Question

Compare the methods of capillary electrophoresis and high performance liquid chromatography HPLC. For each method, give an example of when it would be more advantageous than the other one.

Answer 1

Capillary electophoresis and high performance liquid chromatography are separation techinques used in the chemical analysis. Both techniques are based in the difference of the flow rates of the susbtance under determinate conditions.

In the HPLC, the analyzed sample in liquid state is passed through an adsorbent material in a column. The interactions of every substance in the sample with the material, due to dipole interactions, will give several velocities and flow rates. A detector can quantify the flow rate of every substance and it can, then, establish the composition of the sample.

For Capillary electrophoresis, the analyzed sample is put under the influence of an electric field. The charged particles in the sample will migrate with several velocities and a detector can quantify it. We don't need an adsorbent material or a column for this technique

The fundamental difference between HPLC and CE is that the first is based in the distribution of the species in the stationary and movil phase of the system; and the second is based on the electrical properties of the same species. Hence, we can assume that CE is recommended for the analysis of ions and coloidal particles, and the HPLC is recommended to uncharged compounds.

For CE an example of a more advantageous application is the analysis of proteins, polimers and polinucleotids that can be ionized under the influence of a electric field. Its application is widely accepted in the molecular chemistry and biology.

For HPLC an example of a more advantageous application is the analysis of non polar compounds and isomers of hydrocarbons, carbohydrates, drugs and other compounds that describe distribution between the phases in the column.