Fig. 1

Correlation of fluorescence intensity of 6-carboxyfluorescein with pH in microfluidic droplets. a Fluorescence intensity of 6-carboxyfluorescein measured in droplets in flow on a microfluidic chip. pH of the bulk aqueous phase before droplet generation was determined by a conventional pH electrode. The arithmetic means of min. 1262 droplets per pH level as black points are depicted. A four parameter logistic model (Boltzman model) described by the equation in the graph was fitted to the data and is displayed as blue line. b Fluorescence intensity of 6-carboxyfluorescein measured for entire droplet populations of different pH in a plate reader. The intensity values for the droplets populations measured at 3 different time points are depicted, to show the variability introduced by long term incubation. A four parameter logistic model was fitted to the data of time 0 h. c Fluorescence intensity of 6-carboxyfluorescein measured for entire droplet populations of different pH during dynamic droplet incubation. Replicates (R) were taken from the same droplet populations after different incubation times and speeds