CRM Nitrites (NO2-) - Aqueous calibration solution ASTASOL® AN90751H

Importance of the Topic

A reliable aqueous calibration solution for nitrite is essential for accurate quantification in environmental, food, pharmaceutical and industrial analyses. Certified reference materials (CRMs) like ASTASOL® AN90751H ensure method validation, traceability to SI units and inter-laboratory comparability.

Objectives and Overview

This document presents the certification of ASTASOL® AN90751H, an aqueous nitrite (NO₂⁻) reference solution. The primary aims are to establish an accurate concentration value, quantify the associated uncertainty, demonstrate homogeneity and stability, and provide direct traceability to kilogram SI units.

Methodology and Used Instrumentation

The calibration solution was prepared by gravimetric dissolution of high-purity NaNO₂ (99.999%) in ultrapure demineralized water (resistivity ≥18 MΩ·cm, 0.22 µm filtered). Key analytical steps include:

• Gravimetric preparation for direct SI traceability.
• Manganometric titration to verify nitrite concentration and calculate expanded uncertainty (k=2).
• Ion chromatography (IC) to detect trace anionic impurities (bromide, chloride, fluoride, iodide, nitrate, phosphate, sulfate), all found below detection limits.

Homogeneity tests confirmed uniform distribution of nitrite across the batch. Accelerated and real-time stability studies validated the solution’s shelf life under specified storage conditions.

Main Results and Discussion

• Certified concentration of nitrite: 1000 mg/L ±2 mg/L (expanded uncertainty, k=2) at 20 °C.
• Solution density at 20 °C: 0.9997 g/cm³ ±0.0005, enabling mass fraction reporting of 1000 mg/kg ±3 mg/kg.
• Trace impurities: all measured anions are below the analytical detection limits, ensuring matrix purity.
• Shelf life: 2 years unopened at 2–10 °C under inert atmosphere; once opened, 12 months within the original shelf life if handled and stored correctly.

Detailed homogeneity and stability data confirm that certified values remain within stated uncertainties when storage and handling instructions are followed.

Benefits and Practical Applications

• Universal compatibility with atomic spectrometry (AAS, AES, ICP-OES, ICP-MS), ion chromatography, molecular absorption spectrometry and electroanalytical methods.
• Direct SI-traceable calibrant simplifies quality assurance and method validation.
• Improves accuracy and comparability in environmental monitoring, food safety analysis, pharmaceutical testing and industrial QC.

Future Trends and Applications

Advancements in reference material development will focus on:

• Multi-analyte calibration solutions combining nitrite with other relevant ions for high-throughput analyses.
• Digital certification formats with machine-readable metadata for seamless integration into LIMS and AI-driven analytics.
• On-site microfluidic systems for on-demand generation of calibration standards, minimizing handling errors.
• Enhanced packaging technologies to further extend stability under variable storage conditions.

Conclusion

ASTASOL® AN90751H provides a high-purity, SI-traceable nitrite standard with low expanded uncertainty and validated homogeneity and stability. Its broad method compatibility and robust certification make it an indispensable tool for accurate nitrite determination in diverse analytical laboratories.

Reference

Certificate for ASTASOL® AN90751H Aqueous Nitrite Calibration Solution, Analytika, spol. s r.o., Certificate Version 01, Date of Issue: 24 October 2023.