CRM Terbium (Tb) - Aqueous calibration solution ASTASOL® AN90581N

Importance of Topic

Certified reference materials (CRMs) for elemental calibration are fundamental in analytical chemistry to ensure accuracy, traceability and comparability of measurement results across laboratories and techniques. Aqueous calibration solutions like ASTASOL® AN90581N provide a reliable standard for the quantification of trace elements, supporting quality assurance in research, industry and regulatory compliance.

Objectives and Overview

The primary aim of the study is to describe the development, certification and characterization of ASTASOL® AN90581N, an aqueous calibration solution of terbium (Tb) at a nominal concentration of 1 000 mg/L. The document follows ISO Guide 31 requirements to guarantee traceability to SI units and to supply users with all necessary information on preparation, homogeneity, stability and intended use.

Methods and Instrumentation

The CRM was prepared by gravimetric dilution of high-purity Tb₄O₇ (99.998 %) in 2 % HNO₃ using sub‐boiling distilled acid and ultrapure water (resistivity ≥ 18 MΩ·cm). Certification of concentration and uncertainty (±2 mg/L, k = 2) was established by complexometric titration against SRM NIST 928 and by comparison with an independent reference solution (SRM NIST 3157a). Trace impurity profiling was performed using atomic absorption spectrometry (AAS), inductively coupled plasma optical emission spectrometry (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS).

Main Results and Discussion

The certified value of terbium is 1 000 ± 2 mg/L (976 ± 3 mg/kg), with a solution density of 1.0251 ± 0.0005 g/cm³ at 20 °C. Detailed impurity data show most elements below 0.1 mg/L, with iron at 0.21 mg/L and zinc at 0.064 mg/L. Homogeneity tests confirm uniform composition among bottles, and stability studies support a five-year shelf life if stored between 5 – 30 °C and handled according to instructions.

Benefits and Practical Application

• Provides a high-purity, SI-traceable standard for atomic and molecular spectrometry (AAS, AES, ICP-OES, ICP-MS) and selected electroanalytical methods.
• Ensures reliable calibration and method validation in environmental, pharmaceutical and industrial laboratories.
• Supports inter-laboratory comparability and quality control in regulatory analyses.

Future Trends and Possibilities

Advancements may include multi‐element CRMs with matched matrices, lower uncertainty through improved analytical techniques, and digital traceability platforms. Emerging methods, such as laser‐based spectroscopy and hyphenated techniques, will benefit from reference materials with certified ultra‐trace levels and expanded element coverage.

Conclusion

ASTASOL® AN90581N is a robust, well‐characterized terbium calibration solution, certified according to ISO and accredited standards. Its reliable concentration, low impurity levels and demonstrated stability make it an essential tool for precise trace element analysis in diverse analytical settings.

Reference

ISO Guide 31: Reference Materials – Contents of Certificates and Labels. NIST SRM 928 Complexometric Standard. NIST SRM 3157a Rare Earth Elements in HNO₃ Solution.