Chromatographic Methods for Environmental Analysis - Fundamentals of Environmental Sampling and Analysis - page 287

22. Draw a schematic diagram showing the essential components of (a) HPLC, and
(b) GC-FID.
23. Describe the general strategy in keeping different temperatures in different zone of GC
(i.e., injector, column oven, and detector)? Why is this important?
24. In ion chromatography commonly employed in ion analysis, explain the following:
(a) the separation principle, (b) Why eluent is important? and (b) Why suppressor
column is essential?
25. For anion analysis, what type (anionic or cationic) of exchange resin is used in analytical
column? What type of exchange resin is used in suppressor column? What if cationic
analysis is performed?
26. Describe the principles of measuring F ,Cl ,NO 3 , and SO 2 4

in water by anionic IC

with Na 2 CO 3 NaHCO 3 as the eluting solvents.
27. Name three most commonly used detectors in GC, and one most commonly used
detector in (a) HPLC and (b) IC.
28. Briefly explain the following components in GC: (a) septum, (b) inlet, (c) split/splitless
injector, (d) liner, (e) on-column injection.
29. Briefly explain the purpose of the following components in HPLC: (a) in-line filter,
(b) guard column, (c) degassing unit.
30. Explain the following: (a) Why ECD is highly sensitive to chlorinated pesticides, such as
DDT? (b) Why PCE is more sensitive than TCE in ECD? (c) Why C 12 hydrocarbon is
more sensitive than C 6 hydrocarbon in FID?
31. Describe the following: (a) What chemical functionalities will contribute fluorescence
and can be measured by fluorescence detectors? (b) How halogen substitution affects a
compound's ability to fluoresce?
32. Compare HPLC UV detectors with HPLC fluorescence detectors in terms of sensitivity.
Why for the latter, a 90 right angle is generally used to measure the fluorescence
intensity?
33. Give examples of universal and selective detectors for both GC and HPLC.
34. Given the following: Five GC detectors and five VOCs or SVOCs, find the best
one-to-one matching between these two. Available detectors are: (1) TCD,
(2) FID, (3) ECD, (4) NPD, (5) FPD; Chemicals to be measured are: (a) Merphos
(CAS 150-50-5; (n-CH 3 CH 2 CH 2 CH 2 ) 3 P; a pesticide); (b) Methyl methanesulfonate
(CAS 66-27-3; CH 3 SO 2 OCH 3 ); (c) Hexachlorobutadiene (CAS 87-68-3;

Cl 2 C

CClCCl

CCl 2 ); (d) Ethylbenzene (CAS 100-41-4; (C 6 H 5 )C 2 H 5 ); (e) Mercury

vapor.
35. For the following compound and the sample matrix, which chromatographic instrument
(GC, HPLC, IC) and detector would you recommend? Suggest an EPA standard method
for each chemical as well. (a) trichloroethene (volatile) in air, (b) PAHs in solid wastes,
(c) BETX in soil, (d) acid rain composition (SO 2 4 ,NO 3 , and Cl ), (e) species of
chromium (Cr 6þ ) in water.
36. Why are HPLC and GC mostly complementary with regard to the chemicals each can
analyze? If a chemical can be analyzed by both methods, in what case one is preferred
over the other? How and why?
37. List the desirable characteristics of (a) GC, and (b) HPLC.