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.
- （Note）
- Once 0.01 M ferric chloride solution is added, excess iron precipitates as ferric hydroxide. It is recommended to analyze samples immediately after adding the 0.01-M ferric chloride solution.
Sample: 100 mg/L each, 10 μL
1.2-Hydroxyethyl)ethylenediamine-N,N’,N’-triacetic acid (HEDTA)
2.Ethylenediaminetetraacetic acid disodium salt (EDTA·2NA)
3.Diethylenetriaminepentaacetic acid dianhydride (DTPA)
Column：Shodex Asahipak ODP-50 4D (4.6 mm I.D. x 150 mm)Eluent：10 mM Na2CO3 + 10 mM NaHCO3 + 10 mM Tetrabutylammonium hydroxide (pH7.0 adjusted with 1 M HCl) Flow rate：0.8 mL/min Detector：UV (254 nm) Column temp.：40 ℃
