Some nonionic sample can be analyzed with the use of deionized water as an eluent.
As the eluent, either a saltaqueous solution or buffer solution with or without a polar organic solvent added to it. The followings are how to select the eluent to be used.
1) Ionic and nonionic hydrophilic samles.
Salt solutions or buffer solutions are generally used as the eluent. Typical aqueous salt solutions are as follows:
(Aqueous salt solutions)
Sodium chloride aqueous solution
Sodium nitrate aqueous solution
Sodium sulfate aqueous solution
Potasim sulfate aqueous solution
Ammonium sulfate aqueous solution
Phosphoric acid buffer solution
Trishydrochroric acid buffer solution
Acetic acid buffer solution
Citric acid buffer solution
(1) Use of salt concentration in the range of 0.05M to 0.3M is recommended. Maxinium usable salt concentration is 0.5M.
(2) pH of eluent should be 3.0 to 10.0.
(3) pH of eluent should be higher than 6.0 when the eluent contains chloride ions.
(4) Boric acid buffer solution is not recommended because di-ol groups of packing material and boric acid make a complex.
2) Nonionic and ionic hydrophobic samples
Addition of polar organic solvents in the eluent is recommended to decrease the hydrophobic adosorption. Addition of salts in the eluent is also recomended when the sample is ionic.
Upper limit of concentration of polar organic solvents are as follows: Polymer-based GFC Columns: OHpak SB-800 HQ
Flow rate should be slower than 0.5mL/min when in-column solvent is changed to an eluent containing polar organic solvent.
In the case of DMSO, flow rate should be slower than 0.3mL/min and column temperature should be 50°C or higher.
3) Protein samples
Urea and 6M guanidine aqueous solutions, which are commnly used as protein modifier, can be used as the eluent. The eluent containing surfactants, such as SDS or Brij-35, is recoummended for the samples, such as membrane proteins, of which solubility in water is poor.
Frequent replacement of the in-column eluent from normal solvent to the above solvent will make the column life short. In such case, it is recommended to use one colunm specifically for the purpose.