Question

Ethylene glycol boiling point-197.30C

1-butanol-117.6C

2-butanol-99.5 C

Butanone-79.4 C

How would a gradient elution(60 C-140 C) impact the chromatogram?

Mobile Phase - Air (Flow Rate = 20 mL/min), Stationary Phase - poly(dimethylsiloxane), Oven Temperature - 75 °C. Ethane-1,2 diol (ethylene glycol), butanone, 1-butanol, 2-butanol In gas chromatography (GC) which component elute first depends on the boiling point. In GC the mixture is first converted to its gaseous states and then passes through the column. The component which has lowest boiling point elutes first and the component which has highest boiling point elutes last

Answer 1

Gradient elution varies mobile phase composition with time where eluting power of the eluent increases during chromatographic run. Effective distribution coefficient ‘k’ is determined by the k of the peak at half distance through the column. In linear gradient the ‘k’ values are about same for all peaks. Hence, all components have similar peak width and resolution does not change over the chromatogram.

In gas chromatography, the analytes in gaseous state passes through the column and the one which has lowest boiling point elutes first and succeeds the one which has highest boiling point. In this way, Butanone elutes first followed by 2-butanol and 1-butanol. finally ethylene glycol elutes.