How Certified Reference Materials Revolutionize Trace Analysis
In a world of chemical measurements, Certified Reference Materials are the unsung heroes that make modern science possible.
When you hear about environmental contaminants in drinking water or heavy metals in food products, you might wonder: how can scientists be so sure about these invisible threats? The answer lies in a remarkable scientific tool that most people never see—Certified Reference Materials (CRMs). These materials serve as the cornerstone of reliable chemical analysis, ensuring that the measurements we depend on for public health and environmental protection are accurate and trustworthy. In the specialized field of inorganic trace analysis, where scientists detect incredibly low concentrations of elements like lead, arsenic, and mercury, CRMs play an especially critical role in separating fact from fiction in chemical measurements.
At its simplest, a Certified Reference Material is a substance or material with one or more properties that are sufficiently homogeneous, stable, and well-established to be used for calibration, method validation, or quality control in chemical analysis. Think of them as the chemical world's equivalent of a standardized ruler—providing an unambiguous reference point against which all other measurements can be compared.
What makes CRMs special isn't just that they contain known amounts of specific elements, but that this known value is backed by a rigorous certification process and accompanied by a detailed certificate stating the certified concentration and its measurement uncertainty. This certification transforms an ordinary chemical solution into a trusted benchmark that laboratories worldwide can rely on for their most critical analyses.
The true power of CRMs lies in their traceability—the unbroken chain of comparisons that links measurements back to recognized standards. As explained by Inorganic Ventures, a leading CRM manufacturer, "CRMs are required to be traceable to the International System of Units (SI). This traceability establishes a chain of comparisons all the way from the SI to your measurements!" 2
In practical terms, this means that when a laboratory uses a CRM to check their instrument calibration, they're effectively connecting their measurement to the international kilogram maintained in Paris. This global measurement harmony allows environmental agencies in Europe to compare data with researchers in Asia, and regulatory bodies in North America to confidently assess products from around the world.
Traceability Chain Visualization
To understand the real-world importance of CRMs, let's examine a landmark effort to develop specialized reference materials for wastewater analysis—a project that highlights both the necessity of CRMs and the extraordinary efforts required to create them.
In the late 1990s, the European Union adopted several directives establishing stringent water quality standards and objectives. This legislation created an urgent need for reliable monitoring of industrial and urban wastewater to protect aquatic environments from dangerous substances. As noted in a Trends in Analytical Chemistry paper, "Reliable results for the determination of trace elements in urban and industrial wastewater are of paramount importance for both checking the performance of sewage treatment and detecting possible sources of urban or industrial contamination" 3 .
Scientists faced a significant challenge: without appropriate reference materials that mimicked complex wastewater matrices, they couldn't verify the accuracy of their measurements for toxic elements like arsenic, chromium, and lead at low concentrations. This recognition sparked a comprehensive project led by the European Commission's Measurements and Testing Programme (formerly BCR) to develop three specialized wastewater CRMs.
The creation of these wastewater CRMs followed a meticulous multi-stage process that demonstrates the extreme care taken in reference material production 3 :
In November 1999, researchers collected 125 liters of each of three wastewater types from a treatment plant in Madrid, Spain. The samples represented different wastewater streams: influent (entering the plant), effluent (leaving the plant), and industrial effluent.
Scientists filled the wastewater into specially cleaned ampoules, then conducted extensive testing to ensure each ampoule contained identical material. They analyzed 20 randomly selected ampoules from each batch, performing multiple measurements to verify that any variation between ampoules was smaller than the required measurement uncertainty.
The ampoules were stored at different temperatures (+4°C, +20°C, and +40°C) and regularly tested over 12 months to confirm the materials would remain unchanged during storage and shipment to laboratories.
Multiple independent laboratories across Europe, using different analytical techniques, analyzed the materials to assign certified values. This interlaboratory approach provided robust, statistically valid concentration values.
The project resulted in three valuable CRMs that became essential tools for water quality laboratories 3 :
| CRM Reference | Sample Type | Certified Elements | Primary Applications |
|---|---|---|---|
| BCR-713 | Effluent Wastewater | As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Se, Zn | Testing treated wastewater before release into environment |
| BCR-714 | Influent Wastewater | As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Se, Zn | Monitoring wastewater entering treatment plants |
| BCR-715 | Industrial Effluent | As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Se, Zn | Tracking industrial contamination sources |
The certification process utilized a remarkable array of analytical techniques, including ICP-MS, atomic absorption spectrometry with various atomization techniques, and nuclear methods. The agreement between these different methods provided strong evidence for the accuracy of the certified values.
| Technique Category | Specific Methods | Elements Measured |
|---|---|---|
| Plasma Spectrometry | ICP-MS, HR-ICP-MS | As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn |
| Atomic Absorption | FAAS, ET-AAS, HG-AAS | Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn |
| Atomic Fluorescence | HG-AFS | As, Se |
| Nuclear Methods | RNAA | Multiple elements |
This comprehensive approach to CRM development meant that for the first time, laboratories could verify their ability to accurately measure trace metals in complex wastewater matrices. The availability of these materials led to improved data quality for regulatory compliance and gave scientists greater confidence in their environmental monitoring results.
Modern environmental laboratories maintain a diverse collection of CRMs to address different analytical needs. These materials form an essential toolkit for ensuring data quality across various applications and sample types.
Examples: Certipur® AAS standards, TraceCERT® single elements
Primary Applications: Instrument calibration, method development
Key Features: High purity, exact concentration known with low uncertainty
Examples: Custom mixtures for ICP-OES/ICP-MS
Primary Applications: Daily quality control, continuing calibration verification
Key Features: Contains multiple elements at specified ratios, matrix-matched to samples
Examples: BCR wastewater CRMs, NIST environmental SRMs
Primary Applications: Method validation, accuracy assessment
Key Features: Mimics complex sample matrix, certified for multiple elements
Examples: ICP-MS internal standard mixes
Primary Applications: Correction for instrument drift and matrix effects
Key Features: Elements not normally present in samples, used for signal correction
These materials are produced under strict quality systems, typically in accordance with international standards such as ISO 17034 for reference material production and ISO/IEC 17025 for testing laboratories 5 . This ensures that each batch of CRMs meets consistent quality requirements and performs as expected in analytical applications.
While CRMs have long been essential tools for quality control in environmental monitoring, their importance continues to grow in new and expanding areas of analytical chemistry. Recent scientific literature has even proposed that journals should require CRM usage for publications involving quantitative measurements 9 .
CRM Usage in Scientific Publications
This proposal highlights a significant challenge in analytical science: despite the availability of CRMs for decades, many published studies still fail to use them to demonstrate measurement quality. As noted in a 2022 feature article in Analytical and Bioanalytical Chemistry, "the majority of papers published in analytical chemistry journals do not mention the use of CRMs" 9 . Making CRM use mandatory for publication would significantly improve the reliability of published data.
The applications of CRMs continue to diversify as well. Beyond traditional environmental analysis, CRMs now support emerging fields including:
For accurate measurement of drugs and toxins in biological samples, ensuring reliable medical diagnoses and legal evidence.
For regulatory compliance and consumer safety in the rapidly expanding cannabis industry.
For drug development and quality control, ensuring medication safety and efficacy.
This expansion reflects a growing recognition across scientific disciplines that measurement reliability is fundamental to producing meaningful results.
In our modern world, where chemical measurements influence decisions about public health, environmental protection, and regulatory compliance, Certified Reference Materials serve as indispensable guardians of accuracy. They create the invisible infrastructure that allows scientists worldwide to speak a common language of measurement, ensuring that a microgram per liter measured in Tokyo means the same thing as a microgram per liter measured in Toronto.
The painstaking work behind CRM development—exemplified by projects like the wastewater CRMs—demonstrates the extraordinary efforts that scientists undertake to create these crucial tools. This work often goes unrecognized outside specialized circles, but without it, our confidence in chemical measurements would crumble.
As analytical chemistry continues to advance, pushing detection limits lower and tackling increasingly complex sample matrices, the role of CRMs will only grow in importance. They remain our most reliable compass in the expanding universe of chemical analysis, guiding scientists toward ever-greater accuracy and helping build a world where we can trust the numbers that shape our understanding of the chemical environment.
For further exploration of this topic, the Trace Analysis Guide from Inorganic Ventures provides detailed information about method validation and CRM usage in analytical chemistry 6 .