Analysis of High Purity Titanium Using an Agilent 9500 ICP-QQQ

Significance of the topic

High-purity titanium is essential for semiconductor and aerospace applications where trace impurities at the ppm–ppb level can degrade functional performance, reliability and mechanical integrity. Reliable analytical methods that achieve ultra-low detection limits and robust interference suppression are therefore critical for quality control and material certification. This study demonstrates how triple quadrupole ICP-MS (ICP-QQQ), specifically the Agilent 9500 with Dual-Cell System and m‑lens, can be applied to quantify trace metal impurities in a high-Ti matrix with high accuracy, reproducibility and long-term stability.

Objectives and overview of the study

The study aimed to evaluate the Agilent 9500 ICP-QQQ workflow for quantifying trace impurities in a representative 200 ppm Ti solution prepared from 99.99% Ti powder. Key goals were to:

• demonstrate effective suppression of Ti-based spectral interferences (Ti2+, TiO+ and hydrides),
• establish detection limits and background equivalent concentrations (BECs) for a panel of 25 elements,
• validate accuracy via spike-recovery experiments and
• assess instrument stability during multi-hour sequences.

Analytical performance was assessed using method of standard additions (MSA), spike recoveries after ASTM E2371-21a digestion, and repeated QC checks during extended runs.

Methodology

Sample preparation and digestion:

• Start material: 1 g of 99.99% Ti powder.
• Digestion followed ASTM E2371-21a: HCl, HF and HNO3 added and heated; final solution diluted to produce a 1% Ti digestion solution, then diluted to obtain a 200 ppm Ti matrix for analysis.
• Spike additions: most analytes spiked at 1 μg/g (1 ppm) prior to digestion; Mg and Fe spiked at higher levels (15 ppm and 25 ppm) due to native abundance.

Calibration and QA:

• Calibration by method of standard additions using procedural blank and Ti matrix spikes.
• Procedural blank measured five times to derive DLs; QC sample (200 ppt spikes) measured regularly every five samples.
• Samples A and B (spiked before digestion) measured in ten replicates for recovery and precision assessment.

Interference control and cell chemistry:

• ICP-QQQ operated in MS/MS mode with Q1 selecting precursor m/z entering the reaction cell and Q2 filtering exit ions.
• Two cell gas conditions were used: H2 and NH3 (10% in He) mixed with H2, configured to remove Ar- and Ti-based interferences and Ti-hydrides.
• Mass-shift and on-mass strategies were applied as appropriate (e.g., mass-shift for Cu measured as Cu(NH3)2+ at m/z 97).

Instrumentation used

The main instrumentation and components applied in the study included:

• Agilent 9500 Triple Quadrupole ICP-MS with Dual-Cell System CRC and optional m‑lens (optimized geometry to reduce background from deposited easily ionized elements).
• Agilent I-AS autosampler and OpenLab ICP-MS software v1.1 for control and acquisition.
• Sample introduction: MicroFlow PFA nebulizer (self-aspiration, ~200 μL/min), temperature-controlled quartz spray chamber, quartz torch with 2.5 mm i.d. injector.
• Interface components: Pt‑tipped sampler cone (Cu base) and Pt‑tipped skimmer cone (Ni base) for m‑lens configuration.

Main results and discussion

Interference mitigation:

• Use of NH3+H2 and H2 cell modes effectively removed major Ti-based interferences (Ti2+, TiO+, Ti hydrides), enabling accurate measurement of Na, Mg, Cu, Zn and other elements in a 200 ppm Ti matrix.
• Mass-shift for Cu reduced its BEC from ≈125 ppt (on-mass) to ≈104 ppt (mass-shift to m/z 97), indicating preferential reaction of Cu+ with NH3 and improved background suppression.
• 68Zn on-mass showed a low BEC (~14 ppt) due to lower abundance of interfering TiO at that mass, illustrating isotope selection as an additional mitigation strategy.

Quantification and detection capability:

• Total impurity burden in the original Ti powder, estimated by subtracting procedural blank BECs from Ti matrix BECs and converting to powder concentration, summed to ≈31 ppm—consistent with stated material purity (>99.99%).
• Individual impurity concentrations included notable Mg (~8 ppm) and Fe (~20.2 ppm), with other elements at much lower levels.
• Limits of quantification for the undiluted digestion solution were in the sub‑ppm to ppt range for many analytes; procedural blank-derived DLs (3×SD) were used to define sensitivity.

Accuracy, precision and stability:

• Spike-recovery experiments (spikes added prior to digestion) returned recoveries within ±10% for all measured elements; most RSDs were 1–3% and all <5% across ten replicates.
• Internal standard (In) response remained within 90–120% over a ~3 hour sequence, indicating robust, stable signal and matrix tolerance.
• QC sample recoveries introduced periodically remained within ±10% for most elements and within ±20% for all, supporting long-term reproducibility.

Practical benefits and applications of the method

The combination of Agilent 9500 ICP-QQQ, controlled reaction chemistry and the m‑lens provides several practical advantages for routine QC of high-purity titanium:

• High interference rejection enables accurate quantification of trace metals in concentrated Ti matrices where conventional techniques (XRF, ICP-OES, GD‑MS) may lack sensitivity or specificity.
• m‑lens design reduces background from deposited elements, allowing high-plasma power, matrix-tolerant conditions and sustained ultra-low BECs essential for ppt-level analysis.
• Automated switching between H2 and NH3+H2 modes simplifies operation while maintaining optimized reaction chemistry for a broad analyte set.
• Achieved analytical precision and recovery meet stringent QC requirements for semiconductor and aerospace materials where impurity control is critical.

Future trends and potential applications

Opportunities and developments that can extend or enhance this approach include:

• Further optimization of cell gas flows and reaction conditions for even lower detection limits when analyzing ultra‑high purity Ti (e.g., 99.999%).
• Expanded use of isotopic selection and alternative mass-shift chemistries for challenging interferences in novel alloy or coating matrices.
• Integration with automated sample preparation and high-throughput workflows for production QC environments.
• Application of the Dual-Cell CRC and m‑lens approach to other high-matrix materials (e.g., Cu, Si) where matrix-based polyatomic interferences limit sensitivity.
• Standardization of ICP-QQQ protocols and inter-laboratory validation to support regulatory acceptance in critical industries.

Conclusion

This application study shows that the Agilent 9500 ICP-QQQ equipped with DCS CRC and m‑lens achieves robust interference suppression, low background equivalent concentrations and excellent accuracy and precision for trace metal analysis in a 200 ppm Ti matrix. The method reliably quantified impurities (total ~31 ppm in the tested powder), delivered spike recoveries within ±10% and sustained stable instrument performance over multi-hour sequences. These capabilities make the system well suited for routine QC of high-purity titanium used in semiconductor and aerospace supply chains.

Reference

1. Sugiyama N., Nakano K. Reaction data for 70 elements using O2, NH3 and H2 with the Agilent 8800 Triple Quadrupole ICP-MS. Agilent publication, 5991-4585EN.
2. Sugiyama N. Analysis of Ultratrace Impurities in High Purity Copper using the Agilent 8900 ICP-QQQ. Agilent publication, 5994-0383EN.
3. Ying Y. Analysis of Ultratrace Impurities in High Silicon Matrix Samples by ICP-QQQ. Agilent publication, 5994-2890EN.