# Chloronitramide Anion Quantitation in Tap Waters by Ion Chromatography with Electrical Conductivity and Ultraviolet Absorbance Detection

## TL;DR

A new method using ion chromatography detects a recently discovered chemical in tap water, showing it's present in both chloramine and free chlorine systems.

## Contribution

First report of Cl–N–NO2– in free chlorine systems and concentrations above 200 μg L–1 in chloramine systems using IC methods.

## Key findings

- IC-EC and IC-UV243 detection limits for Cl–N–NO2– were 9.3 μg L–1 and 6.2 μg L–1 respectively.
- Cl–N–NO2– concentrations in chloramine systems ranged from 22–314 μg L–1 and in free chlorine systems from 2–7 μg L–1.
- IC-UV243 showed strong correlation (R2 = 0.997) with HILIC–UHRMS measurements and less measurement bias.

## Abstract

Chloronitramide anion
(Cl–N–NO2
–) is a recently
discovered inorganic chloramine
decomposition product,
with prior quantitation by hydrophilic interaction liquid chromatography–ultrahigh-resolution
mass spectrometry (HILIC–UHRMS). Here, Cl–N–NO2
– quantitation was evaluated by ion chromatography
(IC) separation with electrical conductivity (EC) and ultraviolet
absorbance at 243 nm (UV243) detection. Using a 5 mL injection
loop and a 14.4 mM Na2CO3 eluent, the Cl–N–NO2
– method detection limit was 9.3 μg
L–1 by IC-EC and 6.2 μg L–1 by IC-UV243. Matrix testing with Cl–N–NO2
– spiked at 15, 25, 50, and 100 μg
L–1 into 12 waters in triplicate matched the expected
Cl–N–NO2
– for IC-EC (R2 = 0.994) and IC-UV243 (R2 = 0.993).
Cl–N–NO2
– was found by
HILIC–UHRMS in all tested tap waters disinfected with chloramines
(n = 8) at 22–314 μg L–1 and free chlorine
(n = 3) at 2–7 μg L–1, and strongly
correlated with IC-EC (R2 = 0.991; average residual,
ri®
= +3.2 μg L–1)
and IC-UV243 (R2 = 0.997;
ri®
= 0.0 μg L–1).
This is the first report of Cl–N–NO2
– in free chlorine systems and concentrations ≳200
μg L–1 in chloramine systems. These IC methods
enable widescale collection of Cl–N–NO2
– occurrence data, with IC-UV243 subject
to lesser measurement bias.