Atomic Spectroscopy for Metal Analysis - Fundamentals of Environmental Sampling and Analysis - page 244

6. Briefly answer the following questions: (a) mechanism of hollow cathode lamp;
(b) atomization procedure in graphite furnace; (c) principles of cold vapor mercury
analyzer; (d) principles for the formation of plasma; (d) how X-ray fluorescence is
produced in XRF.
7. Describe (a) nebulizer and atomizer in the FAA; (b) is there a nebulizer in GFAA?
8. Briefly describe: (a) advantage of GFAA over FAA; (b) why CVAA rather than FAA
should be particularly useful for Hg analysis; (c) advantage of ICP over flame AA;
(d) principal advantage and drawback of XRF and why XRF is unique among all atomic
spectroscopic techniques?
9. In comparing the flame atomic absorption (FAA) and the electrothermal (graphite
furnace) atomic absorption (GFAA): (a) Explain why atomization efficiency is very low
for FAA; (b) Explain why GFAA is much more sensitive than FAA; (c) Explain why
GFAA analysis usually is slower (2-3 min per sample) than FAA (few seconds); (d) What
is the major problem with GFAA.
10. Briefly define what are (a) spectral interference; (b) chemical interference; and

(c) physical interference.
11. The standard method 3500-Li B determines lithium (Li) at a wavelength of 670.8 nm
using a flame emission photometric method. In the Interference section, it states: ''A
molecular band of strontium hydroxide with an absorption maximum at 671.0 nm
interferes in the flame photometric determination of lithium. Ionization of lithium can be
significant in both the air-acetylene and nitrous oxide-acetylene flames and can be
suppressed by adding potassium.'' (a) Describe the spectral interference of this method;
(b) Describe why lithium ionization is a problem and how the addition of potassium can
mitigate such a problem.
12. Sulfate (SO 4 2 ) and phosphate (PO 4 3 ) ions hinder the atomization of Ca 2þ by the
formation of nonvolatile salts. Explain why EDTA (ethylenediaminetetraacetic acid) can
be added to protect Ca measurement from SO 4 2 and PO 4 3 interference.
13. Explain why cesium (Cs) salt should be used to minimize the ionization interference
when analyzing K and Na using FAA.
14. Explain how Zeeman background correction is used to minimize spectral interference.
15. Explain why NH 4 NO 3 is added to seawater when Pb and Ca are analyzed by GFAA
(Hint: NH 4 NO 3 þNaCl ! NH 4 Cl þNaNO 3 ).
16. Explain why (a) HCl cannot be used as a sample matrix when Cu, Pb, Zn, Ca are
analyzed using GFAA; (b) why moisture is needed to be removed in cold vapor gas cell.
17. What are the major factors (criteria) in selecting which atomic spectroscopic instruments
for metal analysis?
18. Generally speaking, which of the following has the lowest (best) detection limits, the
widest linear range, the fastest sample throughput, or the lowest purchasing price:
(a) FAA; (b) GFAA; (c) ICP-OES; (d) ICP-MS?
19. Explain: (a) Why XRF is particularly useful as a tool in screening test of contaminated
site; (b) What problem occurs if flame atomization is used for mercury analysis.
20. ICP-OES has become increasingly popular in environmental labs for metal analysis
and it seems that the flame and flameless AA techniques are diminishing. (a) Explain
why; (b) List major advantages and disadvantages of ICP-OES for elemental (metal)
analysis.