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Interactions of Transition Metal Ions with Organophosphorus Pesticides Probed by Electrospray Ionisation Mass Spectrometry Bernd O. Keller, Department of Pathology and Laboratory Medicine, UBC 48th Annual Western Canada Trace Organic Workshop,

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Interactions of Transition Metal Ions with Organophosphorus Pesticides Probed by Electrospray Ionisation Mass Spectrometry

Bernd O. Keller, Department of Pathology and Laboratory Medicine, UBC

Ag+ Hg2+ Cu2+

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48th Annual Western Canada Trace Organic Workshop, Vancouver, BC, May 13, 2013.

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Topics:

  • What are Organophosphorus Pesticides (OPs)?
  • What is the relevance of the interactions of OPs

with transition metal ions?

  • What information can Electrospray Ionisation Mass

Spectrometry (ESI‐MS, ESI‐MS/MS) provide?

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Quinalphos Diazinon Fenitrothion

  • 40 OPs registered in US
  • Use of >32,000 tons p.a.

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http://www.ecifm.rdg.ac.uk/pesticides.htm

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Degradation of OPs:

  • Microbiologically
  • Photo‐catalytically
  • Hydrolysis

P O O N N O S H5C2 C2H5 N N O H P O OH O S H5C2 C2H5

+H2O PA‐OH HQ PA‐Q

Hydrolysis of Quinalphos (PA‐Q)

Diethyl ‐ phosphorthioic acid (PA) 2‐Hyroxyquinoxaline (HQ)

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Hydrolysis of Quinalphos – Half‐life Determination dd H2O Na+, K+ Hg 2+ Ag + Cu 2+ Half‐ life 119 d 119 d 19 sec 9 h 27 d

  • HPLC‐UV
  • pH 4.0 (dil. HNO3)
  • salts added as nitrates
  • 1‐ 30 molar excess of salts

P O O N N O S H5C2 C2H5 N N O H P O OH O S H5C2 C2H5

+H2O PA‐OH HQ PA‐Q

Hamid Esbata, Thesis, Queen’s University 2005

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Silver: mining, photo‐processing, use as antibiotic Copper: fertilizer, e.g. foliar sprays (Cu(OH)2), mining Mercury: deposition from atmosphere (coal combustion), seedling protection, other agricultural uses, gold amalgamation Entry into the environment, besides chemical manufacturing and wastewater: Ag+ Hg2+ Cu2+

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ELEMENTS September 2005 v. 1 no. 4 p. 205‐210

  • Transition metal ions are tightly bound to soil solids
  • They can be very mobile if bound to colloids (<1 um)
  • Distribution with ground‐ and surface‐ waters

Presence of >10 pesticides and heavy metal ions in Rankala Lake (India) reported at medium to high ppb levels

J Bioremed Biodegrad 2012;3:143

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  • Q1: Single isotope selection
  • In‐source fragmentation:

allows “pseudo‐MS3”

  • TOF‐analyzer: accurate mass

measurement (< 5 ppm)

  • Direct infusion of low μM

solution mixtures at pH 4

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1.0 0.8 0.6 0.4 0.2 0.0 Signal Intensity (Arb. Units) 400 350 300 250 200 150 100 50 M/Z

[PA‐Q +107Ag+] 405

‐C2H4 ‐C2H4

[HQ+Ag]+ 253 Ag+ 107 [HQ+H+] 147 231 203

‐C2H4

P O S O C2H5 Ag

+

[ ]

1.0 0.8 0.6 0.4 0.2 0.0 Signal Intensity (Arb. Units) 400 300 200 100 M/Z

255 [PA‐Q +109Ag+] 407 233 205 [HQ+H+] 147 109

Isotope selection in Q1 allows discerning of Ag+‐containing fragments

107/109Ag+

1:1

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[PA‐Q + Ag+]

m/z 405

[PA‐C2H5 + Ag+]

m/z 231 ‐[PA‐Q] ‐[PA‐H]

[HQ+Ag+]

m/z 253

[HQ+H+]

m/z 147 ‐[(PA‐2H)‐ + Ag+]

[Ag+]

m/z 107 ‐[HQ] ‐[PA‐C2H5] ‐[HQ] ‐[C2H5]

1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 Signal Intensity (Arb. Units) 450 400 350 300 250 200 150 100 50 M/Z

405 253 107 231 147

‐28 ‐28 ‐28

[PA‐Q + Cu+]

m/z 361

[PA‐C2H5 + Cu+]

m/z 187 ‐[PA‐Q] ‐[PA‐H]

[HQ+Cu+]

m/z 209

[HQ+H+]

m/z 147 ‐[(PA‐2H)‐ + Cu+]

[Cu+]

m/z 63 ‐[HQ] ‐[PA‐C2H5] ‐[HQ] ‐[C2H5]

(A)

1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 Signal Intensity (Arb. Units) 360 320 280 240 200 160 120 80 40 M/Z

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(B)

361 209 187

‐28 ‐28 ‐28

63

2.5 2.0 1.5 1.0 0.5 x10

  • 3

65 60

63Cu+

Cu(I)

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H2O

Charge reduction mechanisms in ESI:

  • Predominantly detection of singly charged ions

Me2+ An‐ An‐ L

  • 1. [Me2+ + L + An‐]
  • verall charge: +1
  • 2. [Me2+ + (L‐H)‐]
  • verall charge: +1
  • 3. Me2+ +An‐  Me+ + An*

[Me+ + L]

  • verall charge: +1

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+ Cu2+

Acridine Ligands ‐ Same Molecular Formula m/z 658 Cu(II) m/z 659 Mostly Cu(I)

Tintaru et. al. J. Phys. Org. Chem. 2009, 22: 229‐233

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Cu(II) Cu(I) Cl* HCl

Cu(II)Cu(I) charge state reduction in the absence of easily removable protons

Tintaru et. al. J. Phys. Org. Chem. 2009, 22: 229‐233

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  • Cu(II)  Cu(I) due to lack of removable protons in vicinity
  • It is not an electrochemical process at the ESI tip

Quinalphos

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Change of solvent system from MeOH/H2O to dry nitromethane (CH3‐NO2) for Hg2+ study

ACN MeOH H2O Dry CH3NO2

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Hg2+

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  • No Hg(II)  Hg(I) charge state reduction observed

(Hg has a lower second ionisation potential compared to Cu)

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Summary:

  • ESI‐MS and ESI‐MS/MS gives insights into structures of

rapidly formed transition metal ion – OP complexes

  • Observed Cu(II)  Cu(I) charge state reduction in

gas‐phase allows statements on removable proton locations in solution complexes

  • Ag+ binds to S > N, Cu2+ binds N > S, Hg2+ binds S>>>N

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Future Work:

  • Studies of interaction of transition metal ions bound to highly

mobile colloidal particles with OPs

  • Studies of fate, distribution of OPs and transition metal ions in

the environment

  • Development of detoxification strategies of OP stockpiles

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Rapid Communications in Mass Spectrometry June 30th edition, 2013 berndkel@mail.ubc.ca

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Gary van Loon Erwin Buncel Hamid & Family in Libya

Thank you!

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