Voltammetric Trace Metal Analysis Research Articles

On Site Determination of Heavy Metal Ions with Portable Electrochemical Instrument Based on Smartphone

Introduction Most heavy metal ions are harmful to human body and may cause a variety of diseases, among which chromium(VI), cadmium, arsenic and their compounds are classified as Group 1 (human carcinogen) by IARC [1]. Heavy metal ions can enter the human body through direct drinking and the enrichment of food chain. Therefore, the allowed concentration of heavy metal ions are recommend by WHO, which are 50 μg/L for chromium(VI), 3 μg/L for cadmium, 10 μg/L for arsenic, respectively [2].Compared with other methods, electrochemical method is gaining wide recognition and has the advantages of fast speed, simple operation and possibility of use in portable detection on site [3]. Therefore, a portable electrochemical instrument based on smartphone was designed, in order to detect the concentration of heavy metal ions in the field. Method A block diagram of the portable electrochemical instrument is shown in Fig. (a). The instruction of controlling electrochemical process is sent out by MCU and executed by potentiostat. The electrochemical signal obtained is simply processed and returned to MCU. The communication between MCU and smartphone software based on Android system is realized through Bluetooth. The completed printed circuit board (PCB) of the instrument is shown in Fig. (b).The determination of chromium(VI) is realized by gold nanoparticles modified gold electrode, in order to obtain a larger electrochemical response. The gold nanoparticle modification was achieved by applying a potential of -0.3 V for 120 seconds with stirring in 0.2 mmol/L chloroauric acid with 0.5 mol/L sulphuric acid, which is simple, stable and repeatable for on site determination. As shown in Fig. (c), the increase of electrode surface area can be observed by Atomic Force Microscope (AFM).After parameters optimization, the detection of Chromium(VI) was carried out in 0.3 mol/L nitric acid by linear sweep voltammetry (LSV) with a potential range of 0.8 V to 0.2 V. There is no accumulation process during detection, so it takes less than 10 seconds. Results and Conclusions The linear sweep voltammograms in chromium(VI) concentration range of 10 μg/L to 100 μg/L with a step of 10 μg/L are shown in Fig. (d). The standard curve of Cr(VI) is shown in Fig. (e), where it shows a linear relationship with the correlation coefficient of 0.98. A detection limit of 6.4 μg/L can be calculated, suggesting the sensitivity of the method for Cr(VI) detection. These results indicate that the portable electrochemical instrument based on smartphone can be a promising alternative for heavy metal ions detection on site. References International Agency for Research on Cancer. (2020). Agents classified by the IARC Monographs, volumes 1-128. http://monographs. iarc. fr/ENG/Classification/index. php.Edition, F. (2011). Guidelines for drinking-water quality. WHO chronicle, 38(4), 104-8.Holmes, J. , Pathirathna, P. , & Hashemi, P. . (2019). Novel frontiers in voltammetric trace metal analysis: towards real time, on-site, in situ measurements. TrAC Trends in Analytical Chemistry, 111, 206-219. Figure 1

Solar UV Photooxidation as Pretreatment for Stripping Voltammetric Trace Metal Analysis in River Water

The application of solar ultraviolet radiation as sample pretreatment or preparation step in stripping voltammetric analysis of trace metals in presence of low levels of dissolved organic carbon (DOC) natural water samples (river water) was studied. River water samples were collected from downstream of Warnow river (Germany) and acidified to pH of2±0.2(by addition of 1 mL of ultrapure 65% HNO3per liter sample). Furthermore, 100 μL/L of hydrogen peroxide solution (ultrapure, 30% H2O2) was added to the samples as photochemical reaction initiator. The samples were transferred to polyethylene terephthalate (PET) bottles and irradiated with solar radiation of UV-A intensity of 3.6 mW/m2for six hours, and the concentrations of Zn, Cd, Pb, and Cu were determined by differential pulse anodic stripping voltammetry (DPASV). The comparison of the values with the results obtained for the original untreated sample and artificial UV-treated one proved that solar UV radiation can be applied to the digestion of dissolved organic carbon in trace metal analysis in natural waters like river water, lake waters, well waters, and so forth.

Application of Anodic Stripping Voltammetry for Zinc, Copper, and Cadmium Quantification in the Aqueous Humor: Implications of Pseudoexfoliation Syndrome

Anodic stripping voltammetric (ASV) procedure, using mercury film electrode, was optimized and applied to determine the concentrations of zinc, cadmium, and copper in the aqueous humor. Concentration levels as low as 1 ppb of the test metals was possible to be detected using short electrolysis times (120 s) and microquantities of aqueous humor (up to 35 μL). As a first application of the voltammetric analysis of trace metals in the aqueous humor, the role of the three selected trace elements in the pseudoexfoliation (PEX) syndrome was examined. Samples from aqueous humor were collected during cataract extraction from patients with and without PEX. The zinc and copper concentration levels in the aqueous humor did not show statistically significant difference in the study and control group. Cadmium was detected in a small number of samples, without however statistical differences between the two groups. ASV proved to be a highly precise and sensitive tool for the quantification of heavy metal ions in aqueous humor. Further studies may lead to useful conclusions for the role of zinc, copper, or cadmium in PEX syndrome.

Ion-exchange and permselectivity properties of poly(sodium 4-styrenesulfonate) coatings on glassy carbon: application in the modification of mercury film electrodes for the direct voltammetric analysis of trace metals in estuarine waters

The present work describes the optimisation and characterization of poly(sodium 4-styrenesulfonate)-coated thin mercury film electrodes (PSS-TMFE) for the direct analysis of trace metals in estuarine waters by square-wave anodic stripping voltammetry (SW-ASV). The morphology, thickness and ion exchange ability of the poly(sodium 4-styrenesulfonate) coatings onto glassy carbon were evaluated and these features particularly favoured the incorporation of cationic species, such as dopamine or lead cation. For the case of the heavy metal cations, a simple, sensitive and very reproducible methodology for their SW-ASV analysis could be developed. In fact, with the PSS-TMFE, a significant increase in the sensitivity of the ASV determination of lead was obtained compared both to the uncoated TMFE (ca. 82%) as well as to Nafion-coated electrodes of similar thickness (ca. 43–49%). Furthermore, the permselectivity of the poly(sodium 4-styrenesulfonate) coatings, based both on electrostatic interaction and molecular size, leads to an improved anti-fouling ability against surfactant species. The analytical usefulness of the poly(sodium 4-styrenesulfonate)-coated thin mercury film electrodes is demonstrated by application to the direct ASV determination of trace heavy metals at the low nanomolar level, in estuarine waters with moderate contents of dissolved organic matter, where the uncoated TMFE failed due to fouling.

Novel photolytic decomposition method of organic compounds with a high output low-pressure mercury lamp for voltammetric trace metal analysis

A high output low-pressure mercury lamp, 400 W L-Hg, was successfully used for the photolytic decomposition of dissolved oganic compounds as the pretreatment for the determination of trace metal ion in aqueous solution by stripping voltammetry. Various amino acids, showing interferences on voltammetric determination of metal ions, can be removed quite easily by intensive UV irradiation at room temperature. Effect of pH, concentration of electrolyte and dissolved oxygen on the efficiency of photolysis are also described. This method uses no additional chemicals such as acids or oxidants and can be carried out in closed clean conditions.

Microfabricated Chemical Analysis Systems for Environmental Applications

Recent contributions to the design, development, and fabrication of microtechnological devices for chemical analysis are summarized. The discussion includes microdisk-electrode arrays for voltammetric analysis of trace metals, and micro total-analysis systems for coulometric nanotitrations of different analytes.

Voltammetric determination of copper in water samples digested by ozone

The applicability of ozone as a digestion agent in voltammetric trace metal analysis of water samples was investigated. It was shown that ozone efficiently destroys dissolved organic matter, causing a significant decrease of the concentration of surface active substances in the sample, thus enabling voltammetric measurements. Ozonolysis times of 30 and 60 min were sufficient for the treatment of river water and biologically treated wastewater samples, depending on their organic load, prior to voltammetric determination of copper using a solid gold electrode.

Effective UV photolytic decomposition of organic compounds with a low-pressure mercury lamp as pretreatment for voltammetric analysis of trace metals

The effectivity of UV irradiation with low and high pressure mercury (L-Hg and H-Hg) lamps on the decomposition of organic compounds in aqueous solutions, as pretreatment for the voltammetric determination of trace metals, is compared. The photolytic decomposition with the L-Hg lamp was much faster than with the H-Hg lamp. The higher efficiency of the L-Hg lamp is caused by its greater light intensity at short wavelengths. Interferences of organic compounds on the voltammetric determination of nickel and indium were eliminated successfully by ∼90 min irradiation with the L-Hg lamp. Humic acid and organic interference with the voltammetric determination of nickel in natural river water were successfully eliminated. The decomposition using the L-Hg lamp can be carried out without added oxidizing reagents and at room temperature, thus eliminating loss of water samples by evaporation at higher temperature.

Investigation of the completeness of digestion procedures prior to voltammetric trace metal analysis of olive leaves

Wet decomposition of olive leaves in open and closed systems, low temperature ashing, UV-irradiation and combinations of these methods have been tested for their application in the determination of heavy metals by anodic stripping voltammetry. Completeness of the decompositon and interferences in the electrochemical determination have been evaluated. Wet decomposition with perchloric acid, low temperature ashing and a combination of pressurized digestion and UV-irradiation were found to be suitable for application in electrochemical measurements. The most serious interferences were observed with well but not fully decomposed samples, such as those obtained by wet decomposition with nitric acid in an open system.

Vermeidung von Kontamination und anderen die Richtigkeit beeinflussenden Einwirkungen bei der voltammetrischen Spurenanalyse in nat�rlichen Gew�ssern

Vermeidung von Kontamination und anderen die Richtigkeit beeinflussenden Einwirkungen bei der voltammetrischen Spurenanalyse in nat�rlichen Gew�ssern

Prevention of contamination and other accuracy risks in voltammetric trace metal analysis of natural waters

Prevention of contamination and other accuracy risks in voltammetric trace metal analysis of natural waters

Prevention of contamination and other accuracy risks in voltammetric trace metal analysis of natural waters

Prevention of contamination and other accuracy risks in voltammetric trace metal analysis of natural waters

Trace metal analysis by anodic stripping voltammetry: effect of sorption by natural and model organic compounds

A variety of model organic compounds representative of the types of organic substances occurring in natural waters were found to sorb onto hanging mercury drop electrodes in the anodic stripping voltammetric analysis of trace metals. Sorption effects on the ASV diagnostic parameters E p and i p (peak current and peak potential) were pH dependent, with greater effect under acidic conditions in some cases, and were significant at organic concentrations in the ppm range. Compounds tested included gelatin and alkaline phosphatase as representatives of soluble proteins. Triton X100 (a nonionic surfactant), and a variety of polysaccharides, including agar, alginic acid and starch. Effects of sorption included depressed i p values, shifts in E p to more positive values, and broader peaks. Implications of these effects on the interpretation of ASV measurements in terms of analysis and speciation of trace metals in natural waters are discussed.