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High precision mixing ratios – SFM-2000 series – Rapid kinetics – Application Note 18

Latest updated: May 6, 2020


Asymmetric mixing is often used in kinetic studies to characterize reaction mechanisms and pathways; however, this is often laborious and time consuming with standard stopped-flow systems requiring physical hardware reconfiguration. Bio-Logic’s SFM-series of stopped-flows use independent stepping motor technology which lets the user freely select mixing ratios in Biokine software. This application note illustrates the precision for both symmetric and asymmetric mixing of the SFM-series of stopped-flows using a dilution test of dichlorophenolindophenol from 1:1 to 1:20 with perfect linearity using standard syringes. No hardware reconfiguration is necessary because the independent stepping motors are controlled by the software automatically, making the SFM instruments unique. Asymmetric mixing ratios of 1:100 can be obtained with optional hardware configurations.



The ability to change mixing ratios easily and precisely is a key technical advantage in stopped-flow technology. It is especially important in protein folding/unfolding studies. In these applications a protein is mixed with a buffer and denaturant. The concentration of denaturant is varied to build Chevron plots, and the ability to change the mixing ratio rapidly is important. Concentration dependence studies in organic/inorganic chemistry or biology also require easily changed mixing ratios to get information about the reaction mechanism rapidly, with the best use of laboratory time. Bio-Logic’s SFM instruments use independent stepping motor technology which lets the user freely select mixing ratios in software. A series of concentration dependent samples can be run in a few minutes. Only Bio-Logic can propose a fully variable control of mixing ratio. Systems based on pneumatic drive or single drive units needs to change volume of one of the drive syringe to change mixing ratio, it means your mixing ratio possibilities are forced by the syringe you have (4 to 5 possibilities maximum). Single drive ram system also has a very limited mixing ratio range.


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