New Green and Sustainable Tool for Assessing Nitrite and Nitrate Amounts in a Variety of Environmental Waters

Abstract

This paper aims to provide improved selectivity and sensitivity with a short analysis time of about 10 min and low residues for quantitation of nitrite and nitrate in waters by liquid chromatography. Ion-pair formation and ion exchange retention mechanisms were considered. The optimized option was in-tube solid phase microextraction (IT-SPME) by means of a silica capillary of 14 cm length and 0.32 mm id, coupled online with a capillary anion exchange analytical column (Inertsil AX 150 × 0.5 mm id, 5 µm) and the use of their native absorbance. Precision of the retention times expressed as % relative standard deviation (RSD) were <1% for both, nitrite (tR = 5.8 min) and nitrate (tR = 10.5 min). Well, river, channel, lake, sea, tap and bottled waters and several matrices of a drinking water treatment plant were analysed, and no matrix effect was observed for all of them. Inorganic anions and several organic acids were tested as possible interferences and suitable selectivity was obtained. Precision expressed as % relative standard deviation (RSD) was between 0.9 and 3%. Low detection limits of 0.9 and 9 μg/L for nitrite and nitrate were obtained, respectively, and low residue generation near 100 µL per run was also achieved.