Elektroda

The room temperature and/or the solution temperature are not constant: The room and solution temperature should be kept stable during the measurements (± 4 °C).

The reference potential is drifting away: Maintenance of the reference electrode should be carried out in accordance with the electrode leaflet.

The measuring vessel and the electrodes have been contaminated with organic additives. Thoroughly rinse the measuring vessel and the electrodes and use fresh VMS.

A. The electrodes were lifted out of the measuring solution when the sample was added. Please use the pipette opening for sample addition.

B. The temperature is instable.

When renaming a database, the path for the database is simply renamed, but if this database is in use (i.e., when a file is open in this path, e.g., during backup, when this database is opened in tiamo, or when Windows Explorer is opened in this path) renaming will fail.

Current sample data under "Single determination" and "Determination series" can be checked with the "Run test for determination(s)" (green check mark or under the "Tools" menu). This checks whether the sample data are complete, whether the required devices and components are available, and whether the method is plausible.

Dismantle the dosing unit as described in the manual for the "807 Dosing Unit" and clean the parts with ultrapure water. If a dosing unit is not being used, rinse it with ultrapure water and drain it.

Video: How to clean the dosing unit

The balance should have a minimum resolution of 0.1 mg.

Crystals have formed (in the dosing cylinder, on the valve disk or in the capillary):

• Check the flow path.
• Rinse the dosing unit and the connected tubing and capillaries (prepare function) when the measuring system is not in use.
• Clean the dosing unit at least every two weeks.

The recovery rate can be calculated if a determination of the sample type "Spiking" is carried out after the "Sample".

The concentrations of the spiking solution are defined in the method. More than one spiking solution can be defined.

A "batch" is a collection of different "Determinations" within a database.

The assignment of determinations to a "batch" can be carried out when entering the sample data at the workplace. An existing or a new batch name can be chosen. In the first case, the determinations are added to the selected "batch", and in the second case, a new "batch" is created. In the database, it is also possible to create or delete a "batch" or to add existing determinations to a "batch".

These determinations can be simply filtered out of the whole set of determinations using the batch names. The batch assignment is used for fast viewing of data that belong together. There are also further options, such as filters, etc., to find data.

The maximum batch size is 500 determinations. If an attempt is made to add more determinations, these will be ignored. New determinations are normally stored in the "Database". No data is lost.

If a "Batch" is deleted, only the links of the determinations to the "Batch" are deleted, but no data.

Our electrode finder helps you to find the ideal electrode for your titration in just a few clicks.

Go to the electrode finder

If the sample amount ranges between the minimum and maximum amount possible (see What is the smallest and what is the largest sample amount that I can use for the determination?), an error of ±10% of the sample weight is irrelevant.

Technical poster

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

After recalculation the result disappears from the view. This is not a bug, but can occur if the database view has been filtered. After recalculation the view is updated, thus a result can «disappear». In this case, the filter must be reset or changed.

In the safety settings, under «Logoff» the option «No processing of workplaces in the BUSY status» must be ticked.

The electrode surface of the Ultra-Trace electrode can be regenerated with the special polishing set, art. no. 6.2802.020.

The reference electrode is not yet equilibrated: After maintenance of the reference electrode, wait for at least 20 min before starting a measurement.

The platinum electrode tip is contaminated: Condition the working electrode in pure VMS.

The platinum electrode tip has been used for a very long time: Immerse the platinum electrode tip in c(NaOH) = 0.5 mol/L for approx. 10 min and then thoroughly rinse with distilled water. Replace the platinum electrode tip if necessary.

The VMS is contaminated: Check whether the reagents are clean. Only reagents with degree of purity "analytical grade" or better should be used.

The water quality is poor: Use distilled water, type-II grade (ASTM D1193-91) or higher.

The measuring solution is contaminated by diffusion: No infeed tubing other than the four-way micro dosing tip (6.1824.000) may be immersed in the measuring solution.

The following prerequisites must be met for the backup function to work:

• BackupServer.exe must be running (check in Task Manager).
• On the server (tiamo multi license) or on the client (tiamo full or light license) a user with appropriate rights must be logged on and remain in Windows.
• This user plus the system user need at least Modify rights for the backup and database directories.
• In the backup directory there must be sufficient space free to create a new copy of the database. The old backup will not be deleted unless this copy has been created. tiamo will thus temporarily need more space.
• The firewall settings must be correct (see «General»).

The cell constant of the conductivity measuring cell used in the Rancimat lies between 1.0 and 1.2 cm-1. For measurements in which the induction time is to be determined, more precise calibration is not required, as only the relative change in conductivity is evaluated in the case of the induction time.

If, however, the stability time is to be determined, in which the absolute change in conductivity is evaluated, we recommend that you determine the cell constants. You can find more detailed information on working with calibrated conductivity measuring cells and determining the cell constants in the manuals for your instrument and the software used.

The columns may only be used in the flow direction. A guard column should always be used. This must be replaced at regular intervals (in the case of a Metrosep RP 2 Guard, only the filter and the frit may need to be replaced). To increase the service life of a separation column, check, e.g., the quality of the chemicals used, the water, and sample preparation (e.g., filtered or dialyzed samples).

The electrolyte vessel can be filled with any electrolyte that is a good conductor. If chloride interferes with the determination, you can use KNO3, for example, instead of KCl. However, you should not change the electrolyte in the internal reference system. Using a different electrolyte here instead of c(KCl) = 3 mol/L changes the reference potential. This is also the case if you are using a different concentration of KCl.

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.

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.

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).

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.

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.

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.

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.

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

 

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.

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.

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.

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 electrode surface of glassy carbon electrodes can be regenerated by polishing with aluminum oxide.

The method and the export and report templates are stored in the determination in addition to the data.

1. Check the sample size.
2. Check whether the titer and concentration of the titrants are correct.
3. Check the calculation formula in the method. Is the correct equivalence point used for the calculation?
4. Check the system for air bubbles in the dosing cylinder and/or in the tubing connections.
5. Check whether the stirring rate is adequate. As a general rule, this should be as high as possible. However, try to avoid the formation of a vortex during stirring.
6. Check whether the titration might be too quick. You can use the titration parameters “signal drift” and “min./max. waiting time” to adjust the titration rate.
7. Check whether the sensor is still suitable for the titration. Sensors that are old or dirty can result in longer response times.

The auxiliary electrode can be immersed for a few seconds in concentrated nitric acid to oxidize an accidentally applied metal coating. If after another measurement foreign metal should be found on the surface again, then the method parameters and electrode connectors need to be checked.

No, the platinum electrode tip may not be treated in an ultrasonic bath. This will irreversibly damage the electrode.

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)

Find more information in our Software Center.

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.

Select the determinations of this standard in the "Database" as well as all determinations of samples that are to be recalculated. In the "Determinations" menu, select "Reprocessing…" or click the corresponding icon. Select the affected standard in the "Reprocessing table" and open the reprocessing of sample data by double-clicking or via "Edit">"Edit line". Correct the "sample type" and then select "Apply" and "Close". Select "Reprocessing" and then the option "From the standards of the reprocessing table". All the determinations are recalculated using the parameters of the selected line. If the result of the reprocessing is satisfactory, save the reprocessed determinations by closing the reprocessing window with "OK". The procedure for further problems during "Reprocessing" is described in the online help under "How to proceed?".

It is not possible to repair the driving axle. The driving axle is a consumable and needs to be replaced at regular intervals. Driving axles with a mercury contact are supplied in a bag under protective nitrogen atmosphere. We recommend keeping the storage time of driving axles with a mercury contact as short as possible.

• EN 14112 «Fatty acid methyl esters (FAME) – Determination of oxidation stability (accelerated oxidation test)»
• EN 15751 «Automotive fuels – Fatty acid methyl ester (FAME) fuel and blends with diesel fuel»
• EN 16568 «Automotive fuels – Fatty acid methyl esters (FAME) fuel and blends with diesel fuel – Determination of oxidation stability by rapidly accelerated oxidation method at 120 °C»

Increased baseline noise can be caused by various components:

• The eluent is not sufficiently degassed: Make sure that the connectors of the eluent degasser are tightly connected.

• The eluent path has a leak: Check the connections.

• 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 pulsation absorber is not connected or is defective: Connect or replace the pulsation absorber.

• MCS – The CO2 cartridge is exhausted: Replace the CO2 cartridge.

• MCS – The vacuum pump is faulty: Please contact Metrohm Service.

MISP method for automatic sample extraction, e.g., extraction of ions from (bio)diesel.

Similar to MiPCT, but with additional Inline Matrix Elimination.

The solvent keeps flowing into the titration vessel after the addition, without the «addition» key being pressed.
Set the solvent bottle up in such a way that the fluid level in the bottle is lower than in the titration vessel.

Solvent is added simultaneously during aspiration.
The drying tube in the titration vessel is blocked:

• Enlarge the hole on the drying tube cover to at least 2 mm
• Refill the drying tube, do not pack too tightly, possibly remove some of the molecular sieve.

The pump conveys no fluid.
Press the «addition»/«aspiration» key more strongly.

• In most cases the bottle attachments are not screwed tightly enough to the reagent and waste bottles
• Check all connections for leak-tightness
• Check whether the 803 Ti Stand is set up correctly

GLP (Good Laboratory Practice) requires, among other things, periodic checking of the analytical instruments for their reproducibility and correctness on the basis of Standard Operating Procedures (SOPs). It is recommended that the instruments are qualified on a regular basis

For more information please contact us.

A. It is usually sufficient to clean the platinum pins of the electrode with a soft paper tissue. However, you should take care to ensure while doing so that the platinum pins are not pressed together. They should always be parallel to one another.

B. In volumetric KF titration, the antidiffusion valve on the buret tip should be checked.

See the photo: good buret tip in comparison with defective buret tips

C. Check if you are using the recommended parameters:

Volumetric KF titration

 

	Ethanol-containing reagents	Methanol-containing reagents
Polarization current Ipol	20 µA	50 µA
Endpoint indication at	500 mV	250 mV

Coulometric KF titration

	Ethanol-containing reagents	Methanol-containing reagents
Polarization current Ipol	10 µA	10 µA
Endpoint indication at	20 mV	50 mV

D. A further cause of overtitration could be that the initial solution no longer contains sufficient methanol or ethanol. In such a case it is worthwhile to renew the cell solution and/or to check whether too much solubility promoter has been used. Read for more details in the following FAQ: «How often must the KF working medium be replaced?».

See table: Solubility promoters for volumetric and for coulometric titration

Volumetric KF titration

Solvent	Percentage	Samples
Formamide	max. 50%	Sugar samples, salts
Chloroform	max. 70%	Oil, grease
Long-chain alcohols	max. 50%	Oil, grease
Xylene, toluene	max. 70%	Crude oils with tars

Coulometric KF titration

Solvent	Percentage	Samples
Formamide*	max. 20%	Sugar samples, salts
Chloroform**	max. 30%	Oil, grease
Long-chain alcohols**	max. 30%	Oil, grease
Xylene, toluene**	max. 30%	Crude oils with tars

 
* Only with generator electrode without diaphragm.
** Use generator electrode with diaphragm if the amount of solubility promoter is higher than 10%.

Additional measures:

E. Increasing the stirring rate.
F. Check whether the platinum pins of the electrode are immersed completely in the cell solution.
G. Check whether the correct reagents were combined: if the titrant of the two-component reagent is used with methanol, the KF reaction cannot take place, because no SO2 is available for the reaction. (Only volumetric KF titration.)

Results may be too high 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 hygroscopic	Here we recommend optimizing the sampling and the sample storage as well as working speedily during the determination.
The sample is inhomogeneous	Increase the sample size. Homogenize the sample prior to the determination.
Overtitration	Read for more details in the following FAQ: «Overtitration took place, i.e., the titrated solution is dark yellow to brown instead of light yellow. How to prevent this?»
Only for volumetric KF titration:
The titer has changed since the last determination	Redetermine the titer.
Air bubbles in the tubing	Flush the tubing system using the Preparation/«Prep» command.
Non-leak-tight tubing system	Check for crystals in the tubing system. Check whether tubing is connected tightly. Check tubing connections.

In exceptional cases, the evaluation algorithm cannot calculate results with the "Nonlinear regression technique" curve type. You should be able to solve the problem by selecting the "Linear Interpolation" curve type.

You can find video sequences and more information to assist you with the maintenance and care of your Metrohm IC system here:

Product Help: IC Maintenance

Undersized peak areas often indicate that the sample quantity is too small.

• There is a leak in the sample path: Check the sample path.

• The sample path is blocked: Check whether the sample is flowing during filling of the sample loop. If the sample flow rate is too low or zero, check the settings and then look for the blockage in the sample path and remove it.

• The sample loop is not completely filled: Adjust the transfer time.

• There are gas bubbles in the sample: Use the sample degasser.

• The MCS (CO2 suppressor) is not connected: Connect the MCS and check the CO2 cartridge.

• 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 original method of regenerating the MSM is based on feeding the regenerating solution using a peristaltic pump. It is also possible to use a Dosino that is specially reserved for this purpose. Dosino Regeneration uses a defined volume of regeneration solution for each procedure. This allows control of the volume and prevents it running empty.

The Metrohm Suppressor Module (MSM) has 3 suppressor compartments that are in turn used for suppression, are regenerated or are rinsed. To ensure that each new chromatogram is recorded under comparable conditions, every analysis is carried out with a freshly regenerated suppressor compartment. The change-over from one suppressor compartment to the next is carried out automatically between the chromatograms. Operation of the Suppressor Module requires a peristaltic pump or a Dosino (Dosino Regeneration) to transport the regeneration solution to the suppressor compartment. In the usual STREAM process, the detector effluent is used to rinse the regenerated suppressor compartment. Alternatively, ultrapure water can also be used as the rinsing medium (via a Dosino or a peristaltic pump). The suppressor should always be regenerated against the eluent flow direction. Therefore, you must install the suppressor in accordance with the labeling on the connecting piece. The Metrohm Suppressor Module must never be switched over when dry because it may jam. The capacity of the suppressor compartments depends on the eluent and flow rate and is exhausted after about 1–2 hours or even earlier. If there are extended pauses between the individual measurements, we recommend using the Autostep function of MagIC Net that automatically changes over the MSM, e.g., at intervals of 10 min.

A. No sample was added. If requested, add the required sample quantity.

B. The sample does not contain any brightener. Make sure that the sample is fresh. The brightener will volatilize over time.

We do not recommend the use of a screen saver.

The potentiostat integrated in the Metrohm CVS instruments can easily measure the smallest current with a high degree of precision. For this reason, it is also possible to get precise measurement results with smaller platinum electrode tip diameters. In a few exceptional cases, the method parameters need to be adjusted.

The background conductivity is defined by the eluents and the suppression reaction. This means that the eluent composition may be incorrect or suppression is incomplete. If suppression is used, make sure that the suppressors (MSM and MCS, if present) are connected correctly. Check the flow of the regeneration solution and the rinsing solution.

You must ensure that the PTFE tubing does not feed the air directly onto the conductivity measuring cell. If gas bubbles are released onto the electrode, then this results in noisy measurement curves.

PTFE tubing position OK:

 

PTFE tubing position not OK:

 

Adjustments and changes made in "Reprocessing" for a series of determinations are only valid for these determinations after closing with "OK".

If these changes are to be applied to the current method, they must be saved in the "Reprocessing" window.