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Halogenated acetaldehydes: analysis, stability and fate in drinking water
Boniface K Koudjonou1, Guy L LeBel
1Chemistry Research Division, Safe Environments Programme, Health Canada, Tunney's Pasture, PL 0800C, Ottawa, ON, Canada K1A 0L2. boniface_koudjonou@hc-sc.gc.ca
Chemosphere
|December 27, 2005
Summary
New standards allowed the detection of various haloacetaldehydes (HAs) in drinking water. These HAs are stable in water under specific conditions but can degrade into trihalomethanes (THMs) at higher temperatures and pH, contributing significantly to disinfection byproducts (DBPs).
Area of Science:
- Environmental Chemistry
- Analytical Chemistry
- Water Quality
Background:
- Chloral hydrate was previously the only identified chlorinated acetaldehyde in drinking water due to a lack of analytical standards for related compounds.
- Recent commercial availability of diverse haloacetaldehyde (HA) standards facilitates comprehensive analysis.
Purpose of the Study:
- To verify the purity and stability of newly available haloacetaldehyde standards.
- To determine the stability of haloacetaldehydes in stock solutions and in water under various conditions.
- To quantify haloacetaldehydes in Canadian drinking water samples and assess their contribution to disinfection byproducts.
Main Methods:
- Purity and stability of commercial HA standards were assessed using a dual-column GC-ECD system.
- HA stability in different solvents (acetone, MTBE) and in water at varying pH, temperature, and storage durations was evaluated.
- Analytical methods were developed for quantifying HAs in drinking water, with speciation influenced by water parameters and treatment processes.
Main Results:
- All commercial HA standards contained minor amounts of other target HAs.
- HAs were stable in MTBE for up to 8 months but degraded in acetone.
- HAs were stable in water for up to 14 days under sampling conditions (pH 4.5, 4°C).
- Trihalogenated acetaldehydes degraded to trihalomethanes (THMs) at elevated pH and temperature.
- Most target HAs were detected in Canadian drinking water, with chloral hydrate comprising 7-51% of total HAs.
- The ratio of total HAs to total THMs (10-46%) indicates HAs are significant disinfection byproducts (DBPs).
Conclusions:
- Newly available HA standards enable broader detection and characterization in water.
- HA stability is dependent on solvent, pH, temperature, and storage time.
- Haloacetaldehydes are prevalent in drinking water and represent a substantial fraction of DBPs, alongside THMs.