<Table> <Tr> <Td> </Td> <Td> This article may be in the wrong category or belong in further categories . Please re-categorize this article to list it with similar topics or add further categories if required . If you are satisfied that the article is in the correct category please remove this tag . (November 2017) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article may be in the wrong category or belong in further categories . Please re-categorize this article to list it with similar topics or add further categories if required . If you are satisfied that the article is in the correct category please remove this tag . (November 2017) </Td> </Tr> <P> In analytical chemistry, a calibration curve, also known as a standard curve, is a general method for determining the concentration of a substance in an unknown sample by comparing the unknown to a set of standard samples of known concentration . A calibration curve is one approach to the problem of instrument calibration; other standard approaches may mix the standard into the unknown, giving an internal standard . </P> <P> The calibration curve is a plot of how the instrumental response, the so - called analytical signal, changes with the concentration of the analyte (the substance to be measured). The operator prepares a series of standards across a range of concentrations near the expected concentration of analyte in the unknown . The concentrations of the standards must lie within the working range of the technique (instrumentation) they are using . Analyzing each of these standards using the chosen technique will produce a series of measurements . For most analyses a plot of instrument response vs. concentration will show a linear relationship . The operator can measure the response of the unknown and, using the calibration curve, can interpolate to find the concentration of analyte . </P>

What is the purpose of constructing a calibration curve