Question

An isothermal chromatogram at 90 °C shows an elution order of 1-pentanol followed by ethylene diamine followed by diethylene glycol. But in order to reduce the overall time of the experiment, a temperature programmed chromatogram is tried, beginning at 60 °C and increasing to 190 °C over 5 minutes then holding at 190 °C for 4 minutes. Predict the elution order of the compounds using the temperature programmed conditions.

Answer 1

The new elution order expected will be the following:

1. ethylene diamine
2. 1-pentanol
3. diethylene glycol

Please see below for details and explanation.

Step-by-step explanation:

Which compound will elute first depends on a number of factors. The compound with the lowest boiling point will elute before another compound with a higher boiling point and so on. By extension, the volatility of the compound will also be considered when predicting elution order. Thirdly, how the solutes interact with each other during the stationary phase. I've listed the boiling points below:

1-pentanol 138 °C

ethylene diamine 116 °C

diethylene glycol 245 °C

The advantage of using temperature programmed chromatogram is that it changes retention times (time needed for the solute to pass through the column). And it will be according to the respective boiling points.

Hope that answers the question, have a great day!