| Summary: | 博士 === 國立中正大學 === 化學所 === 97 === Nowadays, many chemistry works are designed to meet the principles of green chemistry, such that environment should be prevented from pollution of chemical waste and reduced or eliminated negative environmental impacts. For the aspect of analytical chemistry, the analytical researchers face with increasingly difficult and complex separation problems and strive for improve separation techniques for both sample pre-treatment and analysis. To enhance the analysis capability, better efficiency and selectivity is the primary subject; also shorter analysis time and broad application are concerned.
It is obvious and not surprising that supercritical fluid techniques of extraction and chromatography are conformed to both of high efficiency and environmental friendly. Due to the properties of low viscosity, high diffusivity and liquid-like solvent strength, supercritical fluids offer a unique versatility for controlling extraction and chromatographic selectivity. Furthermore, the solvating power of supercritical fluids can be adjusted via pressure and temperature. Supercritical fluid extraction (SFE) and chromatography (SFC) also provide several advantages over traditional high performance liquid chromatography (HPLC), such as reduced extraction and analysis time, practical use of longer columns, a normal-phase retention mechanism, and reduced the use of organic solvents.
Chromatography is a powerful separation technique for both qualitative and quantitative analysis. This dissertation deals with the extraction and chromatography with supercritical carbon dioxide (scCO2) in pharmaceutical applications. Using scCO2 as mobile phase with various types of stationary phases, including reversed-phased C18 stationary phase, chiral stationary phase (CSP) and ionic liquid (IL) functionalized stationary phase, were investigated for the retention mechanism of related analytes.
The fundamental properties of the supercritical fluid and the features of SFE and SFC were described. Moreover, to improve the application of supercritical fluid techniques by adding the organic modifiers and additives to supercritical fluid will be concerned.
The application in SFE of camptothecin (CPT) from Nothapodytes foetida with an experimental design, L9(34) was investigated to obtain the optimal conditions, including the parameters of pressure, temperature, modifiers and additives, for the extraction of CPT.
Due to the properties of high diffusivity and low viscosity of scCO2, the analytes can be easily carried by scCO2 to contact with the active sites of the stationary phase that results in enhanced adsorption and leads to the increase of retention time or peak tailing as compared with those of HPLC. The effect of active silanol on the separation of basic compounds in SFC was investigated with L18(21×37) orthogonal array design (OAD).
In addition, SFC provides several advantages and expands the application on chiral separation 50 racemic compounds with modified scCO2 mobile phase. In the application of peptides separation, using macrocyclic glycopeptides stationary phase to separate the structure closely related peptides and various sequence peptides with quaternary co-solvent (MeOH/MeCN/H2O/TFA) modified scCO2 mobile phase.
The preparation and performance of an ionic liquid (IL) - functionalized column for the SFC separations of acidic, basic, and neutral compounds was described. The results indicate that hydrogen-bonding and hydrophobic interactions between the analytes and the IL-modified stationary phase seem to involve in the separation process. Simultaneous separation of acidic, basic, and neutral compounds via SFC was successful at a co-solvent content of 20% MeOH, a pressure of 110 bar, and a column temperature of 35 ℃. The relative standard deviations of the retention times and peak areas at 50ppm were all less than 4 and 8% (n = 6), respectively.
The dissertation presents the application of SFE and SFC with carbon dioxide containing various stationary phase. Moreover, to discuss the detail of SFE and SFC, the effects of experimental parameters, including pressure, temperature, modifiers and additives, etc., were investigated on different stationary phases in each chapter. The results indicate that SFE and SFC are the powerful tools for extraction and separation.
|
|---|
