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Application of an optimized total N-nitrosamine (TONO) assay to pools: placing N-nitrosodimethylamine (NDMA) determinations into perspective

Application of an optimized total N-nitrosamine (TONO) assay to pools: placing N-nitrosodimethylamine (NDMA) determinations into perspective
Application of an optimized total N-nitrosamine (TONO) assay to pools: placing N-nitrosodimethylamine (NDMA) determinations into perspective
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 mL 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 microL 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.
0013-936X
3369-3375
Kulshrestha, Pankaj
f75d2d4e-54b0-49bf-8b90-e806c998d05e
McKinstry, Katherine C.
fbfa4e2e-fa6f-4a49-8248-0e07a054aea9
Fernandez, Bernadette O.
27babc73-7646-4908-86e2-6c29d79fb938
Feelisch, Martin
8c1b9965-8614-4e85-b2c6-458a2e17eafd
Mitch, William A.
49dd4ffb-653f-49e6-9a20-759e79e2c9a2
Kulshrestha, Pankaj
f75d2d4e-54b0-49bf-8b90-e806c998d05e
McKinstry, Katherine C.
fbfa4e2e-fa6f-4a49-8248-0e07a054aea9
Fernandez, Bernadette O.
27babc73-7646-4908-86e2-6c29d79fb938
Feelisch, Martin
8c1b9965-8614-4e85-b2c6-458a2e17eafd
Mitch, William A.
49dd4ffb-653f-49e6-9a20-759e79e2c9a2

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, 44 (9), 3369-3375. (doi:10.1021/es100361f). (PMID:20355696)

Record type: Article

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 mL 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 microL 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.

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Published date: 1 May 2010
Organisations: Clinical & Experimental Sciences

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Local EPrints ID: 337696
URI: http://eprints.soton.ac.uk/id/eprint/337696
ISSN: 0013-936X
PURE UUID: 0d3be23d-7bb9-400a-b325-794a90fa719a
ORCID for Martin Feelisch: ORCID iD orcid.org/0000-0003-2320-1158

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Date deposited: 02 May 2012 12:48
Last modified: 15 Mar 2024 03:41

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Contributors

Author: Pankaj Kulshrestha
Author: Katherine C. McKinstry
Author: Bernadette O. Fernandez
Author: Martin Feelisch ORCID iD
Author: William A. Mitch

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