Determining the Solubility of Nifedipine and Quinine in Supercritical Fluid Carbon Dioxide Using Continuously Stirred Static Solubility Apparatus Interfaced with Online Supercritical Fluid Chromatography

Abstract

A high pressure vessel equipped with continuous magnetic stirring has been interfaced directly online with supercritical fluid chromatography (SFC). The interface consists of an oven housing a recirculation pump that maintains a constant flow of supercritical fluid solution from the vessel through a sample injection valve for online SFC analysis. The method involves increasing the vessel pressure in controlled steps to produce a series of progressively more saturated supercritical fluid carbon dioxide solutions for online SFC solubility measurements. The integrated static solubility system provides a convenient means to ensure equilibrium is established prior to performing online SFC solubility measurements and also facilitates a self-validation accuracy check procedure. For nifedipine, solubility data was obtained at 333.15 and 353.15 K through the pressure range from 12.5 to 27.5 MPa using 2.5 MPa steps. For quinine, solubility data was obtained at 323.15 and 343.15 K through the pressure range from 12.5 to 27.5 MPa using 3 MPa steps. All sets of experimental solubility data for each compound were correlated using the Mendéz-Santiago and Teja model.

Solubility Measurements of Chloramphenicol in Supercritical Fluid CO2 Using Static Solubility Apparatus Interfaced with Online Supercritical Fluid Chromatography

“…Although some compounds rapidly reach equilibrium, it has been demonstrated that 3−12 h stirring may be necessary for some compounds before solubility measurements can be reliably performed. 8,10,27 According to the findings of this study, chloramphenicol provides a slow dissolution rate in SF-CO 2 . This can be rationalized due to its high polarity especially with the contribution made by the N-oxide resonance structure shown in Figure 1.…”

“…As previously reported, significant differences in published SF-CO 2 solubility data for the same compound is a common occurrence and the various factors that might give rise to this situation have been cited. 8,9,20 In situ checking procedures to ensure solubility measurements are performed at fully established equilibrium dissolution using the relevant system mixing conditions are vital to obtain reliable results. Although some compounds rapidly reach equilibrium, it has been demonstrated that 3−12 h stirring may be necessary for some compounds before solubility measurements can be reliably performed.…”

“…The resultant SF-CO 2 solution was initially tested to determine when equilibrium dissolution was attained using an established procedure. 8,9 After the first set of chloramphenicol solubility measurements were determined, the SF-CO 2 pressure within the SSV was incremented in 2 or 3 MPa steps to prepare a series of increasingly more saturated chloramphenicol solutions.…”

“…Application of the MST Model. The semiempirical density-based model developed by Meńdez-Santiago and Teja 19 in an equation simplified by Hansen et al 28 has been previously successfully applied to correlate SSV−SFC experimental solubility data obtained for a range of compounds including: nifedipine and quinine, 8 PAHs, 9 caffeine, 20 and benzoin and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride. 29 Therefore, the utility of the modified MST model was further evaluated by its application to the SSV−SFC solubility results measured for chloramphenicol.…”

Adsorption of N,N,N′,N′-Tetraoctyl Diglycolamide on Hypercrosslinked Polysterene from a Supercritical Carbon Dioxide Medium

“…We have earlier [ 31 ] proposed a static approach to sorption analysis in SC media based on on-line supercritical fluid chromatography (SFC). A similar approach was applied in several works to determine the substance solubility in SCF [ 32 , 33 , 34 , 35 ] and distribution coefficients in the liquid-SCF system [ 36 , 37 , 38 , 39 , 40 ], and to control chemical reactions [ 41 , 42 ]. It allows fast quantitative analysis of the considered system components without depressurization or special sample preparation.…”