CRM Indium (In) - Aqueous calibration solution ASTASOL® AN90261N

Importance of the Topic

Certified reference materials (CRMs) for aqueous calibration solutions play a critical role in modern analytical chemistry by providing well‐characterized standards for instrument calibration, method validation and quality assurance. Reliable calibration directly impacts the accuracy, precision and comparability of results across laboratories and techniques such as AAS, ICP‐OES and ICP‐MS.

Study Objectives and Overview

The document describes the certification of an aqueous indium calibration solution (ASTASOL® AN90261N) at a nominal concentration of 1000 mg/L. Key objectives include:

• Establishing gravimetric preparation and SI traceability of the solution.
• Determining the certified concentration of indium and its expanded uncertainty.
• Assessing homogeneity, stability and trace impurities for user information.

Methodology and Instrumentation

The CRM was prepared gravimetrically using high‐purity indium metal (99.999%) dissolved in 2% v/v sub-boil distilled HNO₃ and ultrapure water. Traceability to the kilogram was achieved by weighing procedures. Verification of the indium concentration and uncertainty was performed using:

• Complexometric titration against NIST SRM 928.
• Comparative measurement with NIST SRM 3124a by atomic spectrometric techniques.

Used Instrumentation

Trace impurity analysis involved a combination of:

• Flame and graphite furnace atomic absorption spectrometry (AAS).
• Inductively coupled plasma optical emission spectrometry (ICP‐OES).
• Inductively coupled plasma mass spectrometry (ICP‐MS).

Main Results and Discussion

The certified indium concentration is 1000 ± 2 mg/L (k=2, 20 °C), equivalent to 976 ± 3 mg/kg based on density. The solution density was measured as 1.0242 ± 0.0005 g/cm³ at 20 °C. Impurity levels for over 70 elements were reported below detection limits or at trace levels; these values inform users but are not intended for calibration. Homogeneity and stability testing confirmed uniform composition across the batch and guaranteed shelf life under specified storage conditions.

Benefits and Practical Applications

The certified indium solution supports:

• Calibration and validation of atomic spectrometric methods (AAS, AES, ICP‐OES, ICP‐MS).
• Method development for environmental, pharmaceutical and industrial matrices.
• Quality control and interlaboratory comparability in trace element analysis.

Future Trends and Potential Applications

Advancements in CRM development may include multi-element and matrix‐matched standards, digital certification dossiers with machine‐readable metadata, and extended use in emerging techniques like laser-based spectrometry. Integration with laboratory information management systems (LIMS) and blockchain technology could further enhance traceability and data integrity.

Conclusion

The ASTASOL® AN90261N indium calibration solution provides a highly accurate, SI‐traceable standard with well‐defined uncertainty and impurity profile. Its reliable homogeneity and stability make it a valuable tool for calibration and quality assurance in diverse analytical workflows.

References

• ISO Guide 31: Reference Materials—Contents of Certificates and Labels.
• NIST SRM 928 and NIST SRM 3124a documentation for titration and spectrometric verification.