Overview
ISO 23166:2018 specifies an analytical procedure for the determination of tantalum (Ta) in nickel alloys using inductively coupled plasma optical emission spectrometry (ICP‑OES). The standard covers quantitative measurement of tantalum in the range 0.1 % to 5 % Ta and defines sample preparation, reagents, instrument performance requirements and calculation/reporting rules for reliable results.
Key topics and technical requirements
- Principle: Complete dissolution of a weighed test portion followed by nebulization into an ICP‑OES and measurement of Ta emission intensity (example wavelength: 240.06 nm).
- Range: Valid for Ta contents between 0.1 % and 5 % in nickel alloy matrices.
- Sample preparation:
- Typical test portion: 0.25 g (weighed to 0.001 g).
- Acid digestion using HF, HCl, HNO3, H3PO4 and fuming with HClO4 (perchloric acid), with alternatives provided for difficult matrices.
- Transfer and dilute to a 100 mL volumetric flask; optional addition of an internal reference element.
- Calibration and matrix matching:
- Calibration solutions must closely match the sample matrix.
- Bracketing is required between 0.75 and 1.25 of the sample’s approximate Ta content to compensate matrix effects and spectral interferences.
- If matrix composition is unknown, a semi‑quantitative pre‑analysis is necessary.
- Instrument and performance criteria:
- ICP‑OES with a nebulizer resistant to hydrofluoric acid; PTFE/PFA digestion vessels and class A volumetric glassware.
- Bandwidth (FWHM) for analytical lines