Recommended Procedure For Analytical Instrument Calibrating

By Author: Calibration Laboratory
Total Articles: 2
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There are many types of instrument available in the market but in calibration process we should select the instrument by which our all requirement for the particular measurement can be fulfilled and the instrument is most convenient for that measurement. So for selection of instrument following point should be considered.

Following are the procedures for calibration of analytics instruments like spectrophotometer, pH meter and conductivity meter, which has been created as per NABL guidelines and shared by leading NABL accredited calibration laboratory in India.

Spectrophotometer Calibration Procedure

> Perform calibration of spectrophotometer (for wavelength accuracy, absorbance, linearity, straylight and matching of cell) as per the spectrophotometer calibration method using at least 3 known concentrations of particular certified reference material.
> Record the value obtained from the spectrophotometer against each certified concentration.
> Put the data of calibration on graph paper (certified concentration V/S absorbance) and prepare calibration curve considering the 3 calibration concentration.
...
... > Check the blank data and 3 point on the calibration curve
> Use the calibration curve for routine analysis to identify the concentration of sample based on the absorbance value.
> Use the calibration curve for one month only.
> Compare the recently prepared calibration curve with earlier calibration curve to detect any system deterioration.

pH Meter Calibration Procedure

> Clean glass and electrodes of pH meter with distilled water and paper. Ensure that the distilled water used in the cleaning of electrodes is having conductivity < 1.5 µS/cm
> Set temperature at 20 °C on pH meter, if the meter is having temperature compensation. If the meter does not have temperature compensation than ensure that the temperature of 20 ± 2 °C
> Ensure that the probe of electrode and temperature sensor is properly connected to the pH meter.
> Dip the electrode of pH meter in 4.0 pH solution. Allow 10 seconds for stability note down the reading. If pH shown by the pH meter is found outside the ± 0.05 pH, adjust It to 4.0
> Remove electrodes from the solution and wash again distilled water.
> Follow the above steps for calibration in solution of 7.0 and 10.0 pH. Note down the readings.
> Record the details in pH meter calibration report for all observation.
> Complete the calibration activities.
> Decide the usability of pH meter after verifying the error against acceptance criteria.

Conductivity Meter Calibration Procedure

> Clean glass and electrodes of conductivity meter with distilled water and paper. Ensure that the distilled water used in the cleaning of electrodes is having conductivity < 1.5 µS/cm.
> Ser temperature at 25 °C on conductivity meter, if the meter allows to adjust temperature compensation. If the meter does not allow temperature compensation than ensure that the temperature of CRM used in the calibration is having temperature of 25 ± 2 °C.
> Ensure that the probe of electrode is properly connected to the conductivity meter.
> Dip the electrodes of conductivity meter in 1000 µS/cm solution. Allow 10 seconds to stabilize. If conductivity shown by the conductivity meter is found outside the ± 0.5% adjusts it to 1000 µS/cm.
> Clean the glass electrodes again and wipe it with paper
> Dip the electrodes of conductivity meter in 100 µS/cm solution. Allow 10 seconds to stabilize. Note down the reading shown by the conductivity meter, must be 100 ± 1%
> Note down the reading shown by the conductivity meter, in the calibration report.
> Clean the glass electrodes again and wipe it with paper
> Dip the electrodes of conductivity meter in 10 µS/cm solution. Allow 10 seconds to stabilize. Note down the reading shown by the conductivity meter, must be 10 ± 2%.
> Note down the reading shown by the conductivity meter, in the calibration report.
> Complete calibration and ensure that all the required details are adequately entered in to calibration report.
> Decide the usability of conductivity meter after verifying the error against the acceptance criteria.

ISO 17025 laboratory consultant written articles concerning ISO 17025 certification, and additionally creates content with what is calibration, calibration process, Thermal calibration and more. I have also offers calibration services, area associates franchisee services offering in India.