Measurements of Binary Diffusion Coefficient and Partition Ratio at Infinite Dilution for Linoleic Acid and Arachidonic Acid in Supercritical Carbon Dioxide

Abstract

The binary diffusion coefficient D 12 and partition ratio k were measured for two ω6 group compounds, linoleic acid and arachidonic acid, at infinite dilution in carbon dioxide at temperatures from 308.15 K to 343.15 K and pressures from 9 MPa to 30 MPa by a tracer response technique with a poly(ethylene glycol)-coated capillary column. The measured D 12 values were well represented by a correlation of D 12 /T versus CO 2 viscosity and by the Schmidt number correlation for each solute, and the k values were well represented as a function of temperature and CO 2 density. Partial molar volumes were also obtained from the k values.

Impulse response techniques to measure binary diffusion coefficients under supercritical conditions

“…Data obtained by single injections were plotted and yielded good reproducibility [40]. Using this technique, binary diffusion coefficients and retention factors were determined for various compounds [14,15,[40][41][42][43][44][45].…”

“…PMV values at infinite dilution of various solutes such as ␣-tocopherol [40], ␤-carotene [40], ubiquinone CoQ10 [41], and unsaturated fatty acids [42,43] were determined using the CIR method, assuming v ∞ s was negligible compared with v ∞ m . This assumption may be valid in the near critical region.…”

“…(3) In carbon dioxide by the chromatographic impulse response (CIR) method [14,15,[39][40][41][42][43][44][45]. (4) In other supercritical fluids by the Taylor dispersion method [86][87][88][89][90].…”

“…Although the accuracy of all of the correlations has not been confirmed, two correlations are effective for compounds over a wide range of molecular mass, as shown in Table 1, which lists data obtained with impulse response methods such as the Taylor dispersion [20,24,25,45], modified Taylor dispersion [13], and CIR method [14,15,[40][41][42][43][44][45].…”

Determination of thermodynamic properties by supercritical fluid chromatography

“…(6) and (7) were used extensively to determine the partial molar volumes of diverse solutes at infinite-dilution in scCO 2 . The selection of solutes included aromatic hydrocarbons [21,22,[56][57][58][68][69][70][71][72][73], C 6 -C 16 n-alkanes and alkylated cyclohexanes [68], benzoic acid and 2-methoxynaphthalene [69,71], C 3 -C 9 aliphatic and C 10 terpenic alcohols [74], coenzyme Q 10 [75], polyunsaturated long-chain carboxylic acids [76,77] and their ethyl esters [78], C 21 -C 40 n-alkanes [79], and β-carotene and vitamin E [80]. The effect of the correction for uptake of scCO 2 by the stationary phase could only be tested in naphthalene [73] where sufficient amount of independentv ∞ 1m data were available [81].…”