Matrix CRM of sewage sludge METRANAL® CRM AN-OK01

Importance of the Topic

The accurate characterization of sewage sludge is essential for environmental monitoring, regulatory compliance and safe reuse or disposal. Certified reference materials (CRMs) support traceable measurements, method validation and quality assurance in laboratories analyzing persistent organic pollutants and trace elements in complex matrices like sewage sludge.

Objectives and Overview of the Study

This work describes the preparation, certification and intended use of METRANAL® CRM AN-OK01, a powdered sewage sludge reference material spiked with selected polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and trace elements. The study aims to deliver a homogeneous, stable CRM with assigned certified and indicative values to support metrological traceability and interlaboratory comparability.

Methodology

The original sewage sludge was ground to a particle size below 100 μm and sterilized by 25 kGy radiation. Organic analytes were introduced by spiking, and inorganic elements were determined in aqua regia extracts following ISO 11466. Homogeneity and short-term stability were verified in accordance with ISO Guide 35. Dry mass corrections were applied by oven-drying at 105 °C.

Used Instrumentation

• Gas and liquid chromatography (for PCB and PAH quantification)
• Flame and electrothermal atomic absorption spectrometry (AAS)
• Inductively coupled plasma optical emission spectrometry (ICP-OES)
• Inductively coupled plasma mass spectrometry (ICP-MS)

Main Results and Discussion

Certified values for seven PCB congeners range from approximately 110 to 310 µg/kg with expanded uncertainties (k=2) of 4–29 µg/kg. PAH concentrations span about 1.2–5.5 mg/kg with uncertainties of 0.12–0.49 mg/kg; several lower-level PAHs were designated as indicative. Elemental contents in aqua regia extracts include arsenic (10.3 mg/kg), cadmium (6.76 mg/kg), chromium (66.8 mg/kg) and zinc (675 mg/kg), among others, with uncertainties reflecting characterization dominance. All results are reported on a dry mass basis.

Benefits and Practical Applications

METRANAL® CRM AN-OK01 provides laboratories with a benchmark for validating analytical methods and calibrating instruments when determining organic pollutants and trace metals in sewage sludge. It ensures method performance, supports accreditation requirements and facilitates the transfer of property values to routine samples of similar composition.

Future Trends and Potential Applications

As regulatory scrutiny of emerging contaminants intensifies, CRMs like AN-OK01 can be expanded to include new analyte classes (e.g., halogenated flame retardants, pharmaceuticals). Advances in high-resolution mass spectrometry and miniaturized sample preparation may benefit from tailored matrix CRMs. Moreover, digital reference data integration could enhance method standardization across global networks.

Conclusion

CRM AN-OK01 addresses critical needs in environmental analysis by offering a well-characterized sewage sludge matrix with certified organic and inorganic values. Its demonstrated homogeneity, stability and metrological traceability underpin reliable analytical workflows and quality control in regulatory and research laboratories.