Ph-meter

Buying guide

What settles a pH meter purchase is rarely the headline resolution figure, because nearly every modern unit reads to 0.01 pH. The electrode decides far more. A sealed gel electrode suits aqueous samples and tolerates neglect; a refillable liquid-junction electrode holds accuracy longer in protein-rich, low-ionic-strength or non-aqueous media but demands upkeep. Match the electrode body to the sample before you compare meters: a spear tip for semi-solids, a flat surface for skin or paper, a micro shaft for NMR tubes and vials. A meter that cannot accept the electrode the work needs is the wrong meter however good its display.

Temperature handling comes next, because pH shifts with it. Automatic temperature compensation with a built-in or separate probe is standard on benchtop units and worth insisting on; a reading taken without it drifts with the room. Check the number of calibration points the meter accepts, three being the practical minimum for work spanning acidic and alkaline buffers, and confirm it stores calibration data you can audit.

On a used unit, the electrode is the part that ages, not the meter. Glass membranes degrade whether used or stored, reference junctions clog, and an electrode past its life gives a slow, drifting reading no recalibration fixes. Treat a used instrument as the meter plus a consumable, and budget for a fresh electrode unless the listing documents a recent one. The meter electronics themselves rarely fail; BNC and screw-cap connectors are the common standards, so verify the fitting matches any electrode you intend to carry over.

Price spans a wide band here. A used benchtop or portable meter is more affordable than a new equivalent, and what fits a budget depends on whether you need a calibrated multi-parameter system or a single-channel pocket tester. Units for sale run from EUR 1 to EUR 34.436, with an average around EUR 599. The lower reaches hold pocket and portable testers and bare electrodes; the upper reaches hold multi-channel benchtop analysers with ion-selective and conductivity inputs. Thermo Scientific, Mettler Toledo, Ohaus, Thermo Fisher Scientific, Fisher Scientific account for much of the mid and upper catalogue, where parts and replacement electrodes are easiest to source.

Types of pH meter

Which pH meter types are listed here?

Among the listings that specify a type, the catalogue divides into a handful of recognisable classes. Benchtop pH meters are the laboratory standard: mains-powered, multi-point calibration, often with inputs for a second parameter, and they anchor routine potentiometry at the lab bench. Portable and handheld pH meters trade some stability for field use, running on batteries for on-site water and soil work. Conductivity meters and broader electrochemical analysers appear alongside them because the same instrument platform frequently reads conductivity, ion-selective potentials and dissolved oxygen through interchangeable probes. Bare pH electrodes make up a large share of their own, sold as replacements for ageing sensors rather than as complete instruments.

Each class serves a distinct buyer. The benchtop analyser belongs in gravimetric and analytical workflows where buffer preparation, titration endpoints and quality-control checks demand logged, temperature-compensated readings. The portable unit belongs to the environmental sampler. The electrode belongs to anyone whose meter still works but whose sensor has drifted.

In the life sciences this instrumentation does quiet but constant work. pH control underpins cell culture, where medium buffered to physiological pH keeps cultures viable, and it governs buffer preparation across molecular biology, protein purification and electrophoresis, where running and transfer buffers must hold a defined pH. A pH electrode for protein purification is a routine fixture at the chromatography bench, and conductivity measurement runs beside it to monitor salt gradients during ion-exchange separations. In microbiology and fermentation monitoring, continuous pH reading tracks the acidification that signals microbial growth, which is why bioprocessing and biomanufacturing lines carry process-grade electrodes rated for sterilisation. Immunoassay and molecular diagnostics work rests on the same foundation, since assay reproducibility depends on reagents held at a known pH.

The brands behind the pH meter listings

The catalogue is led by Thermo Scientific, Mettler Toledo, Ohaus, Thermo Fisher Scientific, Fisher Scientific. For a buyer, that concentration matters in practical ways rather than as a mark of prestige. Replacement electrodes, calibration buffers and spare junctions for these makers are widely stocked, so a used meter from one of them is less likely to become an orphan. Their model lines are also well documented, which makes it straightforward to compare two listings on calibration points, input channels and electrode compatibility before committing. Where a listing names a maker outside this group, confirm the electrode connector standard and buffer availability before treating it as a like-for-like alternative.

What a used pH meter costs here

The condition split runs heavily to used stock: 88 percent of the listings are used against the remainder new. Prices for sale range from EUR 1 to EUR 34.436, averaging around EUR 599. That spread reflects the gap between a bare electrode or pocket tester at one end and a multi-parameter benchtop analyser at the other. Where a need falls outside this, manuals and documentation can be requested through Questpair, and replacement parts sourced the same way.