Ammonium sulfate is a common nitrogen fertilizer. However, during its production process, sulfamic acid and ammonium thiocyanate may form as impurities and they are known to interfere plants germination. According to Japanese Testing Methods for Fertilizers (2016*), "Ion chromatography method" under "5.7 Sulfamic acid (amide sulfate)" and "5.8 Ammonium thiocyanate (thiocyanate compound)" should be carried out with a column filled with hydrophilic methacrylate gel modified with quaternary ammonium groups. The method mentions that this analysis is applicable to ammonium sulfate, and IC NI-424 as a suitable column. In this application, a standard solution of sulfamic acid and ammonium thiocyanate, and an ammonium sulfate sample solution spiked with sulfamic acid and ammonium thiocyanate standards, were analyzed using NI-424. It was confirmed that sulfamic acid and ammonium thiocyanate can be measured in the sample solution without being affected by the presence of matrix.

Sample Preparation according to "(4.1) Extraction"

1. (1)Weigh 1500 µg each of sulfamic acid and ammonium thiocyanate, add them to 1 g of ammonium sulfate, and prepare a standard-spiked sample.
2. (2)Add water to dissolve and make up to 100 mL in a volumetric flask.
3. (3)Dilute this aqueous solution 12.5-fold with water, then filter through a 0.45-µm membrane filter and use it as a sample.

*The version at the time of the application acquisition.

Sample: 20 µL
(Standard solution) 3 mg/L each f Sulfamic acid and Ammonium thiocyanate in H₂O
(Sample solution) 1.2 mg/L each of Sulfamic acid and Ammonium thiocyanate  in 800 mg/L Ammonium Sulfate solution

1. 1.Sulfamate
2. 2.Thiocyanate