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The three-electrode system is the most commonly used configuration in electrochemistry. This system uses three electrodes: a working electrode (WE, working electrode), reference electrode (RE, reference electrode) and an auxiliary electrode, also called a counter-electrode (CE, counter/auxiliary electrode).

During an electrochemical measurement, current flows between the working electrode (WE) and the counter electrode (CE). The potential difference is controlled between WE and CE, while precise potential measurement is performed between the working electrode (WE+S) and the reference electrode (RE).

In a three-electrode system, the measuring clamp S (sense) is connected to the working electrode (WE), so that the potential of WE relative to RE can be accurately measured and/or controlled.

The four-electrode system is used in applications where it is necessary to precisely measure the potential difference (measured between the reference electrode RE and the measuring electrode S), which is created as a result of current flowing through a precisely defined phase boundary - between the working electrode (WE) and the counter-electrode (CE).

This type of configuration is not commonly used in classical electrochemistry. It is most often used to study ion transport across membranes or two-phase systems of immiscible liquids.

This system enables the determination of interfacial resistance or membrane conductivity by separating the current path (WE–CE) from the potential measurement path (RE–S), which minimizes the influence of ohmic drops on the measurement result.

Reference electrode (RE, reference electrode) is an electrode with a stable and well-defined potential against which the potential of the working electrode (WE) is measured.

Its main function is to act as a reliable and repeatable potential reference point in an electrochemical system, enabling accurate measurement of the working electrode potential.

W hereby The study lists the most commonly used reference electrodes and their scope of applications.

Auxiliary electrode (CE, counter/auxiliary electrode) is designed to "collect" current in an electrochemical system. To ensure the potential stability of the reference electrode (RE), no current should flow through it. Due to the electrometer's very high input impedance, current in the system flows only between the working electrode (WE) and the auxiliary electrode (CE).

It is important that the auxiliary electrode is made of an electrochemically inert material so that it does not generate by-products that could disrupt the system being tested.

Additionally, the surface of the auxiliary electrode should be larger than the surface of the working electrode, which helps to limit its polarization and ensure the correct measurement process.

The lowest current range on the device represents a setting optimized for measuring very low currents (high sensitivity), while the actual lowest measurable current can be several orders of magnitude lower – and is limited by factors such as noise, electrochemical system properties, measurement conditions, cabling, etc.

Current resolution, in turn, is determined by the number of bits in the analog-to-digital converter (ADC) and the selected current range. It defines the smallest current change that the instrument can resolve, but it does not indicate the smallest current that can be reliably detected.

To achieve the best measurement quality, select the lowest possible current range that does not overdrive the signal—this maximizes resolution. However, it's important to remember that the actual detection threshold in practice is most often determined by noise and the limitations of the entire measurement system, not just the nominal range or resolution of the equipment.

Open Circuit Potential (OCP, open-circuit potential) is the potential of the working electrode (WE) relative to the reference electrode (RE) in the absence of current flow through the system (i.e., with an open circuit). The open-circuit potential (OCP) is of great importance in electrochemical studies because it constitutes a reference point — the resting potential of the system, measured without disturbing it by applying current or potential.

OCP corresponds to the equilibrium potential at the electrode-electrolyte interface, where the rates of oxidation and reduction reactions at the electrode surface are equal. As a result, there is no net current flow, although electrochemical processes continue to occur in both directions. This is a good indicator of the equilibrium state in an electrochemical cell. OCP is a key parameter in assessing the thermodynamic stability of materials, analyzing their corrosion behavior, and monitoring changes occurring on the electrode surface.

Additionally, it serves as a reference point for other electrochemical techniques, such as electrochemical impedance spectroscopy (EIS) or corrosion measurements.

The rise time of a potentiostat is defined as the time interval required for the output signal to increase from 10% to its final amplitude of 90%. This parameter is particularly important in experiments involving very fast electrochemical phenomena.

Reliable measurement of such fast processes is only possible if the time constant of the electrochemical system is shorter than the analyzed time intervals.

For all Metrohm Autolab potentiostats, the standard measuring cable length is 1.5 m. Device specifications are tested and guaranteed only using cables of this length.

However, it is possible to order and use longer cables. To do this, please contact us.

Compliance voltage: refers to the maximum voltage that the potentiostat's internal circuitry can deliver to the auxiliary electrode (CE) to achieve and maintain a given voltage at the working electrode (WE) relative to the reference electrode (RE). This can be considered the device's limit. If the electrochemical system's resistance or the experimental requirements require a higher voltage than the potentiostat's limit, the device reports an "overload," meaning it cannot maintain the set potential. A higher value of this parameter provides greater flexibility, so advanced models—such as the VIONIC (±50 V)—are better suited for high-resistance or more demanding electrochemical systems.

Applied voltage / potential: This is the user-set voltage that the potentiostat should maintain or scan at the working electrode (WE) relative to the reference electrode (RE). It is therefore a given experimental condition that forces an electrochemical reaction to proceed or enables its measurement.

The key difference between a potentiostat and a galvanostat is what is being controlled during measurement:

• Potentiostat controls voltage and measures current.
• Galvanostat controls current and measures voltage.

Both devices are commonly used in electrochemical experiments, and the mode chosen depends on whether a constant potential (potentiostat) or constant current (galvanostat) is required. All Metrohm Autolab instruments offer both modes of operation, providing flexibility for a variety of electrochemical applications.

Potentiostatic mode is typically used when:

• the system impedance is high,
• it is required to scan the potential in a specific range (e.g. in cyclic voltammetry),
• the aim is to study reaction mechanisms, redox potentials or electrochemical kinetics,
• the current response to a controlled potential is analyzed (e.g. in diffusion studies or Tafel analysis).

Galvanostatic mode is typically used when:

• the system impedance is low (e.g. testing batteries and cells),
• it is required to maintain a constant current, e.g. in an electrolyte or during electrochemical deposition.

The VIONIC potentiostat will handle any K-type thermocouple.

In Autolab AUT302N, AUT204 potentiostats and in M101/M204 multi-channel systems, the PX1000 module is required to support Metrohm Pt1000 sensors.

For more information, please contact us.

In a state Cell-Off the electrochemical system is switched off in the sense that no current flows between the auxiliary electrode (CE) and the working electrode (WE), but the potential is still measured between the reference electrode (RE) and the measuring terminal (S).

In case of Cell-Isolated There is no electrical connection between the electrochemical system and the VIONIC potentiostat electronics. This condition can occur due to the system's protection tripping or the device entering an error state. In this state, no current or potential values are transmitted to the potentiostat.

For detailed information, please refer to the user manual. INTELLO and VIONIC.

When any part of the electrochemical system (including the measuring cell or electrolyte) is connected to ground (earth), electrochemical measurements may only be made using a potentiostat/galvanostat with floating electronics.

Otherwise, it is recommended to use non-floating mode for optimal measurement performance.

VIONIC is equipped with the ability to select floating operation mode in 3 grounding variants.

Metrohm Autolab rotators used in RDE, RRDE, and RCE experiments are controlled and fully integrated with both INTELLO and NOVA software. They also offer single-speed manual control.

Hydrodynamic data analysis is available in NOVA and can be used for both INTELLO and NOVA measurements.

All Metrohm Autolab instruments come with a 3-year warranty.

Instruments and software will be supported for at least 10 years after the end of production of a given model.

A potentiostat/galvanostat is a precision device used to control and measure electrical parameters—potential and current—in an electrochemical system. It is a fundamental tool for conducting electrochemical experiments such as cyclic voltammetry, chronoamperometry, and chronopotentiometry, providing precise control of the applied potential or current.

An electrochemical impedance analyzer is a specialized add-on module, often integrated with a potentiostat/galvanostat. It allows for the application of AC signals over a wide frequency range and measurement of the impedance of an electrochemical system. This technique, known as electrochemical impedance spectroscopy (EIS), provides detailed frequency-dependent information about electrochemical processes.

EIS data allow the description of electrochemical systems by providing information on processes occurring at the electrode-electrolyte interface, such as charge transfer, diffusion, double layer charging, adsorption, and other parallel or sequential phenomena.

For an electrochemical impedance spectroscopy (EIS) measurement to be correct and interpretable within the framework of impedance theory, the following basic conditions must be met:

Linearity: The electrochemical system must respond linearly to an applied AC signal. This means that doubling the input signal amplitude should result in a proportional (doubling) increase in response, without the creation of harmonics—the response should consist solely of the fundamental frequency component.

Constancy over time: The system must remain in a steady state throughout the measurement. Its basic properties (e.g., surface condition, concentration profiles, layer thickness, temperature) should not change.

Causality: the system response must be directly induced by the applied AC excitation, without the influence of external disturbances disturbing the input-output relationship.

Finiteness: The real and imaginary parts of the impedance must assume finite values over the entire frequency range under consideration. This means that at very high and very low frequencies, the impedance tends to limit values or predictable behavior.

Yes. EIS measurements above 1 MHz require the use of special equipment (VIONIC or ECI10M module) and specially designed measurement cables.

EIS measurements above 1 MHz can be performed in potentiostatic mode.

Yes, the VIONIC can be connected both to a network and directly to a computer. The number of connected VIONIC devices depends on the capacity and performance parameters of the given network. Each VIONIC potentiostat has a factory-programmed IP address, but this can be changed to suit the network's requirements.

Measurements can be performed simultaneously on multiple VIONIC instruments using a single computer running INTELLO software.

 The number of instruments connected in this way depends on the performance of the network and computer.

It is recommended to contact your IT department to prepare the appropriate network settings to connect VIONIC to the network.

The VIONIC's built-in memory can store up to 10 million data points, depending on the type of measurement being performed.

If the computer is disconnected from VIONIC during an experiment, the INTELLO software informs the user how long the measurement can continue without a connection to the computer.

INTELLO is the new control and data acquisition software for VIONIC potentiostats. NOVA is the control and data acquisition software used in the AUT302N, AUT204, AUT101, Autolab IMP systems, and the M101/M204 multi-channel potentiostats.

The two software packages are not compatible with each other, however, data measured in INTELLO can be directly exported to NOVA if necessary.

Yes. INTELLO includes a complete library of default procedures covering all electrochemical techniques. These procedures are ready to use and can be edited, allowing you to save modified procedures.

INTELLO allows both routine and exploratory work: you can use basic parameters by changing only selected values, as well as edit measurement sequences using advanced commands such as repetition loops, automatic data export and other functions.

Editing procedures allows you to save and copy their fragments, but it is not possible to transfer them between INTELLO and NOVA programs.

Topography measurements are suitable for samples with microscale roughness (analysis range of approximately 1–60 µm). Additionally, samples must be diffusive, i.e., opaque. Sample height is limited to 22 mm.

The minimum and maximum droplet size depends on the type of liquid and the needle used, as well as the substrate. The table below provides approximate values for water.

All volumes refer to drops suspended from the needle (except for the picoliter dispenser). This is because the amount of liquid transferred from the needle to the substrate depends on the surface area:

• if the substrate is highly hydrophilic, more liquid is transferred
• if it is highly hydrophobic, the amount of liquid on the surface may be less than in the needle

Please note that the values given are approximate and depend on the measuring system and environmental conditions.

When comparing the results obtained using the ring and plate methods, they may differ depending on the liquid—especially in surfactant solutions. This is due to differences in the measurement principle.

In the Wilhelmy plate method, the plate is stationary during the measurement, which means that the surfactant molecules have time to arrange themselves at the phase boundary, which lowers the surface tension value.

In the Du Noüy ring method, the interface is constantly changed as the ring moves during the measurement. Therefore, surface tension values are often slightly higher than those obtained using a plate. This effect can be observed even in water with minor impurities. For surfactant solutions, the Wilhelmy plate method is preferred.

The plate should be rinsed with pure ethanol and water, then fired with a Bunsen burner (~1000°C). Too low a temperature can leave impurities that cause measurement errors. The plate should be heated red-hot in the hottest part of the flame, then removed before turning off the burner. Clean before and after use.

The ring should be rinsed with ethanol and water and then fired with a Bunsen burner (~1000°C) as with the plate. Avoid low-temperature flames, as they can leave residue. The ring should be heated until red-hot and then removed before extinguishing the burner. Clean before and after use.

The powder particle size must be larger than the pore size of the holder.
– Glass holder: 1 µm
– Steel handle (Sigma 700): 5 µm
The powder must not be soluble or react with the liquid
The powder contact angle should not exceed 90° (to allow the liquid to capillary uptake)

There is no strict viscosity range because it also depends on the density, elasticity of the liquid, probe type and measurement parameters.

• up to approx. 1000 mPa s: usually measurements possible
• above 10,000 mPa s: mostly impossible
• intermediate range: requires compatibility testing

The probe should be rinsed with ethanol and distilled water. You can't use a Bunsen burner flame because the probe is not resistant to it.

At the beginning of the liquid-liquid measurement, the heavy phase (water) is first poured into the trough.

We immerse the Wilhelmy liquid-liquid plate approximately halfway down its surface and check the cleanliness of the surface by squeezing it.

Next, carefully pour the lighter liquid onto the surface. It can be poured onto the step that expands at the liquid-liquid interface. Be careful not to pour it directly onto the heavy phase, as this can cause the phases to mix. The light phase liquid must be sufficient to cover the entire Wilhelmy plate, and the plate should not be immersed in air.

Open the barriers, zero the balance, and inject the material into the interface. Wait the appropriate time for the sample to stabilize at the interface, then begin measurement as usual.

For detailed instructions on standard measurement, please refer to the LB user manual and the Monolayer kit manual.

The trough and barriers are made of Teflon and Delrin. The standard trough is made of Teflon, and the standard barriers are made of Delrin. If you're unsure whether you have a standard system, you can test the materials by placing a drop of water on both the trough and barriers. The drop will have a high contact angle on the Teflon and a low contact angle on the Delrin.

Always wear rubber gloves when handling these components. Remove the trough and barriers and wash them over the sink. Using a soft brush, cover the entire surface with pure ethanol, then rinse with clean, deionized water.
Delrin, from which the barriers are made, I don't tolerate Chloroform, but chloroform or other cleaning agents can be used to clean the Teflon trough. If a long time has passed since the trough was last used, it is worth first washing it with a commercially available detergent.

In SPR, the ligand is a molecule immobilized on the sensor surface. The analyte is the molecule in the flow, and its interaction with the immobilized ligand is measured.

Immobilization is the (usually covalent) attachment of a molecule to a sensor surface. Various immobilization methods can be used, such as trapping or conjugating an amine, thiol, or aldehyde. Amine conjugation is a commonly used method, where a molecule, such as a protein, is covalently bound to the sensor surface via its amine group.

Immobilization involves at least three steps: surface activation, ligand coupling, and surface deactivation.

The volume effect is a phenomenon that occurs when the refractive index (RI) of a sample differs from the RI of the running buffer. This difference in RI is typically caused by additives (e.g., residual base solvent) in the sample. During sample injection, the change in composition causes a shift in the SPR signal, and this is called the volume effect.

The volume shift is clearly noticeable in the measurement and can interfere with the measurement of sample binding, and it occurs simultaneously with binding. In molecular interaction experiments, the volume effect is typically compensated for by reducing the response of the reference channel (no ligand) from that of the measurement channel (ligand). MP-SPR angular measurement also provides a unique internal reference for the volume effect. We call this feature PureKinetics.

Regeneration involves removing the analyte from the ligand, leaving the ligand intact and active on the surface.

Successful regeneration allows the ligand surface to be reused and another analyte to bind to the same surface. Regeneration is required for analytes that dissociate slowly. The appropriate regeneration solution depends on the interacting molecules and the type of interaction. Typically, appropriate regeneration solutions must be determined empirically.

Most often, regeneration solutions are low pH solutions, such as 10 mM glycine, or high pH solutions, such as 50 mM NaOH. Ligand activity must be confirmed after regeneration to ensure reliable results.

The selection of an appropriate carboxymethyldextran (CMD) sensor depends on the size of the analyte molecule.

If the analyte is a low molecular weight compound (e.g., a low molecular weight drug), the amount of ligand immobilized on the surface should be larger to obtain a sufficient signal. In this case, the ligand should be immobilized on the surface of the 3D CMD sensor to obtain more analyte binding sites on the surface.

If the analyte is a larger molecule (e.g., an antibody), the ligand should be immobilized on the 2D CMD surface.

A good rule of thumb is that if the analyte is less than 20 kDa, a 3D surface should be used.

Changing the buffer changes the refractive index at the surface, which causes a shift in the SPR signal.

Long measurements in an open cuvette will cause solvent evaporation and thus an increase in its concentration, which should be avoided. Close open buffer flasks, and for long experiments, cover 96-well plates and sample vials with appropriate lids.

It is very important to always clean the glass side before inserting the sensor into the instrument. When the flow cell is closed, the prism is tightly connected to the glass side of the sensor slide via an elastomer with a matching index. If the glass side is not clean, particles will adhere to the prism elastomer and interfere with measurements.

The glass side is cleaned gently by wiping it with KimWipes (lint-free paper) moistened with ethanol or isopropanol.

The gold sensor can often be completely cleaned by oxidation (using e.g. ammonia and H2O2) and the sensor is usually recyclable multiple times.

Hydrogel-coated sensors cannot be cleaned without removing the dextran coating.

The correct cleaning procedure depends on the sensor coating.

Typical SPR sample volumes for all biochemical interaction experiments are 100 to 300 µl (up to 500 µl in the semi-automatic SPR Navi 200 and MP-SPR Navi 200 OTSO models).

Please note that the amount of sample needed per injection is actually concentration x volume!

A wide range of different coatings are available, suitable for both covalent and non-covalent protein conjugation.

We offer sensor functionalization for all of the above methods.

MP-SPR works well with many lipid forms. It offers the advantage of being able to check the conformation of the formed layer before injecting the protein. Based on its thickness and refractive index, it is possible to verify that the film is properly formed and is indeed a bilayer/liposome layer. For supported lipid bilayers, we recommend our SiO₂-coated sensors. For liposomes, the CMD sensor is recommended.

MP-SPR measurements have also been performed on lipid-binding sensors. The sensor has a three-dimensional hydrogel surface and lipophilic anchor groups that capture liposomes through nonspecific interactions. Other methods include the use of biotinylated liposomes, His-tagged proteins embedded in liposomes, DNA fragments embedded in liposomes, or silica surfaces (which self-adsorb liposomes).

The standard flow cell material is PDMS and is compatible with, in addition to aqueous buffers, e.g., glycerol, ethylene glycol, and DMSO (dimethyl sulfoxide).

Highly chemically resistant flow cell materials include PEEK and Kalrez, and a much wider range of solvents can be used with them.

The MP-SPR Navi 200 OTSO also uses PDMS as the standard peristaltic tubing material. An external syringe pump can be used if other organic solvents are required.

A complete list of compatible solvents and vessels can be found in the appendix of the MP-SPR Navi user manual.

Experiments can be performed with soluble and membrane proteins as well as proteins embedded in lipid vesicles.

The standard configuration will work with materials with a solid-state RI from n=1 to n=1.4, and even up to 1.45 when multi-wavelength systems are used.

If an even higher RI is required (for certain organic solvents), BioNavis offers a separate high RI configuration. The RI of the measuring liquid can then be up to n=1.51.

The most common problems with liposome deposition are due to surface and instrument cleanliness or changes in liposome size.

To achieve consistent lipid bilayer formation on the SiO₂ SPR sensor, cleaning before each lipid deposition is essential. An effective cleaning protocol involves using a CHAPS-Helmanex-ethanol-water mixture before each liposome deposition. The sensor should be used immediately after cleaning prior to deposition.

Hydrophobic layers can cause air to form or be trapped in the flow cells. This air bubble will prevent good liquid-to-surface contact, negatively impacting SPR signal quality.

If an air bubble becomes trapped on the surface, consult your device's user manual for instructions on how to remove it. To prevent bubble formation, carefully degas buffers and be careful not to introduce air bubbles during sample injection.

EDC/NHS coupling typically binds a large number of proteins, but the binding conversion efficiency is higher than that of 100%. Stabilization (injection) after immobilization is necessary to remove unbound, adsorbed protein from the layer, which may negatively impact the experiment in the subsequent analysis phase.

Sometimes, after regeneration injections, a stabilization period (several minutes) is required when using the CMD-3D sensor. Regeneration solutions typically exhibit significant chemical differences from the measurement buffer and can cause hydrogel swelling/shrinkage or salt adsorption/desorption, leading to a small but systematic drift. In such cases, adding a few extra minutes to the baseline time between measurements is a good idea and will save time later in the analysis.

Deionized or purified water is recommended for buffer preparation. Filtered liquids, buffers, and samples help prevent the suspension from accidentally adhering to surfaces and affecting the SPR signal. Degassing solutions will also contribute to more stable results.

BioNavis LayerSolver software is software specifically designed to calculate the thickness and refractive index of a layer.

Typical procedure based on the measurement of two wavelengths:
1) Measurement of the cleaned sample surface at two wavelengths simultaneously
2) Measurement of the deposited layer at two wavelengths
3) Analyzing both wavelengths simultaneously using LayerSolver
4) The dn/dlambda (RI wavelength increment) is required for the given material or similar type of materials.

Initial parameters for BioNavis gold sensors and 670 nm wavelength:

The minimum SPR peak angle can be roughly converted to 10 RU, or 1 ng/cm² at 785 nm. The constant intensity angle depends on the sensor surface area. These values can be converted to surface protein concentration (moles/cm² = surface amount) if the molecular weight of the proteins is known (using the formula: Amount = Mass/Molar Mass, n = m/M). Surface coverage scaling can be enabled in the "Scaling Options" in both Viewer and Control software.

It's important to remember that this is an approximation (though widely accepted) and only works for proteins. This is because the optical properties of proteins are similar in most cases. For more exotic samples, knowledge of the RI (mass) vs. concentration (dn/dc) relationship (from the literature or measurements) is necessary to obtain an accurate conversion.

Below is the full conversion of SPR peak angle change to surface concentration in moles. Note that because protein molecular weight is taken into account, this formula is not actually the same for different proteins, but varies slightly for each one.

Amount (moles/cm²) = (SPR angle (degrees)*1000*10^-9 (g/cm²/degrees))/ protein molecular weight (g/mol)

You can leave the device on all the time if you plan to use it every day.

However, if you don't need to use the device every day, it's better to turn it off to save energy. If the power line is not stable enough or you experience occasional power outages, please add a UPS (uninterruptible power supply) to the device.

The MP-SPR Navi should be placed on a stable table. The device is very sensitive to mechanical shock, so avoid exposing it to vibrations that could disrupt measurements. Select a location where the device is not exposed to external heating or cooling sources, such as direct sunlight, near vents, or air conditioning units. External heating or cooling can cause temperature fluctuations and disrupt measurements.

Suitable storage conditions for BioNavis systems:

Temperature +15°C – +30°C, stable temperature.
Relative humidity from 25% to 60%.
Low dust, ISO-9 class room according to ISO-14644-1 standard ("room air" conditions according to US FED STD 209E standard)
Stable and grounded power source (USP recommended)
Keep away from direct sunlight
Keep away from sources of ignition
Keep away from direct drafts such as fans or air conditioners

The maximum injection time depends on the flow rate and loop volume.
If the instrument contains 250 µl loops and the flow rate is 30 µl/min, the maximum injection time is 7 minutes.
It is recommended to only inject 80% loop volumes when concentration is critical for measurement, as the sample tail will be diluted (depending on the instrument model). In automated models, the injected sample can be protected from dilution by air segments. Watch an animation and learn how flow injection works here.

Also remember that you do not have to inject the entire volume of the loop, you can perform shorter injections.

Once the sample is empty, the buffer will flow into the measurement channel.

The standard loop size is 250 µl, but the loop can easily be replaced with a smaller or larger one.

The automated instrument models (210A VASA, 220A NAALI, and 420A ILVES) allow for partial loop injection, which allows the loop to be filled with less sample than its total volume. This is a very useful feature when only a small amount of sample is available and does not require a loop change.

Yes, BioNavis offers the ability to measure SPR and fluorescence signals simultaneously.

There are three options available:

• fluorescence coupled to surface plasmons (option 1)
• beam splitting fluorescence (option 2)
• fluorescence of fiber bundles (option 3).

The BioNavis device is flexible and user-friendly. Therefore, we do not mark channels in the injection ports.
In MP-SPR Navi 200 OTSO the standard connection is as follows: left the injection port is connected to upper channel, and the right injection port to the lower flow channel.

However, there is an easy way to check this:
Once all the lines are dry, insert the gold sensor into the device and begin angular measurement. Fill one (!) of the channels with approximately 10% ethanol or water, and leave the other injection loop empty (air). Start the pump (no buffer, just air) with the injection valve set to "injection." Check which channel changes the signal. Remove the sensor and check which channel is wet.

When the flow chamber is closed, the prism is tightly connected to the glass side of the sensor slider via an elastomer with a matching index. If the flow chamber is closed for a long time, the elastomer may become damaged. A damaged elastomer would interfere with measurements.

You can check if the elastomer is in good condition by observing it with the naked eye for scratches, particles, dried salts, or by testing it.

Place the glass sensor (without coating) in the instrument and perform a full angular scan. The curve should increase to approximately 1° and remain flat. If this does not happen, the prism elastomer can be wiped with isopropanol (see the appropriate instrument's instruction manual, "Troubleshooting" section) and the instrument calibrated. If calibration does not resolve the issue, the prism will need to be replaced.

Note that spatial resolution is typically quoted for instruments that use a CCD camera as the detection component, such as SPR imaging. These instruments are typically limited by the camera resolution and do not offer as good sensitivity as focused beam or MP-SPR instruments.

In our case, the detection principle is based on a true goniometric configuration. The actual angular resolution of the goniometer is 0.001 degrees (the smallest goniometer step), but because we use advanced peak detection algorithms to find the minimum, the SPR minimum position is actually determined more precisely than the goniometer step.

The diameter of the laser "spot" on the sensor plate surface is approximately 0.5 mm. The MP-SPR measurement results are averaged over this area (i.e., the thickness is an average over an area of 0.2 mm²).

If by spatial resolution we mean the detection limit of the instrument, then the resolution depends significantly on the measurement system and the analyte. The amount of signal produced by the analyte can be increased by the sensor structure (three-dimensional hydrogels instead of two-dimensional monolayers), and for three-dimensional hydrogel sensors, the estimated accuracy of direct detection of low-molecular-weight analytes is in the nano-micromolar range (or approximately 300 fg/mm² – femtograms per square millimeter), BUT it depends on the interactions themselves.

The key difference lies in the optical system. Traditional SPR uses a focused beam system, which provides an angular range of several degrees and measures only a single parameter—the SPR peak minimum, which is then plotted on a sensor image. The typical RI (refractive index) range of traditional SPR is 1.3–1.4 (the RI of the liquid).

MP-SPR utilizes a Kretschmann configuration and goniometric optics, enabling a scan range of 38 degrees and an RI of 1.0 to 1.4. In addition to measuring the SPR peak, the full SPR curve is monitored and other parameters are recorded. Parameter cross-correlation enables a unique PureKinetics feature. Wavelength measurements using multiple lasers enable characterization of layer thickness and refractive index, providing insight into, for example, molecular conformation changes or layer swelling.

The MP-SPR's special optical configuration enables a much broader range of applications in life sciences, biosensor development, and materials characterization. An exceptionally wide range of sensor surfaces is also available, including Ag, Cu, Al2O3, SiO2, PET, PS, cellulose, and CaP (calcium phosphate). MP-SPR can measure thin films (e.g., a single 3.7 Å graphene monolayer) as well as thicker films (several micrometers thick, e.g., polyelectrolytes or living cells), and measurements can be performed not only in the liquid phase but also in the gas phase.

Angular scanning is the recommended measurement mode for most experiments.

In this mode, the light source scans continuously over a selected angle range, and the SPR peak (angle vs. intensity plot) can be monitored. Several SPR peak parameters can be tracked over time (e.g., PureKinetics, minimum peak position, minimum peak intensity). Thickness and refractive index can only be calculated from angle scan data!

In angle mode, the light angle is constant (the light source does not move), and the reflected light intensity is monitored as a function of time. Angle measurement allows for increased sampling rates—up to 250 points per second (4 ms sampling time), but collects less information about surface changes. In angle mode, the typical sampling rate is 2 seconds.

In angle mode, more information can therefore be collected from the measurement compared to angular measurement, so we strongly recommend using the angle scan mode.

The temperature range is +20/-7°C from ambient temperature. This is approximately 15-45°C under typical laboratory conditions.

Temperature is controlled using a Peltier element. The well plate area of the MP-SPR Navi 220A NAALI and 420A ILVES models can be cooled to +4°C.

The standard instrument is equipped with a 670 nm laser in each flow channel.

Standard instruments with an additional laser kit (option -L) are equipped with 670 nm and 785 nm lasers in each channel.
Two wavelengths per flow channel are necessary to determine the thickness and refractive index.
Higher wavelengths have deeper penetration, greater dynamic range, but lower sensitivity.

We can also provide other wavelengths, subject to availability. To date, we have installed custom wavelengths: 635, 650, 670, 785, 850, and 980 nm.

We can also provide a custom input, allowing you to use your own light source (including fluorescent). The light source must be equipped with an external trigger.

Using a micropipette, apply a 60 µL drop, ensuring that it covers the entire three-electrode system (working, auxiliary, and reference electrodes).

Alternatively, the electrode can be immersed in the solution – just make sure that all three electrodes are in contact with the solution being tested.

Use the cables and box connectors appropriate for your potentiostat, e.g. CAC or DSC4MMH.

The electrodes are ready to use, so there is no general pretreatment protocol. Screen-printed electrodes (SPE) avoid the time-consuming polishing required for classic solid electrodes before measurement.

However, electrochemical pretreatments are used in some applications. For example, for gold electrodes, a procedure involving several cycles in a 0.1 M sulfuric acid solution over a range of 0–1.6 V at a scan rate of 100 mV/s can be used.

SPE electrodes are designed as disposable platforms for developing various (bio)sensors. We recommend using them as consumables, as this is how we guarantee their best performance.

In specific cases, it is possible to reuse electrodes. The number of times they are used depends on many factors and should be determined individually during the optimization process.

Most electrodes are manufactured on a ceramic substrate (alumina). White and transparent plastic (PET), PCB (FR4), and glass (Pyrex) substrates are also available.

Manufacturing electrodes on other materials can be considered upon request as part of a custom product.

The difference between AT and BT electrodes lies in the different gold pastes used for printing. AT paste is baked at a high temperature (approx. 900°C), while BT paste is baked at a low temperature (approx. 150°C).

Both types were developed to provide a wider range of electrochemical properties for gold electrodes. In practice, this means that the AT and BT models may exhibit similar or different behavior depending on the specific experiment, i.e., the redox system being studied.

There are no clear criteria describing the properties of each type, as they depend on the specific sensor, the electrode itself, and the redox molecule used. For example, ferricyanides exhibit better electron transfer at AT electrodes than at BT.

In general, it can also be said that AT models sometimes have better reproducibility, while BT models are often chosen for biosensor development.

To select the appropriate electrode, you can use the DRP-AUMIX kit, which contains a mixture of gold electrodes fired at high and low temperatures.

SPE electrodes are designed to work in solutions water, however, under certain conditions they are resistant to some organic solvents.

If you plan to use SPE in organic solvents, please contact the manufacturer for information about the tests performed.

It depends mainly on the type of substrate and the presence of a dielectric layer (green polymer):
Ceramic SPE with dielectric layer: up to approx. 100 °C
Ceramic SPE without dielectric layer (e.g. IDEAU200): up to approx. 800 °C
Electrodes on plastic substrate: up to approx. 80 °C
Glass-based electrodes: up to approx. 450–500 °C

Standard Metrohm DropSens screen-printed electrodes (SPEs) utilize a silver pseudo-reference electrode. Compared to a classic Ag/AgCl reference electrode, a potential shift of approximately -131 mV is observed in 0.1 M KCl solution.

If an Ag/AgCl pseudoelectrode is required, catalog models are available (e.g. DRP-11L and DRP-C11L).

Any model from the catalog with an Ag electrode can also be made using Ag/AgCl paste as a custom model.

The metal is deposited on a ceramic substrate using the PVD method, obtaining a thin layer of pure metal with a thickness of approximately 1 µm.

The roughness of these electrodes corresponds to the roughness of the substrate, i.e. Ra ≈ 1 µm.

The PEDOT layer applied by screen printing has a thickness of 3 ± 1 µm.

Brush electrodes on a glass substrate are fabricated by photolithography. The resulting layers have thicknesses ranging from 150 to 200 nm.

To achieve better adhesion of gold or platinum to the glass substrate, a thin layer of titanium is applied before sputtering the gold or platinum.

Yes, these electrodes are stable at room temperature. However, it is recommended to store them at 2–8°C in a refrigerator where temperature conditions are well-controlled.

Check the electrode description to see at what temperatures they should be transported and stored.

For transmission analysis during electrochemical testing, it is recommended to use transparent working electrodes designated PEDOT10, COTE10, ITO10, or AUTR10. Various materials—PEDOT, carbon, indium tin oxide (ITO), and transparent gold—allow for obtaining a good transmission signal.

All of these electrodes can be tested by selecting the OTEMIX mixed kit.

The cover is very stable, and high flow rates can be achieved. For example, a flow rate of 4 ml/min can be used during measurement. However, the optimal flow rate should be determined experimentally, as it depends on the specific measurement system.

Users of DropSens instruments are entitled to receive software updates free of charge for an unlimited period of time.

Minimum requirements:
Screen resolution 1024 × 768 (1280 × 1024 recommended)
64-bit processor (x64)
RAM 16 GB (32 GB recommended)

Digital and analog inputs/outputs are configured in this menu; the window that appears allows you to enable or disable selected programmable I/O pins (PIOs).

Yes, it is possible and very simple using the "Manual Control Script" which allows you to create a current charge/discharge profile with cut-off values.

The DropView 8400 software has a "Manual Control Script" option with various commands available for this and other applications.

Floating mode can be achieved both when operating on battery power and when connected wirelessly to a computer; therefore, all instruments with a wireless option are suitable for operation in these conditions.

If you need to conduct long experiments in floating mode, you can use the USBFLOATING cable, which allows you to switch the instrument to floating mode (compatible with: μStat 300, μStat 400, μStat-i 400, μStat-i 400s, μStat ECL).

The μStat-i MultiX can optionally be configured with floating channels.

The maximum number of data points is 65,000.

The wireless connection in our devices is very useful for wireless data transfer and remote control. You can place the instrument inside a glove box, optical box, etc., while control is performed from a computer.

DropStat and DropStat Plus are readers designed primarily for the stage where the sensor has already been developed and optimized. They are programmed according to user specifications and display the concentration of the analyte for which the electrochemical sensor was developed. DropStat and DropStat Plus will display the final concentration values for the developed sensor. Based on the calibration curve, they can display values such as peak height, peak position, peak width, peak area, current, or directly the concentration.

They are ideal as proof of concept in the final design stage, but are primarily intended for OEM production in large series and subsequent commercialization.

If the sensor is still in the research phase and not optimized, it is recommended to use a standard potentiostat for development work.

To program such a reader, contact the manufacturer (info.dropsens@metrohm.com), who will provide a questionnaire to complete. The main required information includes: electrochemical technique parameters, a calibration curve, and a sample signal obtained.

SPELEC instruments are very versatile and compatible with many systems available on the market.

The connectors in SPELEC are of the SMA 905 standard, so any optical fiber with such a connector will be compatible.

However, please note that a wide range of spectroelectrochemistry accessories are available, including targets and optical fibers offered by Metrohm DropSens.

Because Raman scattering is inherently weak and of limited use for low-concentration samples, SERS is widely used in a variety of applications. It involves amplifying the Raman signal through the interaction of molecules with metallic surfaces.

Metal printed electrodes (SPEs) are promising SERS substrates because they are available in a variety of materials, such as gold, silver, and metal nanoparticles. They are readily available, inexpensive, disposable, and require only a small sample volume.

Examples of recommended SPEs are the C013 model with a silver working electrode and the 220BT with low-temperature hardened gold.

The RAMANPROBE has a focal length of 7.5 mm, allowing it to be adapted to a variety of measurement setups. The RAMANCELL is designed with this in mind, but is supplied with a variety of spacer plates to optimize the distance between the probe and the electrode surface, thus easily improving the Raman signal.

Other RAMANPROBE probes with different specifications can be supplied on request.

RAMANPROBE is a probe non-immersion, so it should be cleaned gently with soft paper and ethanol.

The RAMANPROBE in an immersion version can be supplied upon request.

The CONNECTOR96X is intended for use in conjunction with the µStat 8000/P multi-channel instrument and the SYNCONN96X with the DIOC8000SYNC96 cable as a high-throughput screening platform capable of reading 96 wells in the SPE 96X format.

At the same time, CONNECTOR96X is a universal connector that allows you to connect any instrument via 2 mm banana cables.

If you want to use your instrument also in combination with SYNCONN96X to automate reading, please make sure your instrument allows script programming and contact us so we can make a suitable DIO cable.

Designed for small-volume analyses involving a three-electrode system (approximately 15 µL), the mesh is made of a monofilament polyamide fabric that fits perfectly into an electrochemical SPE cell.

The volume of the electrochemical chamber defined by the O-ring in the flow cell is 8 µl.

The DRP-FLWCL was tested at flow rates up to 6 ml/min.

You can work with SPE in two ways: by applying a drop or by immersing the electrode in the solution.

1. Using a micropipette, apply a 40–50 µL drop to cover all three electrodes (auxiliary, reference, and working). You can use the DSC connector for this purpose (as shown).
2. For working in solution, a CELL cell (5–8 mL volume) can be used to cover the entire three-electrode system, in combination with a CAST cable (using the DropSens potentiostat) or a CAC cable (using any other device).

Graphene is an allotrope of carbon with a structure of a single layer of sp² hybridized carbon atoms. It is a single layer of carbon atoms connected in a hexagonal (honeycomb) crystal lattice.

Graphene oxide It is considered a graphene precursor or graphene material in its own right, as it is graphene functionalized with oxygen groups. It has lower electrical conductivity than graphene.

DropSens provides enzymatic substrates for alkaline phosphatase. Upon hydrolysis, these substrates produce electrochemically active products, such as p-aminophenol from p-aminophenylphosphate, hydroquinone from hydroquinone diphosphate, and paracetamol from phosphorylated paracetamol.

Thanks to the formation of these electroactive products, it is possible to obtain high sensitivity of measurements.