Home > Flashcards > Print Preview
The flashcards below were created by user
on FreezingBlue Flashcards. What would you like to do?
AA requires the analytes to be a ___ state
Each element absorbs in only one particular wavelength (True/False)
False. One particular element has many different possible electronic transitions and therefore many specific wavelengths it absorbs
The ___ electrons undergo transitions when an atom absorbs light in AA
What type of peaks result from atomic absorption?
Very well defined, sharp peaks
An atomic absorption spectrum is also referred to as a
A molecular absorption spectrum is also referred to as
- A continuous, or band spectrum
- It is a broad peak
Two types of line broadening
- Doppler broadening
- pressure broadening
This type of broadening can be minimized by adjusting the flow rate
This type of broadening is worse at higher temperatures
If you're getting unwanted molecular spectral lines, what can you do? What species are likely causing them?
- Change wwavelength
- Use a higher temperature fflame
- Caused by OH-, CN-, other radicals
The line spectrum from the HCL is ____ than the atomic vapor spectra
Sharper, since the HCL is at a lower temperature and pressure than the flame
What element can't be used in a HCL?
Mercury ( it would pour out)
Electrodeless discharge lamp
An EDL uses the __ of a metal, which is ionized when an ___ is excited by ____
A ___ has a higher light intensity (10-100x) but is less stable than ___
A chopper splits the light, which corrects for
- Electronic noise
- variations in lamp intensity
The process by which a sample is vaporized and decomposed to its atoms
The formation of a fine suspension of liquid droplets
Only about ___ of the sample actually reaches the flame
5% or less
Name three types of flameless AA
- Graphite ffurnace
- Hydride generation
- Cold vapor
Name two types of burners
- Total consumption burner
- laminar flow premix burner (what we've used)
Which type of flame tends to be noisier?
Name three zones of the flame, which one is usually used for the AA light beam?
- Primary combustion zone
- interconal region, most common, hottest area
- outer cone
Burner height has an affect on
As temperature increases, the number of atoms in ground state...
As wavelength increases, atoms in ground state...
Two ways to control flame temperature
- Adjust air flow or fuel flow
- switch fuel type or air type
Graphite furnace atomic absorbance
Two ways in which matrix modifiers work
- Cause the interferences to vaporize before the analyte
- Keep the interferences tied up so that the analyte vaporizes first
Why can't you simple heat up your sample in the graphite furnace as fast as possible?
The sample will splatter, making threport ductilereport ductile
Graphite furnace is a good technique for which elements?
Metalloids (almost metals) such as As, Se, Te, also lead
Hydride generation atomic absorption spectrometry
Order the following from lowest to highest detection limit: ICP, Hydride Generation, Flame AA, Graphite Furnace
- Hydride Generation (0.2 ppb)
- Graphite Furnace (1 ppb)
- ICP (40 ppb)
- Flame AA (100 ppb)
Does HGAAS use a nebulizer?
Does the oxidation state of the metalloid matter for hydride generation?
Yes, it is crucial
What is dangerous about the waste from HGAAS?
It is strongy acidic
What moves the generated hydride gas into the optical cell?
An inert purge gas pushes it through
Is time from chemical reaction to the optical cell important in HGAAS?
Yes, shorter time is best and it must be consistent
Cold Vapor AA is useful for what element?
Why can mercury be analyzed with Cold Vapor AA?
It has a high vapor pressure
What are some advantages of Cold Vapor AA?
- Fewer matrix interferences
- Fewer spectral interferences
- Improved detection limits
What chemical reactions must occur to prepare the mercury for analysis by Cold Vapor AA?
- Oxidation (releases Hg from its compounds)
- Reduction (converts all Hg ions to elemental Hg)
Why is a scrubber needed after Cold Vapor AA analysis?
Because the mercury vapors are toxic
What are 2 disadvantages of Cold Vapor AA?
- Intensive sample prep
- Hg contamination in the lab
If another element in your sample absorbs at the same wavelength as your analyte, what could you do?
- Choose a different wavelength
- Do sample prep before analysis to separate the interfering species
Which emits a broader band - deuterium lamp or the HCL?
Deuterium (its a molecule)
Name 2 limitations of deuterium correction
- Udercorrection or overcorrection can occur
- The HCL and D2 lamp must be aligned perfectly
The term for the splitting of electronic energy levels using a magnetic field so that several absorption lines are formed for each electronic transition.
The Zeeman effect is mainly used for what AA technique?
Name two types of chemical interferences
- Formation of unwanted compounds
Two ways to deal with interferences caused by unwanted molecules forming with your analyte
- Releasing Agent - add something which reacts with the interferant more than your analyte does, thus freeing up the analyte
- Protective (Masking) Agent - Forms a complex with the analyte preventing anything else from getting to it
Which type of flame is ionization more of a problem with?
What can you do if you're experiencing ionization interferences?
Add an ionization suppressor such as K
Easily Ionizable Element
What element may cause ionization problems (by being greedy for electrons)?
Mercury typically has a ___ hold time than other elements. Why?
- Shorter (Hg has a 26 day hold time instead of 6 months)
- It's more volatile