Spectroscopy: Chapter 9

Question 1

Which Oxidant results in flame tempuratures ranging from 1700-2400 degrees?

Answer 1

**Air **

Question 2

Which Oxidant results in flame tempuratures ranging from 2500-3100 degrees?

Answer 2

oxygen or nitrous oxide

Question 3

What happens when the flow rate of a flame is **SLOWER **than the burning velocity?

Answer 3

a flashback occurs

Question 4

What happens when the flow rate of a flame is **FASTER **than the burning velocity?

Answer 4

the flame will blow off of the burner!

Question 5

Draw the structure of a flame and label important parts.

Answer 5

• Primary combustion zone
• Interzonal region
• Secondary combustion

Question 6

How high (in cm) is the maximum temperature located in the flame.

Answer 6

2.5 cm above the primary combustion flame

Question 7

How are flow rates controlled?

Answer 7

with double-diaphragm pressure regulators

Question 8

how are flow rates measured?

Answer 8

using a rotameter

Question 9

What is the most common source for atomic absoption measurements?

Answer 9

Hollow Cathode Lamps

Question 10

How narrow are absorption lines in atomic absorption?

Answer 10

0.002 - 0.005 nm

Question 11

How are electrodeless discharge lamps energized?

Answer 11

by an intense field of radio-frequency or microwave radiation.

Question 12

What does a photomultiplier tube serve as in Atomic absorption instruments?

Answer 12

a transducer

Question 13

What two types of interferences can arise in atomic absorption spectrometry?

Answer 13

1. Spectral interferences
2. Chemical Interferences

Question 14

What are the methods for correcting Spectral interferences?

Answer 14

• Two-Line Correction Method
• The Continuum-Source Method
• Background Correcting Based on the Zeeman Effect

Question 15

What is the Zeeman Effect?

Answer 15

when an atomic vapor is exposed to a strong magnetic field causing a spltting of electronic energy levels of atoms, which leads to formation of several absorption lines that happen to be **exactly equal ** to that of the original line from which they were formed

Question 16

what are releasing agents and how do releasing agents aid in the reduction of chemical interference?

Answer 16

they are cations that react with the interferant in order to minimize intereaction with the analyte.

Question 17

what is a protective agent?

Answer 17

protective agents prevent interference by forming stable but volatile species with the analyte.

Question 18

What are three common protective agents?

Answer 18

• EDTA
• 8-hydroxyquinoline
• APCD

Question 19

What are two common releasing agents?

Answer 19

• lanthanum
• strontium

Question 20

What is the most common type of chemical interference?

Answer 20

anions that form compounds of low volatility with the analyte

Question 21

How do you eliminate the effects of shifts in ionization equilibria?

Answer 21

by the addition of an ionization suppressor

Question 22

How does an ionization suppressor eliminate the effect of shifts in ionization equilibria?

Answer 22

it provides a relatively high concentration of electrons to the flame

Question 23

Define Atomization.

Answer 23

the process by which a sample is vaporized and decomposed into atoms usually by heat.

Question 24

Describe a Hallow Cathode Lamp.

Answer 24

has a tungsten anode and a cylinder shaped cathode containing the analyte.

Question 25

How does a Hallow cathode lamp work.

Answer 25

inert gas are ionized, cathode is bombarded and emits atoms, some are excited.

Question 26

What is alvagadros number?

Answer 26

6.02 x 10²³ atoms

Question 27

Define Sputtering

Answer 27

Sputtering is the process in which gaseous cations bombard a cathode surface and eject atoms from the surface into the gas phase.