All connections between injector, column and detector must be as short as possible, have a low dead volume and be absolutely tight. The PEEK capillary after the detector block must be free from constriction (the measuring cell is tested to 5 MPa = 50 bar back pressure).

For the preparation of the eluents only chemicals of a purity degree of at least "p.a." should be used. For diluting please use only high purity water.

Fresh eluents should always be microfiltered (0.45 µm filter) and degassed (with N₂, He or vacuum). For alkaline eluents and eluents with low buffering capacity one should preferably use a CO₂ absorber.
 

Use degassed and CO₂-free ultrapure water for eluent preparation. Dissolved CO₂ will shift the pH and therefore the retention times.

In case of alkaline eluents, CO₂ from the ambient will be dissolved in the eluent and change the eluent pH. To prevent the eluent from CO₂ absorption you should use a CO₂ absorber.

There might be evaporation in the eluent container. The supply vessel containing the eluent must be closed as tightly as possible to avoid excessive evaporation. This is primarily important with eluents containing organic solvents (e.g. acetone), the evaporation of which can lead to drifts in the long term. If work is performed in a very sensitive range, even if one drop of condensate falls back in the eluent this can cause a noticeable change in the background conductivity.

You can prepare your own standard solutions from salts or you buy standards by chemical suppliers.

Please check if the pH of the solutions fits with the specifications of your separation column.

Standards and reagents especially for ion chromatography are available here.

• The pump tubings used by the peristaltic pump are consumable material with a limited lifetime and should be exchanged at regular intervals (approx. every 4 weeks under continuous use).
• Different positions can be used, the position should be changed monthly.
• The pressure of the pump tubing cartridge should not be too high: increase the pressure step by step until you observe a flow; add then 2 more steps.
• Use 3-stopper long-life tubings: 6.1826.3X0
• Inline filters have to be used and exchanged quarterly or if the backpressure is too high.
   

• Use in flow direction
• Precolumn should be used and replaced frequently (PR Guard can be exchanged)
• Analytical column: How can life time be increased? E.g. check the quality of chemicals, water and sample preparation (e.g. filtrated or dialyzed samples)
   

The attainable quality of analyses with a Metrohm Compact IC depends to a large extent on the separation efficiency of the column used. When purchasing an IC column you should ensure that the separation efficiency suffices for the analysis problems at hand. Ascertain the characteristic data of the IC column on the standard chromatogram enclosed with the column such as capacity factors, selectivity, plate number and resolution and check these data with your own measurements. If any difficulties arise, you should always first check the quality of the column by recording a standard chromatogram.

You will find additional general tips on handling IC separating columns in the 8.732.2003 Metrohm Monograph "Ion chromatography" and in the 8.792.2013 Metrohm Monograph "Practical ion chromatography", as well as detailed information on the separating columns available from Metrohm in the leaflets supplied and in the special Application Notes and Bulletins available free of charge from your nearest Metrohm agency.
 

To protect the column against foreign particles which could have an adverse influence on the separation efficiency, we advise you to subject both the eluents and all samples to microfiltration (0.45 µm filter) and to siphon the eluent through the 6.2821.090 Aspirating filter.

To avoid contamination by abrasive particles arising from piston seals of the high-pressure pump, it is advantageous to install an in-line filter between the pump and the injection valve.

The use of readily interchangeable precolumns serves to protect the actual separating columns and increase their service life appreciably.

Always store the separating columns closed when not in use and filled in accordance with the manufacturer's specifications.

If the separation properties of the column have deteriorated, it can be regenerated in accordance with the column manufacturer's specifications. With the separating columns available from Metrohm, the instructions for regeneration can be found on the leaflet enclosed with every column.

Regenerate a column only if extended rinsing with a strong eluent did not improve the resolution.

In the case of separating columns with carrier material based on silica, only solutions with pH 2...7 may be used for regeneration, otherwise the columns could be damaged.
 

• MSM Suppressor
• PTFE capillaries are soft, don't close the screws too tight; if the capillaries are squeezed, cut off the first millimeter using a capillary cutter.
• Don't step the suppressor under dry conditions!
• In case the background conductivity is too high check the flow rates of the sulfuric acid and ultrapure water.

Protection
To avoid contamination of the suppressor module by foreign particles or bacterial growth, the two 6.2821.120 Inline Filter 2 µm supplied must be installed between peristaltic pump and inlet capillaries of the suppressor module.

Operation
The Metrohm Suppressor Module MSM comprises a total of 3 suppressor units which are in turn used for suppression, regenerated with sulfuric acid and rinsed with water. To record every new chromatogram under comparable conditions, work is normally carried out with freshly regenerated suppressor. Switching takes place automatically together with the valve switching.
For operation of the suppressor module, a two-channel peristaltic pump is needed which conveys the regeneration solution (normally 50 mmol/L H₂SO₄) and the rinsing solution (normally dist. H₂O) to the suppressor units (flow rate of 0.5 mL/min).
The suppressor units must never be regenerated with H₂SO₄ in the same flow direction used for the eluent. You should thus always install the inlet and outlet capillaries.
The suppressor module must never be switched in the dry state as there is a danger of blocking. Before every switching operation of the suppressor module, the three suppressor units must have been rinsed for at least 1/2 h with eluent, regeneration and rinsing solution.
The capacity of the suppressor units is exhausted after approx. 2 h or less, depending on the eluent and the flow rate. With longer interruptions between the individual measurements it is recommended that, depending on the separating column used, that a method is started that steps the MSM e.g. every 20 min during the pauses.

Maintenance
In the event of reduced capacity or high counter-pressure the suppressor module must be regenerated, cleaned or exchanged.
 

The Metrohm CO₂ Suppressor (MCS) requires CO₂-free air therefore:

• Water and CO₂ absorber cartridges have to be used.
• Water absorber material can be regenerated by heating (<140°C -> see color indicator)
• CO₂ absorber material has to be replaced frequently (see color indicator)
   

No, the color indicator used is free from the previously used cobalt chloride.