Restek occasionally receives requests from customers on extending the expiration date on their certified reference material or standards that we manufacture. The short answer to this question is no, Restek conducts real-time stability studies and accelerated stress tests to establish reliable expiration dates. Use beyond the identified expiration date is neither recommended nor guaranteed. While this short explanation gets to the point, a little more clarity on this subject may help you understand the importance of the expiration date.
A day to day example very familiar to most is the expiration date given on milk. This date is established by milk producers to ensure milk quality on an unopened bottle of milk is good for a specific time frame. I don’t drink milk fast or consume a large quantity so I always look at this date before purchasing to provide ample time for consumption. However once you get the milk home and open the bottle, you must take the necessary steps to keep the milk fresh. Storage in the refrigerator under recommended cold temperatures, keep the lid on the milk secure and not cross threaded to let air into the container. I’m unsure of the accuracy of this information, but I’ve heard when stored in a glass bottle the milk tastes better but has shorter shelf life due to exposure to light.
There is a parallel associated with reference standards. The reported expiration date given to the reference standard is for unopened ampules stored at recommended conditions. Through on-going short term and long term stability studies, Restek ensures the reliability and accuracy of these expiration dates. Extension past these dates is unadvisable; we simply have no data to substantiate product quality. It is a good idea to check the expiration date of the standard prior to purchasing. Some standards have long shelf lives (i.e. n-alkanes, 31878) and can be purchased in bulk for convenience. Other standards have much shorter shelf lives (i.e. Acrolein) and should only be purchased on an as needed basis. Expiration dates can be found on the COA’s of each lot under the documentation tab at Restek.com or when placing the order, you can ask our customer service representative.
Under certain circumstances, we have on occasion found it necessary to shorten the expiration dates on certain reference standards. This occurs when a standard’s performance is unexpectedly diminished prior to the established expiration date. By shortening the shelf life, the product reliability can be ensured, and the end-user will be able to use the standard worry free.
Once an ampule is opened, the stated expiration date is no longer valid. The end user should take the necessary precautions to ensure the quality during the usage of the standard. After contents are transferred to the working vial, continue to follow the manufacturer’s suggested storage and handling conditions. Frequent monitoring of the standards with comparison to the initial calibration curve is recommended by methods such as EPA 8260B for opened standards. If the standard is to be diluted, use high purity solvents to prevent contamination or any unintended compound interferences.
Regulatory agencies require analysts to demonstrate the reliability of the standards they have made. The best solution is to turn to manufacturers who take the steps to provide Certified Reference Materials for the analyst to use. A need for worldwide acceptance for Certified Reference Material has prompted manufacturers such as Restek to seek accreditation through regulated agencies such as International Organization for Standardization (ISO). Restek has taken the steps to develop standardized guidelines established through this process are followed to ensure the product will perform as required. Therefore establishing a documented shelf life for these reference materials is critical when reporting data to a regulating agency.
For more information you can visit our frequently asked questions on reference standards.