1.) What factors affect Rf values in thin-layer chromatography? 2.) What factors affect the separation on...

1.) What factors affect Rf values in thin-layer chromatography?

2.) What factors affect the separation on the column in column chromatography?

3.) What factors affect the resolution of the substances and their retention times in gas chromatography?

Expert Solution

1. Factors affecting Rf value in TLC

(a) Solvents - Solvent is the carrier for the chemical in the TLC plate, polar solvents reduces the interaction between chemical compounds and TLC place and makes the chemical move faster, and non-polar solvent move slower.

(b) TLC plate - Most TLC plates are made up of silica or alumina, the interaction of chemical with silica or alumina will be different hence affects the Rf value.

(c) Temperature - Temperature changes the solubility of particular chemical in a solvent which also affects the Rf value.

2. Factors affecting the separation on the column in column chromatography

(a) Stationary phase - Depending on silica or alumina, the interaction of the chemical will be different and afects the separation. Similarly the particle size of the Stationary phase change the available surface are hence, particle size of stationary phase also influence the separation.

(b) Solvents - Similar to TLC solubility of a chemical in a particular solvent, polarity of the solvent etc influence the separation.

(c) Column length - The longer the column the better the separation.

(d) Solvent flow rate - the slower the flow rate better the separation.

(e) Temperature.

3. Factors affect the resolution of the substances and their retention times in gas chromatography

(a) Column length - Longer column gives longer retention time , which provide better separation, but peak width get broader.

(b) Gas flow rate - Faster carrier gas flow, reduces the retention time and hence poor separation.

(c) Temperature - Larger temperature means shorter retention time and poor separation.

(d) Properties of the component - Chemical and physical properties of the component such as boiling point, polarity etc. affect the retention time in the column.

queen_honey_blossom answered 2 years ago

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