Role of Water in Ion Analysis

1. Role of Water in Ion Analysis Telis Dimitrakopoulos, Alan Mortimer & Paul Whitehead ELGA LabWater, Lane End Industrial Park, High Wycombe, HP14 3BY, UK www.elgalabwater.com Thursday Sept 21st 2010 IICS 2010: 22nd International Ion Chromatography Symposium

2. Outline • Define the purity of ultra-pure water and compare it to other solvents used in analytical research and testing applications. • Study the impact of ultra-pure water impurities on the reliability and reproducibility of ion chromatography. • Examine the background levels of ultra-pure water for ultra-trace HPLC and ion chromatography analysis. • Geological Age Determination by Ultra trace Analysis.

3. Background • Pure water is a crucial reagent for analytical research and testing applications. • Elements and compounds in the parts per billion (ppb) range or lower could affect results by interacting with samples or system components. • One hundred per cent pure water consists solely of water molecules in equilibrium with hydroxyl(OH-) and hydrogen (H+)ions (10-7M at 25ºC) • Characteristic electrical resistivity of 18.2 Mohm.cm. • Type 1 ultra-pure water is by far the purest reagent used in a laboratory.

4. Sample preparation - extraction - dilution - rinsing Standard preparation - dilution Blanks Data analysis Role of Water in Analytical Chemistry Analytical method Chromatography Other methods - mobile phase - AA, ICP, MS - rinsing

5. Water challenge • Water has the ability to: • dissolve almost every chemical compound to some extent • support nearly every form of life • Water purity is under continual threat from five types of impurities: • Suspended particles; • Inorganic compounds; • Organic molecules; • Dissolved gases; • Micro-organisms including their associated biomolecules

6. Producing high purity Lab Water • High purity lab water is produced from mains drinking water via a series of purification steps to remove the 5 different types of impurities.

7. Maintaining high purity lab water • A range of techniques maintain the purity of ultra-pure water within the purifier: • composite vent filter protects the water reservoir from external contamination • periodic recirculation of water through the final purification technologies e.g UV photo-oxidation, adsorption and ion-exchange • regularly sanitizing the system to minimise bacterial growth

8. Ultra-pure water specification • Ultra-pure water needs to be free from all 5 types of impurities for the whole range of analytical and experimental applications. • Measuring the levels of impurities in ultra-pure water is limited by the measurement technique’s sensitivity and the testing environment. • Current ultra-trace techniques, ultra-pure water is: • ≥99.99999975 % pure • Maximum total non-gaseous impurities: • < 1.5 µg/l (ppb) • Organic compounds: • <1.0 µg/l for other elements and ions.

9. Comparing ultra-pure water purity to other analytical and research testing solvents ICP-MS Analysis : Comparison of Elemental Impurity Specifications of ultra-pure Water and Top Grades of Common Solvents for Analytical Research and Testing. All non-gaseous elements were effectively absent from ultra-pure water i.e. most had detection limits of less than 1 ng/l (ppt ) which is orders of magnitude less than all the other solvents tested.

10. The impact of ultra-pure water contaminants on IC, reliability & reproducibility Effects of water impurities on ion chromatography: (a) on the system and (b) potential impact on experimental results.

11. The impact of ultra-pure water contaminants on IC, reliability & reproducibility Summary of effects of water impurities on ion chromatography: • The effects of contamination from ions, organics, colloids, bacteria and gases can all impact on sensitivity and reproducibility to some degree, thereby compromising and potentially negating results. • Contaminating ions tend to have a significant but short-term effect, producing high blanks, high background and chemical interferences that directly impact results. • Organics, colloids and bacteria affect background/blanks but also tend to have a longer-term impact through media fouling and surface coating that can affect parts of the instrumentation, such as the chromatography column, the detector or inner surfaces of the system itself.

12. The impact of ultra-pure water on backgrounds for HPLC and ion chromatography HPLC analysis: UV detection at 210nm. • Significant improvements in background for HPLC with UV detection at 210nm was obtained using ultra-pure water with very low TOC compared to pure water with higher TOC.

13. The impact of ultra-pure water on background of ion chromatography IC Analysis: Ultra-trace cation analysis by pre-concentrating 20 ml sample. • Using ultra-pure water minimises background levels, enabling highly sensitive and accurate results in analyses using ion chromatography.

14. Geological Age Determination by Ultratrace Analysis • Institute for Geochemistry at Tübingen University (Germany) • Understand the structure & chemical composition of the earth’s crust • Geochronological work to reconstruct regional & plate-tectonic processes • U – Pb isotopic age determination • Clean room environment • Zirconium minerals are collected and weighed • Disintegrated via Teflon vessel with HF @ 210°C under pressure • Preconcentrated and separated by IC • Determination of Pb & U isotope ratios via TIMS

15. Geological Age Determination by Ultratrace Analysis

16. Geological Age Determination by Ultratrace Analysis Zircon ages based on U-Pb isotope ratios

17. Lab Water Considerations for Geochronological Isotopic Analyses • Ultra-pure water level suitable for ultra-trace analyses • Consistant ultra-pure water quality on demand (18.2 MW) • Sample preparation , dissolution & dilution • Blank values for Pb & U (& other elements of interest) • < 2 ppb TOC level

18. Acknowledgement Prof. Wolfgang Siebel, Tübingen University, Germany

19. Thank You Presentation by: Dr Telis Dimitrakopoulos Business & Technical Special Advisor, ELGA LabWater Lane End Industrial Park, High Wycombe, HP14 3BY, United Kingdom. www.elgalabwater.com