Dodecylbenzene sulfonate-coated magnetite nanoparticles as a new adsorbent for solid phase extraction-spectrophotometric determination of ultra trace amounts of ammonium in water samples

A new method was proposed for the determination of ammonium based on the preconcentration with dodecylbenzene sulfonate modified magnetite nanoparticles. Ammonium was oxidized to nitrite by hypobromite and then the nitrite produced was determined spectrophotometrically, using sulfabenzamide and N-(1-naphthyl) ethylenediamine after solid phase extraction. The azo dye produced was desorbed by an appropriate small volume of sodium hydroxide prior to the absorbance measurement. The linear calibration graphs were obtained in the concentration range of 0.03–6.00 ng mL−1 ammonium. The relative standard deviation and recovery percents were 1.0 and 99.0, respectively, for 1.0 ng mL−1 ammonium, and the limit of detection was 3.2 ng L−1 ammonium. The interfering effects of a large number of diverse ions on the determination of ammonium were studied. The method was applied to the determination of ammonium in various types of water resources. The results revealed a high efficiency for the recommended ammonium determination method.

Graphical abstract. Zero- (A: analyte and B: blank) and first-derivative (C: analyte and D: blank) spectra of the back-extracted solution against water for the proposed ammonium determination method.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► We introduce dodecylbenzene sulfonate modified magnetite nanoparticles as an adsorbent. ► Ammonium was preconcentrated and determined by forming an azo dye. ► Drying of the sorbent phase was performed after extraction prior to back-extraction. ► A low volume of sodium hydroxide solution was used for back-extraction of the formed azo dye.