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

Document ID

Document ID TE2603

Published Date

Published Date 07/17/2018
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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.

Cobalt Standard Solution, 1000 mg/L as Co (NIST), 100 mL (Product # 2150342)
Silica 3 Reagent Powder Pillows, pk/100 (Product # 27169)
Sodium Sulfite, Anhydrous 454 g (Product # 19501H)

 

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