Answers to Questions - Forensic Applications of Gas Chromatography - page 145

R = (3.51 - 3.32)/(0.5 (6.5 + 7.9))
Or now, more correctly (after converting all units to seconds),
R = (211 - 199)/(0.5 (6.5 + 7.9))
R = (12)/(0.5 (14.4))
R = (12)/(7.2)
R = 1.7 (no units)
Therefore, compound A and compound B are separated
(resolved).
Chapter 4
1. If two peaks were coeluting with each other at the beginning of a
chromatographic separation at 80°C (isocratic), what could be done
to the method to try to obtain resolution (spread them out)?
Answer: Decrease the temperature at the start of the run; this may
result in a temperature ramp to elute all analytes (if more are
present).
2. If there is a large gap of 6 min in the chromatogram between the
fourth and fifth peaks of a five-analyte mixture, how could the gap
be reduced?
Answer: Introduce a quick temperature ramp.
3. If your first (solvent) peak does not elute from the GC system until
6 min, what can be done to try to reduce the retention time of the
first peak?
Answer: Increase the initial temperature on the temperature pro-
gram to 10°C below that of the solvent.
Chapter 5
1. List the four Qs and explain their purpose in instrument qualification.
Answer: The four Qs are design qualification (initial consider-
ation of what is required of the instrument, including software
requirements; the space and money available, and the training
required), installation qualification (checking the modules and
electrical plugs of the instrument against the purchase order;