Silver(I) Ions Ultrasensitive Detection at Carbon Electrodes―Analysis of Waters, Tobacco Cells and Fish Tissues

Sona Krizkova,Ales Horna,Ladislav Havel,Libuse Trnkova,Rene Kizek,Olga Krystofova,Miroslava Beklova,Vojtech Adam,Jaromir Hubalek

doi:10.3390/s90906934

Abstract

We used carbon paste electrodes and a standard potentiostat to detect silver ions. The detection limit (3 Signal/Noise ratio) was estimated as 0.5 μM. A standard electrochemical instrument microanalysis of silver(I) ions was suggested. As a working electrode a carbon tip (1 mL) or carbon pencil was used. Limits of detection estimated by dilution of a standard were 1 (carbon tip) or 10 nM (carbon pencil). Further we employed flow injection analysis coupled with carbon tip to detect silver(I) ions released in various beverages and mineral waters. During first, second and third week the amount of silver(I) ions releasing into water samples was under the detection limit of the technique used for their quantification. At the end of a thirteen weeks long experiment the content of silver(I) ions was several times higher compared to the beginning of release detected in the third week and was on the order of tens of nanomoles. In subsequent experiments the influence of silver(I) ions (0, 5 and 10 μM) on a plant model system (tobacco BY-2 cells) during a four-day exposition was investigated. Silver(I) ions were highly toxic to the cells, which was revealed by a double staining viability assay. Moreover we investigated the effect of silver(I) ions (0, 0.3, 0.6, 1.2 and 2.5 μM) on guppies (Poecilia reticulata). Content of Ag(I) increased with increasing time of the treatment and applied concentrations in fish tissues. It can be concluded that a carbon tip or carbon pencil coupled with a miniaturized potentiostat can be used for detection of silver(I) ions in environmental samples and thus represents a small, portable, low cost and easy-to-use instrument for such purposes.

Highlights

Due to many anthropogenic activities the environment has been polluted by a number of organic as well as inorganic compounds, and the concentrations of these undesirable and in most cases highly toxic substances have been steadily increasing
Due to competing equilibria and kinetics of water hydrated silver ions, Ag+, this species may be present in surface waters, which relates to the fact that Ag+ has been shown to be highly toxic to aquatic life [7]
The binding into an active site of the enzyme leads to the expressive inhibition of enzyme activity. This effect was observed by using of simple spectrometric test, in which we studied inhibition of urease activity by silver(I) ions (Figure 2B)

Summary

Introduction

Due to many anthropogenic activities the environment has been polluted by a number of organic as well as inorganic compounds, and the concentrations of these undesirable and in most cases highly toxic substances have been steadily increasing. The mechanisms of their effects can be very heterogeneous. The highest amounts of silver ions have been using in photographical industry (about 40% of the worldwide usage), followed by electrochemistry, medicine and others (Figure 1) They contaminate atmosphere as well as aquatic environment or soils [6]. A number of papers reporting investigations on the influence of silver(I)

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