The administrative order of the Ministry of Health, Labour and Welfare #261 (July 22, 2003) specifies the acceptable levels for F^-, Cl^-, NO₂^- and NO₃^-. Their concentrations are measured using ion chromatography. Here, anions in tap water were analyzed using IC NI-424 (an anion analysis column for non-suppressor method) though NO₂^- could not be detected in tap water.
Please refer to 'Regulation for Water Supply '.


Sample : Tap water, 100 μL
1. F^-
2. Cl^-
3. NO₃^-
4. SO₄^2-

Column       : Shodex IC NI-424 (4.6 mm I.D. x 100 mm)
Eluent       : 8 mM 4-Hydroxybenzoic acid + 2.8 mM Bis-Tris + 2 mM Phenylboronic acid 
               + 0.005 mM *CyDTA aq.
 
Flow rate    : 1.0 mL/min
Detector     : Non-suppressed coductivity
Column temp. : 40 °C

* CyDTA: trans-1,2-Diaminocyclohexane-N,N,N',N'-tetraacetic acid