Spectrometric determination of ammonium-nitrogen with quinol in aqueous medium

  • P.O. Okolo
  • J.M. Okuo


Quinol is proposed as a reagent for the spectrometric determination of ammonium-nitrogen (NH4+-N) in aqueous medium. Quinol forms a pink complex with ammonium salt in aqueous medium. Hydrogen peroxide is needed for colour accentuation. The quinol/ammonium charge transfer complex has absorption maximum (λmax) at 420nm with molar absorptivity (ε) of 1.067x103lmol-1cm-1. Beer's law is obeyed up to 6.0μg NH4+-N/ml.The correlation coefficient (r) is 0.9962. The optimum quinol concentration and optimum pH are found to be 0.6% (m/v) and 5.00, respectively. The calculated sensitivity is 0.07μg NH4+-N/ml. The extent of ionic interference has also been quantitatively evaluated. The most tolerated ion is NO3- (8.00x10-3moll-1 maximum) and the least tolerated ion is Fe3+ (1.25x10-6moll-1 maximum). Recovery of NH4+-N from spiked water sample shows results in the range of 98.49 to 99.69%. The proposed method has been applied to the determination of NH4+-N in potable water. Results are in good agreement with those obtained by Nessler's method.
Key words: ammonium-nitrogen, aqueous solution, spectrometry, quinol.

(Global Journal of Pure and Applied Sciences: 2003 9(4): 495-502)

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