Perchlorate : Perchlorate April 14, 2004 An Integrated Approach to Ensure Reliable Perchlorate Analytical Results ﴀ
Agenda : Agenda Perchlorate Chemistry and Sources
Current Methods for Testing
Ion Chromatography
LC/MS/MS
An Integrated Approach
A Success Story
Summary and Conclusions
Perchlorate Ion : 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.
Natural Sources of Perchlorate : Natural Sources of Perchlorate Chilean fertilizer deposits
New Mexican potash
Canadian potash
Californian hanksite
Bolivian playa crusts
Anthropogenic Sources of Perchlorate : Anthropogenic Sources of Perchlorate Rocket Fuel
Fireworks
High explosives
Flares
Herbicides
Automobile airbags
Tracer munitions
Detergents ?
How is perchlorate measured? : 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
How is perchlorate measured? : 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
Ion Chromatography : Ion Chromatography
Ion Chromatography : 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.
Ion Chromatography : 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. Diagram from Fundamentals of Analytical Chemistry, Skoog, 1988. Detector
Ion Chromatography : Ion Chromatography Component B is almost completely separated from component A.
The boundary between the two components is more distinct. Diagram from Fundamentals of Analytical Chemistry, Skoog, 1988. Detector
Ion Chromatography : 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). Diagram from Fundamentals of Analytical Chemistry, Skoog, 1988. Detector
Ion Chromatography : Ion Chromatography 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. Diagram from Fundamentals of Analytical Chemistry, Skoog, 1988. Detector Solvent
Slide14 : Diagram from Fundamentals of Analytical Chemistry, Skoog, 1988.
Identification of Perchlorate by Ion Chromatography : 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
IC Perchlorate Standard : IC Perchlorate Standard
High Conductivity : High Conductivity
Carry Over : Carry Over
Matrix Spike Confirmation : Matrix Spike Confirmation
Matrix Spike Non- Confirmation : Matrix Spike Non- Confirmation
Matrix Spike Non- Confirmation : Matrix Spike Non- Confirmation
Liquid Chromatography/Mass Spectrometry/Mass Spectrometry : Liquid Chromatography/Mass Spectrometry/Mass Spectrometry
LC/MS/MS : LC/MS/MS Leading edge technology
DoD Recommended
Pending Regulatory Approval
API MS/MS : API MS/MS
Bowling Balls and Feathers: a simplification of mass spec separations : Bowling Balls and Feathers: a simplification of mass spec separations
Identification By LC/MS/MS : 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
Detection By LC/MS/MS : 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.
Non-detect Analysis by LC/MS/MS : 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.
Comparison of LC/MS/MS : Comparison of LC/MS/MS Non-Detect Detect
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. Detect Analysis by LC/MS/MS
Perchlorate Decision Tree : Perchlorate Decision Tree
Success Using the Perchlorate Decision Tree : 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.
Summary : Summary Why use 314.0?
Cost
Capacity
Availability
Promulgated Methods
When to use LC/MS/MS?
Definitive Data
Critical Samples
Small Projects
Thank You : Thank You Contact
Elizabeth Wessling at 303.935.6505
elizabeth.wessling@amec.com Questions and Comments