Title page for ETD etd-051499-093134


Type of Document Dissertation
Author Hamner, Vincent N.
Author's Email Address hamner_v@hotmail.com
URN etd-051499-093134
Title Hydroxypropylmethylcellulose: A New Matrix for Solid-Surface Room-Temperature Phosphorimetry
Degree PhD
Department Chemistry
Advisory Committee
Advisor Name Title
Dessy, Raymond E. Committee Chair
Anderson, Mark R. Committee Member
Glanville, James O. Committee Member
Merola, Joseph S. Committee Member
Tissue, Brian M. Committee Member
Keywords
  • Outliers
  • Cellulose
  • Cohesion (or Solubility) Parameters
  • Robust Statistics
  • Phosphorescence Spectroscopy
  • Hydroxypropylmethylcellulose (HPMC)
Date of Defense 1999-01-21
Availability restricted
Abstract
HYDROXYPROPYLMETHYLCELLULOSE: A NEW MATRIX FOR

SOLID-SURFACE ROOM-TEMPERATURE PHOSPHORIMETRY

by

Vincent N. Hamner

R.E. Dessy, Chairman

Chemistry

(Abstract)

This thesis reports an investigation of hydroxypropylmethylcellulose (HPMC) as

a new solid-surface room-temperature phosphorescence (SSRTP) sample matrix. The

high background phosphorescence originating from filter paper substrates can interfere

with the detection and quantitation of trace-level analytes. High-purity grades of HPMC

were investigated as SSRTP substrates in an attempt to overcome this limitation. When

compared directly to filter paper, HPMC allows the spectroscopist to achieve greater

sensitivity, lower limits of detection (LOD), and lower limits of quantitation (LOQ) for

certain phosphor/heavy-atom combinations since SSRTP signal intensities are stronger.

For example, the determination of the analytical figures of merit for a

naphthalene/sodium iodide/HPMC system resulted in a calibration sensitivity of 2.79,

LOD of 4 ppm (3 ng), and LOQ of 14 ppm (11 ng). Corresponding investigations of a

naphthalene/sodium iodide/filter paper system produced a calibration sensitivity of 0.326,

LOD of 33 ppm (26 ng), and LOQ of 109 ppm (86 ng). Extended purging with dry-

nitrogen gas yields improved sensitivities, lower LOD's, and lower LOQ's in HPMC

matrices when LOD and LOQ are calculated according to the IUPAC guidelines.

To test the universality of HPMC, qualitative SSRTP spectra were obtained for a

wide variety of probe phosphors offering different molecular sizes, shapes, and chemical

functionalities. Suitable spectra were obtained for the following model polycyclic

aromatic hydrocarbons (PAHs): naphthalene, p-aminobenzoic acid, acenaphthene,

phenanthrene, 2-naphthoic acid, 2-naphthol, salicylic acid, and triphenylene.

Filter paper and HPMC substrates are inherently anisotropic, non-heterogeneous

media. Since this deficiency cannot be addressed experimentally, a robust statistical

method is examined for the detection of questionable SSRTP data points and the deletion

of outlying observations. If discordant observations are discarded, relative standard

deviations are typically reduced to less than 10% for most SSRTP data sets. Robust

techniques for outlier identification are superior to traditional methods since they operate

at a high level of efficiency and are immune to masking effects.

The process of selecting a suitable sample support material often involves

considerable trial-and-error on the part of the analyst. A mathematical model based on

Hansen's cohesion parameter theory is developed to predict favorable phosphor-substrate

attraction and interactions. The results of investigations using naphthalene as a probe

phosphor and sodium iodide as an external heavy-atom enhancer support the cohesion

parameter model.

This document includes a thorough description of the fundamental principles of

phosphorimetry and provides a detailed analysis of the theoretical and practical concerns

associated with performing SSRTP. In order to better understand the properties of both

filter paper and HPMC, a chapter is devoted to the discussion of the cellulose

biopolymer. Experimental results and interpretations are presented and suggestions for

future investigations are provided. Together, these results provide a framework that will

support additional advancements in the field of solid-surface room-temperature

phosphorescence spectroscopy.

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