How can I stabilize my bulk turbidity Stablcal® standards to make them last longer?

Document ID

Document ID TE931

Published Date

Published Date 08/01/2019
Question
How can I stabilize my bulk turbidity Stablcal® standards to make them last longer?
Summary
Stabilizing bulk Stablcal® standards
Answer
The expiration date that is printed on the labels of our chemistry is a “closed bottle” expiration. Once the bottle is opened Hach cannot guarantee the stability or the accuracy of the product. Hach would recommend that you use the Stablcal® within 30 days of opening the bottle. You can perform your own stability study experimentally to determine how long the product is accurate after opening; this process involves analyzing the solution weekly or monthly depending on the product.

The instructions below detail transferring the bulk standards to sample cells. If properly performed, the solution in the vial should have stability for up to a year.

The provided alternative can be used for the 100mL or 500mL bottles of Stablcal® standard. Empty sample cells and caps are necessary.

1. Wash the vial and cap with a liquid detergent and water. Liquinox® or equivalent is recommended. (Household liquid detergents or powdered lab detergents are OK).
2. Immediately follow with at least 10 rinses with distilled or deionized water.
3. (Do not perform this step for the <0.1 NTU solution) Gently invert the bottle a minimum of 20 times to completely mix the standard.
4. Immediately rinse the vial and cap 2 times with the Stablcal® standard provided in the 500 mL bottle.
5. Fill the vial to the index band with the Stablcal® and immediately cap the vial.
6. Wipe the outside of the vial until it is dry.
7. Label vial (on the white index band) with NTU value from the bottle.
8. Repeat for all NTU values.
9. Store out of direct sunlight and, optimally, between 20-25° C.