Retention times during capillary column separation

Figure 4.8 illustrates both effects for a capillary column test mixture. At 90°C, dodecane is eluted last at around 11 min. As the temperature increases in 10° increments, all of the peaks retention times decrease, and the entire separation takes only 3.6 min at 120°C. The solutes retention times decrease by about half for every 15-20°C increase in colmnn temperature. However, the last two peaks merge at 100-110°C, and naphthalene becomes the last peak at 120°C. Thus, careful attention must be paid to unambiguous peak identification during a separation optimization that includes the column temperature. 

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