Kulshrestha, Pankaj, McKinstry, Katherine C., Fernandez, Bernadette O., Feelisch, Martin and Mitch, William A.. (2010) Application of an optimized total N-nitrosamine (TONO) assay to pools: placing N-nitrosodimethylamine (NDMA) determinations into perspective. Environmental Science & Technology, Vol.44 (No.9). pp. 3369-3375. ISSN 0013-936X

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Abstract

Although N-nitrosodimethylamine (NDMA) has been the most prevalent N-nitrosamine detected in disinfected waters, it remains unclear whether NDMA is indeed the most significant N-nitrosamine or just one representative of a larger pool of N-nitrosamines. A widely used assay applied to quantify nitrite, S-nitrosothiols, and N-nitrosamines in biological samples involves their reduction to nitric oxide by acidic tri-iodide, followed by chemiluminescent detection of the evolved nitric oxide in the gas phase. We here describe an adaptation of this method for analyzing total N-nitrosamine (TONO) concentrations in disinfected pools. Optimal sensitivity for N-nitrosamines was obtained using a reduction solution containing 13.5 lit glacial acetic acid and 1 mL of an aqueous 540 g/L iodide and 114 g/L iodine solution held at 80 degrees C. The method detection limit for N-nitrosamines was 110 nM using 100 mu L sample injections and NDMA as a standard. N-nitrosamines featuring a range of polarities were converted to nitric oxide with 75-103% efficiency compared to NDMA. Evaluation of potential interfering species indicated that only nitrite and S-nitrosothiols were a concern, but both interferences were effectively eliminated using group-specific sample pretreatments previously employed for biological samples. To evaluate the low TONO concentrations anticipated for pools, 1 L samples were extracted by continuous liquid-liquid extraction with ethyl acetate for 24 h, and concentrated to 1 mL. N-nitrosamine recovery during extraction ranged from 37-75%, and there was a potential for artifactual nitrosation of amines during solvent reflux in the presence of significant nitrite concentrations, but not at the low nitrite concentrations prevalent in most pools. Using the 1000-fold concentration factor and 56% average extraction efficiency, the method detection limit would be 62 pM (5 ng/L as NDMA). The TONO assay was applied to six pools and their common tap water source in conjunction with analysis for specific nitrosamines. Even accounting for the range of N-nitrosamine extraction recoveries, NDMA accounted for an average of only 13% (range 3-46%) of the total nitrosamine pool.

Item Type:	Journal Article
Subjects:	T Technology > TD Environmental technology. Sanitary engineering G Geography. Anthropology. Recreation > GE Environmental Sciences
Divisions:	Faculty of Medicine > Warwick Medical School > Metabolic and Vascular Health Faculty of Medicine > Warwick Medical School
Journal or Publication Title:	Environmental Science & Technology
Publisher:	American Chemical Society
ISSN:	0013-936X
Date:	1 May 2010
Volume:	Vol.44
Number:	No.9
Number of Pages:	7
Page Range:	pp. 3369-3375
Identification Number:	10.1021/es100361f
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
Funder:	Water Research Foundation (WaterRF)
URI:	http://wrap.warwick.ac.uk/id/eprint/6006

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