Analytical application of microcalorimetry: A stop-flow mixing device

A stopped-flow (stop-start) mixing device for use in connection with a bench-top microcalorimeter has been designed and constructed. The device employs a ball mixer for rapid combination of solutions pre-equilibrated in spirals of tantalum tubing. Following the mixing procedure, the resultant heat is measured by pumping the mixed solution into Teflon coils situated within the sensing volume of a microcalorimeter. The sensitivity of the flow mixer is comparable to other types of mixers employed in the same instrument and allows serial analyses once equilibrium has been obtained. The sealed nature of the flow cells allows reactions that are sensitive to their environment to be carried out without resorting to inert atmospheres.