Storage of Laboratory Standards
Laboratory standards play a crucial role in validation of analysis. It is just not possible to imagine any qualitative or quantitative analysis which does not make use of a standard reference material at some stage of its method development and validation. The proper storage of standards is essential to obtain accurate and repeatable analysis results. Although not all reference standards have special storage instructions, the following general guidelines should assist you with the proper storage of these critical resources.
Several Common Storage Methods
The storage method of standards depends on their chemical properties and stability. Here are several common storage methods:
- Storage at room temperature: It is suitable for storage of chemically stable products, and the products should be stored in a dry and cool place at the same time.
- Refrigerate at 2-8 ℃: It is suitable for storage of the substance that is not very stable at room temperature.
- Freeze at -20 ℃: It is suitable for storage of the substance whose chemical properties is not stable and that is easy to decompose under normal temperature.
- Freeze at -80 ℃: It is suitable for storage of bioactive substances.
Note: A number of materials are sensitive to light and thus require protection from exposure to light. Such materials should be stored in amber coloured or aluminium foil wrapped vials or bottles. In addition, light exposure of such materials should be minimized during weighing or volumetric transfer operations.
Storage of Standards Prepared into Solution
It is not recommended to use volumetric bottles as storage containers for standards which is formulated into solutions, due to contamination and transpiration issues. Store the standard in containers that will not contribute to contamination of the standard. Low density polyethylene (LDPE) is an excellent container for most inorganic standards. In addition, store the solution in a cool, dry place at room temperature unless the product label indicates refrigerating or freezing. Because the substance is not easy to decompose at low temperatures, but the low temperature reduces the solubility of the compound, which may lead to the crystallization of the compounds that are difficult to dissolve at normal temperature, and it is difficult to dissolve again once the crystallization.
How to Store the Standards After Opening
Once opened, the standards are generally stored in accordance with the storage conditions specified in the certificate. The shelf life can refer to the shelf life when the product is not in use. The standards of solution type should be used as soon as possible after opening, and it is best to use them all at once. If it cannot be used up, please try to transfer it to a container that can avoid volatilization of the solution, and store it according to the storage conditions given by the certificate, and check the quantity before each subsequent use.
Proper Storage of Volatile Standards
When standards containing highly volatile or gaseous components, it should be pay special attention to their storage way. All standards are packaged in containers that are suitable, if unopened, for long-term storage, as indicated on the label. However, once opened, standards must be transferred to new containers. Micro reaction vessels with valves or capillary bottle are recommended to maximize shelf life and minimize possible ingredient loss. The size of the container should be matched to the volume of the standard to minimize evaporation of volatile components into the headspace.
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