Three chelating agents were analyzed using Asahipak ODP-50 4D, a polymer-based reversed phase chromatography column. The chelating agents are pretreated to convert into chelating compounds (iron chelates) before analysis.

Sample pretreatment

• Dissolve chelating agents in a mixture of 10 mM sodium carbonate, 10 mM sodium bicarbonate, and 10 mM tetra-n-butylammonium hydroxide solution (pH 11) for an efficient complex salt formation.
• Add an excess amount of 0.01 M ferric chloride solution*, approximately about 2 mL of 0.01 M ferric chloride solution to 20 mL of 100 ppm solution.
  *Dissolve 0.135 g of ferric chloride in 5 mL of 1 M hydrochloric acid aqueous solution, then make up to 50 mL with water.

Sample: 100 mg/L each, 10 μL

1. 1.2-Hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid (HEDTA)
2. 2.Ethylenediaminetetraacetic acid disodium salt (EDTA·2NA)
3. 3.Diethylenetriaminepentaacetic acid dianhydride (DTPA)