Trace Instrumentation

FTIR can analyze __ (states of matter)

solids, liquids, and gases

FTIR is a non-___ technique

destructive

FTIR produces an increase in ___ in order to collec an __

vibrational energies of molecules, absorbance spectrum

For the vibrations to be IR active, changes must occur in the ___

dipole moment

molecules that don’t have dipole moments

diatomic molecules, H2, O2, N2

\# of vibrational modes for non-linear polyatomic molecules

3n-6

\# of vibrational modes for linear polyatomic molecules

3n-5

Symmetric stretching

two bonds stretch in phase

asymmetric stretching

one bond stretches while another compresses

fingerprint region is from

500-1000 cm-1

4 parts of the FTIR

source, IR beam splitter, sample chamber, detector

The FTIR source is made up of a

tungsten filament lamp

The IR beam splitter’s job

beam is split and reflected off a stationary mirror and moving mirror and recombined before traveling through the sample

The IR Beam Splitter allows for

better resolution of closely spaced peaks

The sample chamber of an FTIR can consist of a __or ____

microscope or ATR

The detector of an FTIR can be either a

Deuterated Triclycine Sulfate Pyroelectric (DTGS) or a Mercury Cadmium Telluride Photoonductivity (MCT)

The FTIR microscope has __ instead of glass refracting lenses

aluminum coated reflective surfaces

What is a Diamond Anvil Cell

sample pressed in between two diamond windows

Why do we use a diamond anvil cell

allows the sample to be prepared thin enough for transmission mode on scope

benefit of a diamond anvil cell

easy preparation of difficult samples

Attenuated Total Reflectance is good for

analyzing the outer layers of paint samples, thin samples like plastic bags and adhesives on tape, and liquids

Micro ATR is different from ATR in that the

surface area of crystal is smaller and it is attached onto the objective of the microscope

the 2 FTIR detectors

DTGS and MCT

DTGS aspects

1. room temperature
2. low cost
3. detects heat
4. slow
5. less sensitive
6. limited by the optics (KBr or CsI) of the instrument

MCT detector

1. needs to be cooled with liquid N
2. more sensitive
3. 2 different levels of sensitivity (narrowband is more sensitive than broadband)
4. detects light


1. good for very small samples with an FTIR microscope

SEM uses __ instead of __

electrons, light

SEM: e- are focused onto a specimen from a __

hot tungsten filament

Secondary Electrons give us information about

the surface layers of the specimen

Steep surfaces and edges appear __ than flat surfaces with a SEM

brighter

Backscattered electrons are created when

the electrons go deeper into the sample

higher atomic number elements appear __ than low atomic number elements

brighter

backscattered electrons give us information about the

atomic numbers

in SEM, the e- are collected and amplified by a

cathode ray or TV tube

The __ converts the e- into an image

cathode ray tube

Advantages of the SEM

1. higher magnification
2. higher resolution


1. great depth of focus

X-rays in the SEM are generated from the

electron beam striking the sample

The X-rays in SEM-EDS tell us __ because __

which elements we have, there are characteristic energy values for each element

The EDS part of the instrument can detect the __ and produce a spectrum

X-ray

SEM/EDS will produce 2 different displays

1. image
2. X-ray display

Metallic Samples on the SEM/EDS have

the least amount of sample prep and are great conductors of e-

Non-metallic samples

sample surface will “charge” due to non-conductive surface

for SEM/EDS, it’s good to __ the sample with __

coat, metal or carbon using a Denton Vacuum sputter coater

metallic samples won’t cause __ because they __

burning, spread out easier

With non-metallic samples, you can either __ or use a __ mode

coat the sample, low vacuum mode

Using low vacuum or environmental mode for non-metallic samples prevents

burning of

microspectrophotometer’s main job

evaluate and compare colored material

how does a MSP work

it measures the intensity of light of a definite wavelength transmitted by a substance or solution

source of a MSP

tungsten-halogen illuminator system 50-100W

Microscope’s job in a MSP

concentrate light on the sample (Koehler Illumination)

MSP measures absorption of light in the __ and __ regions

UV and Visible

if you’re absorbing in one color, the __ is being emitted

complementary color

we can’t use the MSP on ___ samples

opaque

isomeric

colors that have the same absorption spectrum

metameric definition

colors that appear similar under certain conditions

source of MSP has __ and __ intensity

high and uniform

MSP contains 4 parts

1. source
2. microscope
3. dispersive system
4. detector

The Dispersive grating System of an MSP’s job

breaks up the light into dif wavelengths

the detector of an MSP can be 1 of 3 things

monochromator, linear diode array, or charge couple device

the monochrometer reads

portions of a spectrum at a time

The LDA or the CCD reads

entire dispersed spectrum at once

the MSP uses __ to focus light onto the sample

mirrors

spectral variation can be caused by a shift in the __ or a __

condenser focus, misalignment of the microscope

pleochroism

a fiber changes color when placed at different orientations to the polarizer on the PL

dichroism

when your sample is changing twice depending on the orientation of the polarizer (goes back and forth)

a way to avoid pleochroism and dichroism

align the known and unknown fibers in the same direction on the MSP

Why would intra-sample variations exist?

due to dyeing techniques of fibers, especially natural fibers

Pyrolysis GC/MS can be used for __ samples like __

solid, fibers/paints/plastics/polymers

the pyrolyzer is a way to __

introduce the sample to the GC

the pyrolyzer’s job is to __

burn up/volatilize samples to inject into the GC

the pyrolysis technique is unfortunately

destructive

tube used for pyrolysis

quartz with heated coils

the mobile phase is usually __ or __

helium or hydrogen

water, oxygen, and hydrocarbon traps are

contaminants

the stationary phase is a

fused-silica capillary column

lengths of capillary columns

15m to 30m

diameter of capillary column

0\.1-0.32 mm ID with film thickness of 0.1-1.0 um

the silica is protected with

polyimide coating

split injection

some of the sample is removed from the overall sample

which technique offers the simplest, most reproducible results?

split injection

splitless injection is when __

the full sample is introduced onto a column head

splitless injection typically injects

80-95% of the sample

advantage of a splitless injection

increase sensitivity for trace components

we require a __ thoughout the oven

uniform temperature

the mass spec works best with __, __ samples

well-separated, pure

what connects the GC to the MS?

transfer line

the transfer line is kept at a __ so that the sample stays volatilized

constant temp

what happens in the ionization chamber?

e- collide with the sample to eject an e- from one e- shell

the ionization chamber is kept at a low pressure in order to __

minimize the secondary ion-molecule collisions

the electron beam is created by a __ with __ eV

heated tungsten filament

result of the electron impact

excess energy causes bonds to break yielding a complex mixture of ions

what does a mass analyzer do?

separates ions according to their mass-to-charge ratio

a common mass analyzer is a

quadrupole

in a quadrupole, two rods have a __ and the other two have __

radio frequency, direct current voltage

ions with a specific __ will pass through the quadrupole at one time

mass to charge value

what allows for the entire mass range to pass?

sweeping ranges of voltages

ions emerge from the quadrupole and are __, __,__ , and ____

detected by an e- multiplier, amplified, and recorded

In the TIC, the ___ is generated, summed, and plotted against time

ion current

SIM stands for

selected ion monitoring

SIM is highly __ and __ for quantitative analysis

sensitive, specific

how much more sensitive is SIM than TIC

10,000x