Determination of nano-molar levels of nitrite in natural water by spectrophotometry after preconcentration using Sep-Pak C-18 cartridge
Journal
International Journal of Environmental Analytical Chemistry
Journal Volume
62
Journal Issue
3
Pages
175-189
Date Issued
1996
Author(s)
Abstract
Abstract Nitrite in natural water was allowed to react with sulphanilamide (SUL) and N-1-naphthylethylenediamine (NED) reagents to form a pink azo dye, which was quantitatively adsorbed onto a Sep-Pak C18 cartridge and was later recovered by eluting with a mixture containing 38% v/v ethanol and 60 mM HCl. The percolate was measured by a spectrophotometer at 543 nm. The molar extinction coefficient of the dye in the final solution was found to be 5 × 104 M−1 cm−1. Using the proposed manual procedure, nitrite in up to 500 mL of freshwater and 1.5 L of seawater could be concentrated to a final 10 mL with a recovery of > 98%. The detection limit was found to be 0.6 nM and 0.2 nM for 500 mL and 1.5 L sizes of sample. A precision of less than 2% at 20–80 nM level could be readily achieved. The cartridge also served for the preservation purpose, as the bound pink azo dye could be stored for up to 4 days without significant change. The proposed manual procedure has been automated by a cycling loop system to suit ship-board determination.
SDGs
Type
journal article