Skip Ribbon Commands
Australian Government: National Measurement InstituteAustralian Government: National Measurement Institute
National Measurement Institute
      

Oxyhalide Disinfection By-products in Drinking Water

glass of waterRecently many drinking water utilities have changed their primary disinfectant from chlorine to ozone, chlorine dioxide and chloramines which reduce regulated trihalomethanes and some organochlorine compound levels, but often increase levels of other potentially toxicologically important compounds. Inorganic oxyhalide by-products such as bromate, chlorite and chlorate have been classified as probable human carcinogens:

  • bromate is formed when source waters containing bromide are ozonated
  • chlorite is formed when chlorine dioxide is used
  • chlorate is formed when chlorine, chlorine dioxide, hypochlorite acid or chloramine are used

Perchlorate is an oxyanion, but in contrast to bromate, chlorite and chlorate its common source is contamination by industrial chemicals.

NMI's Capabilities

NMI uses modified US EPA Method 302.0 and US EPA Method 314.2 to test for common oxyhalides and perchlorate respectively. Our two-dimensional ion chromatography can accommodate samples with relatively high matrix content and achieve very low limits of detection. Hyphenated-multiple ion chromatography techniques are becoming more prevalent and NMI is one of the first laboratories to utilise this new technology. NMI’s limits of reporting are shown in the table.

NMI’s limits of reporting, preservation and holding times

Analyte
Limits of reporting (mg/L)
Preservation
Holding time
Chlorite (ClO2-)
0.000 1
0.8
0.7
50 mg/L EDA, cool to 4 °C
14 days
 
Chlorate (ClO3-)
0.000 1
not determined
0.7
50 mg/L EDA, cool to 4 °C
(AS/NZS 5667.1:1998 recommends refrigeration for 1 week without preservative)
28 days
Bromate (BrO3-)
0.000 1
0.02
0.01
50 mg/L EDA, cool to 4 °C
(AS/NZS 5667.1:1998 recommends refrigeration for 1 week without preservative)
28 days
Perchlorate (ClO4-)
0.006
not determined
not determined
sterile filtration, cool to 4 °C
28 days

 

Ethylenediamine (EDA, CAS# 107-15-3) is a preservative for chlorite, chlorate and bromate. If residual chlorine dioxide is suspected in the sample, the sample must be purged with an inert gas (helium, nitrogen or argon) for about 5 min or until no chlorine dioxide remains. This must be conducted prior to EDA addition at time of sampling. To minimise the loss of perchlorate due to anaerobic biodegradation, EPA 314.2 method recommends sterile sample filtration through a 0.2 µm membrane into a sterile container followed by storage at 4 °C. Samples should be collected in plastic or glass bottles, and bottles used for chlorite analysis must be opaque to protect the sample from light. NMI’s sampling and preservation requirements are shown in the table (US EPA Method 300.1).

NMI’s laboratories have NATA accreditation for a wide range of services. NATA accreditation for testing oxyhalides is in progress.

For further information please contact customerservice@measurement.gov.au, 1300 722 845 or use our on-line form.