Cations in tap water were analyzed using IC YK-421. Ion chromatogaraphy is used for in Japanese regulations for tap water. Ion chromatography is very useful method for the simultaneous analysis of monovalent and divalent cations such as Na⁺, K⁺ and Mg²⁺.

Sample: 15 µL
Std. solution

1. 1.Li⁺ 2 mg/L
2. 2.Na⁺ 10 mg/L
3. 3.NH₄⁺ 10 mg/L
4. 4.K⁺ 20 mg/L
5. 5.Ca²⁺ 20 mg/L
6. 6.Mg²⁺ 10 mg/L

Tap water

1. 2.Na⁺
2. 4.K⁺
3. 5.Ca²⁺
4. 6.Mg²⁺