PRETREATMENT OF SAMPLE

PURPOSE:To achieve an anion detection with a high certainly, by passing a sample liquid containing cation of bivalent or higher valency through a cation exchange resin with univalent ions (excluding H) as counter-ion before it is analyzed using an alkaline elution liquid. CONSTITUTION:When an alkaline elution (e.g. p-hydroxy benzoate, carbolic acid and benzoic acid) is used, it often obstructs the determination of desired ions if, for example, tap water is injected without pretreatment. To remove this obstruction, a sample is pretreated by a cation exchange resin (a resin having acid group such as sulfonic group and carboxylic group) with univalent cations (e.g. Li, Na, NH4, K, Rb and Cs, excluding H) as counter-ion. So that, a pretreatment column having a tube 20 filled with an ion exchange resin 22 is used. The ion exchange resin 22 is held with a filter 24 fixed at the top and the bottom thereof. A sample is passed through a pretreatment column with an injection cylinder inserted into an injection cylinder insertion port 21. Thus, ions of bivalent or more in the sample are removed by being replaced with the counter-ion of the cation exchange resin.