Enrichment of trace anions from water with 2,2'-diaminodiethylamine cellulose filters

Cellulose filters with immobilized 2,2'-diaminodiethylamine (DEN) functional groups are studied for trace anion preconcentration from aqueous solution, with subsequent x-ray fluorescence measurements. For most oxoanions with a central metal atom, nearly quantitative collection can be achieved by 10-cm² DEN filters under the following optimized conditions: pH 3–6, filtration rate up to 0.5 ml cm^-2 min^-1, and sample volume up to 100 ml cm^-2. The collection yield is independent of the trace oxoanion concentration up to at least 1.5 μmol cm^-2. Although the DEN filter exhibits some selectivity towards oxoanions with a central metal atom, ionic strength affects the results; the collection efficiency is strongly depressed with salt (e.g. NaCl) concentrations above 0.01 M. The applicability of the DEN filter in anion collection is therefore limited to dilute solutions.