By Vvon Engineering Team | Published | Updated
The instrument is the part of an electrochemistry bench that gets specified. The cell, the reference electrode and the polishing kit are the parts that decide whether the data is worth keeping.
An electrochemistry instrument purchase is incomplete if the required cell, electrodes, leads and preparation tools have not been specified. Do not assume these accessories are included: request an itemised list for the exact model and intended experiments.
The electronics, cells, reference electrodes and working electrodes have different maintenance and replacement needs. Budget the components that contact the electrolyte as part of the measurement system, with quantities and material compatibility agreed before ordering.
Three-electrode arrangements control the working-electrode potential against a reference while the counter electrode carries the current. Two-electrode arrangements remain appropriate for many complete-cell battery, conductivity and device measurements; the correct arrangement follows the question being measured.
In the CH Instruments accessory range those three roles are three separate part numbers. CHI115 is a platinum wire counter electrode. CHI111 is a silver / silver chloride reference with a porous Teflon tip. CHI104 is a 3 mm diameter glassy carbon working electrode, in the same family as the 2 mm gold, platinum and silver discs catalogued as CHI101, CHI102 and CHI103. Confirm whether each is included in the quoted package.
A four-terminal connection may separate current-carrying and voltage-sensing leads to reduce contact-resistance errors. Other four-electrode arrangements are used for liquid/liquid interfaces. The wiring must follow the instrument and cell design: CH Instruments describes these uses for its 1100D series.
CH Instruments split their range by what the electronics has to do, not by price band, and the split maps closely onto research groups.
| Series | What it is | The work that needs it |
|---|---|---|
| 600F | General purpose potentiostat and galvanostat with a fast function generator and dual channel acquisition | Voltammetry, pulse techniques, corrosion, impedance. The default first instrument |
| 700F | Bipotentiostat and galvanostat controlling two working electrodes | Rotating ring disk work and dual channel detection. Behaves as a 600F when used single channel |
| 800D | Electrochemical detector monitoring current through a flow cell | Liquid chromatography and flow injection detection, down to picoamperes |
| 1000D | Eight channel potentiostat | Eight independent cells, or eight working electrodes sharing one reference and counter |
| 1100D | Power potentiostat; galvanostat available on the 1140D model | Battery testing, electrolysis, electroplating, large area corrosion |
| 1200C | Handheld potentiostat and bipotentiostat, USB powered | Teaching laboratories and field work, with no adapter or battery to carry |
| 1400 | Four channel potentiometer combined with a four channel potentiostat | Reading open circuit sensors such as ion selective electrodes at the same time as amperometric ones |
| 920D | Scanning electrochemical microscope, bipotentiostat plus a three dimensional nanopositioner | Mapping chemical reactivity across a surface rather than averaging over one |
Choose channel count from the number of simultaneous experiments and whether cells need independent references and counter electrodes. For teaching, compare the selected handheld model’s techniques, current range, computer requirements and connection arrangements against the practical list.
A battery experiment must fit the instrument’s current, voltage, compliance, control modes and duty limits, regardless of whether the cell is a coin or pouch format. In the CHI1100D family, galvanostatic operation is model-specific: the manufacturer identifies the 1140D as the version with a galvanostat. Specify the complete model suffix.
If a laboratory is going to be careless about one component, it will be this one, and every potential it ever reports will be wrong by an unknown offset. The reference is not an accessory. It is the calibration.
Choose it by the electrolyte, not by habit.
Follow the reference electrode’s own instructions for filling solution, storage, junction cleaning and reconditioning. A dried junction may require assessment or replacement; do not assume every electrode can be stored in the same solution or safely refilled by the same procedure. Mercury-containing electrodes also need the laboratory’s hazardous-material arrangements.
Where the cell is a flow cell rather than a beaker, the reference changes again. CHI134 is built for the CHI130 thin layer flow cell with a polyacetal body and a VYCOR glass frit junction on a 4 mm tip, and CH Instruments state plainly that it suits mild solvents such as acetonitrile and that the plastic does not stand up to strong solvents such as THF. That is the kind of limit worth reading before an order, not after a cell body has softened.
Solid disc electrodes arrive polished and ready to use, and they stop being ready after the first few experiments. Surface renewal is a routine, not a repair, and CHI120 is the kit that makes it one: 1.0, 0.3 and 0.05 micron MicroPolish powders, glass plates for the pads and three grades of 73 mm disc and pad. The published routine works down through the three grades until the surface is mirror shiny, starting at the 1200 grit Carbimet disc if scratches will not lift. A laboratory without a polishing kit is a laboratory whose voltammograms drift week by week for reasons nobody can name.
Small electrodes can exhibit radial diffusion and lower total currents, which may reduce ohmic-drop effects. The current scale still depends on electrode dimensions, concentration, kinetics and time scale; it is not always in picoamperes. Check background, shielding and the reference arrangement with a suitable control measurement.
Interdigitated arrays sit somewhere between the two. The gold, platinum and carbon IDA electrodes catalogued as 012125, 012126 and 012127 all carry 65 pairs of generator and collector bands, each 10 micron wide and 2 mm long at a 5 micron interval, so a species oxidised at one set of bands is reduced at the other and cycles continuously between them. That redox cycling is what lifts the signal, and dual mode preserves the sample compared with single mode. They are quartz glass, they need the 011066 cable kit to connect, and they break if handled like a metal disc.
For sensor development and for teaching, screen printed strips remove the polishing problem entirely. SE101 is a 3 mm printed carbon working electrode with a published 0.071 cm2 working area, supplied in packs of 40. TE100 puts working, reference and counter on one strip at the same 3 mm working diameter, with 2 mm and 1.5 mm versions catalogued as TE101 and TE102. They are disposable or reusable, need no polishing and can be chemically modified, which is exactly what a sensor group spends its time doing.
The cell decides how repeatable the geometry is between runs. CHI220 is the simple cell stand in stainless steel and Teflon, supplied with four glass cells, and CH Instruments note that it is not remote controllable. Additional or replacement glass cells are CHI222. Two parts carry an explicit warning worth repeating: CHI221, a cell top with a platinum wire counter electrode already fitted, and CHI223, a Teflon cap, are not replacement parts for the CHI220 stand. That single line has caused more wrong orders than any other in this range.
Specialist cells follow the technique. CHI127 is the EQCM cell, completed by the CHI128 reference and CHI129 platinum wire counter, with a CHI125A gold coated quartz crystal as the working surface, and it exists to support the Model 400C Series Time-resolved Electrochemical Quartz Crystal Microbalance (EQCM), where mass change at the electrode is recorded alongside potential, current and charge. CHI130 is the thin layer flow cell, with glassy carbon, gold and platinum working electrodes as CHI131, CHI132 and CHI133 and a 25 mm spacer as CHI135, supplied four to a pack. CHI140A is the spectroelectrochemical cell kit, built around a thin layer quartz cell with a platinum gauze working electrode, and it ships without a reference: 012167 for aqueous work or 012171 for non-aqueous has to be ordered alongside it.
Below about a nanoampere, the room becomes part of the experiment. CHI200(B) combines a picoamp booster with a Faraday cage; the two halves are also catalogued separately as CHI201 and CHI202. The booster places the preamplifier close to the electrode for lower bias current and noise, its sensitivity matching the 1x10^-12 A/V internal range of the 600 series but at a lower bias current, and it switches itself in automatically at sensitivity scales of 1e-8 A/V and below. It stands down for automatic sensitivity switching techniques such as Tafel plots and bulk electrolysis, and for galvanostatic work. On a bipotentiostat it affects the primary channel only. The cage removes line frequency interference, and CH Instruments recommend adding it wherever a cell is picking up noise from its surroundings.
Low-current measurements may benefit from a properly grounded Faraday cage and careful cable routing. Investigate interference with blank or dummy-cell measurements; shielding does not cure every source of drift or pickup.
At the other end of the current scale, CHI680D extends measurement to 2 A and stacks with the host instrument. Note the two published limits: a Faraday cage may still be needed above 50 mV per second, and the cell control signals for purge, knock and stir are disabled while the booster is connected. Where a sequence of cells has to run unattended, CHI684 is the multiplexer, switching working, sensing, reference and counter lines across up to 64 cells one at a time and saving data to file after each run.
The same catalogue produces very different sensible orders depending on who is buying.
A battery group needs current before it needs anything else. The Model 1100D Series Power Potentiostat/Galvanostat in its four electrode configuration, a cell arrangement matched to the cell format being studied, and reference electrodes chosen for the electrolyte chemistry rather than for convenience. Where the interest is in mass change during deposition or intercalation, the 400C series with a CHI127 cell and CHI125A crystals adds a measurement that no purely electrical instrument can give.
A corrosion group needs a general purpose workstation with impedance, so a Model 600F Series Potentiostat/Galvanostat, plus a cell that presents a defined and repeatable area of the specimen to the electrolyte, and a reference chosen for the test solution. Tafel work and bulk electrolysis both use automatic sensitivity switching, which is precisely when the picoamp booster stands itself down, so budget for the cage rather than the booster if that is the main technique.
A catalysis group may need an area-averaged current, impedance or rotating-electrode measurement, or it may need spatially resolved activity. Choose SECM only where surface mapping or probe experiments are part of the research plan, and include compatible tips and training in the scope.
A sensor group wants throughput and disposability. Screen printed TE100 strips in packs of 40, a 1200C series handheld unit per bench, and the Model 1400 Series 4-Channel Potentiometer/Potentiostat where open circuit and amperometric sensors have to be read at the same time, as they are in electrode array characterisation and real time cell metabolism work.
That list is not long and it is not expensive relative to the instrument. What it does is make the difference between a workstation that produces data in week one and one that sits under a dust cover until the next financial year. The same argument applies to four point probe work, where the geometry and the correction factor matter more than the meter, as set out in where four point probe measurements go wrong.
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