Ion chromatography (IC)
Ion chromatography can be used to separate and measure inorganic and short-chain organic anions and cations. Columns packed with ion exchange resin ensure the retention of ions based on their affinity.
This system from Methrohm, essentially consists of :
- The 919 auto-sampler
- The 818 anion system
- The 883 cation system
- The computer with MagIC Net software
The purpose of the auto-sampler is to provide a way of analyzing up to 56 samples in a row without any manual labor required. The auto sampler is filled with specific vials of 14 mL in volume. To be analyzed, such vial should contains at least 3 mL of sample/standard.
The anion and cation system are completely separated. The only thing that connects them, is the sample tubing, that goes through both. This ensures that the same sample can be analyzed by both the anion and cation system. Apart from that, they work independently. Both devices have an HPLC pump to push eluent “mobile phase” at high pressure and accurate flow rate through the columns “stationary phase”. At the end of the column, a conductivity detector measures the signal produced by each separated ion species. These are plotted in the software and each signal peak represents a certain concentration. The anion system is slightly more complicated than the cation system. It requires chemical suppression, which means that the background signal of the eluent is lowered by exchanging all Na+ with H+ before going to the conductivity detection. Chemical suppression is provided by the Metrohm Supressor Module (MSM). A CO2 stripper further lowers the strength of the background signal, making the signal as low as 1 µS/cm.
The computer with MagIC Net software ties everything together. The software tells each device what to do and in a fixed protocol (hereafter referred to as method) these steps are repeated for each measurement. The software also links peak detection of standards to that of samples, providing the user with the requested results.