WCPS: Direct determination of Al, B, Co, Cr, Mo, Ti, V and Zr in HF acid-digested nickel alloy using the Agilent 4210 MP-AES

Importance of the Topic

Nickel alloys are critical materials in sectors requiring excellent high- and low-temperature strength and corrosion resistance, such as chemical process vessels, gas turbines, and jet engine components. Precise quantification of alloying elements (Al, B, Co, Cr, Mo, Ti, V, Zr) is essential because minor compositional changes can significantly impact mechanical properties and service life.

Objectives and Study Overview

This study evaluates a direct analytical method for determining Al, B, Co, Cr, Mo, Ti, V, and Zr in HF-acid-digested nickel alloy using the Agilent 4210 MP-AES. The goals include: establishing a robust sample preparation protocol, demonstrating inert sample introduction to avoid HF neutralization, and validating accuracy, sensitivity, and stability through certified reference material (IN 100 alloy CRM) analysis.

Methodology and Instrumentation

The sample digestion involves mixing ~0.15 g nickel alloy with HNO₃ (3 mL), HCl (9 mL), and HF (2 mL) in PTFE vessels, followed by microwave-assisted dissolution (Milestone UltraWave SRC) under a two-step temperature program (ambient to 250 °C, 1500 W). Digests are diluted to 40 mL with ultrapure water and prepared in triplicate. Calibration standards are matrix-matched in 20 % aqua regia/5 % HF, covering 0–576 mg/L ranges, with lutetium (Lu) as an online internal standard.

Instrumentation:

• Agilent 4210 MP-AES with nitrogen plasma excitation
• Easy-fit inert torch and double-pass spray chamber
• OneNeb Series 2 inert nebulizer with humidifier accessory

Main Results and Discussion

Calibration curves showed excellent linearity (R²>0.999 for all elements except B at 0.997). Method detection limits ranged from 0.003 to 0.10 mg/L in solution, corresponding to 2.8–89 mg/kg in solid samples. An 8-hour continuous measurement demonstrated long-term stability with average recoveries within ±10 % of certified values and precision <5 % RSD. Analysis of the IN 100 CRM yielded recoveries between 93 % and 107 %, confirming accuracy and demonstrating the wide dynamic range capability of MP-AES for simultaneous ppm to percent-level determinations without sample re-dilution.

Benefits and Practical Applications

• Rapid, multi-element analysis of metallurgical samples
• Avoidance of expensive and hazardous gases
• Elimination of HF neutralization steps due to inert introduction system
• Wide dynamic range supports trace and major element determination in one run
• Ideal for QA/QC in alloy production, aerospace, and petrochemical industries

Future Trends and Applications

Advances in MP-AES instrumentation and automation will drive higher throughput and in-field alloy testing. Integration with miniaturized, automated digestion systems could further streamline workflows. Extension of this method to other HF-soluble matrices (e.g., superalloys, ceramics) is a promising direction.

Conclusion

The combination of microwave-assisted HF digestion and the Agilent 4210 MP-AES with inert sample introduction offers a robust, precise, and efficient approach for comprehensive elemental analysis of nickel alloys. The method delivers low detection limits, excellent accuracy, and long-term stability without HF neutralization.

References

1. Amorin A., Kulikov E., Direct determination of Al, B, Co, Cr, Mo, Ti, V and Zr in HF acid-digested nickel alloy using the Agilent 4210 MP-AES, Agilent Technologies, EWCPS17 P# 367.
2. Bureau of Analysed Samples Ltd, Certified reference material IN 100 alloy (BCS/SS-CRM No. 345).