Application of Microporous Membranes to Chemiluminescence Analysis
Nau, Vance James, Jr.
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https://hdl.handle.net/2142/67263
Description
Title
Application of Microporous Membranes to Chemiluminescence Analysis
Author(s)
Nau, Vance James, Jr.
Issue Date
1981
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Analytical
Language
eng
Abstract
A novel approach to reagent introduction into flowing streams is accomplished using a microporous membrane to separate a reagent reservoir from an analyte stream. Evidence is presented to support the contention that upon pressurization of the reagent reservoir a locally high concentration of reagents is established near the surface of the membrane in the analyte stream. Using reagent flow rates of only a few (mu)L/min, reagent introduction using microporous membranes is shown to provide high sensitivity and good reproducibility when tested using the luminol-cobalt (II)-hydrogen peroxide chemiluminescence system. The limit of detection for cobalt(II) is about 10('-10) M (10 parts per trillion); typical precision is (+OR-) 3%. The advantages of using microporous membranes for chemiluminescence analysis are discussed and possible areas of future application are described.
An attempt was made at the development of a clinical analyzer using microporous membranes as a mechanism for the physical entrapment of an enzyme. Physical entrapment merely by irreversible pore collapse was not sufficient to completely immobilize the enzyme; significant leaching occurred. An analysis for uric acid using the luminol-cobalt-base chemiluminescence system and immobilized uricase lacked sensitivity. Problem areas are identified and possible remedies suggested.
Due to the very low chemiluminescence background levels observed using the new method for reagent introduction, the use of photon counting (PC) is ideal when working at analyte concentrations near the detection limits. However, the high sensitivity of chemiluminescence methods can quickly exceed the linear range of most photon counters while still at only moderate analyte concentrations. Thus, an alternate means of signal processing (i.e. direct current amplification--DC) would also be required. A photometric detector has been developed which integrates photon counting (PC) and direct current (DC) detection into a single unit, which features (1) real time evaluation of the photomultiplier tube output and automatic selection of the optimum mode of operation--either PC or DC, (2) a built-in calibration cycle to normalize the DC output to the equivalent of photon counts per second, and (3) an autoranging time base to maximize the total number of counts displayed. The integration of these two techniques allows operation to greater than the equivalent of 120 MHz PC rate with less than 1.4% nonlinearity without compromising any of the advantages separately available with either technique.
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