# Presentation: 463748

## Perchlorate Analysis by Ion Chromatography The CA DHS Protocol

- H.S. Okamoto, D.K. Rishi and S.K. Perera

## Disclaimer

- Mention of trade names or commercial products does not constitute endorsement or recommendation for use.

## Topics

- Equipment
- Eluent Composition Study
- Linear Calibration Range
- MDL Study
- Interferences
- Sample Collection and Preservation
- Method Performance
- Method Advantages
- Method Limitations
- Additional Needs

## Equipment 

- Ion chromatograph:  autosampler, dual piston pump, ion suppressor, conductivity detector and data system.
- Sample loop:  740 μL (12’ x 0.02” tubing)
- Column: Dionex IonPac® AS5 (4 x 250 mm)
- Chemical regenerant:  Dilute sulfuric acid
- Eluent:  120 mM NaOH + 2 mM p-cyanophenol

## Eluent Composition Study

- High concentration of NaOH (120 mM) is employed in the eluent.
- p-Cyanophenol modifier must be added to the eluent to deactivate the AS5 ion exchange column.
- In initial tests, the p-cyanophenol concentration was varied while maintaining the NaOH concentration at 120 mM.

## Effects of p-Cyanophenol on the Elution of ClO4-

- 15 ppb Perchlorate
- Eluent:  120 mM NaOH + X mM p-Cyanophenol

## Linear Calibration Range

- 2.5 to 100 ppb Perchlorate

## MDL Study

## MDL Study

## MDL Study

## Interferences

- Pump noise (pressure pulses) - oscillating baseline.
- Air bubbles trapped in the pump head or conductivity cell -- baseline spikes and/or oscillating baseline.
- Improperly adjusted chemical suppression -- high background conductivity, low perchlorate response.
- Detergents and other organics -- column, suppressor and detector fouling.
- High sample TDS -- column and detector overload; may severely affect baseline response.

## Anions Known Not to Colute with Perchlorate

- Arsenate		Cyanide 		o-Phthalate
- Arsenite		Humic Acid	Selenate
- Bromate		Iodate 		Sulfate
- Bromide		Iodide 		Sulfite
- Carbonate		Molybdate		Thiocyanate
- Chlorate		Nitrate		Thiosulfate
- Chloride		Nitrite
- Chromate		o-Phosphate

## Sample Collection and Preservation

- Sampling container: HDPE plastic bottles
- Sample storage:  store at 4oC
- Holding time:  28 days (likely to be more)

## Holding Time Study -  Stored at 4oC

## Holding Time Study

- Tap water sample fortified with perchlorate
- Stored for 10 months at 4oC
- Stored for 10 months at room temperature

## Method Performance

- Single Operator Accuracy and Precision

## Method Performance

- Sample Duplicate Analysis & MS/MSD
- Single Operator Accuracy and Precision

## Inter-Laboratory Performance

- Tap Water
- Conductivity = 840 μS/cm
- ClO4- TV = 18.1 μg/L
- Acceptable Range:  14.3 - 21.9 μg/L
- No. of Labs = 11
- Mean Value Reported = 18.6 ± 1.8 μg/L

## Method Performance

- Capable of meeting the QC requirements in EPA 300.0 for ion chromatography:
- QCS result within ± 10% of known value.
- Instrument performance check solution results within ± 10% of calibration.
- Method blank results less than the MDL.
- Lab fortified blank results within control limits of 90 - 110%.
- Laboratory fortified sample matrix recovery results within 80 to 120%.

## Method Advantages

- Uses current technology that is available in many water utility and commercial analytical laboratories.
- Based on EPA 300.0 - many analytical laboratories are familiar with the QA/QC requirements.
- Requires very little sample preparation for drinking water samples.
- Quick and easy to perform.
- Provides the sensitivity required for the current California DHS provisional action level of 18 ppb in drinking water.

## Method Limitations

- Requires a large sample volume of 740+ μL to achieve the necessary sensitivity.
- Due to the large sample volume, high TDS in a sample may cause interference in the detection and/or quantification for perchlorate at very low levels.
- High TDS in a sample may also cause column, suppressor, and/or detector fouling that can result in a noisy and unstable baseline.
- AS5 column activity causes perchlorate to tail without a modifier (p-cyanophenol) added to the eluent.

## Additional Needs

- Need for confirmatory procedures, including identification.
- Need for improved detection limits.
- Need for clean up methods.
- Need to keep method simple and transferable to water utility and commercial analytical laboratories.
- Need for a more comprehensive storage and holding time study.
- Need for a more comprehensive inter-laboratory performance study.

## Acknowledgements

- D.K. Rishi and S.K. Perera, CA DHS
- F. Baumann, (retired) CA DHS
- W. Steeber and staff, CA DHS
- A. Fitchett and K. Anderson, Dionex Corp.

## References

- Record 269, Dionex Chromatogr. Database 4.2.0, Dionex Corp.
- Haddad, P.R. & Jackson, P.E., Ion Chromatogr.: Principles and Applications, J. Chromatogr. Lib. 1990: 46:Ch. 4.
- CFR 40, Ch. 1, Part 136, Appendix B
- US EPA Method 300.0: Determination of Inorganic Anions by Ion Chromatography, Rev. 2.1, Aug. 93

## Contact

- Howard Okamoto
- CA Dept. of Health Services - SRLB
- 2151 Berkeley Way
- Berkeley, CA 94704
- Ph. (510) 540-2205
- email  hokamoto@ix.netcom.com