Extraction of ammonia and nitrite using modified magnetite iron oxide nanoparticles before spectrophotometric determination in different water samples

A new analytical approach was developed for the extraction and determination of ammonia and nitrite in environmental water samples involving magnetic solid-phase extraction (MSPE) with magnetite nanoparticles (MNPs) as the adsorbent. The procedure is based on the derivatisation of ammonia based on Berthelot reaction. The obtained indophenol dye was extracted using MSPE and determined spectrophotometrically at 655 +/- 3nm. Nitrite ion is determined after its reduction to ammonia in the presence of Zn/HCl. The main factors that affected the extraction efficiency were studied and optimised. The method gave calibration curves for ammonia with good linearity in the range 10-550 mu gL(-1), and correlation coefficients (r) higher than 0.99. The detection and quantification limit was found to be 3.1 and 10.2 mu gL(-1), respectively. The method showed good precision and accuracy, with intra- and inter-assay precisions of less than 6.6% at all concentrations. The recoveries ranged 89-105% and 88-105%, for ammonia and nitrite determination, respectively. The method was applied to the determination of the target analytes in real samples.