1. 5 mM tartaric acid + 1 mM dipicolinic acid Eluent + 1.5 g/L boric acid
The eluent of 5 mM tartaric acid + 1 mM dipicolinic acid + 1.5 g/L boric acid is the one generally used for the analysis of cations such as Na⁺, NH₄⁺, K⁺, Ca²⁺ and Mg²⁺ which are most commonly contained in actual samples. Although Mn²⁺ elute just after K⁺, all the other transition metal ions elute at Vo.
Separation can be adjusted by changing the eluent concentration as follows :
* Tartaric acid------5 mM is used most commonly. The use of higher concentrations such as 6 mM to 7 mM, causes cations to elute faster.
* Dipicolinic acid---1 mM is used most commonly. It is added to make divalent cations elute faster.
At a higher temperature such as 50 °C, Sr²⁺, Ba²⁺ elute faster.

(Preparation of eluent)
1) Put 0.750 g of reagent grade L(+)tartaric acid, 0.167 g of reagent grade dipicolinic acid and 1.5 g of reagent grade boric acid into a volumetric flask.
2) Dilute with purified water to make up a 1 liter solution.
3) Dissolve applying ultrasonic vibration.
4) Pass through a 0.2 μm membrane filter before use.
(Remark) Since tartaric acid deteriorates so fast, this eluent should be prepared just before the use.

2. Addition of crown ether
The separation between Na⁺ and NH₄⁺ can be largely improved by adding crown ether in the eluent of 5 mM tartaric acid + 1 mM dipicolinic acid + 1.5 g/L boric acid.
For example, Na⁺ and NH₄⁺ in serum of which concentration ratio is 1 : 300 can be separated well.

3. Addition of acetonitrile
Acetonitrile can be added up to 70 % in nitric acid aqueous solution. Therefore, in addition to organic cations, ethanolamine and short chain alkylamines which could be analysed using the old version column(YF-421), long chain alkylamines can also be analysed using IC YK-421.