Importance of ultra pure water for analytical research and testing techniques

-impact of laboratory water handling and storage procedures on its purity

Dr Paul Whitehead, Laboratory Manager, ELGA R&D Facility

• 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.

• Determine the affects that certain general laboratory dispensing and storage procedures have on the purity of ultra pure water.

Objectives

• Pure water is crucial 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 substance used in a laboratory.

Background

• 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; • microorganisms including their associated biomolecules

Water challenge

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

Producing 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 sanitising the system to minimise bacterial growth

Maintaining high purity lab water

• 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.

Ultra pure water specification

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.

• Water may be used in many aspects of an analysis:• preparation of samples, • dilutions, standards, blanks, eluents • rinsing instruments

The impact of ultra pure water contaminants on ion chromatography, reliability and 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 ion chromatography, reliability and 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 contaminants on ion chromatography, reliability and reproducibility

HPLC analysis: UV detection at 210nm.

The impact of ultra pure water on backgrounds for HPLC and ion chromatography

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.

ICP-MS Analysis: Ultra-trace cation analysis by pre-concentrating 20ml sample.

The impact of ultra pure water on background of ion chromatography

• Using ultra pure water minimises background levels, enabling highly sensitive and accurate results in analyses using ion chromatography.

Results

• Within seconds the ultra pure water starts to absorb CO2 from the air forming carbonic acid. This procedure occurs more rapidly with stirring and reduces the resistivity of the water from 18.2 Mohm.cm to a minimum of about 1.3 Mohm.cm.

• Though this carbon dioxide does not degrade the water for most applications, its effect on resistivity can mask the contamination of the water by other ions.

The effect of exposing ultra pure water to air over time, with and without stirring

• Analysis clearly showed that negative ions, particularly nitrite ions, were detected at higher concentrations when splashing had occurred.

• When ultra pure water is dispensed impurities in the air can also reduce the water’s purity therefore it is important that air entrainment is minimised.

Contamination from the atmosphere due to different water collection methods

Negative ion chromatography analysis: (a) water collected with splashing; (b) water collected by flowing it along the vessel i.e no splashing

• GC-MS scans show that ultra pure water passed through flexible PVC tubing can be contaminated with N-butyl-benzene sulphonamide plasticiser illustrating that tubing organic release agents or plasticisers can leach into the water.

• A pharmaceutical company survey showed that the average total viable bacterial count in water from 22 water purifiers without tubing was 0.7 CFU/ml. Thisincreased to 26 CFU/ml for 7 units with dispense tubing.

Plasticizer contamination from passing ultra pure water through plastic tubing

GC-MS analysis of ultra pure water: effect of plasticizer in tubing.

Assessing ultra pure water contamination after storage in glass v plastic bottles

LC-MS Analysis: comparison of phthalate ester contamination from glass versus plastic wash-bottles* after 2 days storage.

References A) Suzuki, Kawaguchi, Enami and Kuroki: Abstract of Proceedings of 15th Environmental Chemistry Forum, 2006, 182-183. (3). B) Clinical and Laboratory Standards Institute. Preparation and Testing of Reagent Water in the Clinical Laboratory; Approved Guideline-Fourth Edition. CLSI document C3-A4, 2006. C) Kuroki: Chromatography, 2006, 27(3), 125-9. D) Kuroki: Industrial Water, 2003, 541, 24-30. (2). E) Horikiri S., Fujita N., Kuroki Y. and Enami T. Abstracts of Proceedings of 54th Mass Spectrometry Analysis General Forum, 2006, 458-459.

Assessing ultra pure water contamination after storage in glass v plastic bottles

LC-MS Analysis: comparison of phthalate ester contamination from glass versus plastic wash-bottles* after 2 days storage

• For trace organic analyses glass bottles are preferable for storing water to plastic wash-bottles i.e. in addition to other impurities, di-n-octyl phthalate was present in the water from the plastic wash-bottle at ppb levels but at much lower levels in glass bottle water.

• To maximise its purity, ultra pure water should be used soon after it is dispensed. In a survey of wash-bottle use, Kuroki et al., found that over 80% of users did not refill their wash-bottles every day with ultra pure water.

• Similar contamination problems can occur if bottled purified water for high sensitivity analysis is stored and reused after opening.

  *Horikiri S. et al . Abstracts of Proceedings of 54th Mass Spectrometry Analysis General Forum, 2006, 458-459.

References A) Suzuki, Kawaguchi, Enami and Kuroki: Abstract of Proceedings of 15th Environmental Chemistry Forum, 2006, 182-183. (3). B) Clinical and Laboratory Standards Institute. Preparation and Testing of Reagent Water in the Clinical Laboratory; Approved Guideline-Fourth Edition. CLSI document C3-A4, 2006. C) Kuroki: Chromatography, 2006, 27(3), 125-9. D) Kuroki: Industrial Water, 2003, 541, 24-30. (2). E) Horikiri S., Fujita N., Kuroki Y. and Enami T. Abstracts of Proceedings of 54th Mass Spectrometry Analysis General Forum, 2006, 458-459.

• The extremely high purity of ultra pure water enables accurate results to be obtained from high sensitivity analyses such as ion chromatography and HPLC.

• The analytical accuracy of ion chromatography and HPLC is dependent, on the use of water from a well designed water purification system to maintain and monitor the ultra pure water’s purity within the system.

• Easy to use ultra pure water dispensing and good laboratory practise during collection and use are essential to maintain the purity of ultra pure water and prevent results being compromised.

Conclusion

Thank You

Presentation prepared by:Dr Paul WhiteheadLaboratory Manager, ELGA R&D FacilityLane End Industrial Park, High Wycombe, HP14 3BY, UK. 

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