FAQ Finder

During measurement, sample components may be absorbed by the plastic. This occurs in particular when measuring biodiesel and can cause the cover to expand. An important measure for counteracting this is to heat the cover after cleaning (see Cleaning after the determination). If heating the cover still does not enable a seal to be formed with the reaction vessel when it is closed, the cover must be replaced.

Metrohm offers service agreements tailored to your requirements. These range from standard maintenance with a priority response time to full support with an all-inclusive package and a guaranteed response time.

The temperature is the measuring parameter that has the greatest effect on the end result (induction time, stability time). If the temperature is not prescribed by a standard, the sample temperature should be selected in such a way that the result lies between 4 and 10 hours.
As a general rule:

• If the sample temperature is increased by 10 °C, the induction time halves.
• If the sample temperature is decreased by 10 °C, the induction time doubles.

Technical poster

8.000.6081 (Determination of the oxidative stability of biodiesel (fatty acid methyl esters, FAME))

tiamo is only installed in the program directory. The databases and backups are set up in the paths selected by the user during the installation procedure. Additional data (logs, etc.) is stored in the ProgramData directory (All Users\Metrohm).

Both the Multi-Mode Electrode and the Multi-Mode Electrode pro can be operated using a maximum of 6 mL mercury (roughly equal to 81.2 g). This amount is sufficient for approx. 200000 drops.

There are a number of possible reasons for a pressure increase in the system. First of all, find out the location of the pressure increase. The best way to do this is to remove one system component at a time from the flow path, starting from the eluent outlet, and check the measured pressure difference. The component causing the pressure increase must then be serviced or replaced. Typical components that can cause a high backpressure are:

• The Inline Filter (6.2821.120): The filter disk (6.2821.130) can be replaced.

• The guard column: Replace the guard column.

• The separation column: Regenerate the separation column according to the column leaflet (should be carried out only if the separation or peak shapes are affected as well). Note: Separation columns should always be operated with a guard column. Samples should always be microfiltered.

• The injector: If the increased backpressure is caused by the injector, you should have it cleaned by a Metrohm Service technician.

In the event of network interruptions, client enquiries to the database (Determination Start, Report, Database, and Export commands) are held until the database is accessible again (without time limit). Device processes are not affected − they continue to run.

The conductivity of the deionized water should not exceed 20 µS/cm. If the value measured at the start of the measurement is higher than this, it is indicative of a problem with the conductivity measuring cell. This is generally caused by the electrode being contaminated with sample residue. To avoid this, the measuring vessel and the conductivity measuring cell should be cleaned thoroughly after each determination (see Cleaning after the determination).

Devices, intelligent modules, and components are automatically detected by MagIC Net and registered under "Configuration". As soon as a new component is detected, a window appears in which the individual details can be adjusted.

Non-intelligent components and accessories can be registered manually in the appropriate category. This allows monitoring of all parts in the IC system that must be maintained or replaced at regular intervals.

A Method is used to define what, how, and when something is carried out and determined.

In MagIC Net, the method is composed of four windows.

"Devices" shows all instruments and modules used in the method along with their parameters. Clicking on the corresponding icon opens the parameters of this component so they can be adjusted.The "Analysis" is also created in this window. "Hardware assignment", "Data acquisition", and "Accessories" are defined here. The window "Evaluation – Components" has the sections Integration, Analysis Components, Standards, Calibration, and Results. Under "Results", it is possible to define "User-defined results", "Statistics", "Monitoring", etc. The third method window, "Time program", defines the exact analysis run. This defines all steps that the IC system or MagIC Net must execute. A time program can comprise a few consecutive steps or complex interleaving of subprograms. The fourth window shows the last chromatogram with the current calibration.

Port 3 of the dosing unit used can be connected to a waste canister using an outlet tubing. The outlet (port) 3 can be defined for the waste in the software (General settings or Configuration). With these settings, a significantly quicker preparation is ensured.

Results may be too low for the following reasons:

 

Cause	Remedy
Side reaction	Read for more details in the following FAQ: «How to recognize a side reaction?», «How to prevent side reactions?»
The sample is inhomogeneous	Increase the sample size. Homogenize the sample prior to the determination.
The sample dissolves incompletely	Read for more details in the following FAQ: «What can I do to improve the release of water?»
The pretreatment of the sample is not optimal.	Read for more details in the following FAQ: «What to do to improve the release of water?»
Titer is incorrect (volumetric KF titration)	Redetermine the titer with certified standards.
Titration stops too soon	Reduce Stop Drift or work with a relative Start Drift.
The sample gives off water even during sample preparation	Here we recommend optimizing the sampling and sample storage, as well as rapid working during the determination sequence.

Trend within the results

One reason for decreasing water contents in a series may be that the solvent is exhausted and must be replaced. Decreasing water contents within a series can also occur with samples which give off water during sample handling. Here we recommend optimizing the sampling and sample storage, as well as rapid working during the determination sequence.

A further possible reason for apparently decreasing water contents within a series in volumetric Karl Fischer titration is that the buret has not been prepared. The titrant in the cylinder and in the tubing is exposed to humidity, which can result in increased titrant consumption at the beginning of a series.
Increasing water contents within a series can occur with hygroscopic samples. Here we recommend optimizing the sampling and sample storage, as well as rapid working during the determination sequence.

Tip: You can recognize very quickly whether your sample is either releasing water, is hygroscopic, or unproblematic by determining the water content of the sample immediately and then leaving the sample to stand in a beaker in the laboratory air and determining the water content again after 10, 30, and 60 minutes.

Separation columns that are not being used must always be sealed and filled in accordance with the manufacturer's instructions before being stored. If there is no information available, the separation column should be stored in a refrigerator at 4–8°C

In the case of two-component-reagents, the water capacity is limited by the amount of SO2 and buffer in the solvent. Decreasing pH values and decreasing SO2 concentrations result in a drop in titration speed. Reagent manufacturers have published the following guideline: The cell solution should be replaced after approximately 30 mL of titrant have been used in the case of cell solutions with 20 to 25 mL of solvent.

One-component reagents have no limiting water capacity, because SO2 and buffer are added with the titrant. Care must nevertheless be taken to ensure that the methanol content does not drop below 25%, because otherwise the endpoint will be shifted.

Info: The water capacity indicates how much water can be determined in a particular titration solution.

Coulometric KF reagents contain iodide instead of iodine. Additional components are sulfur dioxide and imidazole, which are dissolved in methanol. Generally, coulometric KF reagents have a water capacity of 1000 mg H2O per 100 mL. Depending on the type of reagent the water capacity can also be lower.

Up-to-date information on the compatibility of MagIC Net with the individual Windows™ versions can be found in the Metrohm Software Center.

This effect is not uncommon. It is caused by degradation products in the bath sample. With successful determination of recovery in a "check standard", the method can be checked at any time.

A loud pump noise indicates that a large pump capacity is required to achieve the set gas flow. This can be caused by either a leak or a blockage in the feed lines to the pump. You should keep track of the cause, as it increases wear and therefore reduces the pump service life in the long run.

Possible leaks:

• Tubing connections on the rear of the instrument are not screwed tightly enough. Tighten connectors securely.
• One of the tubing connections on the rear of the instrument is defective. Replace tubing connection.
• The cover of the drying flask is not tightly screwed. Screw the cover on tightly.

Possible blockages:

• The dust filter on the rear of the instrument is clogged. Replace filter, see also Regular maintenance – Dust filter (6.2724.010).
• The filter tube (6.1821.040) in the drying flask is clogged due to dust from the molecular sieve. Remove dust by tapping out the filter tube. Replace the aspiration filter (6.2821.090), if necessary.

It is possible to count the sample injections in MagIC Net. As soon as the corresponding number is reached, you can use the "Time program command">"Insert new line" in the "Sample table" to insert a sample line with the data of the sample for a check standard.

You can prepare your own standard solutions from the appropriate salts or you can buy them directly from a chemicals supplier.

Please check that the pH value of the solutions is suitable for the respective separation columns. Standards and reagents especially for ion chromatography can be found for example here

The electrode cable has accidentally been jammed in the measuring head cover or a cable contact has been bent: On the 894 Professional CVS you can replace the electrode cable set (see 894 Professional CVS manual). On the 797 VA Computrace this needs to be handled by Metrohm Service.

All Metrohm Service technicians must undergo extensive service training and are certified by specially qualified trainers. Metrohm Service technicians have a corresponding service pass that is valid for two years.

The cables are not connected or not connected correctly:

• Connect the cables in accordance with the instructions in the manual.

The tubing connections are leaking:

• Check the tubing connections and tighten, if necessary.

The rinse and/or waste canister are sealed air-tight:

• Loosen the caps on the canisters a little or remove them.

With local installations (light and full) such problems can occur if the processor load is constantly high (>80%). This situation, however, is unusual, and therefore the on-site administrator should check why the processor is so overloaded. Normally the processor workload is >10%, with load peaks in between.

With a multi system the reasons for this may vary: server load very high, the network is unstable, above all under load (low response times), the network connection has briefly been interrupted.

We advise against mechanical treatment of platinum electrodes, e.g., by polishing with aluminum oxide!

If a titrator with Dosing Unit is not used for several days, then it is best to empty the Dosing Unit with the «Empty» command. In this way, you will avoid the formation of crystals in the Dosing Unit, the tubing, and the buret tip (antidiffusion valve).

If work is being done with an Exchange Unit, then you should immerse the buret tip in methanol in order to avoid crystallization. To accomplish this, you can either fill the storage vessel with methanol or continue to leave the buret tip in the closed cell filled with working medium, where it is immersed in the working fluid.

The Exchange Unit, the tubing, and the buret tip should all first visually inspected for crystals before the system is returned to operation. If crystals are present, then the tubing should be flushed with methanol or ethanol and then dried afterwards.

If no crystals are visible, then a small amount of reagent should nevertheless be dosed in order to check whether crystals have formed in the flat stopcock of the Exchange Unit. If reagent escapes from the flat stopcock, then the Exchange Unit must be disassembled and cleaned (see manual for the Exchange Unit).

Afterwards, flush the Exchange Unit by means of the Preparation/«Prep» command in order to make it ready for operation again.

Most likely, the VMS in the measuring vessel is contaminated. The contamination might have been caused by the chemicals used but also by organic additives.

Yes. See also «The more data there is, the slower tiamo becomes», under Databases in general.

The analytical quality attainable with Metrohm IC chiefly depends on the separation of the ions of interest on the deployed column.

When buying an IC column, you should make sure that it provides sufficient separation for the intended analytical samples. You can assess this using the reference chromatograms in the Column Catalog.

If problems should occur during your analyses, the first step is always to check the quality of the column and record a standard chromatogram. Compare the data on the column leaflet, e.g., retention factors, selectivity, number of plates, and resolution, with your own measurements.

Further information on handling IC separation columns is given in the brochures supplied with the column, in the Column Catalog, or in our column finder.

Column Finder

Statistics functions are available in the method for multiple injections. They can be used to calculate the mean value, the absolute and relative standard deviation as well as the minimum and maximum value of a "Result".

A correct reference potential of the reference electrode is an important factor for perfect results in CVS analysis. We recommended that you change the reference electrolyte c(KCl) = 3 mol/L at least every three days.

The problem can be rectified as follows: Go to the Windows system properties and select «System performance». Then select the «Expand» tab and click on [Settings]. The «Performance options» dialog will then be displayed. Select the «Visual effects» tab and deselect the «Show window content when dragging» checkbox.

 

Solid samples must be broken up before they are weighed into the reaction vessel. The particle size should be as uniform as possible.

Samples of this type are not mixed by the air flow during the determination. Only a small sample amount should be used to avoid a nonhomogeneous temperature distribution within the sample. We recommend selecting the sample amount in such a way that the base of the reaction vessel is covered evenly. A sample amount of 0.5 g is frequently used.

We also recommend using shorter air tubes for PVC (140 mm, order number 6.2418.120) with solid samples.

Dirty platinum pins can be cleaned with an abrasive agent such as Alox (polishing set, art. no. 6.2802.000) or toothpaste. Afterwards, they should be rinsed with ethanol or methanol. It is often sufficient to wipe off the indicator electrode with a soft paper tissue. This is particularly important when the electrode was immersed previously in an overtitrated solution, because deposits can form there that are not visible but nevertheless lead to overtitrations. If the sample itself adheres to the electrode, clean it off, either with an appropriate solvent or mechanically. Clean the platinum pins on the indicator electrode with a soft paper tissue and take care to ensure that the pins do not become deformed (pressed together) while doing so. They should always be parallel to one another.

The "User administration" has three predefined user groups ("Administrators", "Users", and "Removed users").

The only predefined user under "Administrators" is "Admin1". The first-time login as "Admin1" does not require a password. Assignment of a password is then prompted automatically afterwards. Administrators have full access permissions for all functions of MagIC Net, particularly for the exclusive editing of user management. The creation of a second administrator access is recommended so that, if one administrator is unintentionally deleted, the user management can still be edited.

Additional "Groups" can be created in addition to the existing group of "Users". The access permissions, signature permissions, and display standards can be freely assigned to these "Groups". Users created within these groups have the permissions assigned to the group. When a user is created, a start password must be assigned. This is a single-use password so that the user can log in once. The user is then prompted to change his or her password.

After pressing [Stop], the Exit track is executed, but if you press [Stop] again, the Exit track will be interrupted. As a result, there will be no database entry.

Detailed information on the maintenance work described below is given in the manual for your instrument.

Aspiration filter: The aspiration filter should be replaced if it is discolored or at least every three months. Contaminated aspiration filters can lead to pressure and baseline fluctuations.

IC pump: The piston, seals, and valves should be serviced at least once a year.

Inline Filter: The Inline Filter should be replaced if the backpressure increases or at least every three months.

Pulsation absorber: Maintenance is not possible. Defective pulsation absorbers must be replaced.

6-way injection valve: If there are problems with the precision, check the installation of the sample loop. More extensive maintenance should be carried out by a service technician.

Suppressor (MSM, MSM-LC, MSM-HC): If the capacity drops or a high backpressure builds up, the Suppressor Module must be regenerated, cleaned, or replaced.

Detector block (conductivity detector): A blocked inlet capillary can be shortened by a few millimeters. Backflushing with the high-pressure pump may also help. Caution: The pressure must be < 5 MPa. The detector block must not be opened under any circumstances.

Detector cell (amperometric detection): The working electrode can be cleaned and polished as described in the manual. The reference electrodes are maintenance-free. The Ag/AgCl reference electrode must be replaced at regular intervals.

MISP method to remove the matrix (unwanted substances in the sample) from the analyte.

The sample is injected into a stream of transfer solution (generally ultrapure water). The analytes are retained on the preconcentration column, and the matrix is then removed using an additional transfer solution. The analytes are injected after this cleaning.

Accessories

The following accessories are generally used to determine the oxidation stability of biodiesel (B100) and biodiesel blends:

• 6.1429.050 Reaction vessel long (250 mm)
• 6.2418.130 Air tube long (248 mm)
• 6.1428.030 Measuring vessel (glass)
• 6.1839.000 Iso-Versinic tubing

All the accessories required for 100 determinations are included in the scope of delivery of the 893 Professional Biodiesel Rancimat.

 

Standard method parameters
Sample amount	7.5 g
Measuring solution (water)	60 mL
Sample temperature	110 °C
Gas flow (air)	10 L/h
Evaluation	Induction time Automatic (2nd derivative) Optional (manual): tangential method

Databases containing a large number of determinations can become very large.

We thus recommend setting up a database management to limit the number and the size of the databases in MagIC Net. Thus databases can be created based on, e.g., weeks, months, projects, sample types, etc.

Databases that are currently not needed can be backed up and deleted from MagIC Net. The data remain as backup copies and can be restored at any time.

If the air tube is always positioned in the same way, the reproducibility of the results improves.

Fitting without foam barrier
If you do not use a foam barrier, we recommend that you position the air tube in such a way that the bottom end does touch the glass wall of the reaction vessel. 

Fitting with foam barrier (6.1451.010)

If you use a foam barrier, the position of the air tube is fixed.

Note! You must ensure that the foam barrier is fitted in the upper half. The foam barrier can melt if it is too deep in the heating block during the measurement.

Calibration method for very small concentration ranges (ng/L to µg/L) using a standard solution with a higher concentration that is easier to manage. This requires an additional injector and a preconcentration column.

This means that the eluent flow rate is not constant. Possible reasons for this are

• A leak in the eluent path: Eliminate the leak.

• A blockage in the eluent path: Eliminate the blockage.

• Gas bubbles in the eluent: Degas the eluent and check the connectors of the eluent degasser.

• The high-pressure pump has contaminated valves: Clean or replace the pump valves.

• The high-pressure pump has defective piston seals: Replace the piston seals and, if necessary, the pistons.

The peak type of each component peak is determined with a result variable (type). The peak type can be displayed using a user-defined result. The peak type is written as a combination of two or more letters. The first two letters describe the start and end of the peak. A two-letter output shows that the peak was integrated automatically. In case of manual integration, the next letter is an M (e.g. BBM, DBHM, etc.).

Inline preconcentration is a method in which the analyte is retained on a short column (the preconcentration column).

This preconcentration column is installed on the injector instead of the sample loop. When the injector is switched over, the preconcentrated analytes are sent to the separation column. Preconcentration is mainly used for very low concentrations (ng/L to µg/L range). It enables preconcentration of analytes from large sample volumes. A Dosino (e.g., with a 5 mL dosing unit) can be used in MiPCT setup for preconcentration of 44,000 µL of the sample solution, an automatic multipoint calibration using one standard solution, or a logical adjustment of the sample volume. This covers a concentration range of the samples of 1:1,000,000 (ng/L to mg/L).

The dosing units available for the 800 Dosino have volumes of 2 mL, 5 mL, 10 mL, 20 mL, and 50 mL. Since the 800 Dosino doses the total volume in 10,000 increments, the unit with the smallest possible volume should generally be used to obtain the highest possible accuracy.

We recommend the following:

• Eluent preparation: 50 mL dosing unit
• MIDT: 10 mL dosing unit
• MiPCT, MiPCT-ME: 5 mL dosing unit
• MiPuT, MiPT, suppressor regeneration: 2 mL dosing unit

If the sample cannot be weighted directly into the reaction vessel, it must be melted carefully in the water bath beforehand.

The temperature of the water bath should only be slightly above the melting point of the sample. If the sample is heated too much, it may change in ways that could affect the end result. The sample amount corresponds to the amount that is also used for liquid samples.

The measuring head is not correctly locked in place on the measuring head arm: Allow the measuring head to snap into place; you need to hear it click.

The sealing rings have aged or are defective: Please contact us.

The Metrohm CO2 Suppressor (MCS) requires CO2-free air. This means that the aspirated ambient air has to be precleaned using a CO2 adsorption cartridge. The CO2 adsorption cartridge must be replaced when approx. three quarters of the material has turned a violet color or at least once per year.

With manual evaluation, the EP is set in the corresponding coordinates selected (in this example the y1 axis represents ERC and the x axis represents volume). In the graph view of the determination, this EP is only visible if ERC has been selected as the y1 axis and volume as the x axis. Because the reading is usually selected as the y1 axis, the manually set EP «disappears» (is not displayed).

CVS measurements are temperature-dependent. Strong temperature fluctuations (+/- 4 °C) should be avoided to get reliable analysis results.

The CVS measuring instrument used should not be near the air outlet.

During the measurement, the temperature of the measuring solution should be kept constant. If a warm or hot bath sample is transferred into the measuring vessel, then the temperature should be adjusted. If necessary, it is possible to work with a measuring vessel with thermostat jacket (see image) and an external thermostat/cryostat. For more information, download our technical poster.

8.000.6027        Temperature dependence of CVS determinations (technical poster)

As a general rule, the auxiliary electrode is maintenance-free and does not require any special cleaning. If you want to mechanically clean the platinum pin, then you can also polish the surface. Make sure that you do not rotate the platinum pin while doing so because otherwise the internal contact may break.

Databases can be manually backed up under "Database manager". This can also be used to restore a backup copy of a database.

Every database can also be backed up automatically. This setting is in "Database manager" under "Properties" of the respective database.

To protect the column against foreign particles that could affect the separating efficiency, we recommend microfiltration of the eluents (0.45 µm filter) and aspiration through the aspiration filter.

Contaminants caused by abraded particles from the piston seals of the high-pressure pump can be avoided by fitting an Inline Filter between the pump and the injection valve.

You can use easily replaceable guard columns to protect the actual separation column and greatly extend its service life.

Samples must be free of particles before they are injected. We recommend filtering all sample solutions through a 0.45 µm filter. Furthermore, Metrohm Inline Ultrafiltration or Dialysis can also protect the column against unwanted components in the sample.

To ensure that MagIC Net operates reliably, all energy-saving functions must be switched off.

Find more information in our Software Center.

The client ID can be changed via Setup Routine and [Modify].

The reaction vessels and air tubes are disposable and should not be cleaned and reused. This is because:

• Removing sample residue is extremely time-consuming and therefore costly.
• Cleaning procedures that are typically applied damage the glass. The altered glass surface impairs the reproducibility and accuracy of the results.
• Poorly cleaned reaction vessels lead to scattered and, in some cases, even incorrect results.

Leading reagent manufacturers offer certified water standards for titer determination. We recommend the use of certified standards. They are simpler to handle, because larger sample volumes can be added here than with titer determination using distilled water.

Standard solutions can be obtained with the water contents 10.0 ±0.1 mg/g and 5 ±0.2 mg/mL, although the latter is not certified.

The possibility also exists of carrying out the titer determination with distilled water or with disodium tartrate dihydrate.

For regulatory reasons, registered users cannot be deleted. An administrator can set the user to "inactive" (no access permission) or to "removed".

Users with a "removed" status are shifted from the original group into the "Removed users" group and no longer have access permission.

The solutions used are pipetted manually: The solution can be added with 800 Dosinos with dosing units to obtain reproducible results.

The solutions are not added through the pipette opening: During a measurement the solutions should only be added through the pipette opening.

A. The reference electrode needs to be maintained. See also Reference electrode.

B. The baseline has not been set correctly. The baseline needs to be defined identically for each addition.