Ion chromatography: Maintenance

The capillary cutter (6.2621.080) is suitable for PTFE and PEEK capillaries. Please make sure you cut the capillaries as short as possible in order to obtain small rinsing volumes. It is important that you use the capillary cutter correctly in order to avoid additional dead volume.

The cutter has two sides, one angled (1) and one straight (2). Use the straight side to achieve the correct cut.

1. Short PEEK pressure screw (6.2744.070): Standard pressure screw for connecting PEEK capillaries.
2. Medium PEEK pressure screw (6.2744.014; 6.2744.010): For connecting PEEK capillaries to the injection valve.
3. Long PEEK pressure screw (6.2744.090): For connecting PEEK capillaries with the MCS or Sample Degasser.

The points of PEEK pressure screws that have already been used are generally compressed. The compression can be expanded using an awl or similar tool. This allows PEEK pressure screws to be reused.

Capillaries may extend to different lengths from the PEEK pressure screw depending on the connection. The example in the video shows both a coupling (1) and the injection valve (2). It is important that the capillaries extend far enough when connecting them to pressure screws.

A new eluent is inserted. Please note that when the IC system is restarted, a coupling (6.2744.040) must be attached instead of a column.

The freshly prepared eluent is aspirated into the syringe. To do this the purge valve must be opened one-half turn and the high-pressure pump must be started in manual mode in the software. After it has been established that there are no more air bubbles in the aspiration tubing, the purge valve is closed again.

The system should be rinsed until a stable baseline is achieved. The column is then attached.

The system pressure (without a column) with a flow of 1 mL/min should be as follows, depending on the setup:

• without suppression < 1.0 MPa
• with chemical suppression (MSM) < 1.5 MP
• with sequential suppression (MSM / MCS) < 2.5 MPa

The guard column and column are attached one after the other. In between the high pressure pump needs to be started. The high pressure pump needs to run for a few minutes until the columns are flushed completely and drops of eluent are coming out. As new connections are made, the high pressure pump needs to be stopped.

At the end, the entire system is started. Wait until the baseline is stable. The entire IC system is started by pressing Start HW. The system must be checked for leak-tightness. Once the baseline is stable, determinations can be started.

The column and guard column are removed and sealed with blind stoppers (6.2744.060). A coupling (6.2744.040) connects the two capillaries. The system is first rinsed with ultrapure water for 10 minutes using a flow of 1 mL/min.

The water bottle is removed. The aspiration filter is replaced. To prevent the formation of air bubbles, the new aspiration filter is dampened with eluent. The new aspiration filter is then screwed back on the eluent tubing.

Caution! Use gloves to carry out this work in order to prevent the contamination of the eluent.

When changing a system from a suppressed to a non-suppressed setup, the capillary connection has to be adapted. The detector capillary is removed from the MCS and put through one of the feed holes of the column oven. The detector capillary is connected to the coupling instead of the PTFE capillary of the suppressor.

After the aspiration filter has been replaced and the MSM / MCS removed, the IC system is rinsed with the new eluent using a flow of 1 mL/min for an additional 10 minutes. The new column can then be attached.

Important: The filled absorption tube must be replaced by an empty one for cation analysis.

The guard column and column are attached one after the other. Inbetween, the high pressure pump is started for a few minutes. The eluent is pumped until the columns are completely flushed. As new connections are made, the high pressure pump needs to be stopped.

The entire IC system is started by pressing Start HW. The system is checked for leak-tightness. The baseline is also observed until it is stable. Determinations can then be started.

The hardware is stopped in MagIC Net. Once the temperature has fallen down to room temperature and the pressure has fallen to 0 MPa, the column and guard column can be removed from the system. The leaflet for the column describes the optimum storage conditions for the column. A coupling (6.2744.040) is necessary to connect the capillaries.

The entire IC system must be rinsed with a 20% methanol solution at a flow of 1 mL/min for 10 minutes before being stored. All three channels of the MSM must be flushed too. Therefore the MSM has to be stepped twice in this time. This procedure is used to prevent bacterial growth. The column must be removed first.

The peristaltic pump tubing in the chemical suppressor (MSM) is rinsed with water for 5 minutes with Level 3. The contact pressure of the peristaltic pump is released at the end.

The eluent bottle must be prerinsed with ultrapure water several times. Only then 2 L of ultrapure water are transferred for degassing. The ultrapure water corresponds in quality to Type I (specific resistance > 18 MOhm * cm (25 °C)).

Prior degassing of the ultrapure water is important because dissolved CO₂ can affect the chemical equilibrium of a carbonate eluent. The water is degassed with a vacuum pump for approx. 5-10 minutes.

The carbonate and hydrogencarbonate that have been weighed out are added and stirred until all the salts have dissolved. Then degas again for 1 minute. The eluent is now ready.

The soda lime in the adsorber tube should be replaced twice a year. The soda lime is encircled by cotton. The cotton only has to be replaced if necessary. (Soda lime pellets with indicator, Merck 1.06839.1000)

The eluent tube is inserted in the cover. The tubing weighting and aspiration filter are then mounted. The end of the tubing should approximately reach to the center of the aspiration filter. The clamping screw is tightened with the wrench 6.2739.000.

Caution! Use gloves to carry out this work in order to prevent the contamination of the eluent.

The aspiration filter (6.2821.090) must be replaced if it takes on a yellowish discoloration, at least every 3 months.

Caution! Use gloves to carry out this work in order to prevent the contamination of the eluent.

To reduce the formation of air bubbles, the new aspiration filter is dampened with eluent using a syringe. The dampened aspiration filter is then screwed back onto the eluent tubing.

Caution! The eluent tubing should only be inserted to the middle of the aspiration filter.

Before dismanteling the pump head, the IC instrument needs to be shut off. Then, the tubing connections and capillaries are disconnected. The eluent tube is sealed with a stopper so that no eluent leaks out. The pump head is then removed using a size 4 hexagon key (6.2621.030).

The orange seal can easily be pulled out using the tool. In any case, it will be damaged after being removed.

The running-in behaviour can be accelerated by soaking new seals in 70% isopropanol. The seals are carefully inserted using the tool. Afterwards the pump head can be completed and built in again. The same procedure applies for the seal replacement of the second piston.

Macro pump head:

• Tool 6.2617.040
• Seal: 6.2741.040

Standard pump head:

• Tool 6.2617.010
• Seal: 6.2741.020

Pulsation in the baseline is often caused by the inlet or outlet valve on the high-pressure pump. The function is checked by spraying water through the valve on both sides. The liquid should only pass through in the flow direction. They must be replaced, if necessary.

Inlet valve: 6.2824.170

Outlet valve: 6.2824.160

The freshly prepared eluent is aspirated into the syringe. To do this, the purge valve must be opened one-half turn and the high-pressure pump must be started in manual mode in the software. After it has been established that there are no more air bubbles in the aspiration tubing, the purge valve is closed again.

The system pressure (without a column) with a flow of 1 mL/min should be as follows, depending on the setup:

• without suppression < 1.0 MPa
• with chemical suppression (MSM) < 1.5 MPa
• with sequential suppression (MSM/MCS) < 2.5 MPa

A sudden drop in pressure will damage the column. The IC system must therefore be switched off first. Once the pressure has fallen to 0 MPa, the purge valve can be opened one-half turn.

Inline filters (6.2821.130) must be replaced every three months. The same applies for the coupling (6.2744.180).

Caution! The filter must not be damaged during insertion.

The stator and rotor can be removed using a 9/64 hexagon key (not included in the normal scope of delivery of the instruments). Both parts are cleaned with 20% methanol in an ultrasonic bath for 10 minutes.

iColumn features:

• Automatic recognition by the MagIC Net software
• All column data immediately available (max. permitted pressure, max. measured pressure, max. permitted flow, max. measured flow, hours of operation, number of injections, etc.)
• Active monitoring of all important column functions
• Traceability of all column parameters

Additional practical tips can be found in the column catalog:

Brochure: The column program 2021 (8.000.5347, PDF, 13 MB)

The old column with a guard column or built-in coupling must be removed first. The guard column and column can then be installed in stages. Inbetween, the eluent should be pumped for a few minutes.

The entire IC system is started by pressing Start HW. The system must be checked for leak-tightness. Once the baseline is stable, determinations can be started.

The filter and frit (6.1011.130) built into the guard column should be replaced if there is a sharp rise in pressure or at least every 4 weeks. Take into account that the filter and frit are mounted planar.

For additional details, download:

Leaflet for 6.1011.030 METROSEP RP 2 Guard (8.107.1246, PDF, 111 KB)

The hardware is stopped in MagIC Net. Once the pressure has fallen to 0 MPa and the column and guard column have reached room temperature, both can be removed from the system.

The optimum storage conditions for the column can be found in the leaflet of the column. Columns are generally stored in eluent. A coupling (6.2744.040) is necessary to connect the capillaries.

It is recommended that the piston and cylinder of the dosing unit be checked regularly (e.g., semi-annually). The cylinder must always be emptied before the dosing unit is opened. The Empty command in the Manual window in MagIC Net can be used to do this. Afterwards, all of the tubings and the adsorber tube must be removed. Replacement of the inline filters is recommended in addition to the cleaning of the buret, when a buret is used for Dosino Regeneration.

The condition of the cylinder and piston can now be checked. The glass cylinder should not exhibit any corrosion. The plastic cover (PTFE) of the piston may not be damaged in any way. The piston can be removed using the piston pliers 6.1546.030.

Caution! Never separate the cylinder from the cylinder bottom.

All parts can now be cleaned. Do not use scouring agents! Allow to air dry.

If parts stick to one another, do not use force to separate them. Do not place parts in an ultrasonic bath. Place the dosing unit in ultrapure water for a few minutes. Very carefully try to loosen the parts by hand (without twisting).

The centering tube and housing are lubricated on their sliding surfaces with paraffin oil (6.2803.010).

Caution! The dosing cylinder and piston, especially their sealing lips, must not be damaged during assembly.

The piston stopper must be flush with the upper edge of the housing. To accomplish this, press the entire dosing unit head first on a tabletop. Then check whether the marking triangles are aligned. Turn to align the marking triangles, if necessary.

If the dosing unit is used on a bottle, then it is recommended that the adsorber tube be used on the Vent connector. The soda lime in the adsorber tube should be replaced twice a year. (Soda lime pellets with indicator, Merck 1.06839.1000)

The dialysis membrane and the filtration membrane must be checked regularly and replaced as necessary. A decreasing recovery rate when analyzing check standard solutions can serve as an indicator. It is recommended that the check standards are measured after every fifth to tenth sample. The cells can be opened with a 5 mm hexagon key (6.2621.070).

The dialysis or ultrafiltration cell can be cleaned with ultrapure water or, if necessary, with a 30:70 mixture of ethanol and water. Other organic solvents, e.g. acetone, will damage the Plexiglas cell. The cell can then be dried with a lint-free cloth.

A new dialysis or ultrafiltration membrane can be conditioned using the tweezers (6.2831.010) in a Petri dish filled with ultrapure water (approx. 2 min). The light blue separation paper has to be removed. The screws have to be tighened diagonally.

6.2714.010 Dialysis membrane (cellulose)

6.2714.030 Dialysis membrane (polyamide)

6.2714.020 Ultrafiltration membrane

Only PVDF pressure screws (6.2744.000) may be used for the capillary connections. Using PEEK pressure screws may lead to stress cracks in the cell! The cell must then be checked for leak-tightness. Moreover, no air bubbles should get caught in the cell.

Peristaltic pump tubings wear out over time. It is recommended that the contact pressure is checked regularly and the position changed monthly. A peristaltic pump tubing should be replaced, if necessary. It is essential that the connector be installed with the filter (6.2744.180) on the pressure side. The peristaltic pump tubing must cover at least three grooves.

The hose clamps must be applied again after installation. To do this, the clamps must be tightened slowly until the liquid flows. Once the liquid is flowing, tighten the clamps two click tighter.

The inline filter (6.2821.130) on the peristaltic pump tubing should be replaced every three months, or more frequently in the case of increased back pressure.

If the MSM leaks, the unit must be disconnected and then cleaned. The surface of the rotor and connecting piece can be cleaned with ethanol using a lint-free cloth. Beware, the rotor must be built into the correct position as indicated. After it is reattached, the back pressure should be monitored. The system pressure (without a column, with a conductivity detector) with a flow of 1 mL/min should be as follows, depending on the setup:

• without suppression < 1.0 MPa
• with chemical suppression (MSM) < 1.5 MPa
• with sequential suppression (MSM/MCS) < 2.5 MPa

Proper tightening when fixing the connector is important. First tighten gently with a finger. Then tighten with somewhat more force (approx. 3/4 turn) until the end stop is reached.

If the so-called Dosino Regeneration is used, then the Inline Filter (6.2821.130) must be replaced every three months. Furthermore, the dosing unit must be checked and cleaned on a regular basis.

It is recommended that the piston and cylinder of the dosing unit be checked regularly (e.g., semi-annually). The cylinder must always be emptied before the dosing unit is opened. The Empty command in the Manual window in MagIC Net can be used for this purpose. Afterwards, all of the tubing connections must be removed.

The condition of the cylinder and piston can now be checked. The glass cylinder should not exhibit any corrosion. The plastic cover (PTFE) of the piston may not be damaged in any way. The piston can be removed using the 6.1546.030 piston pliers.

Caution! Never separate the cylinder from the cylinder bottom.

All of the parts can now be cleaned. Do not use scouring agents. Allow to air-dry.

If parts stick to one another, do not use force to separate them. Do not place parts in an ultrasonic bath. Place the dosing unit in ultrapure water for a few minutes. Afterwards, attempt to loosen the parts very carefully by hand (without twisting).

The centering tube and housing are lubricated on their sliding surfaces with paraffin oil (6.2803.010).

Caution! The dosing cylinder and piston, especially their sealing lips, must not be damaged during assembly.

The piston stopper must be flush with the upper edge of the housing. To accomplish this, press the entire dosing unit head first on a tabletop. Afterwards, check whether the marking triangles are aligned, rotating them if necessary to accomplish this.

The adsorber tube should be used for certain applications, e.g., "Inline Eluent Preparation". The soda lime in the adsorber tube should be replaced twice a year. (Soda lime pellets with indicator, Merck 1.06839.1000)

Depending on the application, barely visible deposits may build up on the lenses over time, which can lead to higher adsorption and therefore to a noisy baseline. If the interference is not being caused by other parts of the system, the flow-through cell must be cleaned. There are three ways to do this:

1. Rinse the flow-through cell with methanol
2. Rinse the flow-through cell with another solvent (e.g. acetic acid and isopropanol in a 1:2 ratio)
3. Disassemble the flow-through cell and clean it manually

In order to disassemble the flow-through cell and clean it manually, the seals (6.2764.000) must be replaced. Also necessary are a slotted screwdriver (size 5) and a lint-free cloth. Be careful when handling the lens in order to avoid scratches. The lenses on both sides of the flow-through cell have to be cleaned.

Caution! The flat side of the lens must face inward.

The complete measuring cell is inserted into the amperometric detector. All of the electrode cables and the inlet and outlet capillaries are connected.

Additional deaeration via the reference electrode chamber is to be recommended at the time of initial start-up and is particularly important when it is used with the glassy carbon working electrode.

The cell must be deaerated each time it is opened in order to ensure that it contains no air bubbles.

Caution! The measuring cell remains switched off during deaeration.

In the Manual Control of the software, the high-pressure pump is started with one-half of the standard flow of the column used. The temperature of the oven and the amperometric detector are activated afterwards. Any eluent that may escape is collected with a cloth.

In order to obtain good measuring results, we recommend that the front cover be mounted.

Caution!

• Do not pinch any capillaries. Use capillary feed-through.
• Do not pinch any cables.

The measuring cell can be switched on afterwards using startup hardware and the system can be equilibrated.

Depending on the application, the measuring cell can be operated with a variety of different spacers. The measuring cell must be disassembled with a 2.5 mm hex key for the replacement of the spacer. The new spacer should be dry and lint-free at the time of use. The cell can be reassembled afterwards.

6.1257.810 Spacer 50 µm to Wall-Jet cell

6.1257.820 Spacer 50 µm to Thin-Layer cell

6.1257.830 Spacer 25 µm to Wall-Jet cell

6.1257.840 Spacer 25 µm to Thin-Layer cell

Electrodes are consumables. Polishing can be used to restore the original electrode activity a few dozen times, if the electrode has not been too severely corroded. In addition to daily checking by wiping with a soft cloth, the following sequence is recommended for the mechanical cleaning:

1. With a pencil eraser: The electrode surface is treated carefully with a pencil eraser.
   
2. With aluminum oxide powder from the 6.2802.000 polishing set: The aluminum oxide powder in the 6.2802.000 polishing set is mixed with distilled water in such a way as to create a thick slurry. The electrode tip is polished in an octagonal movement for approximately 10 s. Rinse afterwards with distilled water. Activation with aluminum oxide powder is recommended at the time of initial start-up for both glassy carbon and platinum electrodes.
   
3. Creating a plane-parallel grind with the 6.2802.200 maintenance set: The 6.2802.200 maintenance set enables plane-parallel grinding of the corroded surface of metal electrodes. Wet-grinding of the working electrode is recommended. This prevents grinding dust from flying about. In addition, it is recommended that a separate grinding disk be used for each electrode material. A coarser grain is used for grinding in the initial step, followed then by a finer grain. The electrode should be inspected visually after every 4 revolutions. Repeat the procedure as needed. The electrode requires grinding with a fine disk after it has been ground with a coarse one. The electrode should be rotated by a one-quarter turn at least twice between the revolutions in order to obtain a uniform grind.

Leaflet on maintenance set for working electrodes 6.1257.2XX (8.110.8025, PDF, 197 KB)

In the video, a gold working electrode before (left) and after the cleaning (right). No visual differences are to be seen in the case of glassy carbon and Pt electrodes. Nevertheless, they should be cleaned when there is a loss in sensitivity.

The auxiliary electrode can be cleaned once the working electrode has been removed from the cell. In addition, it is essential that the reference electrode be removed in order to prevent the dissolution of the palladium oxide layer.

A soft paper towel or cotton swab is soaked in 2 mol/L nitric acid. The electrode is carefully wiped off. Afterwards, rinse the entire measuring cell with ultrapure water and dry it with a lint-free cloth.

Tip: If the cleaning with nitric acid is not sufficient, then the auxiliary electrode can be rubbed clean with a cotton swab soaked in aluminum slurry in a manner analogous to the use of nitric acid. To accomplish this, the cell must be disassembled and the electrodes and the spacer must be removed.

Learn how to clean the combustion tube of your combustion IC system step by step.