Automated Sequencing of Elemental Speciation Methods Using HPLC-ICP-MS with a Quick Change Valve Head

Significance of the Topic

HPLC-ICP-MS is the preferred technique for trace multi-element speciation across environmental, food and consumer safety laboratories. Automating the exchange of columns and mobile phases addresses the growing demand for high-throughput, reliable analysis of multiple species under different chromatographic conditions.

Objectives and Study Overview

This application note evaluates an automated sequencing approach using an Agilent Quick Change valve head to switch between three distinct speciation methods for arsenic, mercury and halogens. The main goals were to assess system flexibility, reproducibility and stability over multiple unattended sequences and varied method orders.

Methodology and Instrumentation

An Agilent 1260 Infinity II LC system equipped with a quaternary pump and an InfinityLab Quick Change 4-column-selector valve head was coupled to an Agilent 7900 ICP-MS via a dedicated LC-ICP-MS interface kit. Three speciation methods were integrated:

• Method 1: Separation of As(III) and As(V) on an anion-exchange column with phosphate/ethanol buffer (10 min run time)
• Method 2: Methylmercury analysis on a reversed-phase column with L-cysteine mobile phase (4 min run time)
• Method 3: Concurrent separation of bromide, bromate, iodide and iodate on an anion-exchange column with phosphate-sulfate-EDTA mobile phase (8 min run time)

Calibration standards and interspersed DIW flush steps were programmed via the Agilent MassHunter software, enabling fully automated run sequences.

Results and Discussion

All analytes exhibited excellent linearity (R² > 0.9995) across three concentration levels. Intraday precision (RSDr) was ≤ 8% and interday reproducibility (RSDiR) ≤ 10% for all species regardless of sequence order. Recoveries ranged from 90% to 110%, and carryover during wash cycles was reduced below 2%. Each full sequence of 43 injections completed within 5.5 hours, demonstrating stable retention times and peak areas over three days of unattended operation.

Benefits and Practical Applications

• Unattended switching between up to eight speciation methods on a single HPLC-ICP-MS system
• Reduced manual handling, analysis time and operating costs
• High flexibility to run methods in any user-defined order
• Supports compliance with regulatory limits for As, Hg, Cr, Br and I species in food and environmental samples

Future Trends and Potential Applications

Future developments will extend automated sequencing to larger valve configurations, integrate triple-quadrupole ICP-MS for interference removal, and apply advanced data analytics. This platform can be adapted for novel sample matrices, expanded speciation panels and high-throughput screening in regulatory, clinical and industrial laboratories.

Conclusion

The Quick Change valve head approach significantly streamlines multi-species HPLC-ICP-MS workflows, delivering high accuracy, precision and productivity for routine elemental speciation analysis.

Instrumentation Used

• Agilent 1260 Infinity II LC with quaternary pump
• InfinityLab Quick Change 4-column-selector valve head (p/n G4237A)
• Agilent 12-position solvent selection valve (p/n G4235A)
• Agilent 7900 ICP-MS with LC interface kit (p/n G1833-65200)

References

1. P. Apostoli et al., Elemental speciation in human health risk assessment, WHO, 2006.
2. World Health Organization, Guidelines for drinking-water quality, 4th edition with 1st addendum, 2017.
3. US FDA, Guidance for Industry: Action Level for Inorganic Arsenic in Rice Cereals for Infants, 2020.
4. K. L. Ackley, J. A. Caruso, in R. Cornelis et al., Handbook of Elemental Speciation, Wiley, 2003.
5. C. A. Ponce de León et al., J. Chromatogr. A 974 (2002) 1–21.
6. M. Marcinkowska, D. Barałkiewicz, Talanta 161 (2016) 177–204.
7. Agilent Technologies, Handbook of Hyphenated ICP-MS Applications, 5990-9473EN.
8. M. Tanoshima et al., Arsenic Speciation in Apple Juice Using HPLC-ICP-QQQ, 5991-0622EN.
9. S. Sannac et al., Mercury Speciation in Food by HPLC-ICP-MS, 5991-0066EN.
10. J. Nelson et al., Iodine and Bromine Speciation in Infant Formula by HPLC-ICP-MS, 5994-0843EN.