References are a key part of analytical testing. Choosing the right type of reference for your testing procedure is an essential part of process design and achieving the right levels of quality management.
In analytical testing, reference materials are used for calibration, quantification and verification. Using a material with known properties makes it possible to deconvolute the response of the analyte from the response of the instrument. In turn, this results in more accurate measurements of concentration, as well as qualitative measures such as the positions of spectral features for spectroscopic measurements or retention times in chromatography.1
Types of References
Inorganic Ventures provides CRMs for many different applications such as ICP-OES and ICP-MS, Ion Chromatography, titrantions, pH, conductivity, water clarity/quality, as well as a range of buffers, and matrix modifiers, and reagents for colorimetric methods.
What are Certified Reference Materials (CRMs)
Certified Reference Materials occupy the second highest rung in the hierarchy of reference materials. The highest level of references is awarded to metrological standards that an authorized body must issue.
Certified Reference Materials are considered to provide the highest level of accuracy, uncertainty and traceability to an SI unit of measurement.
Key Features of CRMs:
- High accuracy
- Lower uncertainties achieved through rigorous manufacturing and testing procedures for CRMs provide tighter certified values and a higher level of accuracy on the certified values.
- Traceability
- You can have confidence in the certified values provided on the certificate of analysis since it is directly traceable through an unbroken chain of comparisons to the SI (International System of Units).
- Certification
- CRMs prepared and certified under ISO 17034 are often required for use in analytical testing labs by regulatory and accreditation bodies. Purchasing CRMs from an accredited, trusted CRM provider allows analysts to feel at ease during audits as the burden of having to prove the accuracy of their standards is lifted off of them and placed on the CRM provider. Inorganic Ventures provides a detailed Certificate of Analysis for all of our CRM products which includes all information an auditor would need to see, plus some additional information that will be helpful to the analyst for use of the standard.
What are Reference Materials
Reference Materials are a rung down from Certified Reference Materials though still must be supplied by an accredited Reference Material Producer.
While Reference Materials do not give the same level of accuracy as Certified Reference Materials, their advantage is that they are significantly easier to produce. They are still compliant with ISO requirements and for less exacting requirements on traceability, they can offer an excellent cost-effective alternative to Certified Reference Materials.
The correct choice of the level of accuracy of the reference material and the particular standard used is process dependent. Accuracy requirements may be dictated by the need for testing methods to comply with a particular regulation, for example, the requirement of highly accurate quantification for pharmaceutical applications for contaminant testing.
Key features of reference standards:
- Cost-Effective:
- Less rigorous vendor requirements allow reference materials to act as a more cost-effective alternative for processes that do not require the use of certified standards, as less time and fewer resources are needed to ensure compliance.
- ISO Compliance:
- While the requirements are less stringent, reference materials must still be produced by an accredited reference material manufacturer, following ISO accredited procedures to ensure reliability and quality.
- Versatility:
- Reference materials can be provided with the same versatile range of options seen in our certified standards - whether analysts are looking for single, multi-element, organic, or inorganic standards they can be sure that Inorganic Ventures is able to provide reliable reference materials tailored to their needs.
When should I use CRMs instead of Reference Standards?
Reference Standards are really intended more for method validation - to ensure the method is able to achieve accurate results for real samples. The reference standard is generally run as if it were a real sample. Alternatively, reference standards can be used for qualitative analysis (checking for the presence or absence of the analyte), or for obtaining a decent estimate of the amount of analyte present in the sample. Certified Reference Materials, on the other hand, are used as the standard for comparison against to accurately quantify the analyte(s) of interest. CRMs would be used to generate the calibration curve, as the spike solution for standard additions, or as the standard for direct comparison, depending on the analyst's desired testing method. CRMs should always be used to analyze samples for which accurate concentration results are required.
How to choose the right Reference Material
Selecting the appropriate reference material is essential for method validation. When selecting a reference material, ensure that the material is representative of the types of samples you will be analyzing and that analytes in the reference material will behave the same way in the reference material throughout sample preparation and analysis as the analytes in your samples. Any matrix components expected to be in your samples should also be contained in the reference material to ensure that you are able to account for and correct those appropriately in your method. You also want to make sure that the concentrations being analyzed in the reference material are similar to the concentrations that will be analyzed in your real samples.
Summary Table: CRMs vs. Reference Standards
|
Feature |
Certified Reference Materials (CRMs) |
Reference Standards |
|
Accuracy |
Highest level of accuracy |
Moderate level of accuracy |
|
Traceability |
Traceable to SI units |
ISO-compliant |
|
Certification |
Includes Certificate of Analysis |
May include Certificate |
|
Cost |
Higher |
More cost-effective |
|
Ideal For |
Regulatory compliance, high precision |
Routine testing, cost-saving |
Frequently Asked Questions (FAQs) About Certified Reference Materials (CRMs) and Reference Standards
Are all CRMs the same?
Not all CRMs are made equally. It is important to always check the traceability on the CoA for your standard to ensure it is being traced through an appropriate unbroken chain of comparisons to the SI. The majority of our CRMs are certified by two independent methods, using two independent NIST SRMs the standard is traced through. This increases the confidence in our certified values. Additionally, our standards trace directly to the NIST SRM through a direct comparison. The longer the chain of comparisons your standard has gone through to get back to the NIST SRM or other primary SI-traceable standard, the greater the uncertainty in the certified values. Another differentiation of our CRMs vs. others is our 5-year shelf-life for most products, achieved through our Transpiration Control Technology (TCT) bags. We stand behind all of our products and offer a 100% satisfaction guarantee. Our team is always here to offer technical guidance, customized products, and one-on-one support to help you troubleshoot issues and optimize workflows in your lab.
What is the importance of traceability in CRMs?
Traceability provides the foundation for the accuracy of a CRM. Without traceability, there can be no confidence in the analyte values provided for that standard since there is no proof to show those values are accurate.
What is included in a Certificate of Analysis (COA) for a CRM?
The Certificate of Analysis can be thought of as the “proof” of a CRM. Some important information that is listed on our CoAs includes ISO Accreditation information, certified values and uncertainties, testing methods, statistical data and error budgets used to calculate the uncertainty, NIST (or SI) traceability, validity period, and trace metallic impurity information (for ICP standards). A chromatogram is provided in place of TMI information for ion chromatography standards. We also include helpful information such as solution density, instructions for use, expected interferences on ICP-MS and ICP-OES, valence state, and more!
How do I choose the right CRM for my application?
You want to choose a CRM that includes all of your analytes of interest, in the same form as the analytes will be in your samples. For example, if your samples will contain arsenite (As+3), you want to make sure the form of arsenic in the CRM you select is also arsenite, and not arsenate (As+5) as arsenite will have a higher transport efficiency to the plasma than arsenate so an arsenate standard would produce false high results.
You also want to ensure that your CRM is either already matrix-matched to your samples, or that you are able to appropriately matrix match the standards to the samples during your dilution/preparation steps. This requires compatibility of the components in your CRM with the matrix components you need to prep in to match the sample. Our chemists have years of experience and a wealth of knowledge and resources related to solution compatibility and stability. We can advise on the appropriate CRMs and prep methods to use for your specific application and sample matrix.
What should I do if I cannot find a CRM that meets my needs?
Inorganic Ventures specializes in custom CRMs. We can provide standards made to your specific needs for analytes, concentrations, matrix, etc. If you don’t see what you’re looking for on our website, please submit a Custom Quote Request and our expert chemists will help to formulate a customized standard to meet the exact needs for your specific application.
Why Choose Inorganic Ventures for your CRM needs?
ISO accreditation
Inorganic Ventures has been manufacturing and supplying a range of reference materials since 1985.
Inorganic Ventures is an expert in creating and applying Certified Reference Materials and Reference Materials, all of which are supplied with a detailed Certificate of Analysis which is based on requirements and recommendations listed in ISO Guide 30.
All of Inorganic Venture’s CRMs are compliant with ISO 17034 & ISO 17025 guidelines (A2LA 883.01 & 883.02) and NIST-traceable for the highest levels of accuracy.
Diverse range of blends
With over 55,000 approved blends available as stock reference, Inorganic Ventures has an extensive range of reference materials suitable for techniques such as ICP, ICP-MS, atomic absorption and wet chemistry.
In particular, Inorganic Ventures specializes in supplying inorganic standards, including platinum cobalt standards for color measurements as part of water testing.
Customizable samples
While Certified Reference Materials are an excellent tool for quality control and highly accurate measurements, one of the challenges of using such materials can be finding appropriate samples for your procedures. Inorganic Ventures can assist with this and develop and provide custom standards to ensure your results are reliable and repeatable.
Custom Solutions
One of the challenges in using CRMs is finding the right samples for your testing procedures.
When looking for both Certified Reference Materials or Reference Materials, there can almost be an overwhelming amount of choice, including whether to opt for single or multi-element standards and choosing the correct concentrations and conditions. Inorganic Ventures can guide you through the process to find the perfect reference for your application.
Enhance your level of quality control
Improve the efficiency of your lab workflows and improve the confidence in your results by making the switch to our stock and/or custom standards. Let us create CRMs that ensure all of your needs are met for your specific application, sample type, and test method. Together, we can ensure that your lab issues related to compatibility, stability, and inaccurate results become a thing of the past!
Contact Inorganic Ventures today to see how your quality control could be significantly enhanced with the right choice of certified reference materials.
Contact the Inorganic Ventures team.