The LCGC Blog: My Own March Madness - Four Dissertations, Analytical Chemistry, and Chemical Education
One of the pleasures associated with being a professor is to see your students grow over time into independent scientists. Over four or five years, graduate students seeking doctoral degrees hone their knowledge and skills and produce exciting new pieces of scientific research. This process requires a guiding and nurturing hand, and by the end, the result is individuals who are making their own decisions, formulating ideas, designing their own experiments, and interpreting their own results. That said, a rough part of the process is the completion of the final dissertation. Ideally, this is a compilation of published papers, but there are several other pieces that guarantee significant editing and proofreading for each dissertation on my part. In this semester, I have four students completing their PhD degrees; each has some chapters that have already been entered into the literature, but each has additional contributions that must be generated anew as part of this process. Currently, there is a mass of reading that I must undertake on top of my normal duties, and it starts to border on madness. Luckily, I am proud to be putting four excellent pupils into the workforce, and I would like to take this opportunity to recognize their efforts.
“Tailored Analytical Methods for Surveying Groundwater Quality in Areas of Unconventional Drilling,” by Doug D. Carlton, Jr.
Unconventional drilling, which includes hydraulic fracturing, is an extremely vital component of the current U.S. economy. This practice, begun as early as the 1950s, was perfected in the recent past to allow for extraction of natural gas and oil from deep shale formations. What has not kept pace is an understanding of the environmental impact of these processes. Because it is happening in and around the rural and suburban landscape throughout the country, it is important to understand and develop best practices for environmental stewardship.
Finding a lack of research in the area, our group began investigating the potential impact of unconventional drilling on private well water quality. We began in 2011 by applying a series of non-targeted methods (liquid chromatography–mass spectrometry [LC–MS], gas chromatography [GC]–MS, and a bioassay for measuring toxicity) to a collection of 100 private well water samples from the North Texas area. As more information came to light, including a congressional report detailing potential ingredients in hydraulic fracturing fluid and other information about drilling practices, we were able to tailor a suite of more-targeted analytical methods (GC–MS, headspace GC–MS, inductively coupled plasma [ICP]-MS, ICP-optical emission spectrometry [OES], ion chromatography, and total organic carbon [TOC] analysis) to survey water quality in sampled private water wells. Doug was instrumental in the design and validation of these methods, which included collecting and implementing best practices from a number of standard EPA and other methods. Doug carried out some basic studies characterizing matrix effects in ICP-OES (1). Most importantly, he drove the analytical work in our study on the water quality of 100 private water wells in and around the Barnett Shale of North Texas (2). In that work, which represented the largest water quality study of its kind to date, we found that about a third of the wells contained elevated levels of arsenic — above the maximum contamination limit of 10 ppb set by the EPA. These levels were attributed to processes that may be indirectly related to unconventional drilling. Lacking baseline levels besides agglomerated historical data, we set out to perform a time course study of well water quality before, during, and after unconventional drilling took place (3). This study, which we expect to report in the next couple of months, will be the capstone of an exceptional dissertation compiled by Doug. We look forward to continuing this line of research over the next several years, to help provide reliable scientific data to the public, and to help develop best practices for industry. There will be more on this topic to come, for certain; in fact, I will be giving an LCGC Editors’ Series webinar on our work in this area to date on May 8 of this year (4).
“Fundamental and Applied Studies of an Ambient Ionization Technique: Continuous Flow Extractive Desorption–Electrospray Ionization–Mass Spectrometry,” by Li Li
One area of analytical chemistry that has exhibited major growth over the past several years is ambient ionization MS. With the introduction of desorption electrospray ionization (DESI) (5) and direct analysis in real time (DART) (6), a flurry of other techniques featuring techniques exhibiting independent optimization of sample introduction and ionization have been reported in the literature (7). In our laboratory, inspired by the concepts of DESI and extractive electrospray ionization (EESI) (8), we developed our own ambient ionization source, termed continuous flow–extractive desorption electrospray ionization (CF-EDESI). CF-EDESI was first demonstrated by one of my previous PhD students, Dr. Sam Yang, as an alternative way to manipulate protein charge states for MS analysis (9). In the meantime it has been further developed, and applications for it have been extended, by my more recent student, Li Li.
The key to CF-EDESI is the introduction of the sample in a continuous bulk liquid flow through a hypodermic needle set orthogonal to a conventional electrospray ionization source, which is set on-axis with the MS inlet. The ESI source and the MS inlet are about 8 mm apart, and the CF needle is placed into the spray plume about 1.5 mm away from the ESI source. In the aforementioned protein charge state manipulation experiment, the proteins (for example, in their native state) can be introduced through the CF needle, and supercharging reagents can be added through the ESI spray solvent. Of course, separations of proteins can also be introduced through the CF needle, and this is a component of Li Li’s dissertation (10). She also discovered that CF-EDESI is highly amenable for the analysis of analytes present in non-ESI-friendly solvents (11). Studies to elucidate the mechanism of CF-EDESI showed that it operated distinctly from EESI, its closest relative. It appears that the mixing of the phases to produce droplets amenable for subsequent charged-droplet desolvation and analyte ionization (vis-à-vis an ESI-type mechanism) is predominant. Li Li has also recently submitted an article demonstrating the coupling of normal-phase high performance liquid chromatography (HPLC) to MS detection and the direct analysis of phospholipid extracts (in methyl-tert-butyl ether [MTBE] solvent) through the use of CF-EDESI (12). A good friend once told me that a new technique is not really a new technique until it is published in three scientific articles. I give Li Li a lot of credit for the work she dedicated to developing CF-EDESI, and I think it has a lot of interesting advantages that should prove useful in expanding the application of ambient ionization MS.
I have written about restricted access media (RAM) before in this blog (13), and our group has recently published a current review of the state-of-the-art on the topic (14). The use of RAM is a great way to develop streamlined ultratrace quantitative analysis methods, including on-line sample preparation, for small molecules from biological fluids. Hui Fan has significantly advanced this research in our group as a major part of her dissertation work. She has developed and validated a RAM-based method featuring bulk derivatization (that is, the derivatization reagent is added directly to the sample of interest without any prior sample preparation) using dansyl chloride for estrogens in cerebrospinal fluid (15). This method will be useful for further investigation of the neuroprotective effects of estrogens in the brain. Hui has also worked closely with a visiting scientist from the Czech Republic, Dr. Barbora Papouskova, to elaborate important method development consideration for avoiding poor peak shape and matrix effects (16). Both of these articles have been submitted and are currently under review. Even though the setup of such methodology requires additional pumps and valves on your LC–MS system, operator attendance and error is significantly lessened, and detection limits in the low parts-per-trillion range can be achieved.
To wrap up her dissertation, Hui has also investigated a new method for coupling direct injection to MS for measuring the oxidation of various species. A continuous stirred tank reactor (CSTR) is a convenient way to create temporal compositional gradient of analyte, while also enabling the monitoring of reaction kinetics. Building from previous work (17) by another recent PhD graduate from my group, Dr. Jeremy Barnes, Hui has been investigating the oxidation of various polyphenolic antioxidants, combining a CSTR with accurate mass and higher order tandem MS data obtained on an electrospray ionization–ion trap–time-of-flight instrument (18). It rounds out a series of studies in Hui’s dissertation to streamline on-line quantitative bioanalytical determinations and expands our group’s capabilities for targeted analysis in complex systems.
“Supporting Traditional Instructional Methods with Constructivist Approach to Learning: Promoting Conceptual Change and Understanding of Stoichiometry Using e-Learning Tools,” by Kenneth M. Abayan
And now for something completely different. For the past four years, I have also been involved in the development of content-intensive collaborative learning programs to support learning and success in high loss chemistry courses. Select groups of freshmen science, technology, engineering, and math (STEM) students in general chemistry courses have had the benefit of this extra instruction to help them successfully master course concepts. As part of this National Science Foundation–funded program (DUE-0856796), I was also able to support a student, Kenneth Abayan, to pursue chemical education research as part of his PhD studies. We settled on the concept of stoichiometry, and we sought to examine optimal methods for effectively communicating this topic to students.
Ken designed an exceptional e-learning platform for evaluating the effect of different interventions for advancing the success of students on a series of stoichiometry assessment activities. Most practicing scientists will be familiar with a dimensional analysis (unit canceling) approach to stoichiometry, but one can also consider a more operational approach, where various steps in the stoichiometry problem are bridged using defined operations. Without going into great detail, what Ken found was very interesting. More important than the specific approach to solving the problem was the importance of the student to be able to construct a schema to arrive at the solution of the problem. Those students who could recognize a particular type of problem (for example, limiting reagent versus mass A à mass B) and develop a problem-solving strategy were the most successful. This work is currently being prepared for submission.
I have always felt that the complete scholarly activity associated with being a university professor should include concerted experiments to improve teaching and learning. Thus, I am especially proud to be the primary advisor of Ken’s dissertation work, essentially the first chemical education–based chemistry PhD produced by our department at U.T. Arlington. I believe that this opens new areas of awareness and interest at our university, and such evolution is important to contributing to the development of a more well-rounded institution.
Disclaimer: By the time you read this, hopefully all has gone well and all four of my students will have successfully defended their PhD dissertations. Congratulations Dr. Abayan, Dr. Carlton, Dr. Fan, and Dr. Li! I am proud of you!
Previous blog entries from Kevin Schug: