Chromatographic Impulse Response Method Research Articles

Measurement of diffusivity in supercritical carbon dioxide via particle dissolution method

A novel method of determining diffusivity in supercritical carbon dioxide is proposed based on the principle of particle dissolution. The dissolution rate of disperse blue 14 (DB14) was measured by in situ UV–vis spectroscopy and compared with a pseudo-steady-state diffusion-driven dissolution model. By minimizing the error between the experimental data and model equation via nonlinear regression, the diffusivities of DB14 at 21.9–25.7 MPa and 320–393 K were determined. The diffusivities were then compared with reference data measured using the chromatographic impulse response method. Positive deviations of 2.88%, 3.11%, and 1.41% were confirmed, suggesting the possibility and potential of the method. Further research is needed to determine and optimize the accuracy of the measurements and generalize the method to other systems.

Measurements of binary diffusion coefficient for platinum(II) acetylacetonate in high temperature supercritical carbon dioxide by the chromatographic impulse response method

Infinite dilution binary diffusion coefficients D12 and retention factors k for platinum(II) acetylacetonate in high temperature supercritical carbon dioxide (scCO2), at temperatures from (323.3–454.2) K and pressures from (11.0–25.0) MPa, were measured by the chromatographic impulse response method. Although diffusion coefficients for various compounds up to 353 K in scCO2 reported in the literature were well represented by the hydrodynamic equation, the present data deviated more from the equation as the CO2 viscosity decreased. The deviating D12 data corresponded to the gas-like scCO2 region whose conditions were situated below the density fluctuation ridge line on the pressure (or density) − temperature phase diagram, as observed for Cr(acac)3 measured in the authors’ previous study. All the present D12 data and those previously measured below 343 K over the entire region from gas-like to liquid-like scCO2 were well represented by the Schmidt number correlation over the temperature range from 308.2 K to 454.2 K with an average relative deviation (ARD) of 6.5% for 109 measurement conditions. The retention factors measured in the present study were correlated with CO2 density, with temperature dependent constants having an ARD of 4.4% for 47 measurement conditions.

Determination of diffusivities of triolein in pressurized liquids and in supercritical CO2

Pressurized liquid extraction and supercritical fluid extraction are attracting attention. The accurate design and scale-up of these processes need the knowledge of transport property, namely, diffusion coefficients. In this study, the measurements of diffusion coefficients D12 of triolein with a high molecular weight were carried out in pressurized fluids with different viscosities. The D12 values in various pressurized liquids of ethanol, methanol, and hexane were determined by the Taylor dispersion method at 298.15 to 323.15 K and pressures of 1.00 to 12.08 MPa. We found that the D12 data in supercritical CO2 cannot be accurately measured by the Taylor dispersion method because the response peaks of triolein in supercritical CO2 obtained by the Taylor dispersion method were severe tailing. However, the tailings were significantly improved by using the chromatographic impulse response method. Therefore, the D12 values in supercritical CO2 were measured by the chromatographic impulse response method at 303.15 to 333.15 K and pressure up to 31.02 MPa. The magnitude of determined D12 of triolein in fluids is in the order of CO2 > hexane > methanol > ethanol. The D12 increased from 0.306 × 10−9 m2 s−1 at 298.15 K and 10.00 MPa in liquid ethanol to 6.323 × 10−9 m2 s−1 at 333.15 K and 13.77 MPa in supercritical CO2. All the diffusivity data of triolein measured in CO2, hexane, methanol, and ethanol in this study can be satisfactorily represented by the hydrodynamic equation over a wide range of fluid viscosity of 37 to 1179 μPa s from liquid to supercritical states.

Measurements of infinite dilution binary diffusion coefficients of acetylferrocene and 1,1’-diacetylferrocene in supercritical carbon dioxide and in liquid organic solvents

The infinite dilution binary diffusion coefficients (D12) of acetylferrocene and 1,1′-diacetylferrocene were measured in supercritical carbon dioxide (scCO2) at (313, 353, 363 and 373) K and at pressures from (11 to 26) MPa using the chromatographic impulse response method, and in atmospheric-pressure liquid organic solvents such as acetone at 303 K, methanol at (313, 323, and 333) K and ethanol at (323 and 333) K using the Taylor dispersion method. The D12 values for both solutes were approximately consistent under all of the investigated measurement conditions and were well represented by the hydrodynamic equation, in which D12/T is expressed as a function of solvent viscosity, over almost the entire range of investigated viscosities ranging from the viscosities of liquid organic solvents to that of scCO2. At 313 K and 11 MPa, the D12 values for both the organometallic solutes deviated from the correlation of the D12 values with the solute molecular mass for nonmetallic organic compounds reported in the literature.

Measurements and correlation of diffusion coefficients of ibuprofen in both liquid and supercritical fluids

The diffusion coefficients of ibuprofen in both liquid and supercritical fluids are presented for the first time. The diffusion values in liquid ethanol were measured by the Taylor dispersion method at temperatures from 298.15 K to 333.15 K and pressures from 0.10 MPa to 30.00 MPa. Those in supercritical CO2 were carried out by the chromatographic impulse response method at 308.15 K–353.15 K and up to 40.00 MPa. The determined diffusion activation energies in supercritical CO2 were Ea =18.6 kJ/mol to 11.0 kJ/mol at P = 15.00 MPa to 35.00 MPa, and those in liquid ethanol were Ea =16.3 kJ/mol to 15.1 kJ/mol at P = 0.10 MPa to 30.00 MPa, respectively. All the diffusion data of ibuprofen in liquid ethanol and in supercritical CO2 were well correlated by the hydrodynamic equation proposed in this study, with an average absolute relative deviation of 2.2 % for 115 data points.

Measurement of binary diffusion coefficient and solubility estimation for dyes in supercritical carbon dioxide by CIR method

Infinite dilution binary diffusion coefficients (D12) of two dyestuffs, disperse blue 14 (DB14) and disperse orange 11 (DO11), were measured in supercritical CO2 at 310–330 K and up to 35 MPa by the chromatographic impulse response (CIR) method and in liquid methanol and ethanol at 308–328 K and atmospheric pressure by the Taylor dispersion method. The retention factors (k) were also measured by the CIR method. The diffusion coefficients were well represented by a hydrodynamic equation, as a function of temperature and solvent viscosity, over a wide range of solvent viscosity from scCO2 to liquid solvents with average absolute relative deviations (AARDs) of 1.7% and 2.6% for 63 and 93 data points of DB14 and DO11, respectively. The solubility data for the two dyestuffs reported in the literature were well correlated with solute retention factor measured in the present study and solvent density with AARD of 7.05% for DB 14 of 109 data points and that of 15.4% for DO11 of 43 data points.

Infinite dilution partial molar volumes of platinum(II) 2,4-pentanedionate in supercritical carbon dioxide

The effects of temperature and density on retention of platinum(II) 2,4-pentanedionate in supercritical fluid chromatography were investigated at temperatures of 308.15–343.15K and pressure range from 8 to 40MPa by the chromatographic impulse response method with curve fitting. The retention factors were utilized to derive the infinite dilution partial molar volumes of platinum(II) 2,4-pentanedionate in supercritical carbon dioxide. The determined partial molar volumes were small and positive at high pressures but exhibited very large and negative values in the highly compressible near critical region of carbon dioxide.

Binary Diffusion Coefficients of Platinum(II) Acetylacetonate in Supercritical Carbon Dioxide

Binary diffusion coefficients (D12) and retention factors (k) of platinum(II) acetylacetonate at infinitesimal concentration in supercritical (sc) carbon dioxide (CO2) were measured by the chromatographic impulse response method with a poly(ethylene glycol) coated capillary column at temperatures from (308.15 to 343.15) K and pressures from (8.5 to 40.0) MPa, and D12 in liquid ethanol at temperatures from (298.15 to 333.15) K and atmospheric pressure by the Taylor dispersion method. As has been seen for our previously reported data on other metal complexes measured in sc CO2 and organic solvents, the D12 data in sc CO2 and liquid ethanol were represented by a function of temperature and solvent viscosity. The D12 values for metal complexes were not related to the solute molecular weights. The k values in sc CO2 were expressed by a function of temperature and CO2 density.

Solubility determination of organometallic complexes in supercritical carbon dioxide by chromatographic impulse response method

The solubilities of organometallic complexes in supercritical CO 2 were determined from retention factors measured by the chromatographic impulse response (CIR) method, in which a solute was pulse-injected into a supercritical CO 2 flowing in a polymer coated open capillary column, and the response curve, i.e. time change of solute concentration, was monitored at the exit of the column. The retention factor and binary diffusion coefficient were simultaneously obtained as two parameters so that the fitting error between response curves of solute species measured and calculated was minimized. The validities of the method and the apparatus employed in this study were verified by determining the solubilities of naphthalene, which have extensively been reported in the literature. Then, the solubilities of organometallic complexes such as ferrocene and cobalt (III) acetylacetonate in supercritical CO 2 were determined. The data determined in this study were in good agreement with the literature data. The solubilities were also correlated with the Chrastil equation including the three adjustable parameters.

Measurements of Binary Diffusion Coefficients for Ferrocene and 1,1′-Dimethylferrocene in Supercritical Carbon Dioxide

Binary diffusion coefficients D12 and retention factors k of ferrocene and 1,1′-dimethylferrocene at infinite dilution in supercritical (sc) carbon dioxide were measured by the chromatographic impulse response (CIR) method at temperatures from (308.2 to 323.2) K over a pressure range from (8.0 to 40.3) MPa for ferrocene and from (8.2 to 40.1) MPa for 1,1′-dimethylferrocene. The D12 data for ferrocene were also measured by the Taylor dispersion method with two injection procedures of ferrocene: ferrocene dissolved both in sc CO2 and in liquid hexane. The D12 values of ferrocene were not affected by the injection methods and agreed with those measured by the CIR method. As has been seen for various organic compounds measured in our previous reports, the D12 data for both metal complexes were correlated with the hydrodynamic equation D12/T = αηβ, where η is the CO2 viscosity and α and β are the constants determined by each solute. The retention factors were also correlated with CO2 density.

Diffusion coefficients of metal acetylacetonates in supercritical carbon dioxide

Binary diffusion coefficients, D 12, of the metal acetylacetonates, palladium(II) acetylacetonate and cobalt(III) acetylacetonate, were measured from 308.2 to 343.2 K over the pressure range from 9 to 40 MPa at infinite dilution in supercritical carbon dioxide using the chromatographic impulse response method. The effects of pressure, temperature, density, and viscosity on D 12 values were examined. It was observed that the D 12 values of palladium(II) acetylacetonate and cobalt(III) acetylacetonate were larger than those of lipids with similar molecular weights, such as arachidonic acid and monoolein, respectively. Furthermore, the measured D 12 data of each metal acetylacetonate were well correlated by the hydrodynamic equation D 12/ T as a function of carbon dioxide viscosity.

Reliability of binary diffusion coefficients determined from tailing response curves measured by the Taylor dispersion method in the near critical region

Two kinds of tracer response measurements, by the Taylor dispersion method using a stainless-steel diffusion column and the chromatographic impulse response (CIR) method using a polymer-coated diffusion column, were carried out by using the curve fitting to determine infinite-dilution binary diffusion coefficients of vitamin K 3 (2-methylnaphthalene-1,4-dione), as a medium polar compound, in supercritical CO 2 at 308.2 K and pressures from 7.75 to 31.00 MPa. The response curves in the Taylor dispersion method showed more significantly tailing closer to the critical point, whereas those did not at conditions away from the critical point. However, the CIR method provided the response curves almost without tailing over an entire range of pressure studied. Consequently, in the CIR method the response curves were accurately reproduced with the determined values of two parameters, binary diffusion coefficient and retention factor. The determined values of diffusion coefficients showed a little slow-down in the near critical region. In the Taylor dispersion method, however, the response curves with tailing were poorly reproduced with the determined values of diffusion coefficients, which apparently led to a steep-down in the near critical region.

Binary diffusion coefficients and retention factors for polar compounds in supercritical carbon dioxide by chromatographic impulse response method

The chromatographic impulse response (CIR) method with curve fitting was employed for measuring binary diffusion coefficients D 12 at infinite dilution for polar compounds such as benzoic acid and C 1 to C 3 mono-alcohols in supercritical (SC) carbon dioxide at 313.2 K and pressures higher than 9.5 MPa. The measured D 12 values for the polar compounds were expressed with two correlations which well represent binary diffusion coefficients for non-polar and weak polar compounds, i.e. the correlation of D 12/ T as a function of CO 2 viscosity and the Schmidt number correlation. Moreover, the slope was −0.5 in logarithmic plot of D 12 versus solute molecular weight over the range of molecular weight from 32 to 1138 at 313.2 K and 11.0 MPa.

Measurement of binary diffusion coefficient from impulse response curve having extremely low absorbance intensity under supercritical condition by noise elimination technique

A noise elimination technique was applied to the determination of binary diffusion coefficients D 12 from the response curves having extremely low absorbance intensities in impulse response methods under supercritical conditions of carbon dioxide. The effectiveness of this technique was experimentally examined for the analyses of response curves through both the curve-fitting and the moment methods in two cases: the chromatographic impulse response method for phenol and β-carotene with a polymer-coated capillary column, and the Taylor dispersion method for acetone with an uncoated capillary column. Unreliable D 12 values were obtained from the moment method of the response curves at lower absorbance intensities, even treated with noise elimination. The curve-fitting method with the noise elimination treatment was quite effective for determining the D 12 values accurately, and was valid at the lowest absorbance intensities, on the order of 10 −4 absorbance unit of UV-Vis multi-detector, corresponding to the smallest quantity of the solute, i.e. 6×10 −5, 6×10 −6, and 5×10 −2 μ mol for phenol, β-carotene, and acetone, respectively, under conditions studied. Infinite dilution regions for binary diffusion coefficients were obtained by injecting various amounts: the binary diffusion coefficients showed constant values at concentrations less than 0.6, 0.004, and 0.08 mol m −3 for phenol, β-carotene, and acetone, respectively, in supercritical carbon dioxide at 313.2 K and 16–18 MPa.

Effects of molecular weight and degree of unsaturation on binary diffusion coefficients for lipids in supercritical carbon dioxide

Infinite dilution binary diffusion coefficients and retention factors for the oleic acid family such as oleic acid, methyl- and ethyl esters, and mono-, di-, and triglycerides at 313.21 K and 8–30 MPa, and for other 13 lipids consisting of C18–C22 unsaturated fatty acid constituents at 313.21 K and 11 MPa were measured in carbon dioxide by a chromatographic impulse response method with a polymer coated capillary column. The binary diffusion coefficients and the retention factors for each compound decreased with increasing pressure. The binary diffusion coefficients could be represented by a Schmidt number correlation and by an empirical equation written in terms of temperature and CO 2 viscosity. The retention factors for each solute could be expressed in terms of CO 2 density. While the binary diffusion coefficients at 313.21 K and 11 MPa decreased with solute molecular weight, those for compounds having the same carbon numbers in each group, such as methyl ester, ethyl ester, and triglyceride, decreased with increasing the number of C–C double bonds.

Influence of Solute Polarity on Diffusion Coefficient in Supercritical Carbon Dioxide by Chromatographic Impulse Response Method

Influence of Solute Polarity on Diffusion Coefficient in Supercritical Carbon Dioxide by Chromatographic Impulse Response Method