How is a calibration curve prepared in a colorimeter or spectrophotometer?

Document ID

Document ID TE778

Published Date

Published Date 11/06/2018
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Question
How is a calibration curve prepared in a colorimeter or spectrophotometer?
Summary
Preparing a calibration curve for a colorimeter or spectrophotometer
Answer
Hach colorimeters and spectrophotometers are carefully calibrated during manufacturing and do not require additional calibration. However, most of these instruments have user-entered calibration options for colorimetric tests if desired.

To calibrate an instrument for a particular test, put the instrument in absorbance mode, select the wavelength for the test, and prepare 3 to 10 different concentrations of standard solutions that span the full test range. Follow the Hach procedure (or your own procedure) to develop color in each standard, and the measure the absorbance of each standard in the instrument. Most Hach instruments can record the absorbance and concentration of each standard, and then calculate a calibration curve. Refer to the instrument manual for instrument specific instructions. After the instrument is calibrated, it will calculate the concentration of unknown samples using the calibration curve. More in-depth information on preparing calibration curves can be found in An Introduction to Standards and Quality Control for the Laboratory in the Hach Learning Library.

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