Russian Journal of Applied Chemistry, 2009, Vol. 82, No. 2, pp. 262−266.
Pleiades Publishing, Ltd., 2009.
Original Russian Text
Yu.V. Tsapko, I.I. Tumkin, S.S. Ermakov, 2009, published in Zhurnal Prikladnoi Khimii, 2009, Vol. 82, No. 2, pp. 268−272.
AND CORROSION PROTECTION OF METALS
Determination of Arsenic in Aqueous Solutions
by No-Reference Inversion Voltammetry
Yu. V. Tsapko, I. I. Tumkin, and S. S. Ermakov
St. Petersburg State University, St. Petersburg, Russia
Received July 17, 2008
Abstract—Electrochemical method for arsenic determination at concentrations characteristic of inversion
voltammetry was suggested. The method does not require calibration of the measuring instrument against standard
solutions or application of the standard-additive technique. The method of no-reference inversion-volammetric
determination is based on calculating the arsenic concentration in solution with the use of the preliminarily
determined coulometric constant of an electrochemical cell.
Arsenic and its compounds exhibit a high degree of
pathologicity (at present, there are about 19 diseases
associated with organism poisoning by arsenic com-
pounds) . Therefore, determination of microscopic
concentrations of arsenic compounds is a topical task.
This problem is aggravated by the tendency toward
increasingly stringent regulations concerning the
content of arsenic in various objects [e.g., the maximum
permissible concentration (MPC) of arsenic in drinking
water, established by the World Health Organization
in 2001, was lowered from 50 to 10 μg l
Modern laboratory practice widely employs for arsenic
determination in aqueous media various techniques, such
as atomic-absorption spectrometry with generation of
hydrides and mass spectrometry with inductively coupled
plasma [3–6]. Together with these methods, the leading
position in determination of low concentrations of toxic
elements is held by inversion voltammetry (IVA). The
comparative simplicity and low cost of the equipment
used, high sensitivity, and possibility of automation of
the determination process predetermine the wide use of
A considerable number of publications has been
devoted to cathodic and anodic versions of arsenic
determination by IVA. Having metrological characteristics
close to those of the anodic IVA (AIVA), the cathodic
version suffers from signiﬁ cant disadvantages: highly
toxic arsine evolves in the stage of the cathodic potential
sweep and no less toxic mercury is used as the material
of the indicator electrode. This restricts the applicability
area of the cathodic IVA, compared with AIVA.
In the stage of pre-electrolysis in the AIVA version,
arsenic is concentrated at the electrode in the form of
a deposit of elementary arsenic. The method is based on
the following reaction:
It follows from Eq. (1) that arsenic accumulates at the
cathode with a lower overvoltage in solutions containing
a large excess of hydrogen ions. Therefore, solutions of
strong mineral acids (0.1–10 M), such as sulfuric and,
most frequently, hydrochloric, are commonly used for
these purposes as a supporting electrolyte .
Because IVA is a comparative method and involves
prolonged routine procedures of construction of
calibration dependences with the use of reference samples,
several alternations of no-reference electrochemical
determination of toxic elements in aqueous solutions
have been suggested recently [8–12].
The chronopotentiometric technique is based on
multiple-cycle dissolution-deposition of a metal from
an amalgam produced in the pre-electrolysis stage and
subsequent finding of the quantity Q
consumed for electroconversion of the whole mass
of a substance being determined, present in solution.
A similar method of “dynamic coulometry,” suggested