NKS - Developing ICP-MS-based methods for regulatory purposes: One example from … · 2018. 1....

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Right Solutions • Right Partner

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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


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?


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?


Is there legislation?

• 2013/51/EURATOM


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


Are there reference materials available?

• U and Th reference materials

– Costs 520 EUR – 1900 EUR


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





– Suggested solutions (few details given)

• Sector field instruments (correct some polyatomic interf.)

Hydride interferences cannot be resolved unless resolution is improved 5-fold






• Sector field instruments

• Mathematical corrections (none mentioned for U or Th)

Does that mean

that none are

needed?

https://www.google.se/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwiQzPrzj7bWAhXlF5oKHVeIClAQjRwIBw&url=https://medium.economist.com/can-we-know-what-animals-are-thinking-83991bc994c4&psig=AFQjCNGu7cdITMZyrS95CCezj3flCG4BBA&ust=1506077980907438






• Sector field instruments

• Mathematical corrections

• Collision and reaction cell technology

No interferences?

Don’t need these!

https://www.google.se/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwiQzPrzj7bWAhXlF5oKHVeIClAQjRwIBw&url=https://medium.economist.com/can-we-know-what-animals-are-thinking-83991bc994c4&psig=AFQjCNGu7cdITMZyrS95CCezj3flCG4BBA&ust=1506077980907438




– 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.







• 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.








Inclusion of a suitable internal standard in the method will allow correction for

non-spectral interferences and correction for instrumental drift.








• 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.









• 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.









• Standard addition technique

• Isotope dilution (costs, purity issues)


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



• 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

https://www.google.se/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&ved=0ahUKEwiDuqbcyLbWAhWEFJoKHXaAAg0QjRwIBw&url=https://www.amazon.com/Nuclear-Radiation-Warning-sticker-decal/dp/B00K9BFES8&psig=AFQjCNF6lulnsIFNA6Lr3GvFqG5DzVZqjA&ust=1506093234156165

http://australiabusinessnews.com.au/news/tax-havens-law-firms-and-world-figures-the-panama-papers/




– 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?



• Google “abundance sensitivity icp ms”



• 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.



• Everything

• Remember to be critical

• Be prepared for paperwork

NKS - Developing ICP-MS-based methods for regulatory purposes: One example from … · 2018. 1....

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