Guidelines for Shodex Column Selection
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Two method are well known as ion chromatography measurement : the suppressed conductivity method and the non-suppressed conductivity method. In the suppressed conductivity method, a special device (suppressor) installed after the analytical column is needed for removing the opposite ionic substances in the sample. The Non-suppressed conductivity method can be easily performed only by adding a conductivity detector and IC columns to an ordinary HPLC system without using a suppressor.
Advantages of non-suppressed method.
Since the use of a suppressor is unnecessary, the system is simple and inexpensive.
Disadvantages of non-suppressed method.
1. Background conductivity is rather high.
(anion analysis: 200 to 250 micro-S/cmFS, cation analysis: 1,000 to 2,500 micro-S/cmFS)
2. Sensitivity is rather low. Detection sensitivity is about tens ppb and minimum sample concentration is about handreds ppb.
3. The usable eluent is limited to low-conductivity solvents such as phthalic acid.
As ion chromatography methods, two are well known: the suppressed method and the non-suppressed method. In the suppressed method, after the eluent has passed through the analytical column, ionic substances of which polarities are opposite of ionic substances in the sample are ridded by use of a special device(suppressor). By this method, the electro conductivity in the eluent can be largely decreased and highly sensitive analysis of anions is possible.
Shodex is offering several kinds of analytical column for the use of anion analysis by supressed method. It is highly recommended to use a line filter to obtain a stable beseline and a guard column to a have long service life of the main column.
Advantages of suppressed method.
1. Background conductivity is low.
(anion analysis: about 20 micro-S/cmFS)
2. Sensitivity is high. Detection sensitivity is several ppb and minimum sample concentration is about tens ppb.
3. Free from temperature fluctuation and stable analysis is possible.
Disadvantages of suppressed method.
The use of a suppressor is essential and the system is rather expensive.