Ion-Selective Electrodes (ISEs): who makes what, when to use them, and why “mini-ISEs” are changing the game
If you need to quantify multiple ions—think ammonium, nitrate, potassium, sodium, calcium, chloride—in water, aquaculture, hydroponics, or environmental monitoring, Ion-Selective Electrodes (ISEs) are still one of the most practical tools around. They’re rugged, reagent-free, and fast. Below is a quick tour of leading suppliers—focusing especially on NT Sensors’ mini-ISE tech—plus some selection tips from our work building multi-ion systems for aquaculture and water-quality clients.
ISEs in 30 seconds
An ISE converts the activity of a specific ion into a voltage that follows the Nernst relationship. In practice: calibrate with two or three standards, measure sample mV, convert to concentration—job done. This makes ISEs well-suited to spot checks, routine QC, and embedded multi-ion probes. ionode.com
NT Sensors: modular mini-ISEs and true multi-ion probes (our pick for compact systems)
Why they stand out: NT Sensors build small-form-factor, solid-state ISEs that slot into customizable, multi-ion probes and companion meters (Imacimus 5/10). The ecosystem is built for field + lab use with quick sensor swaps and low sample volumes.
Mini-ISE format (Ø≈4.6 mm): The “Mini ION 4.6” series brings advanced miniaturisation with modular tips, so you can assemble probes for the ions you care about and keep the footprint tiny—handy in tight flow cells or small vessels. NT Sensors
Low sample volume: Some mini-ISE tips specify ~1 mL minimum sample volume (e.g., the Li⁺ mini electrode)—useful for sap, R&D rigs, or micro-reactors. NT Sensors
Multi-ion probes: Off-the-shelf bodies accept up to seven ISEs (e.g., K⁺, Na⁺, Ca²⁺, Mg²⁺, NH₄⁺, NO₃⁻, Cl⁻) so you can log concurrent readings from a single insertion. NT Sensors
Imacimus meters: Portable analyzers that run multiple ISE channels alongside pH, conductivity, and water hardness (Imacimus 5: up to 4 ions + pH; Imacimus 10: up to 7 ions + pH + EC + hardness). Great for rapid nutrient panels in ~60 seconds. NT Sensors
Materials science angle: The company highlights carbon-nanotube-based tech in its marketing, aimed at fast, reliable multi-ion measurement. Imacimus Water Quality Meter
Where we like them: compact inline manifolds, benchtop multi-ion stations for hatcheries, mobile testing kits for farms and RAS facilities.
EDT directION (UK): half-cells, mini-ISEs, and process options
EDT’s directION line covers classic half-cells, combination electrodes, and notably a wide range of mini-ISEs at accessible price points (NH₄⁺, Ca²⁺, Cl⁻, Br⁻, etc.). They’re a solid UK source for building custom, multi-channel rigs with separate references, or for swapping between mini and full-size form factors. EDT Direction
Hanna Instruments (often misspelled “Hannah”): broad library of solid-state & combination ISEs
Hanna offers many ions in both half-cell and combination formats (e.g., chloride, silver/sulfide, cyanide, iodide). If you’re standardizing across a lab that already uses Hanna meters and buffers, their ISE catalog is an easy add-on.
Thermo Scientific Orion: the lab-standard workhorses
Thermo’s Orion ISEs are widely used in H2O labs and academia. If you need deep documentation, validated methods, and compatibility with existing Orion meters, this can be the “safe default.” Their brochures cover ion lists, accessories, and method notes across water, food, and bio samples. Thermo Fisher Documents
Metrohm, Mettler Toledo, Ionode & HORIBA: specialisms worth noting
Metrohm: Excellent application notes and care guides; their ISE content is useful even if you don’t buy their sensors (e.g., ranges, polishing, maintenance). metrohm.com
Mettler Toledo: Strong integration with titrators and automated workflows when you’re combining ISE with titration methods. mt.com
Ionode (AU): Durable lab/industrial ISEs and a handy primer on ISE theory for training new users. ionode.com
HORIBA LAQUAtwin: Pocket ISEs (e.g., Na⁺) for ultra-small sample volumes—nice for quick field triage or leaf sap checks. horiba.com
Choosing an ISE setup: quick buyer’s checklist
Ions & ranges: Confirm your expected concentration window vs. the sensor’s linear range and selectivity. Cross-interference (e.g., K⁺ vs. NH₄⁺) can matter—matrix-match standards where possible. metrohm.com
Form factor:
Mini-ISE / multi-ion probes (NT Sensors, EDT mini) for compact manifolds and simultaneous panels.
Full-size half-cells/combination (Hanna, Orion, Ionode) for classic lab setups and rugged routine testing.
Reference strategy: Combination electrodes are simple; half-cells let you share a reference across channels to save space in multi-ion rigs. (EDT calomel, double-junction options etc.). Environmental Expert
Calibration workflow: Keep standards fresh, bracket your sample, and log slope in mV/decade. Consistent ionic strength and temperature control improve reproducibility. (Metrohm’s maintenance notes are gold.) metrohm.com
Operational mode: Decide between portable spot checks (Imacimus, LAQUAtwin) and continuous/online monitoring (consider ISE probes paired with your logger—YSI’s best-practice note is a good read for wastewater/aeration contexts).
Spotlight: why NT Sensors’ mini-ISE approach is compelling
One probe, many ions: Up to seven ISEs in a single body is a tidy hardware win—fewer penetrations, simplified wiring, simpler field handling.
Small-volume, modular tips: Mini tips reduce sample requirements and let you re-configure your probe as projects evolve (e.g., swap Mg²⁺ for NO₃⁻ mid-trial).
Fast multi-parameter reads: Pair with Imacimus 5/10 to capture multi-ion + pH/EC/water-hardness in one go—ideal for nutrient panels, influent/effluent checks, or hatchery make-up water.
Where ISEs shine (and where to be careful)
Great for:
Rapid, reagent-free multi-ion quantification in water quality workflows.
Field validation of process changes (e.g., dosing, biofilter performance, fertigation recipes).
Embedded use in compact manifolds or robotic samplers (mini-ISEs).
Watch-outs:
Ionic strength and interferents can bias readings—matrix-match standards and use ionic strength adjusters as needed.
Temperature matters—use compensation, or calibrate and measure at similar temps.
Membrane care is not optional—follow the polishing/conditioning and storage guidance per vendor. metrohm.com
Bottom line (and how we use them)
Between NT Sensors’ mini-ISE ecosystem, EDT directION’s flexible mini and half-cell range, and the deep catalogs from Hanna, Thermo Orion, Metrohm, Ionode, and HORIBA, there are excellent options for anyone who needs multi-ion quantification without hauling a full wet-chem lab.
At Fyto, we’ve been building multi-ion sensing systems around these platforms for clients in aquaculture and water quality—from compact, inline manifolds to portable kits that deliver rapid nutrient panels on site. If you’re weighing up ions, ranges, or probe geometry for your application, we’re happy to suggest a stack (and calibration plan) that fits your sample matrix and workflow.
