Stopped-flow/quench flow

SFM2000/3000/4000 Stopped-flow.

A versatile stopped-flow mixing system designed to offer extreme precision as well as minimize the consumption of often expensive samples.

A range of single, double or triple stopped-flow mixing systems designed to ensure the shortest possible dead time.

The stopped-flow mixing system offering accuracy, precision, and versatility

A stopped-flow mixing system is an essential instrument for rapid kinetics investigations. A complete stopped-flow instrument is a mixing device coupled to a detection system. Two, three or four sample solutions are rapidly mixed and injected into an observation cell. When the flow is stopped, the kinetics are recorded with a detector chosen according to the chemical properties of the solutions and the information of interest (e.g. particle size, the environment of fluorophore, chromophore).

The SFM-4000 stopped-flow series is available for single, double or triple mixing applications (two reaction steps or one reaction step and one concentration change step before the final observed reaction). The SFM-4000 stopped-flow family has been designed to ensure the shortest possible dead time the highest precision and to minimize sample consumption as much as possible.

Applications include protein folding/refolding, protein-protein interactions, fluorescence resonance energy transfer (FRET), ligand binding, water and ion transport in vesicles and membranes, enzyme/substrate reactions, coordination reactions in inorganic chemistry, as well as identification or capture of intermediates, and more. Virtually any application with a timescale in the range of 0.5 ms. to minutes is observable by our stopped-flow systems. The same stopped-flow mixers can be used with chemical quench or freeze quench accessories to collect time point samples for EPR, NMR, Mossbauer, or GC/MS analysis when the reaction has no appropriate optical signature.

Free mixing ratio change

Mixing ratios can be freely changed by the user because our stopped-flow mixers use independent stepping motor technology. This technology provides microliter precision and accuracy at all flow rates, over a wide viscosity, temperature, and mixing ratio range. The user has a full control of volume, speed and mixing ratio from within Biokine software. A series of shots at various concentration can be programmed and run quickly without refilling or changing syringes. Advanced Berger-Ball technology mixers are used to provide the best turbulent mixing over the widest range of flow conditions.

Short dead time

With our SFM series technology, it is possible to achieve sub-microsecond dead times for following kinetics with a rate constant up to 3500 s-1. The standard dead time reachable by our SFM-4000 family systems is 700 µs, and 200µs is possible using the optional microcuvette for the most demanding applications. This extremely low dead time is achievable thanks to the precision drive mechanism and the quality of the stop mechanism. Quench flow and freeze quench applications have minimum ageing times of 2 ms.

Stopped-flow Modularity

The stopped-flow is easily adaptable to a wide variety of rapid mixing techniques and applications. The unique design is based on open access to the mixing chamber and the use of independent stepping motor technology. Therefore, the stopped-flow system can be switched from optical stopped-flow to chemical quench-flow, to freeze quench, to cryo stopped-flow to a beamline, to laboratory designed optical benches, all in minutes, with off the shelf options. A range of off-the-shelf accessories enables you to adapt the SFM-series to your specific needs in the lab, without buying a complete new system. Additionally, our R&D team provides special development services to customize the stopped-flow system and produce bespoke systems to meet your specific needs and applications.

10 years warranty

Bio-Logic offers a 10 years warranty on the stepping motors. Our 10 years warranty reflects our confidence in the high quality of our design, engineering, and product performance.

Bio-Logic instruments are designed to be future-proof. They are instruments that will withstand the tests of time, the rigors of the laboratory and the ever-increasing demands of your research.


Bio-Kine is user-friendly software that controls the stopped-flow, the detection device, follows the acquisition, and analyzes data.

Single mixing applications

Two levels of operation are provided for mixer control. The first level is designed for rapid and easy experiment design. The user sets the mixing ratio, the size of the cuvette and the volume of samples. Color coded windows display calculated values and alert the user to out of range conditions. The estimated dead time is automatically displayed, and a pre-trigger is also available to be sure the stationary state is reached accurately. This interface is ideal for routine mixing designs, occasional users, or students.


  • Mixing ratio from 1:1 to 1:100
  • Exact control of flow rate
  • User-selectable syringe volumes
  • 2, 3 or 4 independently controlled syringes and 1, 2 or 3 mixers
  • Dead time down to 200µs with the microvolume cuvette
  • Fully variable mixing ratio from 1:1 to 1:100
  • Sample Economy
  • Automated concentration dependence studies and double mixing
  • Standard Stopped-Flow configuration for all optical mode : absorbance, fluorescence, circular dichroism, fluorescence anisotropy.
  • A range of observation cuvettes
  • Exact control of flow rate
  • Extended temperature range

Is my stopped-flow compatible with all organic solvents?

(SFM-2000 / SFM-3000/ SFM-4000)

Yes. SFM is equipped with Viton™ O-rings in standard for all biochemical applications but FFKM o-rings are available in option to be full solvent compatible. SFM can also be customized to work with Grignard reactant.

Can I do triple mixing experiment?


Yes. SFM-4000 has 4 independent syringes and 3 mixers so triple mixing steps can be designed.

What is the shortest dead time I can achieve using my SFM?

(SFM-2000 / SFM-3000/ SFM-4000)

Shortest dead time is 200 µs using the microcuvette accessory. Microcuvette accessory can be installed in few minutes on all SFM models.

What do I need to change mixing ratio?

(SFM-2000 / SFM-3000/ SFM-4000)

Syringe of SFM are independent so mixing ratio is changed in Biokine software. You can freely select mixing ratio you need (it can be 1:3 or 1.2:5.1), warning message will inform you if you exceed recommended values.

Can I change the observation cuvette in the middle of one experiment ? How fast it can be done ?

(SFM-2000 / SFM-3000/ SFM-4000)

Yes. Changing the cuvette to adapt light path to your experiment is easy. Change of cuvette can be done in less than a minute. You just need to unlock hard-stop and to remove head cap to get access to the cuvette. No need to stop water bath circulator and no need to drain the internal lines.

Can I change o-rings myself?

(SFM-2000 / SFM-3000/ SFM-4000)

Yes. A spare o-ring kit is included with all new systems for preventive maintenance. The kits includes a technical drawing with positions of all o-rings in the instrument. A technical video is also available in the support section to guide you through the process.

LEDs on my MPS-70 are blinking and I cannot move syringes manually, what can I do ?

(SFM-2000 / SFM-3000/ SFM-4000)

It means the MPS-70 is locked by the software because a driving sequence is ready, so MPS-70 is just waiting for a start signal to do a shot. To unlock MPS-70 you need to close the driving sequence and LEDs will stop blinking immediately. Locking the MPS-70 is a safety feature to avoid losing precious sample in case a MPS-70 button would be accidentally touched during data acquisition.

Can I do quench-flow with my SFM ?

(SFM-2000 / SFM-3000/ SFM-4000)

To do chemical quench-flow you need three syringe so only SFM-3000 and SFM-4000 can do that. If you have quench-flow head then just install it in place of the stopped-flow head. The change takes 2 minutes. If you do not have the quench flow valve contact Bio-Logic or local representative


The following accessories are relevant to the SFM series:

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