When is it recommended to perform a zero calibration on the IntelliCAL™ LDO101 Standard Luminescent/Optical Dissolved Oxygen probes?

Document ID

Document ID TE2603

Version

Version 2.0

Status

Status Published

Published Date

Published Date 27/05/2017
Question
When is it recommended to perform a zero calibration on the IntelliCAL™ LDO101 Standard Luminescent/Optical Dissolved Oxygen probes?
Summary
Zero calibration for IntelliCAL™ LDO101 probes
Answer
If the expected dissolved oxygen concentration is below 1 mg/L O 2, it is advisable (and necessary for the most accurate results) to perform a zero calibration along with the 100% water saturated air calibration on the LDO probes. At about 0.50 mg/L O 2, the probe will start to have extremely slow equilibration times. It may take up to 30 minutes to read down to 0.05 mg/L. The probes are capable of reading down this low, however the zero calibration would be needed to obtain accurate results.

Hach does not sell a zero dissolved oxygen standard, but we do sell the individual components to make up the solution.


Zero solution
1. Measure about 150 mL of sample or deionized water into a 250-mL beaker. Add a magnetic stir bar.
2. Add 0.25 g sodium sulfite or the contents of one Silica 3 Reagent Powder Pillow to the water. Stir to dissolve the reagent.
3. Catalyze the reduction of dissolved oxygen by adding 0.1 mL of a 1000 mg/L Cobalt Standard solution to the water.
4. Place the probe in the stirring sample for at least 10 minutes. This solution is good for 30 minutes or more.
 
Silica 3 Reagent Powder Pillows, pk/100 (Catalog Number/Order Code 27169)
Sodium Sulfite, Anhydrous 454 g (Catalog Number/Order Code 19501H)
Cobalt Standard Solution, 1000 mg/L as Co (NIST), 100 mL (Catalog Number/Order Code 2150342)