Date of Award

Winter 12-6-2016

Degree Type

Dissertation

Degree Name

PhD. Chemistry

Department

Chemistry and Biochemistry

Advisor

Nicholas H. Snow, Ph.D

Committee Member

Wyatt R. Murphy, Ph.D

Committee Member

Yuri Kazakevich, Ph.D

Committee Member

Cecilia Marzabadi, Ph.D

Keywords

Polyol Induced Extraction, essential oils, PIE, extraction, acetonitrile, glycerol

Abstract

Polyol Induced Extraction (PIE) was developed and patented at Seton Hall University by Drs. John R. Sowa Jr., Wyatt R. Murphy, and Mithilesh Deshpande. It was originally discovered and implemented as a method to recycle and reuse waste acetonitrile during the production shortage in 2008. Through the use of PIE, a solvent mixture containing acetonitrile and water can be separated by employing a polyol mass separating agent, which induces a phase separation. The system is separated into its corresponding aqueous and organic phases, with the organic phase being a highly purified organic liquid. Based on the successful experimental results that were obtained, it was decided to assess the potential of PIE as a sample extraction technique. The goal of this work was to demonstrate that PIE can be applied for the extraction of essential oils which can then be analyzed using gas chromatography-mass spectrometry (GC/MS). The research is broken down into a fundamental application, two comparison applications and a final optimization application of PIE.

Chapter 1 provides background information on essential oils and their importance and significance, as well as basic theory of GC/MS. Essentials oils are generally complex mixtures of compounds extracted from plants with the most abundant compound present said to be the “essence” of the plants fragrance. Many different techniques for the extraction of essentials oil from their corresponding botanicals exist with four major techniques dominating: steam distillation, solvent extraction, cold-pressing, and enfluerage. The applications and uses of essential oils are widespread, with flavors and fragrances and as therapeutic agents being the most common.

Since essential oils contain volatile organic compounds, they are excellent candidates for analysis using GC/MS. Gas chromatography is an analytical separation technique that separates compounds based on their vapor pressure and intermolecular interactions with the stationary phase. Following separation of the mixture on a column, quantitation and identification of the components is carried out through the use of detectors that are coupled to the column. Quantitation for organic compounds is most commonly assessed using a flame ionization detector (FID) with identification of these compounds being established through the use of a mass selective detector (MSD). Accurate quantitation at or near the limit of detection (LOD) of the MSD is achieved through the use of analytical standards and operating in specialized modes such as full scan and selected ion monitoring (SIM) simultaneously.

The first application study involves the partitioning of essential oils in acetonitrile and water solvent systems using glycerol as a mass separating agent. The six essential oils that were investigated were subjected to PIE and then analyzed via GC/FID. Method validation was performed which included extraction efficiency, percent recovery, and partition coefficient calculations. The thermodynamic properties of PIE were also addressed, which included Gibbs free energy (ΔG), enthalpy (ΔH), and entropy (ΔG). Finally, the GC/MS compositional profiles of the extracted essential oils were compared to essential oils extracted by traditional extraction techniques.

The second application is a comparison study in which PIE was compared to QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe). QuEChERS was discovered to be particularly adept for polar and basic compounds, which is why it is considered the “gold standard” of extraction techniques for the analysis of pesticides from a variety of different matrices. PIE is similar to QuEChERS in the sense it uses an organic solvent and a mass separating agent to generate a phase separation, with the analytes of interest being extracted into the organic phase for analysis. Based on this, it was decided to compare and contrast these two techniques. The same six essential oils that were analyzed previously were subjected to both extraction techniques and then analyzed via GC/MS. Method validation was carried out in terms of extraction efficiency (where percent recovery and partition coefficients were compared), limit of detection (LOD) and limit of quantitation (LOQ). Finally, the compositional profiles of the essential oils for both techniques were evaluated using GC/MS in order to determine matrix suppression ability as well as the abundance of the main component present in each essential oil.

The third application concentrates on the organic solvent that is used in the PIE process. Acetonitrile is considered to be a safer, green, less toxic solvent than halogenated solvents such as dichloromethane, which are often used for solvent extractions. However, acetonitrile is not considered to be generally recognized as safe (GRAS), so the idea to investigate PIE with GRAS solvents was initiated. The Flavor and Extract Manufactures Association (FEMA) and their Expert Panel make determinations on the toxicology of compounds and there recommended use level that are destined to be used in flavor and fragrance applications. The only GRAS solvents that are fully miscible with water in all concentrations are acetone and Isopropyl Alcohol, so these solvents were investigated for use with PIE. The same six essential oils were subjected to PIE using acetone and isopropyl alcohol as solvents and then analyzed via GC/MS. Method validation was evaluated in terms of extraction efficiency, where percent recovery and partition coefficients were compared. Limit of detection (LOD) and limit of quantitation (LOQ) were also compared. Finally, the compositional profiles of the essential oils and the abundance of the main components in each oil were assessed using GC/MS in order to determine matrix suppression ability for both techniques.

The last application focuses on the optimization of the PIE process through the use of pH adjustment. Essentials oils are generally made up of compounds that are categorized as phenolic terpenoids or propanoids. These compounds contain a phenol moiety, which acts as a weak acid, so therefore is ionisable at pH values greater than the molecule’s pKa. Based on this concept, it was believed that by adjusting the pH of the extraction solvent system, a highly purified essential oil could be obtained. This was taken a step further by applying the idea to highly purified commercial steam-distilled essential oils that were to be sold to consumers. For this study, three essential oils that contain compounds belonging to the phenylpropanoid class of compounds were subjected to pH optimized PIE and then analyzed via GC/MS. The experiments compared the abundance of constituents present in the organic phase for the initial essential oil before extraction and to the essential oil components after pH optimized extraction.

The final portion of this work includes a brief look at future work and applications that can be performed using PIE. There are many possible uses of PIE and are truly unlimited as different solvent combinations with different polyols can be explored and tailored to fit the application at hand. Method automation for the extraction of essentials oils on an industrial scale is certainly an excellent next step as this would be a more cost effective alternative to current essential oil extraction techniques. Other areas of interest for PIE include the extraction and purification of biochemical and inorganic analytes such as proteins and metal complexes.

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