Process analysers

Buying guide

What a process analyser has to measure is the first thing to settle, because it determines the detection principle and almost everything that follows from it. A gas analyser reading oxygen in a flue stream, a dissolved oxygen sensor in a fermenter and a water quality analyser tracking conductivity are not variants of one device; they are different measurement physics in different housings. Fix the analyte, the expected concentration range and the required accuracy first, then the matrix it sits in, a wet gas, a pressurised liquid, a sterile broth, because the matrix decides whether a sensor survives the environment at all. Only once those are known does a model shortlist mean anything.

For a used unit the sensing element is where the value and the risk both concentrate. An electrochemical cell, an optical window or a membrane ages with exposure and has a finite service life regardless of how the surrounding electronics behave, so verify what the sensor is, how old it is, and whether a replacement element is still available before the price looks attractive. Ask for the last calibration record and check that the unit was stored, not left installed on a stream after its last run. A filter integrity tester or a bioprocess sensor pulled from a validated line may carry documentation worth as much as the hardware; a gas analyser with a spent cell may need a new sensor that approaches the cost of the instrument. Where documentation or a replacement element is in question, that is a point to raise against the individual listing, and warranty on Questpair is arranged in consultation for the specific unit rather than set as a blanket term.

The price band here is wide because the category holds both ends of the measurement chain. A bare dissolved oxygen sensor and a full multi-stream gas analysis cabinet both appear, so a quoted range of EUR 22 to EUR 645.667 says little until you know which end of the chain you are pricing. The average listing at EUR 6.791 is more useful as a reference point for a complete working instrument. Set your budget against the measurement task rather than the category, because a water quality analyser for a single parameter and a bioprocess analyser for a regulated line occupy different parts of that range entirely. Within it, Thermo Scientific, Mettler Toledo, Millipore, Agilent, Cytiva account for much of what is listed, and a used or refurbished unit from one of them is more affordable than its new equivalent while keeping parts and calibration support straightforward. For a buyer working to a fixed budget, the units for sale from established makers are the ones easiest to compare on specification and to maintain over a service life.

Types of Process analysers

Which process analyser types are listed here?

Among the listings that specify a type, six recur, and they divide by what they measure rather than by how they look. Gas analysers are the largest group, reading a single species or a mix in a flowing gas stream, used in emissions monitoring, combustion control and bioprocess off-gas analysis. Dissolved oxygen sensors measure oxygen in a liquid, most heavily in cell culture and fermentation, where oxygen transfer governs how a culture grows. Water quality analysers track parameters such as pH, conductivity and turbidity in process and environmental water. Filter integrity testers confirm that a sterilising filter holds before and after a run, a verification step in sterile biomanufacturing and aseptic processing. Bioprocess sensors cover the probes that sit inside a bioreactor, reading pH, oxygen and biomass during a run. The general analytical instruments round out the list, the detectors and controllers that read a signal a sensor produces. The split reflects where continuous measurement earns its place: online rather than in a laboratory afterward.

The brands behind the process analyser listings

Thermo Scientific, Mettler Toledo, Millipore, Agilent, Cytiva make up the bulk of what is listed, and each carries a known position in continuous measurement. For a buyer that presence matters in three practical ways. Parts and replacement sensors for these makers are the easiest to source, which keeps an ageing analyser serviceable; the models are documented well enough to compare on specification across listings; and a used instrument from one of them holds a resale and support base that a niche maker does not. Dissolved oxygen and bioprocess probes in particular depend on a steady supply of replacement elements, so a maker with a wide installed base is the safer bet for a unit expected to run for years.

What a used process analyser costs here

Condition is where this category skews hard: 95 percent of the listings are used. Prices run from EUR 22 to EUR 645.667, with the average near EUR 6.791. That spread is not a single market but several, a bare sensor at one end and a multi-stream analytical cabinet at the other, and the figure that matters is the one for the measurement task in front of you. Within genomics, proteomics and cell culture work, where these instruments read fermentation off-gas, dissolved oxygen in a bioreactor, or sterile filter integrity, a used unit from an established maker is listed below its new price while keeping the calibration and parts path open. The practical reading of the range is to price the complete working instrument you need, not the category it belongs to.