Laboratory standards play a crucial role in validation of analysis. It is just not possible to imagine any qualitative or quantitative determination which does not make use of a standard reference material at some stage of its method development and validation.
Traceability of the standard material to its origin is an essential pre-requisite for the use of the material otherwise the reliability of results becomes questionable. It is for this reason that standard reference materials are very costly and cannot be used each and every time that an analytical determination is carried out. A practical approach is to make use of working standards which are prepared using the certified reference material as a benchmark for day to day analytical requirements.
The standard material needs to be preserved under its prescribed conditions otherwise due to degradation its assay and other characteristics will change over the storage period. Even under ideal storage conditions its stability is limited and there is a need to re-validate its parameters .The storage requirements are described here.
Standards should be properly sealed and stored within the recommended storage temperature range. The container material should be inert towards the contents.
Humidity control is also an essential requirement during the storage period. Higher humidity levels often result in faster degradation. For this reason the vials or bottles containing standards should be properly sealed and stored in dehumidified rooms or inside desiccators.
A number of materials are sensitive to light and require protection from exposure to light. Such materials should be stored in amber coloured or aluminium foil wrapped vials or bottles. Light exposure of such materials should be minimized during weighing or volumetric transfer operations.
Handling of standards
The first and foremost requirement is careful handling as spills and breakages can result in considerable monetary loss and drop in sample throughput of laboratories. As the vials and bottles are usually small such containers should be handled carefully to prevent accidental losses.
Transfer of material
Always make use of micropipettes with disposable tips for transfer of standards. Never take out aliquots with the help of droppers as this can lead to contamination. Similarly excess quantities of solid powders should not be returned to the original container after weighing as it can lead to contamination. Make sure to properly reseal the container securely to prevent air oxidation or moisture intake damage over the storage period.
Use clean spatulas
Always use clean spatulas for taking out material from vials. It is advisable to wear disposable gloves when handling standards.
Handling of standards stored under sub-ambient temperatures
Standards stored under sub-ambient conditions need special handling and care. Removal from laboratory refrigerators needs sufficient care to prevent spillage of the required standard or any other material. On removal from lower temperatures water condensation can make the container slippery so extra handling care is required. Further sufficient time should be given to allow it to attain ambient laboratory temperature so that volumes can be correctly measured and errors due to temperature variations can be avoided.
Care during handling and storage in addition to traceability to the source are equally important for standard reference materials. The main objective is to avoid undue material loss, degradation during storage and prevent contamination from other materials. Only when such precautions are taken you will be able to guarantee the validity of your results.