By Marvin McMaster
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From these data, we can calculate a retention factor k (also called the capacity factor), a separation factor a and an efﬁciency factor n. Finally, using these values, we can produce a resolution equation combining all of these factors. 2 Gas chromatograph column parameters. 3 SEPARATION PARAMETERS AND RESOLUTION 33 make in a separation during methods development or as diagnostic aids in following separation changes due to column aging over time. 5, tr, B$1, and $2. Since we have baseline resolution between the two peaks, we have a useable separation.
Variation in the injector pressure will lead to variations in chromatographic retention times. Automated electronic pressure control (EPC) was introduced to control this variable. It also offers potential as gradient control variable similar to solvent programming in HPLC. By reducing the pressure at speciﬁc points in the chromatographic run, compressed areas of the separation can be allowed further interaction with the column to improve resolution. Widely separated peaks can be eluted more rapidly by increasing the pressure.
Temperature is the major control variable used in gas chromatography. Elevated temperature decreases retention time k, but it also can lead to separation a effects. Peak positions do not always maintain their relative position as the temperature is increased. This can be useful when the effect causes peak changes in the correct direction, but the effect is difﬁcult to predict. Because the effect is not instantaneous, there is a lag time that varies with oven design. This leads to some variations in methods when running samples on different manufacturers’ equipment.