Page 167 - Illustrated Pocket Dictionary of Chromatography

168 RESPONSE FACTOR

response factor The response factor for any given analyte in a
specified system is defined as the peak area (or height)/concentration.
In instances where (1) the system is extremely stable and repro-
ducible, (2) the sample concentration is near that of an external stan-
dard, and (3) the concentration is well within the linear range of the
method, the response factor can effectively be used as a system suit-
ability factor.

a
response index, a A proposed method for comparing how close
a detector response to its ideal response:
+
log R = a logC b
where R is the detector response, C is the analyte concentration, and
b is a constant. In essence, the response index is the slope of the plot
of log R versus log C.
t
response time, t A parameter that is uniquely tied to and differ-
ent for every type of detector. It is typically defined as the time
required for the detector to attain a percent of the final response signal
level (98%). Too slow a response time leads to peak distortion.
restrictor Used to maintain pressure in a chromatographic
system. For example, a restrictor might be placed between the
pressure transducer and the injector when low-viscosity solvents
(e.g., hexane) are used in LC so that the check valve system seats
properly and keeps flow constant and in the direction of the pump to
the detector.

retention factor, k The ratio of the amount of solute in the sta-
tionary phase, N sp, compared to the amount of solute in the mobile
phase, N mp:
k = N sp N mp

The retention factor is most commonly used in describing GC equi-
libria and is a strong function of film thickness (k increases as film
thickness increases).

retention time, t r The time required for a solute to travel from
injection to the detection for set instrument conditions. The value for
t r is designated as occurring at the peak maximum.