Laboratory diluters: how can sample dilution be standardised quickly?

Essential in microbiology and quality control, the laboratory diluters automate the preparation of initial dilutions (1:10, 1:100…) from solid or liquid samples. The gravimetric principle calculates, in real time, the volume of diluent to add according to the weighed mass, delivering precise, reproducible and aseptic dilution. The result: fewer manipulations, fewer errors, full traceability and a streamlined workflow, compliant with ISO 6887/7218 and the requirements of food, pharmaceutical, cosmetics, environmental and research laboratories.

What are the different types of laboratory diluters?

Two main families cover most needs. The gravimetric dilutor couples a load cell with a pump (usually peristaltic) to automatically deliver the exact volume of diluent according to the sample mass, typically into a sterile bag. It guarantees accuracy, repeatability and reduced cross-contamination. The dilutor/dispenser adds sequential distribution of the dilutions to multiple containers (bags, plates, tubes), speeding up inoculation and standardising throughput.

Key selection criteria: volume range (e.g. 50–375 mL and beyond), dosing speed (prepare a 1:10 dilution in seconds), gravimetric accuracy, ISO 6887/7218 compliance, materials (stainless steel 316L), sterile options (single-use circuits or autoclavable), ergonomics (foot pedal, bag holder), traceability (methods, IDs, LIMS/USB export) and ease of cleaning.

From an environmental standpoint, favour reusable autoclavable circuits where the hygiene plan allows, low-power standby modes and proven mechanical durability. On quality, look for calibration routines using test masses, built-in diagnostics and weighing error alerts.

Type	Principle	Applications
Gravimetric dilutor	Sample weighing, automatic calculation and addition of the exact volume of diluent via pump	Preparation of primary 1:10, 1:100 dilutions in sterile bags
Dilutor/dispenser	Dilution then sequential distribution to multiple containers	Inoculation chains, high-throughput QC in food/pharma
Diluent/medium dispenser	Repeatable volumetric dosing of media or diluents	Standardised filling of plates, tubes or vials

In which sectors and applications is a laboratory diluter used?

• Food & beverage: standardised preparation of sample dilutions (meat, dairy, plant matrices) prior to enumeration. Compliance with ISO 6887/7218 and shorter preparation times.
• Pharmaceuticals & cosmetics: bioburden monitoring and microbiological cleanliness testing with full parameter traceability and audit trails.
• Environmental: analysis of water, sludge and soils; rapid, reproducible dilution to minimise measurement uncertainty.
• Chemistry & R&D: standardising dilutions of complex samples for analytical testing and in-house methods.
• Quality control laboratories: high daily throughput, reduced MSD risk and secure data capture (sample ID, operator, methods).

The different types of dilution systems available

Frequently asked questions about laboratory diluters

How does a gravimetric dilutor work?
It weighs the sample, calculates the required volume and dispenses the diluent via a pump, ensuring precise, rapid and aseptic dilution.

Which standards must be met in microbiology?
Preparations generally follow ISO 6887/7218 for initial dilutions and aseptic sample handling.

Disposable or autoclavable: which should I choose?
Disposable fluid paths minimise contamination; autoclavable circuits reduce waste. The choice depends on your hygiene plan and throughput.

What accuracy can I expect?
Gravimetric systems offer excellent repeatability. Check the manufacturer’s specifications and perform checks with calibration weights.

Can I trace my methods and results?
Yes, most systems record sample/operator IDs, methods and volumes, with USB export or LIMS integration.

How do I maintain a dilutor?
Daily surface cleaning, periodic tubing replacement, calibration checks and verification of the weighing cell.

Is it compatible with all bags?
Check the compatibility of the holder and the nozzles/fittings. Sterile microbiology blender bags are generally supported.

What time savings can I expect?
A 1:10 dilution is prepared in a few seconds, with fewer steps and better standardisation than manual pipetting.