Spectroscopy: Chapter 10

Question 1

What are some types of Atomic Emission Spectrometry?

Answer 1

• Plasma
• Arc
• Spark

Question 2

What are the four advantages of plasma, arc, and spark atomic emisssion spectrometry (AES) over flame and electrothermal atomic absorption spectrometry (AAS)?

Answer 2

• 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)

Question 3

What are the disadvantages of atomic emission spectrometry?

Answer 3

Increased Spectral interferences

More expensive

Question 4

What is a plasma?

Answer 4

an electrically conducting gaseous mixture containing large amounts of cations and electrons.

Question 5

What kind of plasma is usually used?

Answer 5

Argon plasma

Question 6

Plasma can reach up to a temperature of ______ K.

Answer 6

10,000

Question 7

What are the three types of high-temp plasma?

Answer 7

1. Inductively Coupled Plasma (ICP)
2. Direct Current Plasma (DCP)
3. Microwave Induced Plasma (MIP)

Question 8

How is sample introduced into the ICP?

Answer 8

by argon flowing at about 1 L/min through the central quartz tube.

Question 9

What is the most common means of sample introduction for an ICP?

Answer 9

concentric glass nebulizer

Question 10

In ICP the sample is transported to the tip by the ________ _______.

Explain how.

Answer 10

Bernoulli Effect.

The high velocity gas breaks up the liquid into fine droplets which are then carried into the plasma.

Question 11

What is another method for introducing liquid and solid samples into a plasma?

Answer 11

electrothermal vaporization.

Question 12

using electrothermal vaporization, it is possible to get as little as about ____ µL of sample and low absolute detection limits of about ____ng

Answer 12

5 and 1

Question 13

What are the advantages of having the torch in ICP spectrometers in the axial arrangement over the radial configuration?

Answer 13

• longer path length and higher precision from increased radiation intensity
• Lower detection limits

Question 14

What are the disadvantages of having the torch in ICP spectrometers in the axial arrangement over the radial configuration?

Answer 14

• the cool plasma tail must be removed from the light path to prevent interference from oxides

Question 15

How long do sample atoms reside in the plasma before reaching the optical path?

Answer 15

2 ms

Question 16

____________ is more complete in plasmas than in flames and _____ chemical interferences occur.

Answer 16

atomization; fewer

Question 17

Why is there a small ionization interference in ICP?

Answer 17

because of the large concentration of electrons in the plasma

Question 18

What are the three basic types of instruments used for emission spectrometry?

Sub question: out of the three What are the two generally used?

Answer 18

1. Sequential Emission Spectrometer
2. Multichannel Emission Spectrometer
3. Fourier Transform

• Sequential Emission Spectrometer
• Multichannel Emission Spectrometer

Question 19

How do sequential instruments work?

Answer 19

they are programmed to measure intensities of one elememt at a time

Question 20

How do multichannel instruments work?

Answer 20

they are designed to measure the intensities of different elements simultaneously.

Question 21

Sequential Instruments use what type monochromator?

Answer 21

holographic grating monochromator

Question 22

What are two types of sequential instruments?

Answer 22

• Slew-Scanning
• Scanning Echelle Monochromators

Question 23

how does a slew-scan spectrometer work?

Answer 23

a grating driven by a multispeed motor that rapidly scans (slews) wavelengths near a line of interest