Laboratory oxygen meters: how can dissolved oxygen be measured accurately?

The laboratory dissolved oxygen meter measures the concentration of dissolved oxygen (DO) and the level of O? saturation in water and culture media. Essential for quality control, bioprocessing, aquaculture and environmental monitoring, it safeguards cell viability, treatment efficiency and regulatory compliance. Depending on requirements, choose portable field meters, high-precision benchtop instruments, or in-line probes for bioreactors. Optical (LDO) and electrochemical (polarographic, galvanic) technologies cover every application, from day-to-day monitoring to metrology-grade measurements.

What are the different types of dissolved oxygen (DO) meters and probes?

Two main families coexist. Electrochemical sensors (Clark cell, polarographic or galvanic) measure a current proportional to O? diffusing through a membrane. They offer excellent sensitivity, but require membrane and electrolyte, regular calibration and a slight flow or stirring. Optical LDO sensors rely on the quenching of the luminescence of a dye by oxygen: no O? consumption, limited drift, low maintenance, stable response, ideal for long-term monitoring and low flow rates.

On the instrument side, there are portable IP67 DO meters for field work, and benchtop multi-parameter models for the laboratory. Key selection criteria: measurement range (mg/L, % sat), accuracy and stability, temperature and pressure compensation, response time, maintenance requirements, GLP compliance, data logging, connectivity, and compatibility with your media/matrices (presence of sulphides, low flow, sterilisation).

Comparison table (types of DO probes)

Type	Principle	Applications
Optical (LDO)	Luminescence quenching, no O? consumption	Long-term monitoring, low maintenance, low flow velocities
Polarographic	Polarised Clark cell, membrane + electrolyte	Accurate laboratory measurement, BOD, stirred media
Galvanic	Self-powered cell, quick start-up	Field work, rapid checks, routine applications

In which applications is an oxygen meter used?

• Life sciences and bioprocessing: monitor and control dissolved oxygen in bioreactors, cell cultures, yeast and bacterial fermentations to optimise growth and productivity.
• Environment and water: monitoring of rivers, lakes and effluents; BOD testing; aeration diagnostics in wastewater treatment plants.
• Food and beverage: managing O? in drinks (beer, wine) and process water to limit oxidation and preserve flavour.
• Pharmaceutical and cosmetics: quality control of aqueous batches, cleaning validation, monitoring of rinsates.
• Chemistry and R&D: kinetic and solubility studies, safety of oxygen-sensitive reactions, process qualification.
• Aquaculture: controlling aeration in tanks and ponds, animal welfare, reduced mortality.
• Education: practicals on respiration, photosynthesis and aquatic ecology.

Available oxygen meter types

Oximeter

Frequently asked questions about dissolved oxygen meters for the laboratory

How do I choose between an optical LDO probe and an electrochemical one?
An LDO sensor is low-maintenance and doesn’t require stirring; an electrochemical sensor is cost-effective and sensitive but needs a membrane, electrolyte and sample flow.

What’s the right calibration method?
Calibrate in air (100% saturation, 1-point) and, if needed, at zero O? (sulphite solution). Record temperature, pressure and salinity for an accurate measurement.

Why does my reading change with salinity?
The solubility of O? decreases as salinity increases. Enable salinity compensation or enter your sample’s salinity.

Do I need to stir during measurement?
Yes, with a polarographic probe (diffusion through the membrane). With LDO it’s less critical, but maintaining sample homogeneity still helps.

What maintenance is required?
LDO: periodic replacement of the optical cap. Electrochemical: replace membrane and electrolyte, clean regularly and check seal integrity.

Can I measure DO in samples containing sulphides?
Sulphides can damage some electrodes. Favour LDO technology or use electrochemical probes specified as sulphide-resistant.