Two new instruments for analytical chemistry: A. Constant potential pulse polarography (CPPP) and differential CPPP (DCPPP) for determination of metals in the presence of oxygen in flowing systems; B. Versatile laser-based analytical instrument for detection of jet-cooled molecular species
Date of Award
Doctor of Philosophy
Dennis C. Johnson
Gerald J. Small
Analytical chemistry as a field is composed largely of methods of measurement and analysis. The needs of analytical chemists have developed a complexity which must be matched by the capability of the techniques in use. This calls for the advent of new methods and techniques suitable for the problems at hand. Two new instruments are described in this work which are small steps in meeting some of the complex needs of analytical chemistry;The first instrument represents one of the older analytical methods, polarography, which has been in use in analytical chemistry for over 65 years. Polarography is a method which has seen a decline in use as more sensitive techniques are discovered, but which is still in wide use. The instrument described herein allows polarographic analysis of metals without removal of dissolved oxygen, previously a time-consuming necessity. Detection is accomplished by constant potential pulse polarography (CPPP). The instrument makes feasible detection in flowing samples by elimination of the required oxygen removal step. CPPP further offers a degree of freedom from interference due to reduction of hydrogen ion in acidic solution. The technique is shown to be sensitive, with a detection limit in the range of 10[superscript]-7 M for the metals studied. A differential method has also been developed, differential CPPP (DCPPP), which is shown to have increased selectivity over CPPP, offering resolution on the same scale as differential pulse polarography (DPP);The second instrument described represents one of the newer analytical techniques, supersonic jet spectroscopy. Analytical usage of this method has been only within the current decade, though recent development has been rapid, chiefly due to the immense selectivity resulting from the cooled analytes. The instrument designed for this work was intended to be versatile, allowing sample introduction by gas chromatography (GC) or by laser desorption (LD). Capabilities of the instrument are shown and a method for analysis is given. The detection limit for jet spectroscopy is hampered by the large dilution of sample which is necessary to accomplish the molecular cooling, but was found to be 9 ppm for aniline in Helium carrier gas under optimized expansion conditions for this instrument using multiphoton ionization (MPI).
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Bryan J. Isaac
Isaac, Bryan J., "Two new instruments for analytical chemistry: A. Constant potential pulse polarography (CPPP) and differential CPPP (DCPPP) for determination of metals in the presence of oxygen in flowing systems; B. Versatile laser-based analytical instrument for detection of jet-cooled molecular species " (1989). Retrospective Theses and Dissertations. 9135.