Analysis of a spring water

Dosing of a sample:

If the concentration of NH₄⁺ ions does not exceed 5 mg.L^-1, sample 50 mL of the water to be analyzed – otherwise, reduce the test sample and make up to 50 mL with distilled water.

Add 2 mL of the colorless double tartrate solution. Stir.
Add 2 mL of Nessler reagent and stir again.
Wait 10 minutes, then carry out the spectrophotometric measurements at 420 nm after adjusting the absorbance to zero on the instrument.

Blank test:

Carry out a blank test: replace the test sample with distilled water.

Calibration:

It is necessary to draw a calibration line with standard solutions of known ammonium concentrations.
Using several 50 mL volumetric flasks, prepare the aqueous standard solutions of NH₄⁺ at the following concentrations: 0; 0.2; 0.4; 1; 2; 3; 4; 5 mg.L^-1 (use long-neck flasks in order to be able to add the double tartrate and Nessler reagent afterwards).
Add 2 mL of double tartrate to each solution. Stir. Add 2 mL of Nessler reagent and stir once again.
Wait 10 minutes, then carry out the spectrophotometric measurements at 420 nm.

 ≈ 20 minutes / sample

Practical tip: prepare the sample, the blank test and the calibration solutions at the same time, in order to save time.