Chromatographic Methods for Environmental Analysis - Fundamentals of Environmental Sampling and Analysis - page 288

38. Explain the common causes in HPLC having the following: (a) low pressure, (b) high
pressure, and (c) pressure fluctuation.
39. Explain the common causes for both GC and HPLC, regarding: (a) fronting peak,
(b) tailing peak, (c) ghost peak, and (d) split peak.
40. Explain the common causes that result in the following baseline problems: (a) noisy and
spikes, (b) drifting, (c) a gradual rise at the end of high temperature range (GC only).
41. What causes GC column bleeding and how could it be prevented?
42. Suppose you are involved in a GC-MS lab, you injected a mixed calibration standard that
included six benzene series compounds (benzene, toluene, o-xylene, m-xylene, p-xylene,
ethylbenzene) and four chlorobenzene series compounds (chlorobenzene; 1,2-dichloro-
benzene; 1,3-dichlorobenzene; 1,4-dichlorobenzene). However, somehow you could not
find all 10 peaks but observed a total of only seven peaks in the total ion chromatogram
(TIC). The GC-MS library search also indicated that benzene is apparently not shown in
the chromatogram. In addition to seven major peaks, you also noticed a small peak that
does not match any of the chemicals listed above. For each of these three observations,
explain what could be the reason(s), and if there are any possible ways, how to solve the
problem and/or improve the method.