NKS - Developing ICP-MS-based methods for regulatory purposes: One example from … · 2018. 1....
Transcript of NKS - Developing ICP-MS-based methods for regulatory purposes: One example from … · 2018. 1....
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www.alsglobal.com
Developing ICP-MS-based methods for regulatory
purposes: One example from a contract laboratory
Douglas C. Baxter, Emma Engström, Dieke Sörlin, Ilia Rodushkin
ALS Scandinavia AB, SE-977 75 Luleå, Sweden
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U and Th isotopes in water
• Why (develop a method for U and Th isotopes in water)?
• Is there a market?
• Is there a standard method?
• Are there reference materials available?
• Is there legislation?
• What could possibly go wrong?
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U and Th isotopes in water
• Why? Customer enquiries
• Is there a market? Yes, if legislation exists or customers
ask for a service
• Is there a standard method? Yes, ISO 17294-2:2016
• Are there reference materials available? Yes, available
from IRMM
• Is there legislation? Yes, 2013/51/EURATOM
• What could possibly go wrong?
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Is there legislation?
• 2013/51/EURATOM
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Is there legislation?
• 2013/51/EURATOM
240 µg/l
0,12 µg/l
1,6 µg/l
0,00086 µg/l
Detection limits not too challenging
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Are there reference materials available?
• U and Th reference materials
– Costs 520 EUR – 1900 EUR
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Is there a standard method?
• The standard – ISO 17294-2
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Is there a standard method?
• The standard – ISO 17294-2
– Spectral interferences
• Isobaric (none tabulated for U or Th)
• Polyatomic (none tabulated for U or Th; hydrides mentioned)
• Note that complicated polyatomic interferences exist
Taylor et al., Int. J. Mass Spectrom., 243 (2005) 71
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Is there a standard method?
• The standard – ISO 17294-2
– Spectral interferences
– Suggested solutions (few details given)
• Sector field instruments (correct some polyatomic interf.)
Hydride interferences cannot be resolved unless resolution is improved 5-fold
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Is there a standard method?
• The standard – ISO 17294-2
– Spectral interferences
– Suggested solutions (few details given)
• Sector field instruments
• Mathematical corrections (none mentioned for U or Th)
Does that mean
that none are
needed?
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Is there a standard method?
• The standard – ISO 17294-2
– Spectral interferences
– Suggested solutions (few details given)
• Sector field instruments
• Mathematical corrections
• Collision and reaction cell technology
No interferences?
Don’t need these!
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Is there a standard method?
• The standard – ISO 17294-2
– Non-spectral interferences (ISO 17294-1)
– Suggested solutions to non-spectral interferences
• Matrix matching or sample dilution
Dilution of samples will eliminate non-spectral interferences. Detection limits
needed to fulfill requirements in legislation are easily met even after samples
are diluted 10- or even 100-fold.
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Is there a standard method?
• The standard – ISO 17294-2
– Non-spectral interferences (ISO 17294-1)
– Suggested solutions to non-spectral interferences
• Matrix matching or sample dilution
• Internal standards
18
Avoid internal standards that are present in the sample or that may cause
spectral interferences. 204
Tl is interfered by 204
Pb and 204
Hg.
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Is there a standard method?
• The standard – ISO 17294-2
– Non-spectral interferences (ISO 17294-1)
– Suggested solutions to non-spectral interferences
• Matrix matching or sample dilution
• Internal standards
Inclusion of a suitable internal standard in the method will allow correction for
non-spectral interferences and correction for instrumental drift.
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Is there a standard method?
• The standard – ISO 17294-2
– Non-spectral interferences (ISO 17294-1)
– Suggested solutions to non-spectral interferences
• Matrix matching or sample dilution
• Internal standards
• Plasma condition optimization
Vanhaecke et al., J. Anal. At. Spectrom., 8 (1993) 1008
Optimize instrumental conditions during
method validation stage. Study effects of
e.g. nebulizer gas flow on U and Th isotopes
as well as on the chosen internal standard in
both the standards and in real samples.
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Is there a standard method?
• The standard – ISO 17294-2
– Non-spectral interferences (ISO 17294-1)
– Suggested solutions to non-spectral interferences
• Matrix matching or sample dilution
• Internal standards
• Plasma condition optimization
17 Right Solutions • Right Partner
Is there a standard method?
• The standard – ISO 17294-2
– Non-spectral interferences (ISO 17294-1)
– Suggested solutions to non-spectral interferences
• Matrix matching or sample dilution
• Internal standards
• Plasma condition optimization
• Standard addition technique
Should never be needed if the method: (i) is based on correctly-optimized
instrumental conditions; (ii) includes a suitable internal standard.
Remember that standard additions will not correct for spectral interferences.
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Is there a standard method?
• The standard – ISO 17294-2
– Non-spectral interferences (ISO 17294-1)
– Suggested solutions to non-spectral interferences
• Matrix matching or sample dilution
• Internal standards
• Plasma condition optimization
• Standard addition technique
• Isotope dilution (costs, purity issues)
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What could possibly go wrong?
• 2013/51/EURATOM
– Only mentions 234
U and 238
U
– Customers may require 235
U and even 236
U, as well
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What could possibly go wrong?
• The reference materials
– Price does not include delivery
– Many carriers will not handle radioactive material
– Register materials with national radiation safety authority
– Complete inventory change documents
– Log all uses of material
– Be prepared for radiation safety authority audit
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What could possibly go wrong?
• The standard – ISO 17294-2
– Look into other resources
– E.g. ref. [15] in ISO 17294-2
Pourcelot et al., J. Environ. Monitor., 13 (2011) 355
What is abundance sensitivity?
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What could possibly go wrong?
• Google “abundance sensitivity icp ms”
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What could possibly go wrong?
• The standard ISO 17294-2
– No mention of abundance sensitivity (234
U, 236
U)
– No info on how to correct for hydrides (235
U1H on
236U)
• Mathematical correction for abundance sensitivity and
hydrides is needed
Hydride correction is element specific.
Abundance sensitivity correction requires
measurement of tailing on low- and high-
mass sides of a single isotope.
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What could possibly go wrong?
• Everything
• Remember to be critical
• Be prepared for paperwork