Question

internal standards are often used when performing an analysis by GC. carefully explain what the desirable properties of an internal standard are, sketch an example of the kinds of calibration curve that would be constructed and how you would determine the unknown analyte concentration from the graph (or the best-fit equation describing the calibration line)

Answer 1

Internal standard is a compound which remains unreactive under the given reaction conditions. The internal standard is added before the start of the reaction and its concentration does not change over the period of reaction time.

A proper calibration curve is dilute a known standard solution with known volumes of diluent. We know the concentration of standard in each solution. Carry the run and note the rentntion time and area for each solution.

Now plot concentration on x-axis and area on y-axis. The straight line plot is obtained. Now the unknown is injected into GC and the area is marked on the plot. The corresponding concentration on x-axis is the concentration of the unknown sample.