Written and maintained by CASRAI Editorial Board
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This page describes products and general use; it is not medical advice.
Who uses it: EEG technologists, neurophysiology and sleep-lab staff, clinic and lab buyers, and students who need to tell electrode materials and types apart. After reading you should be able to say what a silver/silver chloride (Ag/AgCl) electrode is, how it differs from silver and gold cup electrodes, and which published facts bear on reusable versus disposable EEG electrodes.
What a silver/silver chloride (Ag/AgCl) electrode is
A silver/silver chloride electrode is a skin-contact electrode whose conducting surface is silver coated with silver chloride. In EEG it is one of the standard cup-electrode materials, alongside plain silver and gold-plated cups. In the United States, electrodes applied to the skin to record signals such as the electroencephalogram are regulated as cutaneous electrodes under 21 CFR 882.1320 (Class II); the FDA product code is GXY.
How EEG cup electrodes are built
An FDA 510(k) summary for one manufacturer’s cup electrodes (K072016, decided 19 October 2007) describes cutaneous electrodes applied to the skin to record EMG, EEG and evoked-potential signals with recording and monitoring equipment. In the reusable version, each disc is silver, silver/silver chloride or gold plated and is permanently attached to a lead wire ending in a touch-proof connector. In the disposable version, the disc is molded ABS plastic with Ag/AgCl plating, for single-patient use.
A trade Q and A in Sleep Review (April 2011, by an R.EEG/EP T. technologist, so expert opinion rather than a standard) adds that disposable and reusable electrodes differ mainly in the cup: the lead wire and connector are the same, and reusable cups are typically 99.9 percent silver with Ag/AgCl or gold plating. Cups are filled with conductive paste or gel; see electrode gel versus paste.
EEG electrode types
| Type | Material | Reuse | Source |
|---|---|---|---|
| Reusable silver cup | Silver disc, lead wire attached | Reusable; can be steam-autoclaved | FDA 510(k) K072016 |
| Reusable Ag/AgCl cup | Silver disc with silver chloride | Reusable; can be steam-autoclaved | FDA 510(k) K072016 |
| Reusable gold cup | Gold-plated disc; plating reported at 2-3 µm | Reusable; can be steam-autoclaved | FDA 510(k) K072016; Gorecka and Makiewicz 2019 |
| Disposable cup | Molded ABS disc with Ag/AgCl plating | Single-patient use | FDA 510(k) K072016 |
K072016 also lists adult and pediatric versions of these cups. Related electrode families have their own pages: ECG electrodes, EMG electrodes and the EEG headband.
Why Ag/AgCl for slow EEG potentials
Gorecka and Makiewicz (Sensors 2019;19(11):2608) state that gold or silver/silver chloride cup electrodes are recommended in the EEG frequency range. They cite earlier work in which, besides the lowest resistance and superior low-frequency noise, Ag/AgCl electrodes had much better DC stability than gold, so that only silver/silver chloride electrodes should be used for recording slow EEG potentials (below 0.5 Hz). They add that the resistance of pure silver at slow frequencies (below 10 Hz) rises exponentially.
Gold cup versus Ag/AgCl: how many EEG examinations per set
In the same study, ten electrodes of each type were tested with electrochemical impedance spectroscopy. Gold electrodes showed the largest impedance and the greatest variability. The authors concluded that a set of gold electrodes is permissible for between 5 and 10 EEG examinations, and a set of Ag/AgCl or other types for between 10 and 20; they proposed that coating degradation caused by cleaning explains the gold result. Scope matters: this is ten electrodes per type, and the paper does not compare reusable with disposable recording quality.
Reusable versus disposable EEG electrodes
- Reusable cups require strict cleaning and disinfection, and the trade Q and A gives about five months as an average life (one technologist’s estimate).
- Disposable cups are usually plastic coated with Ag/AgCl; according to the same source they avoid cross-contamination risk but add inventory and handling cost.
- The FDA record describes disposable versions as single-patient use and reusable versions as steam-autoclavable.
Cup versus flat: the Q and A reports that body heat can melt paste in cups and cause pops, while flat electrodes hold paste more consistently. The same source says electrodes have no rating system.
How to choose
The published criteria are few. For slow EEG potentials (below 0.5 Hz), Gorecka and Makiewicz cite earlier work saying only Ag/AgCl electrodes should be used. For single-patient use, the FDA record describes the disposable form; the reusable form is described as steam-autoclavable. Follow the manufacturer’s instructions for use for the specific product.
Safe use and handling basics
- These are non-invasive devices intended for use with recording and monitoring equipment (FDA 510(k) K072016).
- The FDA record labels the disposable version for single-patient use.
- Reusable versions are described as steam-autoclavable; the study above proposes that cleaning-related coating degradation explains the wear seen in gold electrodes. Cleaning and disinfection follow the manufacturer’s instructions for use.
Common mistakes
- Treating all cup electrodes as interchangeable: the material changes low-frequency behavior.
- Assuming a reusable set lasts indefinitely: the study found impedance changed with repeated examinations.
FAQ
What are disposable EEG electrodes made of?
In the FDA record K072016, disposable cup electrodes are molded ABS discs with Ag/AgCl plating, for single-patient use.
What is a gold cup electrode?
A reusable cup electrode with a gold-plated disc; the study reports plating in the 2-3 µm range and a permissible 5 to 10 examinations per set.
What are the types of EEG electrodes?
This page covers cup types: reusable silver, Ag/AgCl and gold-plated, and disposable Ag/AgCl. Placement naming is covered in the 10-20 system guide.
Are reusable EEG electrodes worth reusing?
Sources state reuse limits (about 10 to 20 examinations for Ag/AgCl in one study) and strict cleaning needs; the published facts here do not rank reusable above disposable.
See also the sleep clinic supply checklist. Diagnostic supplies are listed under diagnostic, monitoring and imaging.
Sources
- 21 CFR 882.1320, Cutaneous electrode, https://www.law.cornell.edu/cfr/text/21/882.1320 (checked 2026-10-31).
- openFDA device classification, product code GXY, https://api.fda.gov/device/classification.json?search=product_code:GXY (checked 2026-10-31).
- FDA 510(k) K072016, Technomed Europe, decided 19 October 2007, summary at https://fda.innolitics.com/device/K072016 (third-party mirror of the FDA record, checked 2026-10-31).
- Gorecka J, Makiewicz P. The Dependence of Electrode Impedance on the Number of Performed EEG Examinations. Sensors 2019;19(11):2608, doi:10.3390/s19112608, https://pmc.ncbi.nlm.nih.gov/articles/PMC6603518/ (checked 2026-10-31).
- Hanson L. Electrodes Q and A. Sleep Review, April 2011, https://sleepreviewmag.com/sleep-diagnostics/in-lab-tests/polysomnography/electrodes/ (checked 2026-10-31; trade magazine, expert opinion).
