# Presentation: 720537

## An Improved Ion Chromatographic Method for Low Level Perchlorate Analysis

- Peter E. Jackson, Ph.D.
- Environmental Market Manager
- Dionex Corporation
- 1228 Titan Way
- Sunnyvale CA  94088-3606

## PERCHLORATE - WHAT ARE THE ISSUES

- Contamination found in CA, NV, UT & WV
- Total extent of the contamination problem across the U.S. is not known
- Is the problem localized or ubiquitous
- No federal or state regulations exist, removal treatment technologies are not available
- Are there appropriate analytical methods for perchlorate analysis

## PERCHLORATE - ISSUES IN CALIFORNIA

- Perchlorate interferes with thyroid gland function
- U.S. EPA reports adequate health protection corresponding to a range of 4-18 ppb
- Urgent problem in CA, action level of 18 ppb
- >22 groundwater production wells shut down
- California Department of Health Services (CDHS) has developed an ion chromatography (IC) method for the trace analysis of perchlorate

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## WHAT IS A POLARIZABLE ANION?

- An anion with an “easily” deformable electron cloud
- The anionic form of a “soft” acid
- A “hydrophobic” anion

## CHARACTERISTICS OF POLARIZABLE ANIONS

- Low hydration energy
- Small hydrated radius (usually)
- Disruptive of water structure (hydrophobic)
- Strong interactions with  electrons
- High refractive index

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## CDHS PERCHLORATE METHOD

- Large loop (740 uL) injection
- Separation on AS5 anion-exchange column
- Eluent of 120 mM NaOH/2 mM p-cyanophenol
- Suppression using AMMS with 35 mM sulfuric acid regenerant
- Measurement using conductivity detector

## CDHS PERCHLORATE METHOD SUMMARY

- MDL in reagent water is 0.7 ug/L (ppb)
- MRL in reagent water is 4.0 ppb
- Linear calibration range of 2 to > 100 ppb
- Recovery of perchlorate spikes at the 1-4 ppb level in the range of 87 - 98%

## OPTIMIZED DIONEX PERCHLORATE METHOD

- Large loop (1000 uL) injection
- Separation on AS 11 anion-exchange column
- Eluent of 100 mM NaOH (no modifier required)
- Suppression using ASRS with AutoSuppression in external water mode
- Measurement using conductivity detector

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## OPTIMIZED PERCHLORATE METHOD SUMMARY

- MDL in reagent water is 0.25 ug/L (ppb)
- MRL in reagent water is ~ 1.0 ppb
- Linear calibration range of 2 to 100 ppb
- Recovery of perchlorate spikes at 2.5 ppb level in the range of 98 - 99%

## PERCHLORATE - FURTHER WORK

- Application Laboratory participation in Collaborative Laboratory Study (Col-Lab-I)
- WQTC method presentation
- Use of 2mm AS11 column
- AWWARF project (RFP 2508) collaboration?
- Development of new polarizable anion column
- Application of EG40 to perchlorate analysis

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## CONCLUSIONS

- Optimized, interference free method for analysis of low ug/L perchlorate in ground and tap water
- Method based on 1000 uL injection, AS11 column, 100 mM NaOH eluent and suppressed conductivity detection using ASRS
- MDL of 0.25 ug/L, MRL of ~ 1.0 ug/L
- Linear calibration range of 2 to 100 ug/L
- Recovery of 98-99% at 2.5 ug/L level

## GLOSSARY OF TERMS

**Ion Chromatography** - Separation-based technique for the analysis of ionic species; typically uses suppressed conductivity detection
**Eluent** - Ionic solution used to “elute” or push ionic species through analytical (separator) column
**Analytical Column** - Resin filled tube which separates ionic species (based on ion exchange interactions) into discrete bands prior to detection
**Suppressor** - Membrane-based device used to reduce eluent conductance and enhance target analyte sensitivity
**MDL** - Method Detection Limit.  Students t-test at the 99% confidence limit applied to 7 replicate injections at ~3x detection limit
**MRL** - Minimum Reporting Limit.  Minimum quantifiable level which may be reported; typically 5x the MDL

## Peter JacksonDionex Corporation

- 1228 Titan Way
- Sunnyvale, CA 94086
- phone:  (408) 481‐4262
- fax:  (408) 737‐2470
- email: peter_jackson@dionix.com