Spectroscopy: Chapter 10 Flashcards
What are some types of Atomic Emission Spectrometry?
- Plasma
- Arc
- Spark
What are the four advantages of plasma, arc, and spark atomic emisssion spectrometry (AES) over flame and electrothermal atomic absorption spectrometry (AAS)?
- not as affected by chemical interferences
- most elements are under a single set of excitation conditions which means multiple elements can be measured at once
- plasma sources allow non-metals to be analyzed (Cl, Br, I, S)
- plasma emission methods have concentrations ranging from several orders of magnitude (AAS only has 2-3)
What are the disadvantages of atomic emission spectrometry?
Increased Spectral interferences
More expensive
What is a plasma?
an electrically conducting gaseous mixture containing large amounts of cations and electrons.
What kind of plasma is usually used?
Argon plasma
Plasma can reach up to a temperature of ______ K.
10,000
What are the three types of high-temp plasma?
- Inductively Coupled Plasma (ICP)
- Direct Current Plasma (DCP)
- Microwave Induced Plasma (MIP)
How is sample introduced into the ICP?
by argon flowing at about 1 L/min through the central quartz tube.
What is the most common means of sample introduction for an ICP?
concentric glass nebulizer
In ICP the sample is transported to the tip by the ________ _______.
Explain how.
Bernoulli Effect.
The high velocity gas breaks up the liquid into fine droplets which are then carried into the plasma.
What is another method for introducing liquid and solid samples into a plasma?
electrothermal vaporization.
using electrothermal vaporization, it is possible to get as little as about ____ µL of sample and low absolute detection limits of about ____ng
5 and 1
What are the advantages of having the torch in ICP spectrometers in the axial arrangement over the radial configuration?
- longer path length and higher precision from increased radiation intensity
- Lower detection limits
What are the disadvantages of having the torch in ICP spectrometers in the axial arrangement over the radial configuration?
- the cool plasma tail must be removed from the light path to prevent interference from oxides
How long do sample atoms reside in the plasma before reaching the optical path?
2 ms
____________ is more complete in plasmas than in flames and _____ chemical interferences occur.
atomization; fewer
Why is there a small ionization interference in ICP?
because of the large concentration of electrons in the plasma
What are the three basic types of instruments used for emission spectrometry?
Sub question: out of the three What are the two generally used?
- Sequential Emission Spectrometer
- Multichannel Emission Spectrometer
- Fourier Transform
- Sequential Emission Spectrometer
- Multichannel Emission Spectrometer
How do sequential instruments work?
they are programmed to measure intensities of one elememt at a time
How do multichannel instruments work?
they are designed to measure the intensities of different elements simultaneously.
Sequential Instruments use what type monochromator?
holographic grating monochromator
What are two types of sequential instruments?
- Slew-Scanning
- Scanning Echelle Monochromators
how does a slew-scan spectrometer work?
a grating driven by a multispeed motor that rapidly scans (slews) wavelengths near a line of interest
