Eliminating interference from iron(III) for ultraviolet absorbance measurements of dissolved organic matter.

The presence of iron(III) has long been recognized as a difficulty when ultraviolet absorbance measurements of dissolved organic matter are desired. This interference was studied in water samples of diverse origins and properties, and a procedure is discussed which uses hydroxylamine to reduce up to 10 mg L(-1) (0.18 mM) of Fe(III) to non-interfering Fe(II). This procedure eliminated the effect of Fe(III) in all samples from about 220 to 400 nm, and removed interference down to 200 nm in most samples. Copyright (c) 2009 Elsevier Ltd. All rights reserved.