Capillary Behavior in High Sensitivity Polarography

Cooke, W. D.; Kelley, M.T.; Fisher, D. J.

doi:10.1021/ac60177a024

Cited by 36 publications

(4 citation statements)

References 14 publications

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“…In our experience, derivative waves recorded in non-aqueous solvents tend to be "noisier" than polarograms recorded at similar sensitivities in aqueous solutions. This appears to be due, in large part, to an increase in "capillary noise"-i.e., irregularities in the growth pattern of the mercury drops and the droptime (3,6). For this reason it is desirable to record derivative waves in nonaqueous solvents at scan rates which are as fast as permissible in order to enhance the signal-to-noise ratio.…”

Section: Methodsmentioning

confidence: 99%

Resistance Compensation in Polarography. Application to High Resistance Nonaqueous Systems and to High Current-Density Aqueous Systems.

Schaap¹,

McKinney²

1964

Anal. Chem.

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Section: Methodsmentioning

confidence: 99%

Resistance Compensation in Polarography. Application to High Resistance Nonaqueous Systems and to High Current-Density Aqueous Systems.

Schaap¹,

McKinney²

1964

Anal. Chem.

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“…One of the major limitations in the quest for high sensitivity a t the D M E by direct as opposed t o integral or pseudo integral measurements is the phenomenon of capillary noise (6,20). Barker suggests that second-order relaxation techniques, because they appear to be less influenced by this factor offer a promising approach.…”

Section: Large Amplitude Relaxation Techniquesmentioning

confidence: 99%

Electrochemical Relaxation Techniques

Reinmuth¹

1964

Anal. Chem.

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ITHIN the past 20 years a wide W variety of electroanalytical techniques have been newly developed and a number of previously conceived techniques have received r2newed attention as a result of electronic advances which facilitated their practical implementation. The purpose of the present review, rather than considering only the advances of the past tv.oyears, will be t o discuss the relative merits of a selection of these methods. No attempt has been made at completely surveying the extensive literature, and discussion is largely confined t o whttt may be termed relaxation techniques.Relaxation methods in general are those in which a perturbing influence, usually in the form of a controlled current or potential, is tipplied to a cell initially a t equilibrium, and the transient relaxation of the system in response to this disturbance (a c u e n t or voltage) is observed. The distinction between small and large amplitude techniques arises naturally on theoretical grounds. In the mathematical treatment of the expected responses, 1 he current and concentrations of electroactive species are normally related through linear algebraic or differential equations, but the relation between concentration and potential (the Nernst equation) or current and potential (absolute rate expression) is an exponential one [cf. (66) for a recent revi1.w of theoretical methods].When the excursions of potential from initial equilibrium are no more than a few millivolts, the exponentials can be expanded t o produce linear equations. Thus, small amplitudl: techniques can be made to yield useful theoretical predictions even for relatively complicated postulated read ion mechanisms. In contrast, the large amplitude techniques, those in which potential excursions are too large to allow expansion of the exponentials with retention of only a few terms, tend t o yield intractable theories for all but the simplest cases. SMALL AMPI.ITUDE RELAXATION TECHNIQUESThe present discussion is limited to qualitative aspects of these techniques. The reader desiring more quantitative and extensive treatment is urged to consult the recent review by Delahay ($5).Although the perturbance from equilibrium in a relaxation technique could in principle be nonelectrical and in fact supersonic waves (84) and ultraviolet and visible radiation (1 1 ) have been employed, most workers have used electrical disturbances in the form of controlled current or voltage waveforms.One of the simplest of the techniques is the voltostatic one studied in detail by Vielstich and Delahay (81). In this case the perturbing influence is a step change in voltage applied t o the cell, and the current is observed, normally oscilloscopically. The technique is useful for studying the kinetics of chargetransfer reactions, but only relatively slow ones. The reason is that the step-change in voltage does not appear instantaneously across the solution-electrode interface but rather a t a rate limited by the R-C time constant associated with the charging of the capacitance of the electrical do...

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“…However, it must be evaluated from data over a finite range of potential. This presents no problem if the residual current maintains a con-If the expressions are equated (4 and 23), the result is a quadratic equation in i\nRid + 8K) 4i(-nRid2 -8Kid) 4-…”

Section: Equations Of Derivative Polarograrhy Including Effects Of Un...mentioning

confidence: 99%

High Resistance and Derivative Polarography. Derivation and Verification of Derivative Equations Useful in Evaluating Uncompensated Resistance in Polarographic Cells.

Schaap¹,

McKinney²

1964

Anal. Chem.

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Capillary Behavior in High Sensitivity Polarography

Cited by 36 publications

References 14 publications

Resistance Compensation in Polarography. Application to High Resistance Nonaqueous Systems and to High Current-Density Aqueous Systems.

Resistance Compensation in Polarography. Application to High Resistance Nonaqueous Systems and to High Current-Density Aqueous Systems.

Electrochemical Relaxation Techniques

High Resistance and Derivative Polarography. Derivation and Verification of Derivative Equations Useful in Evaluating Uncompensated Resistance in Polarographic Cells.

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