Ammonium Analysis

Reagents

By Jared L. DeForest

Sodium Salicylate Solution

In a 100 ml volumetric flask of DI water mix

• 6.8 g sodium salicylate
• 5.0 g sodium citrate
• 5.0 g sodium tartrate
• 25 mg sodium nitroprusside

NaOH Solution

In a 100 ml volumetric flask

• 6 g sodium hydroxide
• Bring to volume.

Bleach Solution

Make fresh each day in 50 ml volumetric flask

• 1 ml bleach
• Bring to volume with NaOH Solution.

Matrix

• In a 1 liter volumetric flask
• 74.59 g KCl (1M KCl) & Bring to volume with DI water.

Standard Dilutions

Concentration (ppm ) | Standard (ml) | 1 M KCl

0         0         10

0.5         0.2         9.8

1         0.4         9.6

2.5          1              9

5              2              8

10           4              6

15           6              4

25           10           0

Standard (25 ppm NH₄)

In 100 ml volumetric flask

1. 10 ml NH₄ standard (Certified 250 ppm NH₄)
2. Bring to volume with matrix
3. Mix standards in 15 ml centrifuge tubes using dilutions from the adjacent table.

Procedure

In a clear 96-wellplate

• Assay the standards in duplicate (Col. 1 & 2) - 50 μl standard.
• Assay the samples in quadruple – add 50 μl of sample to each well.  A 96-wellplate can hold 20 samples with standards.
• Add 150 μl salicylate solution to each well using the multi-channel pipette.
• Add 150 μl bleach solution to each well using the multi-channel pipette.
• Tap edge of plat to mix well and incubate 50 min. Read plate at 650 nm.

Method detection limit: 0.1 - 50 ppm

Created 7/20/07 Revised 10/10/11