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Standards are a key component in accurate chemical quantitative analysis; without accurate and precise standards the data that is produced can be suspect. Reference materials and standards are necessary to the analytical process giving the analyst the ‘known’ to compare against their ‘unknown’.
Despite being a critical part of the laboratory workflow, the scope of standards, certified reference materials and uncertified reference materials is not always clearly delineated. There are many challenges in the creation, analysis, and maintenance of reference materials. The modern analyst and reference material supplier face more challenges and regulations to incorporate into their analysis than ever before.
This presentation will examine the definitions, function and roles of standards and CRMs as well as the current accreditations, regulations, and challenges. We will look at the proper uses, dilutions, and analysis of standards to reduce error and their role in method validation and verification.
Patricia Atkins – Senior Applications Scientist Spex®, an Antylia Scientific company
Patricia Atkins is a Senior Applications Scientist. She is a graduate of Rutgers University in NJ and was laboratory supervisor for Ciba Specialty Chemicals in the Water Treatment Division. Patricia later accepted a position conducting research and managing an air pollution research group within Rutgers University’s Civil & Environmental Engineering Department. In 2008, Patricia joined Spex as a senior application scientist in our certified reference material’s division and spends her time researching industry trends and developing new reference materials. Patricia has been involved with many industry-focused advisory and regulatory groups including AOAC, ASTM, ACIL, NACRW and the Emerald Conference. She is a frequent presenter and speaker at numerous conferences including NACRW, NEMC, Pittcon and AOAC and is a published author with her work appearing in various journals and trade publications including Spectroscopy, LCGC and Cannabis Science and Technology where she is a columnist for analytical issues in cannabis testing.
It depends upon the type of laboratory you work in and the quality management system you follow. ISO 17025 laboratories are required to purchase and use certified standards from an ISO 17034 provider. If you are involved in R&D or other types of non-regulated activities, you may not be required to purchase certified standards, but, if you are involved in generating defensible data or in a QC environment, you are probably required to use some sort of commercial standards when available.
Many quality management systems have a procedure for creating in-house standards and reference materials when commercial products are not available. Check with your quality manager to discuss. Otherwise, just because a particular compound or element does not appear to be commercially available in a RM supplier’s catalog, it does not mean that you cannot request a custom standard to be made with the targets you need. It is always a good idea to contact us at Spex to see if we can help you fill your standards needs.
Serial dilutions are a common way to make curves, but they can also be a source of error if there is a mistake in the measurements. Calibration curves can be generated in many ways including using a single verified stock solution or stock standards. You can then use that concentration to make each dilution individually. It is sometimes also possible to perform mass on column calibration curves where the autosampler injection volume is changed to create different points. You should check which of these strategies are part of the SOPs governing your instrumentation and analyses. Not all techniques are valid for all systems and analyses.
Purchasing prepared standards can save you time, energy, personnel, and money. A lot of time can be invested in searching out the correct purity and grade of materials and a lot of cost in the acquisition of the chemicals, not to mention the time to do raw materials testing, validation, and QC before their use to make standards. Add in the time and manpower it takes to prep the standards and QC them. You will find that it can be a time-consuming and expensive processes using manpower which could be dedicated to other processes. In addition, there are costs of disposal of excess or expired raw materials. These materials may be purchased for only a few analyses and then sit unused from that point forward until they expire and need disposal.
There are different processes for inorganic and organic standards from the use of acids and water to solvents. Inorganic instrumentation calibration curves are expected to be very linear and almost always pass through zero for most instruments, but organic instruments often have higher matrix effects with cal curves that are sometimes less than linear and have often measurable noise.
It depends on the standard and the method. In many cases, reference materials and standards are high-purity compounds in a solvent matrix, so the methodology is straightforward. For matrix matched or solid RM, the methods are often employed around the regulation or testing requirement the standards are produced to meet. For example, the testing of phthalates in children’s toys by Consumer Products Safety Commission (CPSC). In this case, the method was tested and validated by CPSC. The standards were made to accommodate the method. Standards are an essential component of validating methods and should therefore be able to be validated or verified by known methods if both the method and the standards are robust.
We would need more information about exactly what you need to accomplish and the materials you are using in your processes. Not all solids, matrices and standards are fit for purpose. If you wish to discuss your process you can contact us at Spex. As for the question as to adding liquid matrix by weight or volume, generally our calculations are weight/volume but as we said earlier, we would have to understand your process to give you better advice.
Spex does not deal in radionucleotide standards. If you are looking for isotopically labeled organic standards or deuterated standards, we do have a few different possibilities. On the inorganics side we have depleted uranium and other standards as well as some isotope standards, but we tend not to deal with active or undepleted materials.
ISO 17025 laboratories are required to purchase and use certified standards from an ISO 17034 provider. Other regulatory agencies may have requirements for the purchase of standards in either their QMS or individual methods; so you must consult your regulatory body and quality assurance manager to make sure you are following your guidelines.
Most custom standards are certified against NIST-traceable standards or weight sets and confirmed using instrumentation depending on the designated custom and its requirements. A very small portion of the standards are certified only gravimetrically. Usually, these are custom standards which fall below analytical limits for Spex instrumentation. They are created using stock solutions compared to NIST-traceable standards and weights, verified by instrumentation, and then diluted under observation gravimetrically to their final form and concentration.
Spex has been manufacturing custom standards in its New Jersey facility for over sixty years.