Perchlorate

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Perchlorate
An Integrated Approach to Ensure Reliable
Perchlorate Analytical Results
April 14, 2004
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Agenda

• Perchlorate Chemistry and Sources
• Current Methods for Testing
• Ion Chromatography
• LC/MS/MS
• An Integrated Approach
• A Success Story
• Summary and Conclusions

3
Perchlorate Ion

• Perchlorate is a compound containing one chlorine
  atom and four oxygen atoms.
• Perchlorate is an ion, meaning it carries an
  electrical charge, as indicated by the negative
  sign.

4
Natural Sources of Perchlorate

• Chilean fertilizer deposits
• New Mexican potash
• Canadian potash
• Californian hanksite
• Bolivian playa crusts

5
Anthropogenic Sources of Perchlorate

• Rocket Fuel
• Fireworks
• High explosives
• Flares
• Herbicides
• Automobile airbags
• Tracer munitions
• Detergents ?

6
How is perchlorate measured?

• EPA Method 314.0
• Ion chromatography/conductivity detector
• Enhanced (Modified) 314.0
• Suppressed Conductivity Detector
• SW-846 Method 9058 (draft)
• Ion Chromatography/conductivity detector

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How is perchlorate measured?

• Other analytical methods that can detect
  perchlorate
• IC Improved Method 314.1 approved use of 2nd
  column confirmation and pre-concentration of
  samples.
• IC/MS (ion chromatography/mass spectrometry)
  Proposed Method 330.0
• LC/MS (liquid chromatography/mass spectrometry)
• LC/MS/MS (liquid chromatography/mass
  spectrometry/mass spectrometry) Method 8321
  Modified, Proposed Method 331.0

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Ion Chromatography
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Ion Chromatography

• An aqueous sample, comprised of components A and
  B, is injected into the ion chromatograph.
• The sample enters the analytical column which is
  packed with a material that can adsorb the
  components of the sample.
• Some components are more strongly adsorbed.

Diagram from Fundamentals of Analytical
Chemistry, Skoog, 1988.
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Ion Chromatography

• Fresh solvent is continuously injected into the
  instrument.
• The solvent carries the sample components, A and
  B, through the column.
• Component B is more strongly adsorbed onto the
  column and is moving thought the column at a
  slower rate.
• The boundary between A and B is indistinct at
  this point.

Detector
Diagram from Fundamentals of Analytical
Chemistry, Skoog, 1988.
11
Ion Chromatography

• Component B is almost completely separated from
  component A.
• The boundary between the two components is more
  distinct.

Detector
Diagram from Fundamentals of Analytical
Chemistry, Skoog, 1988.
12
Ion Chromatography

• Component B is completely separated from
  component A.
• Component A exits the column through the detector
  at time t3.
• The detector records component A as a peak
  (pictured below the column) in the sample
  chromatogram (graph).

Detector
Diagram from Fundamentals of Analytical
Chemistry, Skoog, 1988.
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Ion Chromatography
Solvent

• Component B exits the column through the detector
  at time t4.
• The detector records component B as a peak
  (pictured below the column) in the sample
  chromatogram.

Detector
Diagram from Fundamentals of Analytical
Chemistry, Skoog, 1988.
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Diagram from Fundamentals of Analytical
Chemistry, Skoog, 1988.
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Identification of Perchlorate by Ion
Chromatography

• 11.2.4 The width of the retention time window
  used to make identifications should be based upon
  measurements of actual retention time variations
  of standards measured over several days. Three
  times the standard deviation of retention time
  may be used as a suggested window size but the
  retention time window should not extend beyond
  5 of the retention time for perchlorate. The
  experience of the analyst should weigh heavily in
  the interpretation of these chromatograms.

EPA Method 314.0
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IC Perchlorate Standard
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High Conductivity
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Carry Over
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Matrix Spike Confirmation
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Matrix Spike Non- Confirmation
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Matrix Spike Non- Confirmation
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Liquid Chromatography/MassSpectrometry/Mass
Spectrometry
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LC/MS/MS

• Leading edge technology
• DoD Recommended
• Pending Regulatory Approval

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(No Transcript)
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API MS/MS
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Bowling Balls and Feathers a simplification of
mass spec separations
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Identification By LC/MS/MS

• Liquid chromatography separates perchlorate from
  other sample components in the same manner that
  ion chromatography does
• Mass spectrometers (MS) are used as detectors in
  place of the conductivity detector used in IC.
• Unlike conductivity detectors, an MS is a
  specific detector

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Detection By LC/MS/MS

• The MS counts the number of ions that have a
  specific molecular weight. Perchlorate has a
  characteristic molecular weight (MW).
• The first MS counts the number of ions that have
  the MW of perchlorate 1 Chlorine (35)
  4 Oxygens (16) 99
• The second MS removes one of the oxygen atoms and
  then counts the number of daughter ions that
  have that MW 1 Chlorine (35) 3 Oxygens (16)
  83
• Chlorine has a less abundant isotope (MW 37), so
  ions with MW 101 are also counted by the first MS
  and ions with MW 85 are counted by the second MS.
• The retention time of the peak for MW 99 must be
  the same as the retention time of the peak for MW
  83 for perchlorate to be confirmed. If the
  retention times are different, then the two
  molecular weight were detected from two different
  components and perchlorate is not confirmed.

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Non-detect Analysis by LC/MS/MS

• Analysis by LC/MS/MS
• Reporting limit is 2 ?g/L.
• Bottom chromatogram shows the counts of ions with
  molecular weight 83 (1 chlorine 3 oxygens).
• Top chromatogram shows the counts of ions with
  molecular weight (the isotope of chlorine).
• Perchlorate is not detected.

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Comparison of LC/MS/MS
Non-Detect
Detect
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Detect Analysis by LC/MS/MS

• Reporting limit 2 ?g/L.
• Bottom left shows MW 83 (1 chlorine 3 oxygens).
• Top left shows MW 85 (the isotope of chlorine).
• Right chromatogram show the 18O internal standard
  (recovery 88).
• Perchlorate is detected.

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Perchlorate Decision Tree
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Success Using the Perchlorate Decision Tree

• Approximately 1000 samples were collected and
  analyzed for perchlorate from August 2003
  through January 2004.
• 89 samples (about 9 of total) were pretreated
  and reanalyzed.
• 39 samples (about 3 of total) were reanalyzed by
  LC/MS/MS - 24 detects and 15 nondetects.
• 10 perchlorate detects (about 0.4 of total) were
  confirmed by LC/MS/MS 58 false positive rate
  and a 0 false negative rate.

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Summary

• Why use 314.0?
• Cost
• Capacity
• Availability
• Promulgated Methods
• When to use LC/MS/MS?
• Definitive Data
• Critical Samples
• Small Projects

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Thank You
Questions and Comments

• Contact
• Elizabeth Wessling at 303.935.6505
• elizabeth.wessling_at_amec.com