Quiet Musings of A Mature (But Not Old!) Person
Dennis C. Johnson
Originally published in SEAC Communications, 14(3), October 1998
During my high school days, I developed interests in electrical circuitry and chemistry; however, I didn’t realize then that those two interests could ever be brought into juxtaposition. The process of merging these interests began when, as a student at Bethel College, St. Paul, Minnesota, my general chemistry instructor, Bob Glaser, demonstrated the electrolysis of water. He showed that the rate of production of H2(g) and O2(g) was minimal without the presence of an ionic compound to function as a supporting electrolyte. From that moment, I began making plans to construct an instrument for the quantitative determination of ionic species in water. The following summer, in the inner sanctum of my workshop back home on the farm, I assembled a dc power supply using components salvaged from an old radio and coupled it to a Heathkit ammeter to monitor electrical current passing in an electrolysis cell. In place of platinum electrodes, I used nichrome wires purchased at a local appliance repair shop. The maiden voyage of my contraption was met with only partial success. I did observe that the cell current increased as a function of added table salt; however, I was distressed that the current appeared to decrease as gas bubbles collected on the electrode surfaces. I deduced that this problem might be eliminated by the application of ac rather than dc voltage. However, before I could revise the circuitry, the summer ended and I returned to college life. During my sophomore year, my youthful inventive spirit was shattered when I learned that someone else, several decades earlier, had invented conductimetry. My analytical professor, Howard Dinsmore, noticed my intense interest in this analytical application of electricity and told me that electroanalysis was a well-established discipline within the chemical sciences. Furthermore, he informed me that Professors Kolthoff and Bruckenstein at the University of Minnesota were leading researchers in electroanalytical chemistry. I soon made it my goal to enroll at the U. of Minnesota and, hopefully, to become involved in electroanalytical research within the Kolthoff tradition.
Professor Kolthoff had retired by the time I began graduate studies in 1963; however, I was able to convince Stanley Bruckenstein to allow me to join his research group. Those were the days when rotated ring-disk electrodes (RRDEs) had been thrust to the forefront of electroanalytical thought by the appearance of the English translation of a monumental text by V.G. Levich.1 My research partner, Duane Napp, and I were challenged to construct ring-disk electrodes in the departmental workshop. This challenge was soon transferred to Ted Hines, Pine Instrument Co., and Duane and I shifted our focus to the design and construction of circuitry for the simultaneous and independent control of the ring and disk electrodes of RRDEs. This effort was aided greatly by two papers from Irv Shain’s laboratory, U. of Wisconsin, that were presented at the Symposium on Operational Amplifiers in Analytical Instrumentation at the 144th National ACS Conference.2,3 We were successful in building a bipotentiostat from vacuum-tube operational amplifiers and the resulting circuit became the basis of an instrument ultimately commercialized by Pine Instrument Co.
Ours was an interesting and fruitful period in Stanley’s laboratory. As students we were in awe of W. John Albery who, during a single summer as a visiting professor from England, generated six theoretical papers describing the response of RRDEs. John also kept a keen eye on the afternoon skies over Minneapolis in hopes of photographing a descending tornado funnel. In Stanley’s laboratory, there existed a sense that professor, visiting scholars and students were co-workers in spite of obvious differences in academic status. Of even greater significance was the allowance of time for us, as students, to follow our own whims. In fact, I can trace nearly everything done in my own laboratory during the last 30 years to a ring-disk study initiated while Stanley was on a leave of absence. In that study, bromide adsorbed at Pt electrodes in acidic media was determined to be oxidatively desorbed as hypobromous acid concomitantly with the anodic formation of surface oxide.
The decade of the ‘60s corresponded to rapid development of atomic emission/absorption spectroscopy. And, with the emergence of this analytical technology, came a rapid decline in the popularity of polarography for the analysis of ores and alloys. Whereas stripping voltammetry persisted throughout the next decade for determinations of trace levels of metallic species, it became clear that those of us in love with electroanalysis must look beyond metallic analytes for worthy research pursuits.
Shortly after joining the chemistry faculty at Iowa State University in 1968, I became impressed by the fact that virtually all organic compounds can be predicted from thermodynamic data to undergo oxidation to CO2 at electrode potentials accessible at the common inert anodes in aqueous media. Therefore, the fact that the predicted electrochemistry was not observed was a consequence of kinetic rather than thermodynamic limitations. In view of this reality, student research in my laboratory became focused on the anodic detection of polar aliphatic compounds at noble metal electrodes. We soon conceptualized the use of pulsed potential-time waveforms to manage transient catalytic states at Pt and Au electrodes for detection of alcohols and carbohydrates in flowing streams by what we called Pulsed Amperometric Detection (PAD). In its early stages, PAD was based on the use of cascaded monostable integrated circuits that controlled the sequence of events responsible for waveform generation and current measurement. Shortly thereafter, we joined hands with Dionex Corp. for further development of PAD for chromatographic detection and Dionex quickly placed PAD under microprocessor control. Several variations of the original waveform have followed, each developed to satisfy unique challenges coming from the extension of noble metal electrodes (primarily Au) to the detection of various amine and organosulfur compounds. With variations in waveform design have come the names Integrated Pulsed Amperometric Detection (IPAD), Reversed Pulsed Amperometric Detection (RPAD), Integrated Voltammetric Detection (IVD) and Integrated Square-Wave Detection (ISWD). These specific detection strategies are now grouped together under the generic classification of Pulsed Electrochemical Detection (PED).
Efforts to overcome the kinetic challenges of anodic oxidations of organic compounds has extended to the design of new catalytic electrode materials that can support organic oxidations without perceptible loss of surface activity even when operated at constant applied potentials. Reactions of interest are those involving anodic transfer of O-atoms from H2O to the oxidation products. Electrodes of greatest interest are those consisting of thin films of mixed oxides prepared by electrochemical or thermal deposition, as well as by anodization of alloys, that have electrocatalytic properties that are unique in comparison to those of the pure component oxides. New electrode materials coming from this research effort are foreseen to have applications as anodic sensors as well as for use in electrochemical syntheses and environmental remediation.
Thus, my early fascination with electrical circuits and electrolysis has led me down a very rewarding pathway. This trek has been possible only because of the gracious mentoring of Stanley Bruckenstein and other teachers, as well as the contributions of industrial collaborators and financial sponsors, and the hard work of students too numerous to be identified here. It is certain that if I could choose to relive my life, I’d choose to follow the same pathway; however, I’d choose to walk more quickly.
1. V.G. Levich, Physicochemical Hydrodynamics,
Prentice-Hall: Englewood Cliffs, NJ, 1962.
2. W.M. Schwarz and I. Shain, “Generalized circuits for electro-analytical instrumentation”,
Anal. Chem. 1963, 35, 1770-78.
3. W. Underkofler and I. Shain, “A multipurpose operational amplifier instrument for electroanalytical studies,”
Anal. Chem. 1963, 35, 1778-83.
Marc D. Porter (Iowa State University), organizer—Introductory Remarks
Richard L. McCreery (Ohio State University)—Presentation of the 1997 Reilley and Young Investigator Awards
AWARD ADDRESS: Dennis C. Johnson (Iowa State University)—Electrocatalytic Detection of Polar Aliphatic Molecules: Past, Present, and Future
Reid R. Townsend (University of California-San Francisco)—High Performance Liquid Chromatography with Pulsed Electrochemical Detection
William R. LaCourse (University of Maryland-Baltimore County)—Pulsed Electrochemical Detection in Bioanalysis [canceled]
AWARD ADDRESS: Ingrid Fritsch (University of Arkansas)—Exploitation of Stability and Structure of Modified Electrodes
Marc D. Porter (Iowa State University)—Mercury Micropumps:
A Novel Approach toward a Miniaturized, Low Power Fluid Delivery System