INSTRUMENTATION BY RALPH H. MÜLLER
Progress in Electroanalytical Methods
Figure 1. The Beckman Electroscan 30 electroanalysis instrument
HE RESEARCH EFFORT in developing
Τ new electroanalytical methods
con tinues at a high rate. The last biennial review issue of ANALYTICAL CHEMISTRY
(April 1964, pp. 2R-472R) covered the subject in seven categories: electroanalysis and coulometric analysis; polarographic theory, instrumentation and methodology; electrochemical relaxa tion techniques; organic polarography; amperometric titrations; titrations in nonaqueous solvents; potentiometric ti trations. The total literature citations add up to 2489 references for the ap proximately two-year interval, hence, a paper on the subject is appearing about every seven hours. As might be ex pected, the approach ranges from sim ple practical techniques to extremely complicated systems. Much pioneering work of a \-ery fundamental nature is being done, much of which can strain or exceed the mathematical resources of the average analytical chemist. The subject has attracted a number of emi nent investigators. A group of them are so expert that, on occasion, they give the impression that they are talk ing only to each other and leaving the rest of us to await the results of their final conclusions. Progress is so rapid that we have witnessed several polemics and quite a few rival claims of priority. In general, as far as progress in analyti cal chemistry is concerned, the subject is in a healthy and active state and new advances can be expected almost daily. We believe all analysts would wel come a treatment of the subject in the nature of a compendium, setting forth
the relative merits of the dozen or more electroanalytical techniques in which they would be assessed on the basis of speed, precision; and cost and heavily cross-indexed with reference to specific determinations. This would be most useful and helpful to analysts in in dustry. There is, of course, no dearth of excellent monographs on electroanalysis and, in the periodic reviews, most authors have provided useful tab ulations and summaries of specific ap plications of a given technique. We feel that a treatise of this sort could lead to a much more widespread use of electroanalytical techniques and in struments. I t has long been axiomatic that application always outruns our fund of basic information. I t would seem, however, that the converse is true in electroanalysis. We hasten to add that most analysts would be ap palled at the prospect of undertaking the task; the author might have to be subsidized unless he happened to pos sess the uncontrollable urge to add a book to his professional scalp belt. N E W ELECTROANALYSIS INSTRUMENT
A most useful step has been taken of a different nature toward the wider use of modern electroanalysis. This is the advent of the Beckman Electroscan 30 on which we wish to comment. I t com bines in one complete, self-contained electrochemical system flexibilities and capabilities previously obtainable only with a combination of instruments and self-constructed apparatus. For an in dustrial research laboratory, faced with an important analytical or control
problem, it would seem to afford a rapid means of examining a variety of techniques for the given analysis from which a specific device could be de signed for plant use. With proper cells and electrodes, the Beckman Electroscan 30 can be used for at least 15 electroanalytical tech niques. In the controlled current mode of operation, (galvanostat mode), the instrument is capable of chronopotentiometry, coulometric titrations at controlled current, electrodeposition and stripping analysis at controlled current. In the controlled voltage mode of operation, (potentiostat mode), the instrument's capabilities are expanded to include the following additional tech niques : controlled voltage coulometry ; chronoamperometry ; controlled volt age electrodeposition and separation; a.c. polarography; three electrode po larography; solid electrode voltammetry; rapid scan voltammetry; cyclic voltammetry and stripping analysis. In addition, the high impedance re corder has general utility in the labora tory and can be used for direct pH and redox potential measurements. Figure 1 shows a general view of the instrument. The controls are grouped for easy accessibility. Those on the left side of the instrument control the recorder functions and include switches or controls for power, recorder func tion, span, mid-scale voltage, tempera ture, pH standardize, chart drive, manual chart drive, chart speed selec tor, and pen lift bar. {Continued on page 186A) VOL 38, NO. 2, FEBRUARY 1 966
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INSTRUMENTATION
Old Reliable
J . he newest, most versatile version of this famous fraction collector, currently serving scientists in more than a thousand laboratories all over the world, is now available for immediate delivery direct to you from Canalco's plant in Rockville, Maryland. W i t h the Canaico 1205 Fraction Collector, you can have accurate volumetric siphoning (2, 5, 10 or 20 ml fractions), timed flow (18 seconds to 2 hours) and drop counting (1 to 400 drops). Interchangeable turntables hold either 150 or 240 test tubes to collect fractions up to either 5 or 20 ml. W a n a l c o ' s own factory-trained technical representatives stand ready to assist in installation and guide you in operation at no extra cost. Canaico thus gives you double assurance of the same dependable, trouble-free performance on which this collector has built its unsurpassed reputation for quality and reliability. A two-year warranty provides added protection. f o r sample collection plus flow analysis, the Canalco 1205 makes an integrated system with Canalco's Wide-Track 85 Ultraviolet Flow Monitor. Available in three models—all with true ratio recorders whose charts are as wide as this full three-column page—the Wide-Tracks give more sensitive detection of both proteins and nucleotides, and cost less, than any other flow analyzers. Options include automatic scale expansion, automatic baseline compensation, extension cables for cold-room use and choice of cuvette path lengths. When ordered together, the Canalco 1205 and Wide-Track come with interconnecting cable for the Wide-Track's event marker pen.
Contact Canaico direct for full details on the Canaico 1205 Fraction Collector and Wide-Track Flow Monitor. Write or telephone:
CANALCO
CANAL INDUSTRIAL CORPORATION 5635 Fisher Lane, Dept. A2. Rockville, Maryland 20852/(301) 427-1515
Sales and Service Offices in · Boston · Houston · New York · Seattle · Chicago · Los Angeles · Pittsburgh · Washington, D.C Cincinnati · Memphis · Cleveland · Minneapolis · San Francisco Circle No. 63 on Readers' Service Card 186 A
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ANALYTICAL CHEMISTRY
Controls on the right side are concerned with initial voltage, damping, current span, electrolysis function, supply current, electrolysis, stop light, working electrode, balance adjust, voltage scan, external scan, recorder input, external monitor, voltage scan range, electrolysis light and supply current per cent of range. An important feature is the use of positive throw, snap action switches which provide an almost instantaneous transition from "full-off" to "full-on." This prevents the constant current amplifier from going out of control due to a momentary open circuit and also prevents a temporary shorting of the cells. It is not possible here to describe all functions of this instrument. Some more pertinent details may be listed. For the controlled current power supply, there are five ranges from 0-10 microamperes up to 0-100 milliamperes continuously with any given range and the polarity is reversible in all ranges. Drift is less than 0.1% of current range after initial warm-up. Current accuracy is 0.21% of current range and reproducibility thereof 0.09%. Current response time, although a function of current selected and cell resistance, is of the order of 1 millisecond. The controlled-voltage power supply, obtainable as an accessory, has an initial voltage of ± 5 volts continuously adjustable over a 10-turn potentiometer. Precision of initial voltage setting is ±10 mv. There are 4 scan voltage ranges of ±0.5, ±1.0, ±2.0, ±5.0 volts per 10" of chart, each with seven scan rates which are 0.5-50, 1-100, 2-200, and 5-500 mv./sec, respectively. The precision of the voltage drive is ±0.5% of range and its linearity is ±0.2%. Among the recorder specifications are a 0.5 second speed for full scale, seven chart speeds from 1-100 seconds per inch, operational a.c. amplifier, and full wave chopper for stabilization. We are pleased to note that Beckman has followed the growing trend to have the recorder scale and up scale pen movement read from right to left. By thus abandoning the sacred Talmudic rite, those of us who are perverse enough can read our final charts from left to right. We expect to hear much in the near future about the research uses of this flexible instrument. With its use and, hopefully, with the appearance of a ready reference compendium, electroanalytical techniques may find applications comparable to more widely used gas chromatographic and spectrophotometric methods.
