Question

what is meant by a calibration curve for a colored substance being studied with a spectrophotometer? How is a calibration curve used to determine the concentration of a solution of unknown concentration of the colored substance?

Answer 1

Answer:

The concentration of the analyte is determined by fitting the absorbance or transmittance obtained by spectrophotometric analysis of the unknown solution into the calibration curve.

Explanation:

In a calibration curve, the instrumental response (absorbance or transmittance), is plotted against the concentration of the analyte (the substance to be measured). The analyst is expected to prepare a series of standard solutions of the analyte within a range of solution concentrations close to the expected concentration of analyte in the unknown solution. The method of least squares may be used to determine the best fit of the line, thus, the concentration of the analyte. This method is only used for the determination of the concentration of coloured substances (spectrophotometry).