Nitrate determination using anion exchange membrane and mid-infrared spectroscopy.
This study investigates the combined use of an anion exchange membrane and transmittance mid-infrared spectroscopy for determining nitrate concentration in aqueous solutions and soil pastes. The method is based on immersing a small piece (2 cm(2)) of anion exchange membrane into 5 mL of solution or soil paste for 30 minutes, after which the membrane is removed, rinsed, and wiped dry. The absorbance spectrum of the charged membrane is then used to determine the amount of nitrate sorbed on the membrane. At the levels tested, the presence of carbonate or phosphate does not affect the nitrate sorption or the spectrum of the charged membrane in the vicinity of the nitrate band. Sulfate affects the spectrum of the charged membrane but does not prevent nitrate determination. For soil pastes, nitrate sorption is remarkably independent of the soil composition and is not affected by the level of soil constituents such as organic matter, clay, and calcium carbonate. Partial least squares analysis of the membrane spectra shows that there exists a strong correlation between the nitrate charge and the absorbance in the 1000-1070 cm(-1) interval, which includes the v(1) nitrate band located around 1040 cm(-1). The prediction errors range from 0.8 to 2.1 mueq, which, under the specific experimental conditions, corresponds to approximately 2 to 6 ppm N-NO(3)(-) on a solution basis or 2 to 5 mg [N]/kg [dry soil] on a dry soil basis.
Linker
Raphael
R
Faculty of Civil and Environmental Engineering, Division of Environmental, Water and Agricultural Engineering, Technion-Israel Institute of Technology, Haifa 32000, Israel. linkerr@tx.technion.ac.il
Shaviv
Avi
A
D003432:Cross-Linking Reagents; D007475:Ion Exchange Resins; D008567:Membranes, Artificial; D009566:Nitrates / Q000032:analysis*; D011137:Polystyrenes; D012987:Soil / Q000032:analysis; D012996:Solutions; D013055:Spectrophotometry, Infrared; D014753:Vinyl Compounds; D014867:Water / Q000737:chemistry
D003432:Cross-Linking Reagents; D007475:Ion Exchange Resins; D008567:Membranes, Artificial; D009566:Nitrates; D011137:Polystyrenes; D012987:Soil; D012996:Solutions; D014753:Vinyl Compounds; D014867:Water; C004985:divinyl benzene