CRM Nitrates (NO3-) - Aqueous calibration solution ASTASOL® AN8076HIC

Importance of the Topic

Reliable calibration solutions are essential for ensuring accurate and traceable measurements in analytical chemistry. Certified reference materials (CRMs) for nitrate determination support critical applications such as environmental monitoring, industrial process control, and compliance with regulatory standards. High-purity aqueous standards enable laboratories to validate methods, assess measurement uncertainty, and maintain quality assurance across diverse analytical techniques.

Objectives and Study Overview

Analytika, spol. s r.o. developed and certified an aqueous nitrate CRM, ASTASOL® AN8076HIC. The main goals were to prepare a stable nitrate calibration solution at approximately 100 mg/L, verify its homogeneity and stability over a five-year shelf life, and establish direct traceability to SI units through gravimetric methods. The certificate follows ISO Guide 31 requirements and aligns with ČSN EN ISO 17034:2017 accreditation standards.

Methodology and Used Instrumentation

• Gravimetric Preparation: Precise weighing of high-purity NH₄NO₃ (99.999 %) and ultrapure water to ensure accurate nitrate concentration and direct traceability to the kilogram.
• Filtration: Passage through a 0.45 µm membrane filter to prevent chromatographic column clogging.
• Density Determination: Measurement at 20 °C to convert mass concentration to mass fraction in mg/kg.
• Ion Chromatography: Quantification of nitrate and trace impurities (bromide, chloride, fluoride, iodide, nitrite, phosphate, sulfate) for informational purposes.
• Comparative Verification: Gravimetric determination cross-checked against NIST SRM 3185 to confirm certified value and uncertainty.

Main Results and Discussion

The certified concentration of nitrate in ASTASOL® AN8076HIC is 100.0 mg/L with an expanded uncertainty of ±0.2 mg/L (k=2) at 20 °C. The corresponding mass fraction is 100.3 mg/kg ±0.3 mg/kg. Trace impurities were found below detection limits (<0.02–0.05 mg/L), confirming high solution purity. Homogeneity tests demonstrated negligible batch-to-batch variation, while accelerated stability studies validated performance over the defined shelf life when stored between 5–30 °C. Clear instructions on storage, handling, and opening procedures ensure maintenance of certified properties throughout use.

Benefits and Practical Applications

• Traceability: Direct link to SI units reduces systematic bias in quantitative analyses.
• Versatility: Suitable for calibration and validation across techniques such as AAS, AES, ICP-OES, ICP-MS, UV/Vis spectrophotometry, ion chromatography, and electroanalytical methods.
• Quality Assurance: Facilitates method performance checks, uncertainty evaluation, and compliance with accreditation requirements.
• Operational Efficiency: Long shelf life and clear handling guidelines minimize waste and laboratory downtime.

Future Trends and Opportunities

The development of multi-component aqueous CRMs, integration with automated sample preparation systems, and digital documentation for real-time quality control represent emerging directions. Advances in microfluidic calibration, on-line monitoring, and enhanced stability through novel packaging materials will further streamline analytical workflows and support sustainable laboratory practices.

Conclusion

ASTASOL® AN8076HIC offers a well-characterized, stable, and traceable nitrate calibration solution tailored for rigorous analytical demands. Its high purity, validated homogeneity, and clear usage protocols make it a valuable tool for ensuring measurement accuracy and reinforcing quality systems in research and industrial laboratories.

Reference

• ISO Guide 31:2015 – Reference Materials – Contents of Certificates and Labels.
• ČSN EN ISO 17034:2017 – General requirements for the competence of reference material producers.
• NIST SRM 3185 – Traceable nitrate reference solution.