Matrix CRM of sewage sludge METRANAL® CRM AN-OK01

Significance of the topic

The reliable quantification of organic pollutants and trace elements in sewage sludge is essential for environmental monitoring, regulatory compliance, and risk assessment. Certified reference materials (CRMs) like AN-OK01 provide traceable standards that underpin method validation, instrument calibration, and inter-laboratory comparability in environmental and industrial analytical laboratories.

Objectives and study overview

This document certifies a matrix reference material, AN-OK01, consisting of sewage sludge spiked with selected polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and inorganic element fractions. The aim is to deliver metrologically traceable values for use in establishing calibration, validating analytical workflows, and transferring property values to similar sample types.

Methodology and instrumentation

The sludge was milled to a particle size below 100 µm, stabilized by 25 kGy radiation, and bottled under controlled conditions. Homogeneity and short-term stability were evaluated following ISO Guide 35. Metrological traceability was achieved via SI-traceable certified calibration solutions and/or simultaneous analysis of a comparable matrix CRM. Sample preparation involves heated aqua regia extraction (ISO 11466) for element analysis and standard EPA methods (8310, 8082A, 8081 or equivalents) for organic analytes. Recommended instrumentation includes

• Gas chromatography for PCB and PAH separation
• Liquid chromatography for PAH profiling
• Flame atomic absorption spectrometry for major metals
• Electrothermal AAS for trace metals
• Inductively coupled plasma optical emission spectrometry (ICP-OES)
• Inductively coupled plasma mass spectrometry (ICP-MS)

Main results and discussion

Certified values for seven PCBs range from approximately 111 µg/kg (PCB-52) to 307 µg/kg (PCB-28), with indicative values for additional congeners. PAH concentrations include benzo[b]fluoranthene at 3.38 mg/kg and pyrene at 5.46 mg/kg, with uncertainties expanded at a coverage factor of k=2. Aqua regia-extractable elements feature certified As (10.3 mg/kg), Cd (6.76 mg/kg), Cu (205 mg/kg), Hg (2.72 mg/kg), Pb (60.4 mg/kg), Zn (675 mg/kg), and others. Indicative values provided in parentheses reflect limited data. Uncertainty is dominated by characterization variability.

Benefits and practical applications

AN-OK01 enables laboratories to achieve metrological traceability, validate multi-analyte methods, conduct proficiency testing, and support quality assurance in environmental, industrial, and regulatory contexts. Its defined shelf life of five years and storage at –18 °C ensures long-term stability and reproducibility of results across routine and research analyses.

Future trends and applications

Emerging needs include CRMs encompassing novel organic contaminants, microplastics, nanoparticles, and isotopic compositions. Digitalization of certification information and integration of blockchain or QR-code verification could enhance traceability. Expansion of CRM portfolios to diverse environmental and industrial matrices will support evolving analytical challenges and stricter regulatory frameworks.

Conclusion

The AN-OK01 sewage sludge CRM provides a rigorously characterized tool for accurate determination of PCBs, PAHs, and trace elements. Its comprehensive certification, validated stability, and SI-traceable values make it a cornerstone for quality assurance and method validation in environmental analytical chemistry.

References

• ISO Guide 31 Reference materials Contents of certificates
• ISO Guide 35 Reference materials General and statistical principles
• ISO 11466 Soil quality Extraction of trace elements by aqua regia
• EPA Method 8082A Polychlorinated biphenyls by GC
• EPA Method 8310 PAHs by GC
• EPA Method 8081 Organochlorine pesticides