Electronic Theses and Dissertations

Identifier

2498

Date

2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Chemistry

Concentration

Analytical Chemistry

Committee Chair

Paul Simone

Committee Member

Gary Emmert

Committee Member

Randy Buddington

Committee Member

Xiaohua Huang

Abstract

1,3-Dimethylamylamine (1,3-DMAA) is a stimulant commercially sold in a variety of dietary supplements as a chemical species derived from geranium plants (Pelargonium graveolens). Whether 1,3-DMAA naturally occurs in geranium plants or other dietary ingredients, it has important regulatory and commercial ramifications. An extraction method combined with HPLC-MS/MS is used to determine 1,3-DMAA and 1,4-dimethylamylamine (1,4-DMAA) concentrations in geranium plants with both external calibration and standard addition methods. Samples from the Changzhou, Kunming, and Guiyang regions of China during both winter and summer were analyzed. Following the detection of DMAA in the Changzhou sample, an extraction and pre-column, chiral derivatization chemistry method was developed for the separation and analysis of the four stereoisomers of 1,3-DMAA and two enantiomers for 1,4-DMAA. Two chiral derivatizing agents (CDAs) were investigated: (-)-1-(9-fluorenyl)ethyl chloroformate [(-)-FLEC] and (R)-(-)-alpha-methoxy-alpha-(trifluoromethyl) phenylacetyl [(-)-MTPA]. Optimization studies and detailed method detection limit (MDL), accuracy, and precision and linearity studies are presented for analysis of the DMAA-FLEC species in geranium plants. The DMAA-FLEC product was found to be unstable and a second, more stable CDA [(-)-MTPA] was employed. A preparatory scale HPLC separation was added prior to derivatization with (-)-MTPA to aid in the separation of all DMAA stereoisomers. The propagation of error prohibited a confident analysis of individual DMAA stereoisomers, but the DMAA-FLEC and DMAA-MTPA methods both confirmed the presence of DMAA in the Changzhou plant samples.Haloacetic acids (HAAs) are formed during the chlorination of drinking water. Previous work detected HAAs in bulk sodium hypochlorite solutions with post column reaction ion chromatography (PCR-IC). A HPLC-MS/MS method was designed to provide confirmation of the presence of HAAs in the sodium hypochlorite solutions. Detailed MDL, accuracy, and precision studies are presented for the analysis of nine haloacetic acids in sodium hypochlorite solutions. Due to the complex nature of the sample matrix a solid phase extraction step was added to the HPLC-MS/MS procedure. The HAAs monochloroacetic acid, dichloroacetic acid, and trichloroacetic acid were detected in the bulk sodium hypochlorite solutions by both the HPLC-MS/MS and the PCR-IC although the two methods disagree on reported concentrations.

Comments

Data is provided by the student.

Library Comment

Dissertation or thesis originally submitted to the local University of Memphis Electronic Theses & dissertation (ETD) Repository.

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