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Vapor-liquid equilibrium data of 1,1,1,2-tetrafluoroethane (R134a) + dimethylformamide (DMF) were measured in the temperature range from (303.30 to 353.24) K by the static analytic method. The results are of interest to test the possibility of using R134a as a refrigerant in combination with an organic absorbent, that is, DMF, in an absorption heat transformer. The experimental data are correlated using the Peng-Robinson equation of state in combination with the Mathias-Copeman R function, MHV1 mixing rules, and the non-random two liquid (NRTL) activity coefficient model. We have compared our experimental results to predictions obtained using the predictive Soave-Redlich-Kwong (PSRK) group contribution equation of state.

The drug delivery through intraocular lenses (IOLs) allows the combination of cataract surgery act and postoperative treatment in a single procedure. In order to prepare such systems, "clean" supercritical CO2 processes are studied for loading commercial IOLs with ophthalmic drugs. Ciprofloxacin (CIP, an antibiotic) and dexamethasone 21-phosphate disodium (DXP, an anti-inflammatory drug) were impregnated into foldable IOLs made from poly-2-hydroxyethyl methacrylate (P-HEMA). A first pre-treatment step was conducted in order to remove absorbed conditioning physiological solution. Supercritical impregnations were then performed by varying the experimental conditions. In order to obtain transparent IOLs and avoid the appearance of undesirable foaming, it was necessary to couple slow pressurization and depressurization phases during supercritical treatments. The impregnation yields were determined through drug release studies. For both drugs, release studies show deep and reproducible impregnation for different diopters. For the system P-HEMA/CIP, a series of impregnations was performed to delimit the experimental range at two pressures (80 and 200 bar) in the presence or absence of ethanol as a co-solvent for two diopters (+5.0 D and +21.0 D). Increase in pressure in the absence of a co-solvent resulted in improved CIP impregnation. The addition of ethanol (5 mol%) produced impregnation yields comparable to those obtained at 200 bar without co-solvent. A response surface methodology based on experimental designs was used to study the influence of operating conditions on impregnation of IOLs (+21.0 D) in the absence of co-solvent. Two input variables with 5 levels each were considered; the pressure (80-200 bar) and the impregnation duration (30-240 min). CIP impregnation yields ranging between 0.92 and 3.83 μg CIP/mg IOL were obtained from these experiments and response surface indicated the pressure as a key factor in the process. The DXP impregnation in P-HEMA was higher than CIP at all the tested conditions (8.50-14.53 μg DXP/mg IOL). Furthermore, unlike CIP, highest DXP impregnation yields were obtained in the presence of ethanol as a co-solvent (5 mol%). NMR spectroscopy was performed to confirm complete removal of ethanol in the co-solvent-treated IOLs.

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The solubilities of 1,1,1,2-tetrafluoroethane (R134a), CF3CH2F, + dimethylether diethylene glycol (DMEDEG), CH3O(CH2CH2O)2CH3, and R134a + dimethylether triethylene glycol (DMETrEG) binary systems were measured, using the “static−analytic” method at temperatures between (303 and 353) K. This work was an opportunity to test the use of R134a as a refrigerant in combination with an organic absorbent, like DMEDEG and DMETrEG, in an absorption heat transformer (AHT), also known as a type II absorption heat pump or a reversed absorption heat pump. The experimental data were correlated using the Peng−Robinson equation of state (PR-EoS) in combination with Mathias−Copeman α function, Huron−Vidal mixing rules, and the nonrandom two-liquid (NRTL) activity coefficient model. The experimental results were compared to the predicted values obtained using the predictive Soave−Redlich−Kwong group contribution equation of state (PSRK-EoS).

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