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Graduate Student

B.S., Lebanon Valley College, Annville, Pennsylvania, 2005 (chemistry)

Study abroad, Monash University,  Australia, July - November 2004 (biomaterials, macromolecules, smart materials and Synthesis of
bioactive compounds)

Coolbaugh Hall 116
1012 14th Street
Golden, CO 80401
Phone: (303) 384-2111

Coolbaugh Hall 327
Phone: (303) 273-3382
Fax: (303) 273-3629

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Justin Engle

Non-traditional MALDI matrices for the analysis of low molecular weight polymers

     Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS) is an analytical technique that is able to provide information such as polymer molecular weight, repeat unit, and polydispersity.  The usefulness of MALDI-TOF/MS as an analytical technique stems from the relatively soft desorption/ionization process where a polymer can be cationized with a singly charged atom, usually sodium or silver depending on the polymer.  Choosing an organic matrix (traditional approach) and cationizing agent to match the polymer has been problematic.  The use of traditional organic matrices complicates the mass spectrum below 1000 Daltons, making the analysis of low molecular weight polymers difficult.

     Current research has focused in different areas of non-traditional approaches with polystyrene (Mw=826 Daltons) and polyethylene glycol (Mw=700 Daltons).  In these approaches, the use of MALDI sample stages (stainless steel and gold) and metal substrates (i.e. copper, aluminum, and brass) have been utilized with a cationizing agent to promote desorption/cationization of low molecular weight polymers.  The use of these metal substrates has significantly improved the quality of the mass spectrum below 1000 Daltons yielding better polymer analysis.  Currently, work is being done looking at the platinum series of metal as substrates with and without organic matrix.

     In addition to using different metal substrates, the use of gold nanoparticles has also been investigated.  Using different sized gold nanoparticles may yield more accurate molecular weight information for polymer analysis for different polymer weights.  The use of gold nanoparticles, like the metal substrates, significantly improves the mass spectrum below 1000 Daltons compared with the traditional organic matrix, with a limited number of random mass being detected. 

Thermal Field-Flow Fractionation of Industrial Important Polysaccharides (Starch)

     Starches are important macromolecules with many industrial applications, particularly in the food and pharmaceutical industries.  Their uses range from gelling agents to drug transport and even energy storage.  Properties of starches vary based on the plant or bacterial source and are connected to the amylose and amylopectin content.  Amylose is a linear polysaccharide with α-1,4 glycoside bonds and has a molecular weight around 106 Daltons.  Amylopectin is a highly branched polysaccharide with α-1,6 glycoside bonds along a α-1,4 glycoside bond chain backbone and has a molecular weight around 107 Daltons [1]. 

      Characterization of starch has previously been performed using size-exclusion chromatography (SEC).  The use of SEC for polysaccharides is limited due to low exclusion limits of the packed column and shear degradation of the ultrahigh molecular weight components.  An alternative to SEC is field-flow fractionation (FFF).  In 1994, Lou et al. reported the use of thermal FFF (ThFFF) to perform the separation of pullulan with varying molecular weight and of corn starch with varying amylose and amylopectin content [2].  ThFFF uses a temperature field applied perpendicular to the carrier liquid flow to promote the retention and fractionation of analytes based on the ratio of thermal diffusion coefficient DT to normal diffusion coefficient D.  The retention time tr of the analyte is therefore controlled by the temperature difference across the channel DT, the size and molecular weight of the analyte, and parameters that affect DT.

     In the past decade, flow FFF has been in the spotlight with respect to polysaccharides analyses [3-5] using an aqueous carrier liquid.  Separation of polysaccharides of starches by flow FFF is based solely on the hydrodynamic size of the macromolecule whereas ThFFF has additional composition sensitivity.


[1] Richardson, S.; Gorton, L. Anal. Chim. Acta. 497, 27-65 (2003).
[2] Lou, J.; Myers, M.N.; Giddings, J.C. J. Liq. Chromatogr. 17, 3239-3260 (1994).
[3] Wittgren, B.; Wahlund, K.-G.; Andersson, M.; Arfvidsson, C. Int. J. Polym. Anal. Charact. 7, 19-40 (2002).
[4] Roger, P.; Baud, B.; Colonna, P. J. Chromatogr A. 917, 179-185 (2001).
[5] Stevenson, S.G.; You, S.; Izydorczyk, M.S.; Preston, K.R. J. Liquid Chromatogr. 26, 2771-2781 (2003).

     Recent Presentations:

Justin R. Engle and S. Kim R. Williams. Gold Nanoparticles as an Inorganic Matrix for
     MALDI-TOF Mass Spectrometry of Low Molecular Weight Polymers.  20th ASC/AIChE
     Rocky Mountain Regional Meeting.  Denver, CO.  August 28th-September 1st 2007. 
     Oral Presentation.

Justin R. Engle and S. Kim R. Williams.  Non-Traditional Approaches to MALDI-TOF Mass
      Spectrometry Analysis of Low Molecular Weight Polymers.  49th Rocky Mountain
      Conference on Analytical Chemistry.  Breckenridge, CO.  July 22-26, 2007.  Oral

Justin R. Engle and S. Kim R. Williams.  Fractionation of Industrial Starch
      Polysaccharides by Field-Flow Fractionation.  13th International Symposium on
      Field- and Flow-Based Separations.  Salt Lake City, UT.  June 27-30, 2007.  Poster

Justin R. Engle, J. Ray Runyon, and S. Kim R. Williams.  Nontraditional Matrices for
      Polymer Analysis by MALDI-TOF Mass Spectrometry.  232nd American Chemical|
      Society National Meeting.  San Francisco, CA.  September 10-14, 2006.  Poster

Teaching Duties

     I am currently teaching a 1st year qualitative chemistry course taken primarily by freshmen students.  This course introduces students to basic wet chemistry laboratory skills and helps them develop a mind set to determine various aspects of periodicity, mass and heat relationships, and the role of molecular structures.  I am also co-teaching the Analytical Analysis Lab (CHGN 337) with Ray Runyon.  This is an advance analytical laboratory which utilizes instrumentation, such as: AA, HPLC, and FT-IR.  In the 2005-2006 academic year, I received two teaching awards for excellence in graduate student teaching: Hach Scientific Foundation and the Lucas-Williams. 


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Last updated 01/29/2008                                                              2006 The Williams Group