Nitrate-Nitrogen by Cadmium Reduction using Flow Injection FIALab 2500(See water procedures for instrument set-up)
Extraction reagent: 0.04 M (NH4)2SO4
To make 10 L: Add 6 L DI water to a 20 L carboy. Weigh 52.80 g (NH4)2SO4 and add to carboy. Dilute to 10 L mark and stir with a magnetic stirrer.
Standards and standard stock
Make 1000 NO3-N stock solution by weighing 0.7218 g dry KNO3 and transferring to 100 mL volumetric flask. Add 1 mL Boric acid preservation solution (see water procedure) then dilute to 100 mL with dionized water.
Make 1, 2, 3, 4 ppm NO3-N solutions by diluting the stock 1:1000, 2:1000, 3:1000, and 4:1000 respectively with dionized water.
- Use 4 mL (approximate 5 g) mineral scoop and scoop soil into an extraction cup.
- Add 25 mL extraction reagent and shake for 5 minutes, then let stand for 30 minutes.
- Filter the extract through Whatman 42 filter paper into nitrate analyzer test tubes.
- Analyze according to flow injection FIALab 2500 instrument procedures.
- Set the 1, 2, 3, 4, standards to read 5, 10, 15, 20 to allow for the 1:5 dilution factor.
Reference: J. Benton Jones, Jr., Laboratory Guide for Conducting Soil Tests and Plant Analysis, p123, CRC 2001.