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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
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.
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.
Role of Water in Analytical Chemistry
Sample preparation
- extraction
- dilution
- rinsing
Blanks
Standard preparation
- dilution
Analytical method
Chromatography
Other methods
- mobile phase
- AA, ICP, MS
- rinsing
Data analysis
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
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.
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
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.
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.
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.
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.
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.
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.
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 & platetectonic 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
Geological Age Determination by
Ultratrace Analysis
Geological Age Determination by
Ultratrace Analysis
Zircon ages based on
U-Pb isotope ratios
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
Acknowledgement
Prof. Wolfgang Siebel,
Tübingen University, Germany
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