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

High Resolution Image Download MS PowerPoint Slide Chloronitramide anion (Cl–N–NO 2 – ) 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–NO 2 – quantitation was evaluated by ion chromatography (IC) separation with electrical conductivity (EC) and ultraviolet absorbance at 243 nm (UV 243 ) detection. Using a 5 mL injection loop and a 14.4 mM Na 2 CO 3 eluent, the Cl–N–NO 2 – method detection limit was 9.3 μg L –1 by IC-EC and 6.2 μg L –1 by IC-UV 243 . Matrix testing with Cl–N–NO 2 – spiked at 15, 25, 50, and 100 μg L –1 into 12 waters in triplicate matched the expected Cl–N–NO 2 – for IC-EC (R 2 = 0.994) and IC-UV 243 (R 2 = 0.993). Cl–N–NO 2 – 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 (R 2 = 0.991; average residual, r i ¯ = +3.2 μg L –1 ) and IC-UV 243 (R 2 = 0.997; r i ¯ = 0.0 μg L –1 ). This is the first report of Cl–N–NO 2 – in free chlorine systems and concentrations ≳200 μg L –1 in chloramine systems. These IC methods enable widescale collection of Cl–N–NO 2 – occurrence data, with IC-UV 243 subject to lesser measurement bias.