Abstract
We introduce a novel approach in simple and highly sensitive fluorometric determination of ammonium nitrogen. The proposed method is based on a fluorescence derivatization with benzyl chloride. The benzyl chloride was converted to a new fluorescent derivative by reaction with ammonium ion (NH4+) in the presence of sodium bicarbonate. The excitation and emission wavelengths were 258 and 284 nm, respectively. The effects of benzyl chloride concentration, sodium bicarbonate concentration, reaction temperature and time, and hydrochloric acid concentration were studied in detail. Under the optimal conditions of the experiment, the linear range for determination of ammonium nitrogen was 0.01-0.60 mg L-1, and the detection limit was 0.008 mg L-1. Relative standard deviation of eleven measurements for 0.40 mg L-1 NH4+-N was 2.6%. The method was successfully applied to the determination of ammonium nitrogen concentration in different water samples. The mechanism of the derivatization was further confirmed by Fourier transform infrared (FTIR) spectra.
Highlights
Nitrogen is an essential nutrient for all forms of life, and even small changes in biologically-available nitrogen levels can affect the levels of microbiological, plant and animal life.[1]
Ammonium is a common alkaline pollutant in freshwater, and acutely toxic to some fish at concentrations of 200 μg N L-1.4,5 High concentrations of ammonium nitrogen in water can lead to nutrient enrichment in water ecosystem, and the subsequent increase in biological activity can lead to algal blooms, oxygen depletion, odor and toxicity problems.[6]
The flask was diluted approximately to the scale with water, and placed in a thermostat water bath at 35 ± 0.2 °C for 4 h, after which 2.0 mL of 0.01 mol L-1 hydrochloric acid (HCl) was added and the mixture was diluted to the mask with water and shaken until a homogeneous solution was obtained
Summary
Nitrogen is an essential nutrient for all forms of life, and even small changes in biologically-available nitrogen levels can affect the levels of microbiological, plant and animal life.[1]. Fluorometry is a popular and attractive detection method because of its high sensitivity in detection field.[21,22] O-Phthaldialdehyde (OPA), usually used in combination with some reductants including sulfite,23,24 2-mercaptoethanol[25,26] and n-acetyl-cysteine,[27] has been widely applied to detect ammonium due to the yield highly fluorescent isoindole derivatives. This fluorometric method is improved by combining with ion chromatography to solve interference problems and enlarge the working range,[28,29,30] but it requires expensive chromatographic equipment and a long diffusion time.[31]. The Fourier transform infrared (FTIR) spectra of BnCl and the corresponding reacted solution were measured using a Nicolet model IR200 FTIR spectrophotometer (ThermoFisher, USA)
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