Spectroscopy: Chapter 9 Flashcards
Which Oxidant results in flame tempuratures ranging from 1700-2400 degrees?
**Air **
Which Oxidant results in flame tempuratures ranging from 2500-3100 degrees?
oxygen or nitrous oxide
What happens when the flow rate of a flame is **SLOWER **than the burning velocity?
a flashback occurs
What happens when the flow rate of a flame is **FASTER **than the burning velocity?
the flame will blow off of the burner!
Draw the structure of a flame and label important parts.
- Primary combustion zone
- Interzonal region
- Secondary combustion
How high (in cm) is the maximum temperature located in the flame.
2.5 cm above the primary combustion flame
How are flow rates controlled?
with double-diaphragm pressure regulators
how are flow rates measured?
using a rotameter
What is the most common source for atomic absoption measurements?
Hollow Cathode Lamps
How narrow are absorption lines in atomic absorption?
0.002 - 0.005 nm
How are electrodeless discharge lamps energized?
by an intense field of radio-frequency or microwave radiation.
What does a photomultiplier tube serve as in Atomic absorption instruments?
a transducer
What two types of interferences can arise in atomic absorption spectrometry?
- Spectral interferences
- Chemical Interferences
What are the methods for correcting Spectral interferences?
- Two-Line Correction Method
- The Continuum-Source Method
- Background Correcting Based on the Zeeman Effect
What is the Zeeman Effect?
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
what are releasing agents and how do releasing agents aid in the reduction of chemical interference?
they are cations that react with the interferant in order to minimize intereaction with the analyte.
what is a protective agent?
protective agents prevent interference by forming stable but volatile species with the analyte.
What are three common protective agents?
- EDTA
- 8-hydroxyquinoline
- APCD
What are two common releasing agents?
- lanthanum
- strontium
What is the most common type of chemical interference?
anions that form compounds of low volatility with the analyte
How do you eliminate the effects of shifts in ionization equilibria?
by the addition of an ionization suppressor
How does an ionization suppressor eliminate the effect of shifts in ionization equilibria?
it provides a relatively high concentration of electrons to the flame
Define Atomization.
the process by which a sample is vaporized and decomposed into atoms usually by heat.
Describe a Hallow Cathode Lamp.
has a tungsten anode and a cylinder shaped cathode containing the analyte.
How does a Hallow cathode lamp work.
inert gas are ionized, cathode is bombarded and emits atoms, some are excited.
What is alvagadros number?
6.02 x 1023 atoms
Define Sputtering
Sputtering is the process in which gaseous cations bombard a cathode surface and eject atoms from the surface into the gas phase.
