/leather/paper used for the painting. Once again, a known authentic painting from this author would need to be analyzed under FT-IR as well to compare to the suspected forgery

o ICP-MS (AAS)
Because ICP-MS requires very little to no sample, a little thread from the canvas or even a small amount of pigment shaved off the edge is enough to test for the 13C/12C isotope ratios
For this to be of use, we must be certain of what kind of canvas or pigment the artist used for his/her work