When Do Certified Reference Materials Really Expire?
Certified reference materials (CRMs) are vital in a range of industries as they ensure measurements are accurate and reliable. They are commonly used in environmental and pharmaceutical industries, as well as mining and scientific research. One aspect that is often questioned is the expiration date of a CRM - which is a crucial consideration, as it signifies the duration of which the material is expected to maintain its certified properties under recommended storage conditions. This blog post will discuss CRM expiration dates, the factors involved, and when CRMs actually expire.
Explanation of Certified Reference Materials (CRMs)
CRMs are high-quality materials with known properties that serve as benchmarks for calibrating and validating measuring systems.CRMs are necessary to ensure the accuracy of many processes across almost every industry.
How CRMs Are Manufactured
CRMs can be manufactured through many different means depending on the material desired. These materials are meticulously characterized by various testing methods and should achieve traceability to at least one base unit International System of Units (SI). This is usually accomplished for trace metal standards by tracing certified values through the National Institute of Standards and Technology (NIST) in the United States.
Key Characteristics of CRMs
Quality CRMs should be homogeneous and stable substances, allowing analysts to compare their measurement results against the certified values given on the CRM Certificate of Analysis (CoA).
Importance of CRMs in Various Industries
CRMs are invaluable assets in a wide array of industries. They provide a standardized foundation for quality control, method validation, and instrument calibration.
CRMs are extremely important in industries like:
Pharmaceutical:
Pharmaceutical companies need CRMs to authenticate drug potency and purity. The pharmaceutical industry is also mandated to test all pharmaceutical products or specific trace metal impurities to assess potential health risks.These elements are classified based on toxicity and potential contamination risk with the elements As, Cd, Pb, and Hg being tested the most frequently.
Environmental Monitoring:
Environmental testing is a critical component to ensuring public health and preventing dangerous contaminants from entering the food and water supplies. This testing is often done following methods established by the Environmental Protection Agency (EPA) in the US. These test methods require proper traceability through CRMs to ensure the accuracy of results.
Research and Development:
In research and development CRMs are essential for developing and validating new analytical methods. The ISO/IEC 17025 standard and ISO Guides further emphasize the necessity of using CRMs for calibration and validation procedures. CRMs can be used as a “known unknown” to validate method accuracy.
What Determines CRM Expiration Dates?
The expiration date of a certified reference material is crucial to ensure its accuracy and reliability. A CRM’s expiration date depends on three crucial factors while using a standard, which are:
- Chemical stability
- Physical stability
- Human error
Inorganic Ventures has eliminated the first factor and greatly reduced the second, leaving the "human factor" as the primary concern.
Chemical stability
Chemical stability is achieved through our rigorous quoting process to ensure the analytes, matrix components, and concentrations requested will remain stable for the duration of the validity period for that CRM. New products are quoted by our experienced chemists who take great care to ensure there is no risk of precipitate formation, volatilization, adsorption, etc. If there is a concern for long term stability of a requested product, the chemist will make recommendations for options to avoid the instability issue and work with the customer to determine the best formulation to fit their specific needs. All new products undergo a two-step review process by our chemists so customers can count on the quality of the products they are quoted.
Physical stability
Physical stability, also known as transpiration, is a present factor in every liquid CRMs because all containers transpire, thus being physically unstable. As the CRM is used, the transpiration rate is increased. If unopened, a bottled standard (125mL) has a shelf-life of up to twenty-one months; however, the more it is used, the less time it can remain on the shelf.
CRMs manufactured by Inorganic Ventures are packaged in Transpiration Control Technology (TCT) bags. The storage of CRMs inside the TCT bag extends product shelf life up to five years. Upon opening the TCT bag, a typical CRM will be valid for a period of 12 months for a 125mL bottle.
Human error
Mistakes happen, so human error plays a large factor in a standard’s shelf life. Contamination of standards can occur from pipet tips, volumetric glassware, mis-matched bottle caps, loosely screwed caps, dust, vapors, and other potential sources of error. This human error is why we at Inorganic Ventures will not extend the period of validity for products.
Regulatory Guidelines for CRM Shelf Life
Most federal and state regulatory agencies recommend expiration dates not exceeding one year, while some are stricter and require expiration dates of half that time. Using a standard for longer than a year increases the risk of contamination or alteration of the chemical components. It is important to note that the expiration date is defined as the amount of time that a standard should remain in use after opening.
Maintaining the Quality of Opened CRMs
To preserve the quality and validity of opened CRMs, laboratories should use strict storage practices. The key actions include sealing containers tightly to minimize exposure to air, moisture, and contaminants and storing CRMs at the required temperature, away from light or heat sources. These are all crucial for preserving their stability.
Best Practices for Storage
Proper storage of CRMs is critical to maintain accuracy. You should always follow the manufacturer’s recommendations on how to store CRMs when not in use. The storage and handling recommendations for Inorganic Ventures CRMs are usually found in section 7 of the product CoA. Typically you should store liquid trace metals CRMs near 20°C as storing them at increased temperatures will increase the rate of transpiration.
Monitoring CRM Quality Over Time
Laboratories have many methods that help determine the quality of CRMs as they are used. Firstly it is common for many labs to perform an acceptance test for any new lot of CRM that is received. This is usually done by comparing the new lot to the lot that is currently being used.
Laboratories may also use calibration check solutions or second-source standards to verify the quality of CRMs as they are used. This process may include the use of control charts to establish when action must be taken to replace a CRM.
Common Causes of Contamination
Contamination is most likely to occur due to human error as described above. Cross contamination with other CRMs or method reagents is most common. When using liquid CRMs, ensure that container caps are refastened tightly and quickly after the CRM is used. It is best practice to pour out a portion of your CRM into a secondary container to be used for testing to limit the risk of cross-contamination and to not return any portions of the CRM back into the original container.
Risks of Using Expired CRMs
Using CRMs past their expiration date is risky as the accuracy of the CRM is no longer guaranteed. This possible inaccuracy could impact your results or cause failures in your calibration verification. Using CRMs outside of the expiration date may also be against your laboratory’s processes resulting in either samples needing to be re-run or a process deviation to be written.
Can expired CRMs still be used under certain conditions?
This is a difficult question and is based on the accreditations and policies of individual laboratories. While we would not recommend using an expired CRM to calibrate your instrumentation, you may find a use for expired CRMs as method control samples. If you are following ISO practices even Calibration Controls should be within the product’s expiration date, but you could use expired CRMs during new method development if you have qualified the risk of doing so.
What steps should labs take if they suspect contamination?
The first step to tracking down contamination is to test your calibration and method blanks. Typically contamination originates from reagents or containers. If your blanks look clean then you can move on to other possible contamination risks including specific analyst technique, preparation environment, and comparing against second-source CRMs.
How Inorganic Ventures Ensures CRM Reliability
At Inorganic Ventures, we do our utmost to ensure our client's needs are met. However, expiration dates are one area we are not flexible on. Due to transpiration, standards should not be used for more than one year, and our extensive studies and scientific data support this.
To learn more about certified reference materials and their expiration dates, contact inorganic ventures today, and let’s have a chat.
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