(161h) Measuring Partition Coefficients of Single Walled Carbon Nanotubes in Aqueous Two Phase Microliter Droplets

The distribution of a dispersed species between two immiscible liquid phases, expressed as the partition coefficient, is a critical parameter for designing and evaluating the performance of laboratory and industrial-scale liquid-liquid separation processes. The lack of data relating the partition coefficient of a compound to experimental parameters continues to present a major roadblock to the large-scale optimization of aqueous two phase separations. This is particularly apparent in the purification of single wall carbon nanotubes, and has restricted their wide-spread application. State of the art methods for screening partition coefficients as a function of experimental parameters such as temperature and composition require milliliters of sample per data point, in addition to labor intensive handling and detection procedures. In this talk, we demonstrate a high throughput, low volume semi-automated platform for mapping the partition coefficient of carbon nanotubes as a function of matrix composition. Our approach uses a microliter droplet-based fluid handling system coupled with inline absorption spectroscopy. Monodisperse droplet slugs are generated that contain aqueous two phase polymer mixtures along with specific surfactants and carbon nanotube samples of interest. Upon phase separation the carbon nanotubes preferentially partition into one of the polymer-rich phases, and inline absorption spectroscopy is used to identify and quantify the concentration in each phase. In this way, the critical parameters for aqueous two phase extraction of nanotubes can be quantified at high compositional resolution.