Application of an Optimized Total N-Nitrosamine (TONO) Assay to Pools: Placing N-Nitrosodimethylamine (NDMA) Determinations into Perspective

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.

Trihalomethane, dihaloacetonitrile, and total N-nitrosamine precursor adsorption by carbon nanotubes: the importance of surface oxides and pore volume

“…Assessment of total N-nitrosamine formation potential (TONOFP) began with a modified SPE procedure from EPA method 521, adapted from Kulshrestha et al 29 SPE columns were conditioned with methanol and Milli-Q water, and then 500 mL sample aliquots were pulled through the columns at a flow rate of 5 mL min −1 . Following 10 minutes of column aspiration, N-nitrosamines were eluted from the SPE columns using 12 mL of methanol.…”

Improving wastewater management using free nitrous acid (FNA)

“…N-nitroso compounds are easily formed by interaction of a secondary amino compound with a nitrosating agent such as NO + (Lijinsky 1999). It is seen that nitrosamine can be formed by the reaction of NO + with an amine, thereby modifying proteins and potentially altering function (Kulshrestha et al 2010). On top of these, the interactions between NO and tyrosyl radicals accounts for the inhibition of ribonucleotide reductase by RNIs, which would limit the availability of precursors for the synthesis and repair of DNA (Lepoivre et al 1991).…”

N-nitrosamines in 21^th Century

“…One of these methods uses a mixture of iodine and potassium iodide in an acidic medium (Kulshrestha et al, 2010). Another method uses denitrosation mixture of cuprous chloride and hydrogen chloride.…”

“…Jedna z metod využívá k denitrosaci směs jodu a jodidu draselného v kyselém prostředí (Kulshrestha et al, 2010). Další z těchto metod využívá denitrosace pomocí směsi chloridu měďného a kyseliny chlorovodíkové.…”