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Search Publications by: Andre Striegel (Fed)

Displaying 26 - 40 of 40

Detection orthogonality in macromolecular separations. Role of the on-line viscometer in characterizing polymers at conditions of spectroscopic invisibility

May 21, 2015

Author(s)

Andre M. Striegel, Leena M. Pitkanen

Much has been written over the last two decades about the advantages of separation orthogonality for the characterization of complex polymers and blends, and of the additive and synergistic benefits of combining various physical and chemical detection

Polysaccharide characterization by hollow-fiber flow field-flow fractionation with on-line multi- angle static light scattering and differential refractometry (HF5/MALS/DRI)

January 20, 2015

Author(s)

Leena M. Pitkanen, Andre Striegel

Accurate characterization of the molar mass and size of polysaccharides is an ongoing challenge, oftentimes due to architectural diversity but also to the broad molar mass (M) range over which a single polysaccharide can exist and to the ultra-high M of

AF4/MALS/QELS/DRI characterization of regular star polymers and their "span analogs"

October 15, 2014

Author(s)

Leena M. Pitkanen, Andre Striegel

Asymmetric flow field-flow fractionation (AF4) coupled with multi-angle static and quasi-elastic light scattering and refractive index detectors was employed for the separation and characterization of regular star-shaped polystyrenes and their linear and

Influence of glycosidic linkage on the solution conformational entropy of gluco- and mannobioses

September 19, 2014

Author(s)

Andre M. Striegel, Mallory J. Morris

Employing size-exclusion chromatography, an entropically-controlled separation technique, we have determined the solution conformational entropy (-delta S) of (1-2)-, (1-3)-, (1-4)-, and (1-6)-linked gluco- and mannobioses with an alpha anomeric

Do column frits contribute to the on-column, flow-induced degradation of macromolecules?

August 15, 2014

Author(s)

Andre M. Striegel

Flow-induced, on-column degradation is a major hindrance to the accurate characterization of ultra- high molar mass macromolecules and colloids. This degradation is a direct result of the large shear rates which are generated within the column, which cause

Does the "C 3 effect" offset the D}2 effect, as regards the solution flexibility of aldoses?

April 21, 2014

Author(s)

Mallory J. Morris, Andre Striegel

The solution flexibility of carbohydrates in general, and of monosaccharides in particular, influences a variety of molecular recognition and regulatory processes, from the cryoprotectant ability of glycoproteins to the relative ease with which certain

Determining the solution conformational entropy of oligosaccharides by size-exclusion chromatography with on-line viscometry detection

March 12, 2014

Author(s)

Mallory J. Morris, Andre Striegel

Introduced here is a method for determining the solution conformational entropy of oligosaccharides (-S) that relies on the on-line coupling of size-exclusion chromatography (SEC), an entropically-controlled separation technique, and differential

Theres Plenty of Gloom at the Bottom: The Many Challenges of Accurate Quantitation in Size-Based Oligomeric Separations

July 26, 2013

Author(s)

Andre M. Striegel

There is a variety of small-molecule species (e.g., tackifiers, plasticizers, oligosaccharides) the size-based characterization of which is of considerable scientific and industrial importance. Likewise, quantitation of the amount of oligomers in a polymer

Size-Exclusion Chromatography of Asphaltenes: An Experimental Comparison of Commonly-Used Approaches

May 4, 2013

Author(s)

Shen Dong, Andre Striegel

Asphaltenes, the heaviest and most polar fraction of crude oil, are responsible for the clogging of oil pipelines and of underground reservoir rocks. Asphaltenes are defined as a solubility class (toluene- or benzene-soluble, n-heptane insoluble), and a

Size-exclusion chromatography

February 1, 2013

Author(s)

Andre M. Striegel

The effect of styrene-methyl methacrylate monomeric arrangement on the ultrasonic degradation of copolymers

August 23, 2012

Author(s)

Mallory J. Morris, Andre Striegel

Ultrasonic degradation is a convenient means of studying the degradation of macromolecules in transient elongational flows. Cavitation results in non-random, near-midchain scission of linear polymers, which reach a limiting molar mass Mlim beyond which

Caveats Regarding the Solvent/Non-solvent and SELS Approaches in Size-Exclusion Chromatography and Related Methods

July 14, 2012

Author(s)

Andre M. Striegel, Kelsey McNeel, Dustin Richard

A rarely documented, yet industrially popular, approach to the size-exclusion chromatography (SEC) and related analysis of polymers that do not dissolve in common solvents (i.e., those solvents that are employed as mobile phases in high-throughput SEC

Hydrodynamic chromatography

June 21, 2012

Author(s)

Andre M. Striegel, Amandaa Brewer

Hydrodynamic chromatography (HDC) has experienced a resurgence in recent years for particle and polymer characterization due, principally, to its coupling to a multiplicity of physical detection methods. Coupled to light scattering (both multi-angle static

The Characterization of Copolymers and Blends by Quintuple-Detector Size-Exclusion Chromatography

June 14, 2012

Author(s)

Andre M. Striegel, Steven Rowland

The properties imparted, oftentimes synergistically, by the different components of copolymers and blends account for the widespread use of these in a variety of industrial products. Most often, however, processing and end-use of these materials

The obstruction factor in size-exclusion chromatography. 2. The interparticle, intraparticle, and total obstruction factors

April 17, 2012

Author(s)

Andre M. Striegel, Dustin Richard

Obstruction factor is a generic rubric under which are usually gathered the interparticle, intraparticle, stationary phase, and total obstruction factors, gamma(e), gamma(p), gamma(s), and gamma(t), respectively. These, in turn, affect longitudinal