Date of Degree

9-2021

Document Type

Dissertation

Degree Name

Ph.D.

Program

Chemistry

Advisor

Ronald Birke

Advisor

Adrian Covaci

Committee Members

Barbara Zajc

Stephen O'Brien

Jianbo Liu

Issa Salame

Subject Categories

Environmental Chemistry

Keywords

LCMS, Explosives, Environmental, Water Analysis

Abstract

Traces of explosives and their degradation products present in explosives contaminated sites from military sources, such as training facilities, impose a great concern over the public health and our eco-system. This work is centered around finding an efficient way to extraction of these chemicals from water samples and their analysis using advanced separation technology: LC-MS/MS Shimadzu Prominence 8050 and AB Sciex Trap 4000 LC-MS/MS. Different extraction methods will be proposed, along with chromatographic and mass spectroscopy method development. Dependent on the target analyte polarity, thermal degradation, solubility and type of matrix, an appropriate method of analysis will be established. The study design incorporates development of a suitable method for identification and quantitation of eight selected explosive compounds, in water samples: NB, 1,3-DNB, 1,3,5-TNB, 2,4,6-TNT, 2,4-DNT, RDX, HMX and PETN. A survey of the published articles and writings provides a foundation to the thesis and gives additional background on the researched topic. Some of the proposed methods in the literature have weaknesses, such as low resolution, low sensitivity, low yield recoveries, extended run times, and one greatly misleading fact where the representative MRMs are not uniquely chosen for each analyte, but rather having common fragment ions. The author has developed a mass spectrometric method, where MRMs are manually selected in such way to offer distinctive fragmentation features for each target compound. As such, this method would be useful in the positive identification of the analytes.

Since there are only a few papers on commonly used organic secondary explosives, where an extensive mass spectrometric evaluation is presented, we furthermore aimed at developing a step-by- step methodology for the optimization of the source and compound-related parameters. The technique yielding the best data and tailored to our scope of developing a general method for explosive compounds is chosen, along with investigation of appropriate chromatographic and mass spectrometric conditions. After an intensive optimization process, we have shown that all eight compounds are being detected with relatively good intensity, when using electrospray ionization source in negative polarity (104 - 106). Therefore, our established method is proven to be a reliable general method.

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