Newly devised spectrophotometric cell for measurements of solubility and slow reaction rate in supercritical carbon dioxide

A spectrophotometric cell for measurements of solubility and slow reaction rate in supercritical carbon dioxide (scCO(2)) up to 30 MPa was developed. A free piston made of a Teflon-coated magnet in the cell is moved up and do wn in the cell cylinder by an outside magnet, which is automatically driven by a gas cylinder at an arbitrary time interval. There is a one-way path i n the free piston, and solution flow in the opposite direction is prevented ; thus, the solution is stirred by circulating scCO(2) in the looped pass. Using the developed cell, the solubilities of 5, 10, 15, 20-tetrakis(pentaf luorophenyl)porphyrin (H(2)tpfpp) in scCO(2) were determined at various tem peratures and pressures. The dynamic process of copper(II) ion incorporatio n into the porphyrin core for the reaction of H(2)tpfpp with Cu(hfac)(2) (h fac = 1,1,1,5,5,5-hexafluoroacetylacetonate) was monitored by simultaneousl y dissolving both reagents in scCO(2) in order to evaluate the applicabilit y of the developed spectrophotometric cell for rate measurements of slow ch emical reactions in scCO(2). (C) 2001 Elsevier Science B.V. All rights rese rved.