pH tip illustration
pH Redox UniAmp
Designed for research applications within:
Environmental Sciences
Biomedical Sciences
Food Science

pH microelectrode

Miniaturized pH electrode

The Unisense pH electrode offers you a fast and reliable research tool. With tip sizes down to 10 µm, you can complete high resolution and non-destructive microprofiles in a wide range of microenvironments. Read more...

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Technical Data
Response Time
Ordering Information & Sizes
Manuals & Videos
pH microelectrode

pH measurement technology

This microelectrode is a miniaturized conventional pH electrode based on selective diffusion of protons through pH glass, and the determination of potentials between the internal electrolyte and a reference electrode. The reference electrode can be either external (separate electrode) or internal. However, we only recommend internal references in applications where it is not possible to place two electrodes in the sample.

pH workshop_1400x800
Cables & Connectors
Feature Standard Options Extra price for option selection
Total length 150-200 mm 70-350 mm 20-50%
Diameter 20 mm from tip <2 mm <1 mm 10%
Diameter 50 mm from tip 8 mm <2 mm 20%
Glass shaft diameter 8 mm
Plastic shaft protection diameter* 11 mm Can be omitted

*When mounted with in situ mini connectors, the shaft has no protection mounted, but fits directly into the in situ sensor mounts with pressure compensation. In situ sensors have a standard length of 130-160 mm.

Cables & Connectors
Item Standard Options Extra price for option selection
Cable Habia
Cable length 1.5-2 m 0-20 m Yes, depends on length
Connector LEMO BNC adapter Yes, order separately
In situ gold pin connector* No Yes

*Due to the small area of the pH-sensitive glass, Unisense pH10 electrodes typically have an inner resistance of 10⁹ Ohm. Therefore, the millivoltmeter input resistance must be at least 10¹³ Ohm.

Attribute Standard
Guaranteed lifetime 3 months
Expected lifetime >6 months
Temperature range -10-60°C
Temperature range tip -10-90°C
Range pH 2-10 (linear 4-9.2)
Detection limit 0.01 pH unit
Internal reference Only as pH-500C*
Spatial resolution Approx. 100-250 µm | PH-500: about 500 µm)
Response Log linear

*Construction of the sensor with an internal reference involves creation of a liquid junction 1 mm from the electrode tip. During measurements, this liquid junction must be submersed in the medium in order to complete the measurement circuit.

Response time
Response time
Response time (90%) <10 s (from pH 7 to pH 4)
Ordering information & Sizes
Ordering information & Sizes
pH Glass Electrode Size and description Outside tip dimensions (diameter x length of sensitive pH glass)
pH-10 8-12 µm - microelectrode 10-19 x 50-100 µm
pH-25 20-30 µm - microelectrode 20-30 x 75-125 µm
pH-50 40-60 µm - microelectrode 40-60 x 100-200 µm
pH-100 90-110 µm - microelectrode 90-110 x 150-250 µm
pH-200 180-220 µm - microelectrode 180-220 x 250-350 µm
pH-500 400-600 µm - minielectrode 400-600 x 400-800µm
pH-500C 400-600 µm (combination electrode with internal reference electrode) 400-600 x 400-800µm
pH-MR 400-600 µm - in guide 400-600 x 400-800µm
pH-N 1.1 x 40 mm - needle electrode
pH-NP 1.6 x 40 mm - needle electrode for piercing
pH-ST-1/4 1/4'' steel tube
pH-SL-1/4 FT-cell 1/4'' Swagelok Tee
pH-SL-1/8 FT-cell 1/8'' Swagelok Tee
pH-PEEK-1/8 FT-cell 1/8'' PEEK Tee
pH-PEEK-1/16 FT-cell 1/16'' PEEK Tee
pH-FT-GLASS-6 Glass FT-cell 6 mm outer diameter
pH-FT-GLASS-8 Glass FT-cell 8 mm outer diameter

Video Guides

Quick Guide pH Microelectrodes

A walk-though of how pH microelectrodes are made, how they work, specifications, and customizations.

pH Calibration Kit Video

Application Scientist Tage Dalsgaard shows you how to perform a calibration using the pH electrode calibration kit

Related publications

Anaerobic sulfide oxidation with nitrate by a freshwater Beggiatoa enrichment culture
Kamp, Anja et all (2006), Applied and Environmental Microbiology, vol. 72, 4755-4760
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Moonmilk Deposits Originate from Specific Bacterial Communities in Altamira Cave (Spain)
Portillo, Maria C. et all (2011), Microbial Ecology, vol. 61, 182-189
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Transient bottom water oxygenation creates a niche for cable bacteria in long-term anoxic sediments of th⁠…
Marzocchi, Ugo et all (2018), Environmental Microbiology, vol. 20, 3031-3041
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Cleavage of trypanosome surface glycoproteins by alkaline trypsin-like enzyme(s) in the midgut of Glossina morsitans
Liniger, Matthias et all (2003), International Journal for Parasitology, vol. 33, 1319-1328
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