Vibrating dropping mercury electrode and polarographic theory

Cover, Richard E.; Connery, James G.

doi:10.1021/ac60282a012

Cited by 22 publications

(17 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Curves 3 at the various pulse amplitudes may be considered the sampled dc polarogram obtained at a drop time 50 ms shorter than obtained in curves 2. The smaller amplitude of the maxima in curves 3 supports the findings of Cover and Connery(26,27) that short drop times are advantageous in that the effects of maxima are Comparison of dp polarograms and the various components thereof for 1 X M Cr(1II) in 1.0 M NaCIO, plus -0.02 M HCIOI without Fe(II1) (curves a) and with 2 X M Fe(II1) (curves b).…”

supporting

confidence: 78%

Measurement of direct currents and pulse components for analytical evaluation of differential pulse polarography and voltammetry

Anderson¹,

Bond²

1980

Anal. Chem.

View full text Add to dashboard Cite

Simple and inexpensive modifications to differential pulse poiarographs enable the dc and pulse components of the experiment as well as their differences to be measured. Using examples of electrochemically reversible and irreversible electrode processes, as well as kinetically complicated ones, demonstrates that access to additional data usually ignored in differential pulse polarography and voltammetry can be a valuable aid in analytical evaluation of the techniques and in methodology development. Theoretical studies would also appear to be substantially aided by access to such measurements.Differential pulse polarography has become one of the most commonly used methods of polarographic analysis. Originally developed by Barker ( I ) , the technique uses a waveform consisting of a fixed amplitude pulse superimposed onto a dc ramp. Currents measured in the absence of the pulse are subtracted from currents in the presence of the pulse producing the differential current readout in which hi is plotted against the dc potential to produce a differential pulse polarogram (2). Theoretical work in differential pulse polarography has lagged far behind the analytical applications and it is only recently (3-8) that papers have appeared dealing with anything other than a reversible electrode process with planar diffusion. Use of the reversible theory has led to suggestions for improved instrumental design of the technique ( S I 2 ) . The basis for most of these innovations has been to eliminate residual terms arising from incomplete subtraction of the dc component of the experiment (9). Unfortunately, many electrode processes are not simple reversible diffusion controlled electrode processes and the validity of many of these ideas to the irreversible electrode process, adsorption, maxima, or all other well known phenomena associated with polarography is far from clear.Experimentally, in almost all theory vs. experiment correlations, and indeed in analytical work, the differential pulse polarograms are all that are measured. In view of the fact that the technique measures the difference between the pulse and dc polarogram, it is difficult to understand why the individual components of the experiment are not routinely monitored and results used for optimization in analytical work and particularly in theory vs. experiment correlations. This need has obviously been previously recognized by workers having access to very expensive computerized systems. The almost complete lack of studies in this area can be attributed to a lack of suitable readily available inexpensive equipment.In the present paper, it is demonstrated how simple modifications to existing circuits associated with differential pulse polarographs can enable far more information to be obtained than is conventionally the case. A qualitative survey of the information that can be readily extracted is presented to demonstrate the general use of these data automatically discarded in almost all previous studies using differential pulse (dp) polarography. EXPERIMENTALInstrum...

show abstract

supporting

confidence: 78%

Measurement of direct currents and pulse components for analytical evaluation of differential pulse polarography and voltammetry

Anderson¹,

Bond²

1980

Anal. Chem.

View full text Add to dashboard Cite

show abstract

“…These include: (a) minimization or complete suppression of polarographic maxima (5,6,14,15,22); (b) reduction or elimination of electrode reaction inhibition effects due to adsorption and precipitation phenomena (6,15,18,22,23); (c) enabling measurements in agitated solutions (1, [3][4][5][6]15); (d) permitting significant alteration of coupled chemical reaction effects, relative to normal drop life observations (2,5,6,14); (e) the production of smaller ohmic potential drop life distortions (17); (f) minimization of spherical diffusion effects with amalgam-forming systems (22); (g) enhancement of slow charge transfer kinetic effects (9,14); (h) enabling in certain instances polarographic procedures without oxygen removal (20); (i) enabling one to effect polarographic measurements in unstable situations, such as when a solution component is decomposing, or when electrode and cell materials are attacked by the solution (e.g., glass capillaries in 0003-2700/78/0350-1073$01.00/0 acidic F" media) (8,10,12,13). In addition to such empirical demonstrations, it has been shown (7,21). that most aspects of the observed RDME polarographic responses' dependence on system parameters are in agreement with rate law predictions derived with more conventional drop times in mind.…”

supporting

confidence: 59%

Rapid drop time on-line Fast Fourier Transform faradaic admittance measurements

O'Halloran¹,

Schaar²,

Smith³

1978

Anal. Chem.

View full text Add to dashboard Cite

“…Indeed, if it can be established conclusively under what conditions the relatively simple theory is valid at short drop times, and the apparent anomaly in the literature can be satisfactorily resolved so as to remove any uncertainty in the minds of users of polarographic techniques, then short drop time polarography could advantageously replace the conventionally recommended 2-5-sec drop time polarography, in many situations. [15][16][17][18][19][20] In addition to using short drop times with dc polarography, other polarographic techniques can gain substantially from using this modification. Derivative dc polarography20 and ac polarography15 are two examples which have been discussed.…”

mentioning

confidence: 99%

Validity of the Ilkovic and other standard direct and alternating current polarographic equations at short drop time

Bond

O'Halloran

1973

J. Phys. Chem.

View full text Add to dashboard Cite

Both short drop time ac and dc polarography, which permit fast scan rates and increase the polarographic time scale several orders of magnitude, are potentially extremely valuable techniques in many kinetic, analytical, and electrochemical investigations. Early work utilizing short drop times indicated that standard polarographic equations were inapplicable to such measurements, and the use of drop times below 2 sec has been generally discouraged in the literature. Recently, however, data have been obtained in the millisecond drop time region which indicated that much of the standard theory can in fact apply in this drop time range. The present study reports an investigation of short drop time polarography in an endeavor to resolve apparent anomalies currently existing in the literature, and to overcome possible unjustified discrimination preventing the much wider use of a valuable technique of polarography. Results demonstrate conclusively that the presence of the short drop time itself does not lead to a breakdown of conditions for which standard ac and dc theories were derived. If short controlled drop times are obtained by mechanically knocking the capillary then the short drop time experiment is found to be critically dependent on the theory applicable to the natural drop, from which the short controlled drop is derived. In obtaining the short controlled drop time, the flow rate of mercury is essentially unaltered. On the other hand, if short drop times are obtained by gravity control, it is confirmed that the standard theory no longer applies, because the flow rate of mercury becomes too large, and it would appear that it is variations in this parameter, rather than the drop time which has caused many of the difficulties encountered in the past.Polarography, the measurement, interpretation, and use of current-voltage curves at a dropping mercury electrode, DME, has been widely used in many branches of chemistry for over 50 years. Workers interested in fundamental electrochemistry, analytical chemistry, kinetics, and a wide spectrum of physical, inorganic, and organic areas frequently have occasion to use the techniques.The fundamental theories and equations in dc polarography have been well established now for several decades.1"3 The theory for diffusioncontrolled limiting currents was first solved successfully in 1934 by llkovic,1-5 and the mathematical formulation describing a reversible polarographic wave in 1935 by Heyrovsky and llkovic. 1-3•6 The validity of these equations, particularly the llkovic equation, and modifications to this theory have come under scrutiny in many publications as summarized in ref 2 and 3.Of particular relevance to this paper is the work of Maas7 and others.8•9 The llkovic equation predicts a linear dependence of the limiting or diffusion current on concentration. These authors have reported that the limiting current relationships do not hold exactly with short drop times. This work has led many authors of reviews arid textbooks to recommend with reasons why polarographic ...

show abstract

Vibrating dropping mercury electrode and polarographic theory

Cited by 22 publications

References 6 publications

Measurement of direct currents and pulse components for analytical evaluation of differential pulse polarography and voltammetry

Measurement of direct currents and pulse components for analytical evaluation of differential pulse polarography and voltammetry

Rapid drop time on-line Fast Fourier Transform faradaic admittance measurements

Validity of the Ilkovic and other standard direct and alternating current polarographic equations at short drop time

Contact Info

Product

Resources

About