• Inspect the complete system for eluent leakage.
• The system can be left filled with buffer overnight. If you are not using the separation unit for a few days,
  1. wash the flow path with distilled water.
  2. Remove the column and the pH electrode
  (optional).
  3. Wash the flow path with 20% ethanol and store it in 20% ethanol. Make sure that all tubing and all flow paths used are rinsed

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Run the Calibrating the pH electrode procedure.

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• Check for leakage. If there is a sign of liquid leaking from the pump
  - Check the tubing connections.
  - Check the O-rings in the connection part. Replace the O-rings if necessary.
• If there are signs of erratic or pressure pulsation, flush the pump with 100% methanol and when distilled water.

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Check the inlet filters visually and replace them if necessary.

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Run the Checking the UPC monitor procedure.

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Run the Check the Flow Restrictor procedure.

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• Run the Cleaning the UV flow cell procedure.
• Change the pH electrode by running the Inserting the pH electrode procedure.

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• Check the drive sleeve on the tube rack. Replace if worn.
• Run the Checking tube shifts procedure to check the number of tube shifts.

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• Check that the top, bottom and moveable seal O-rings are in good condition. Replace if necessary.
• Check that the bottom end pieces are clean and undamaged.

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• Check that the mixer chamber is clean and without damage, run the Replacing mixing chamber procedure if required.
• Check the tubing connectors.

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Check for external or internal leakage. Run the Changing channel plate and distribution plate if required.

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Run the Replacing mixing chamber procedure.

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Replace O-rings

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• Run the Cleaning the conductivity flow cell procedure.
• Run the Cleaning the pH electrode procedure.

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Run the Cleaning and replacing check valves in the pump procedure.

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A good laboratory routine is to calibrate the pH measurement once a day, when the electrode is replaced or if the ambient temperature changes. The pH electrode is calibrated using standard buffer solutions in a two point calibration. The two buffer solutions can have any pH value as long as the difference between them is at least 1 pH unit. The calibration procedure can be done with the pH electrode either fitted in or removed from the flow cell.

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When calibrating the electrode out of the flow cell and changing from one buffer to another, rinse the electrode tip with distilled water and dab it carefully with a soft tissue to absorb the remaining water. Do NOT wipe the electrode as this may charge it and give unstable readings.

The steps below describe the procedure used with the electrode removed from the flow cell.

1
Remove the pH electrode from the flow cell and immerse the electrode in the first standard buffer solution (normally pH 7.0).

2
From the main menu, select menu Set Parameters by pressing the up or the down button. Press OK.

3
Select menu Setup and calibration. Press OK.

4
Select menu Setup pH and press OK.

5
Select menu Calibrate pH. Current calibration values are displayed (buffer 1– buffer 2).

Buffer 1 = fixed lower calibrated pH value. Range=0.00-14.00
Buffer 2 = fixed higher calibrated pH value. Range=0.00-14.00

Note: The values for buffer 1 and 2 must differ by at least 1 pH unit.

6
Press OK to access the settings menu. The order of calibration, buffer 1 or buffer 2, is optional. Press OK to start with buffer 1, or press the down button to start with buffer 2. In this example, we start with buffer 1.

7
This text disappears when the reading is stable and the following text is then shown:

Calibrate pH Buffer 1
( 7.00 ) 7.00

8
Adjust the pH value in the display with the up and down buttons so that it corresponds to the known pH value of the first buffer solution. Press OK.

9
At the buffer 2 calibrating menu, rinse the electrode tip with distilled water and then immerse the electrode in the second buffer solution (e.g. pH 4.0 or 9.0). Then press OK.

10
The text opposite disappears when the reading is stable and the text below is then shown.

11
Adjust the pH value in the display with the up and down buttons so that it corresponds to the known pH value of the second buffer solution. Press OK.

12
After the calibration with buffer 2, the system automatically enters the Calibrated Electrode menu. This menu shows the slope of the calibration curve, where 100% corresponds to 59.16 mV per pH step at 25°C. The asymmetry potential at pH 7 is shown as a mV value. Press Esc repeatedly to return to the Set Parameters menu.

13
Before use, rinse the electrode using distilled water.

A new electrode typically has a slope of 95–102% and an asymmetry potential within ±30 mV. As the electrode ages, the slope decreases and the asymmetry potential increases.

As a rule, when an electrode has an asymmetry potential outside ±60 mV and a slope lower than 80%, and no improvement can be made by cleaning, the electrode should be changed.

An electrode is still usable at lower slopes and higher asymmetry potentials but the response will be slower and the accuracy diminished.

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When calibrating with the electrode fitted in the flow cell, follow the above procedure but let at least 30–35 ml (with 2 ml mixer) of standard buffer solution be pumped through the system to stabilize pH. Leave the pump running while calibrating. Switch to the second standard buffer solution and repeat the procedure.

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The relationship between pH and the output signal from the pH electrode is temperature dependent. For accurate measurements during temperature changes, the pH measurement can be temperature compensated. In normal applications, when the temperatures of the buffers and calibration buffers are identical, temperature compensation is not necessary. When using temperature compensation, it is important that the temperature of the pH electrode is the same as that of the conductivity flow cell since that is where the temperature is measured.

1
From the main menu, select sub menu Set Parameters and press OK.

2
Select sub menu Setup and calibration. Press OK.

3
Select sub menu Setup pH and press OK.

4
Select sub menu Set pH Temp Comp. The current setting for showing pH is displayed. If on is shown, Tc is displayed in the running display. If off is shown (default), Tc is not displayed. Press OK to change the setting.

5
Select the desired setting and press OK.

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1
Select menu Check and press OK.

2
Select menu Check Lamp Intensity.

Note: R 215.5 S 214.7mV

If:
R<300mV for 254 nm,
R<150mV for 280 nm, or
R<150mV for 214 nm,

replace the lamp assembly according to the Changing the lamp assembly procedure (optional), or contact your your local GE Healthcare service representative for lamp replacement.

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1
Select menu Check and press OK.

2
Select menu Check Lamp Run Time.

Note: Hg 2300h Zn 340h

• The lifetime of a Hg lamp at 254 nm is typically 7000 hours in room temperature (in coldroom, typically 2000 h).
• The lifetime of a Hg lamp at 280 nm is typically 3500 hours in room temperature.
• The lifetime of a Zn lamp is typically 2000 hours in room temperature.

When necessary, replace the lamp assembly according to Changing the lamp assembly procedure (optional), or contact your your local GE Healthcare service representative for lamp replacement.

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The internal absorbance value for autozero can be checked to test the consistency of buffers.

1
Select menu Check and press OK.

2
Select menu Check Autozero. The autozero absorbance value for the wavelength used is shown.

Note: AZ 0.0001 AU

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1
Use a screwdriver to detach the end plate by removing one and loosening the other of the two holding screws on the lamp housing to be removed.

2
Slide the lamp housing off the filter housing.

3
Detach the end plate, as in step 1 above, from the lamp housing to be fitted to the optical unit.

4
Slide the lamp housing onto the filter housing. The lamp and signal cables should be on the same side. As you slide the lamp housing into position, depress the two pressure pads on the filter housing in sequence to facilitate the installation.

5
Refit the lamp housing end plate.

6
Slide the lamp housing firmly into place. There will be a faint click when the housing is positioned correctly. The Hg lamp housing can take up two positions, one for 280 nm, marked by on the filter housing, and the other marked by for all other wavelengths. The Zn lamp housing has only one position.

7
Set the wavelength to be used by selecting lamp position (indicated by a dot on the lamp housing) in combination with the appropriate filter, i.e. the dot on the lamp housing should be adjacent to the symbol on the filter housing corresponding to the symbol on the filter wheel for the filter to be used. A click will indicate that the filter is in position.

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Check that flow restrictor generates the following back-pressure: 

FR-902: 0.2 ±0.05 MPa

Check the back-pressure as follows:

1
Disconnect the flow restrictor.

2
Connect a capillary to port 1 of the injection valve.

3
Run the pump manually at 10 ml/min with water. Note the backpressure on the display.

4
Connect the flow restrictor to the open end of the capillary.

5
Run the pump at 10 ml/min with water. Note the backpressure on the display.

6
Calculate the backpressure generated by the flow restrictor. Replace it if it is not within limit.

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Pump a cleaning or sanitising agent through the flow cell. The standard recommendation is to pump 1 M NaOH for 30 minutes and then wash out with buffer.

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A clean flow cell is essential for ensuring the correct operation of the UV monitor.

1
Connect a syringe to the inlet of the flow cell and squirt distilled water through the cell in small amounts. Then fill the syringe with a 10% surface active detergent solution like Decon 90, Deconex 11, RBS 25 or equivalent, and continue to squirt five more times.

2
After five squirts, leave the detergent solution in the flow cell for at least 20 minutes.

3
Pump the remaining detergent solution through the flow cell.

4
Rinse the syringe and then flush the flow cell with distilled water (10 ml).

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Note: Handle the pH electrode with care

CAUTION! The tip of the pH electrode consists of a thin glass membrane. Protect it from breakage, contamination and drying out or the electrode will be destroyed. Always store the electrode with the end cover filled with a 1:1 mixture of pH 4 buffer and 2 M KNO3. Do NOT store in water only.

1
Unpack the pH electrode. Ensure that it is not broken or dry.

2
Before using the electrode, remove the electrode end cover and immerse the glass bulb in buffer for 30 minutes.

3
Carefully insert the electrode in the flow cell.

Tighten the nut by hand.

Note: If the flow cell is full of liquid, it is not possible to insert the electrode. If so, loosen the inlet connection while inserting the electrode to allow the liquid to run out from the flow cell. Remember to re-tighten the connector.

Note: If the electrode is not fully inserted, the system will leak and a dead volume will occur in the holder.

4
Connect the pH electrode cable to the socket pH-Probe on the rear of the system.

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1
Select menu Check and press OK.

2
Select menu Check Tube Shifts.

Check Tube Shifts
17564

When required, contact your local GE Healthcare service representative for replacement.

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1
Make sure the pump is stopped.

2
Place the buffer bottles lower than the mixer to prevent draining, and then remove the inlet and outlet tubing.

3
Open the chamber lock holding the mixer chamber. A spring is securing the chamber in position when the lock is opened.

4
Pull out the mixer chamber gently.

5
Move the stop plug to the right-hand inlet of the new mixer chamber.

6
Insert the new mixer chamber and close the lock.

7
Replace the inlet and outlet tubing.

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Replacement kits, Valve kit IV-908 and Valve kit PV-908, are available see Spare parts recommended to keep on site in the Spare parts section for code no.

1
Ensure that the valve is disconnected from the pump and the tubing are disconnected.

2
Remove the 4 screws on the front using the supplied 3 mm Allen key. Loosen each one equally in turn so the distribution plate comes off parallel to the valve body.

3
Slide the screws out.

4
Remove the distribution plate containing the 8 peripheral ports.

5
Remove the old channel plate and insert a new one.

6
Remount a new distribution plate so that the text i/o is horizontal and to the right of the central tubing connection. Using the Allen key, tighten the 4 screws in turn, a little at a time, until the distribution plate is fixed to the valve body.

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A replacement kit, Valve Kit INV-907, is available, see Spare parts recommended to keep on site in the Spare Parts section under the Related Products tab for code no.

1
Ensure that the valve is in position 1 and then disconnect it from the pump.

2
Remove the 4 screws on the front using the supplied 3 mm Allen key. Loosen each one equally in turn so the distribution plate comes off parallel to the valve body.

3
Slide the screws out.

4
Remove the distribution plate containing the ports.

5
Remove the old channel plate and insert a new one.

6
Remount a new distribution plate so that the text 3 is horizontal and to the right of the central tubing connection. Using the Allen key, tighten the 4 screws in turn, a little at a time, until the distribution plate is fixed to the valve body.

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Pump a cleaning or sanitising agent through the flow cell. The standard recommendation is to pump 1 M NaOH for 30 minutes and then wash out with buffer.

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If the conductivity measurements are not comparable to previous results, the electrodes in the flow cell may be contaminated and require cleaning. To clean the flow cell:

1
Pump 15 ml of 1 M NaOH at 1 ml/min through the flow cell either by using a pump or a syringe.

2
Leave it for 15 minutes.

3
Rinse thoroughly with 50 ml distilled water.

Note: If the flow cell is totally blocked, the blockage can be removed using a needle or a wire with a diameter less than 0.8 mm.

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Note: The pH electrode has a limited lifetime and should be replaced every six months, or when the response time is slow or the slope is out of range (<80%).

Use one of the following procedures to clean the electrode to improve the response:

• Salt deposits: Dissolve the deposit by immersing the electrode, first in 0.1 M HCl, then in 0.1 M NaOH, and again in 0.1 M HCl. Each immersion is for a period of 5 minutes. Rinse the electrode tip in distilled water.
• Oil or grease films: Wash the electrode tip in liquid detergent and water. If the film is known to be soluble in a particular organic solvent, wash with this solvent. Rinse the electrode tip in distilled water.
• Protein deposits: Dissolve the deposit by immersing the electrode in a 1% pepsin solution in 0.1 M HCl for five minutes, followed by thorough rinsing with distilled water.

If these procedures fail to rejuvenate the electrode, the problem is most likely a clogged liquid junction. 

Use the following procedure:

1
Heat a 1 M KNO₃ solution to 60-80 °C.

2
Place the electrode tip in the heated KNO₃ solution.

3
Allow the electrode to cool while immersed in the KNO₃ solution before retesting.

If these steps fail to improve the electrode response, replace the electrode.

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Faulty operation of the check valves is usually indicated by irregular flow, very low flow, or unstable pressure traces. Probable causes are air, dirt, or a damage in a check valve preventing it from closing to seal and hold the pressure. Liquid appearing at a banjo fitting might indicate that a check valve O-ring is damaged.

Required spare parts

• Check valve (there are four different check valves.)
• O-ring kit

 

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Try to clean the check valves in-place by pumping 100% ethanol for approximately 10 min. If this does not correct the problem, follow the instructions below to remove and then clean the valves.

If necessary, a check valve or O-rings might need to be replaced.

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If the condition of the check valve is not improved by in-place cleaning, remove it as follows:

1
Run the Remove the connection part procedure listed below.

2
The check valves in the connection part are locked in position with banjo fittings. Remove the check valves using the screwdriver/allen key.

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Before disassembling the pump, move the input liquid bottle below the level of the pump to prevent siphoning.

1
Turn off the system with the mains power switch.

2
Disconnect the inlet and the outlet tubing from the connection part.

3
Release the pump from the system.

4
Unscrew the two attachment screws using a 4 mm hex wrench.

5
Remove the connection part.

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1
Immerse the check valves in 100% ethanol and place in an ultrasonic bath for 5–10 minutes.

2
Repeat the ultrasonic bath with distilled water.

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Liquid appearing at a banjo fitting might indicate that a check valve O-ring is damaged. It might also cause reduced flow or pressure fluctuation.

Carefully replace both O-rings on the check valve with new ones if you suspect that an O-ring is damaged.

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If cleaning of the check valve off-line does not correct the fault, replace the check valve with a new one.

Note: Make sure that the check valves are installed in their correct positions. By mistake, an inlet check valve can be installed incorrectly in an outlet check valve position, and vice versa.

The check valves are of four different types:

– Inlet check valve short (1 pc.)
– Inlet check valve long (2 pcs.)
– Outlet check valve short (2 pcs.)
– Outlet check valve long (1 pc.)

The inlet check valves have line-shaped holes.
The outlet check valves have round holes.

Inlet check valve long

Inlet check valve short

Outlet check valve long

Outlet check valve short

To install a check valve:

1
Carefully insert the check valve fully.

Note: Make sure that the inlet check valves are installed next to the inlet (lower) port on the connection part, and the outlet check valves next to the outlet (upper) port.

2
Fasten the check valve using the screwdriver.

3
Run the Reinstall the connection part procedure below.

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1
Wipe the back of the connection part and the other parts behind the connection part with a clean cloth.

2
Check that none of the seven O-rings on the rear side of the connection part has come loose.

3
Fit the connection part in position. Fasten the two attachment screws using the 4 mm hex wrench.

4
Reconnect the inlet and the outlet tubing.

5
Purge the pump carefully and check that the fault is corrected.

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