Simultaneous electrochemical determination of arsenic, copper, lead and mercury in unpolluted fresh waters using a vibrating gold microwire electrode

In this work, a simple, rapid, reliable and low cost method for simultaneous electrochemical determination of As, Cu, Hg and Pb ions, on a vibrating gold microwire electrode combined with stripping voltammetry, is described for the first time.The multi-element detection was performed in the presence of oxygen by differential pulse anodic stripping voltammetry (DPASV) in HCl 0.1 M with NaCl 0.5 M. This media was found optimum in terms of peak resolution, peak shape and sensitivities, and has a composition similar to seawater to which the method could potentially be applied. The gold microwire electrode presented well defined, undistorted, sharp and reproducible peaks for trace concentrations of Cu, Hg and Pb and As presented a reproducible peak with a small shoulder. Using a gold vibrating microwire electrode of 25 μm diameter and 30 s deposition time, the detection limits of As, Cu, Hg and Pb were 0.07, 0.4, 0.07 and 0.2 μg L⁻¹, respectively. Possible effects of Al, Cd, Cr, Fe, Mn, Ni, Sb and Zn were investigated but did not cause any significant interferences.Finally, the method was applied for the simultaneous determination of these four metals in unpolluted river water samples and the results were validated by Atomic Absorption Spectroscopy with Electrothermal Atomization (AAS-EA) or by Inductively Coupled Plasma Mass Spectrometry (ICP-MS).     

Simultaneous Anodic Stripping Voltammetric Determination of Pb and Cd,Using a Vibrating Gold Microwire Electrode,Assisted by Chemometric Techniques

Simultaneous anodic stripping voltammetric determination of Pb and Cd is restricted on gold electrodes as a result of the overlapping of these two peaks. This work describes the quantitative determination of a binary mixture system of Pb and Cd, at low concentration levels (up to 15.0 and 10.0 µg L^?1 for Pb and Cd, respectively) by differential pulse anodic stripping voltammetry (DPASV; deposition time of 30 s), using a green electrode (vibrating gold microwire electrode) without purging in a chloride medium (0.5 M NaCl) under moderate acidic conditions (HCl 1.0 mM), assisted by chemometric tools. The application of multivariate curve resolution alternating least squares (MCR‐ALS) for the resolution and quantification of both metals is shown. The optimized MCR‐ALS models showed good prediction ability with concentration prediction errors of 12.4 and 11.4 % for Pb and Cd, respectively. The quantitative results obtained by MCR‐ALS were compared to those obtained with partial least squares (PLS) and classical least squares (CLS) regression methods. For both metals, PLS and MCR‐ALS results are comparable and superior to CLS. For Cd, as a result of the peak shift problem, the application of CLS was unsuitable. MCR‐ALS provides additional advantage compared to PLS since it estimates the pure response of the analytes signal. Finally, the built up multivariate calibration models, based either in MCR‐ALS or PLS regression, allowed to quantify concentrations of Pb and Cd in surface river water samples, with satisfactory results.     

Simultaneous Voltammetric Determination of Zn(II), Pb(II), Cu(II), and Hg(II) in Ethanol Fuel Using an Organofunctionalized Modified Graphite‐Polyurethane Composite Disposable Screen‐Printed Device

A disposable screen‐printed device containing working, auxiliary, and reference electrodes is proposed for the simultaneous voltammetric determination of Zn(II), Pb(II), Cu(II), and Hg(II) in ethanol fuel. The working electrode was printed using an ink modified with 2‐benzothiazole‐2‐thiol organofunctionalized SBA‐15 silica, in order to increase sensitivity. The performance of this electrode was compared with that of bare and SBA‐15‐modified electrodes. After optimizing the experimental parameters, the device was applied in determination of the analytes in commercial ethanol fuel samples, using 0.10 mol L^?1 KCl/ethanol ratios of 30 : 70 (v/v), with [H⁺]=10^?5 mol L^?1. After 5 min of preconcentration at ? 1.3 V (vs. pseudo‐Ag/AgCl), four well‐resolved signals were obtained, enabling simultaneous determination of the four analytes using a differential pulse anodic stripping voltammetry (DPASV) procedure. The limits of detection were 0.30, 0.065, 0.030, and 0.046 µmol L^?1 for Zn(II), Pb(II), Cu(II), and Hg(II), respectively. The results of these analyses were in agreement with those obtained using graphite furnace atomic absorption spectroscopy (GFAAS) for Pb(II), Cu(II), and Hg(II), and high‐resolution continuum source flame atomic absorption spectrometry (HR‐CS‐FAAS) for Zn²⁺, at a 95 % confidence level. Analytes originally present in the samples could be detected, and the interference of some cations and anions was evaluated.     

Simultaneous Voltammetric Determination of Heavy Metals by Use of Crown Ether‐modified Electrodes and Chemometrics

A three‐sensor array consisting of a graphite‐epoxy composite electrode (GEC), 4‐carboxybenzo‐18‐crown‐6‐GEC and 4‐carboxybenzo‐15‐crown‐5‐GEC was employed for the simultaneous determination of Cd(II), Pb(II) and Hg(II) by differential pulse anodic stripping voltammetry (DPASV). Sensors were firstly studied for the determination of Hg(II); secondly, peak current responses confirmed that all sensors showed differentiated response for the three considered metals. A response model was developed to resolve mixtures of Cd(II), Pb(II) and Hg(II) at the µg L^?1 level; Discrete Wavelet Transform was selected as preprocessing tool and artificial neural network used for the modelling of the obtained responses.     

Voltammetric Determination of Pb,Cu and Hg in Biodiesel Using Gold Screen‐printed Electrode: Comparison of Batch‐injection Analysis with Conventional Electrochemical Systems

This article compares the use of batch‐injection analysis (BIA) with a conventional batch system for the anodic stripping voltammetric (ASV) determination of Pb, Cu and Hg in biodiesel using screen‐printed gold electrode (SPGE). The optimized BIA conditions were 200 µL of injection volume of the digested samples at 5 µL s^?1 directly on the working electrode of the SPGE immersed in 0.1 mol L^?1 HCl solution. Therefore, BIA‐ASV presented the advantages of low sample consumption, which extended the SPGE lifetime to a whole working day of analyses, and potential for on‐site analysis using battery‐powered micropipettes and potentiostats. Although presenting lower sensitivity than conventional systems, the BIA‐ASV presented detection limit values of 1.0, 0.5 and 0.7 µg L^?1, respectively for Pb, Cu and Hg, a linear range between 20 and 280 µg L^?1, and adequate recovery values (90–110 %) for spiked biodiesel samples.     

Simultaneous Detection of Copper,Lead and Zinc on Tin Film/Gold Nanoparticles/Gold Microelectrode by Square Wave Stripping Voltammetry

In this work, three heavy metals (Cu(II), Pb(II) and Zn(II)) in wide potential window were simultaneously detected on tin film/gold nanoparticles/gold microelectrode (Sn/GNPs/gold microelectrode) by the method of square wave stripping voltammetry. The Sn/GNPs/gold microelectrode was fabricated by in situ plating of a Sn film on a gold nanoparticles (GNPs) modified gold microelectrode. The influence of hydrogen overflow on stripping of Zn(II) on the gold microelectrode was reduced by modification of GNPs, which made the stripping potential of target metals shift positively. The interference of sulfhydryl groups was reduced and the selectivity of the microelectrode was improved due to the addition of Sn in the detection solution. After accumulation at ?1.4 V for 300 s in acetate buffer solution (0.1 mol L^?1, pH 4.5), the Sn/GNPs/gold microelectrode revealed a good linear behavior in the examined concentration ranges from 5 to 500 µg L^?1 for Cu(II) and Pb(II), and from 10 to 500 µg L^?1 for Zn(II), with a limit of detection of 2 µg L^?1 for Cu(II), 3 µg L^?1 for Pb(II) and 5 µg L^?1 for Zn(II) (S/N=3). When compared with a Sb/GNPs/gold microelectrode and a Bi/GNPs/gold microelectrode, the Sn/GNPs/gold microelectrode showed the best stripping performance to Cu(II), Pb(II) and Zn(II). As a new type of environment‐friendly electrode, the Sn/GNPs/gold microelectrode has potential applications for detection of heavy metals.     

Bismuth‐Coated Iridium Microwire Electrode for the Determination of Trace Metals by Anodic Stripping Voltammetry

This work reports the utility of an iridium microwire plated in situ with a bismuth film for the simultaneous determination of Pb(II) and Cd(II) by square‐wave anodic stripping voltammetry (SWASV). The experimental variables (concentration of the bismuth plating solution, preconcentration potential, accumulation time) were investigated. The limit of detection was 1 µg L^?1 for Pb(II) and 1.5 µg L^?1 for Cd(II) (at 300 s of preconcentration) and the % relative standard deviations were lower than 4.9 % and 5.5 %, respectively, at the 20 µg L^?1 level (n=8). In addition, a study was made of coating the iridium‐based bismuth‐film microsensor with a film of Nafion for operation in the presence of surfactants. Finally, the electrode was applied to the determination of Pb(II) and Cd(II) in wastewater and tapwater samples.     

Bismuth Film Voltammetric Sensor on Pyrolyzed Photoresist/Alumina Support for Determination of Heavy Metals

Voltammetric sensors based on bismuth film electrodes are an attractive alternative to other sensors for application in electroanalysis of heavy metals. Bismuth film electrodes can be formed by a similar method on the same substrates as mercury. These systems were used most frequently for simultaneous determination of heavy metals such as Pb, Cd and Zn by anodic stripping voltammetry. Our voltammetric sensor was fabricated on an alumina substrate. A photoresist film prepared by pyrolysis of positive photoresist S‐1813 SP15 on the alumina substrate was used as an electrode support for bismuth film deposition. The influence of the Nafion membrane on the measurement sensitivity of the sensor and mechanical stability of the bismuth film were investigated. The sensor was successfully applied for determination of Pb, Cd and Zn in an aqueous solution in the concentration range of 0.2 to 10 µg L^?1 by square wave anodic stripping voltammetry on an in‐situ formed bismuth film electrode with Nafion‐coating. Parameters of the sensor such as sensitivity, linearity, detection limit, repeatability and life‐time were evaluated. In the best case, the detection limits were estimated as 0.07, 0.11 and 0.63 µg L^?1 for Pb, Cd and Zn, respectively. Finally, the applicability of the sensor was tested in analysis of Pb, Cd and Zn in real samples of tap and river water using the method of standard additions.     

A screen-printed carbon electrode modified with a bismuth film and gold nanoparticles for simultaneous stripping voltammetric determination of Zn(II), Pb(II) and Cu(II)

The authors report on a disposable sensor for the differential pulse anodic stripping voltammetric (DPASV) determination of the ions Zn(II), Pb(II) and Cu(II). Simultaneous detection is accomplished by using a screen-printed carbon electrode (SPCE) co-modified with an in-situ plated bismuth (Bi)) film and gold nanoparticles (AuNPs). The synergistic effect of the Bi film, and the large surface and good electrical conductivity of the AuNPs strongly assist in the co-deposition of the three ions. Four well-defined and fully separated anodic stripping peaks, at 540 mV for Zn(II), 50 mV for Pb(II), 140 mV for Bi(III) and 295 mV for Cu(II), all vs. Ag/AgCl, can be seen. The modified SPCE was characterized by scanning electron microscopy, X-ray diffraction, cyclic voltammetry and electrochemical impedance spectroscopy. Under the optimized conditions, the sensor has a good response to these ions. The detection limits (at an S/N ratio of 3) are 50 ng·L^?1 for Zn(II), 20 ng·L^?1 for Pb(II), and 30 ng·L^?1 for Cu(II). The method was applied to the determination of the 3 ions in spiked lake water samples.

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Graphical abstract Schematic of screen-printed carbon electrode (SPCE) co-modified with a bismuth film and gold nanoparticles for electrochemical simultaneous determination of Zn(II), Pb(II) and Cu(II) by differential pulse anodic stripping voltammetric (DPASV).

     

Anodic Stripping Voltammetry Determination of Pb(II) and Cd(II) at a Bismuth/Poly(aniline) Film Electrode

Abstract

A novel voltammetric method—anodic—using a bismuth/poly(aniline) film electrode has been developed for simultaneous measurement of Pb(II) and Cd(II) at low µg L^?1 concentration levels by stripping voltammetry. The results confirmed that the bismuth/poly(aniline) film electrode offered high‐quality stripping performance compared with the bismuth film electrode. Well‐defined sharp stripping peaks were observed for Pb(II) and Cd(II), along with an extremely low baseline. The detection limits of Pb(II) and Cd(II) are 1.03 µg L^?1 and 1.48 µg L^?1, respectively. The bismuth/poly (aniline) electrode has been applied to the determination of Pb(II) in tap water samples with satisfactory results.     

Anodic Stripping Voltammetry Using a Vibrating Electrode

This work proposes a vibrating microwire electrode as working electrode in stripping voltammetry. The vibration was found to maintain a constant and thin (1–2 μm) diffusion layer during the deposition step. The electrode vibration eliminated the need for external stirring of the solution, thus facilitating in situ detection in the environment. The vibration was effected by fixing a low‐voltage (3 V), asymmetric, electrical rotor to the working electrode (a gold microwire of either 5 or 25 μm). The sensitivity of the vibrated electrode was ca. 22×greater than stationary. Measurements of copper (4 nM) by anodic stripping voltammetry using the vibrating electrode had a low standard deviation (1% for n=6) indicating that the diffusion layer had only minor variability. The agitation mechanism was unaffected by water moving at >2 m s^?1 and by water pressure equivalent to a depth of >40 m, indicating its suitability for in situ measurements. The vibrating probe was used for in situ detection of copper by anodic stripping voltammetry to a depth of 6 m. Using a 5 min deposition time, the limit of detection for labile copper was 38 pM.     

Simultaneous Determination of Pb and Cd Traces in Water Samples by Anodic Stripping Voltammetry Using a Modified GC Electrode

The determination of Pb and Cd with a Nafion‐modified glassy carbon electrode and Cu‐DPABA complex (Cu‐DPABA–NA/GCE; DPABA is methyl 3,5‐bis{bis‐[(pyridin‐2‐yl)methyl]amino}methyl‐benzoate) as an alternative electrode for anodic stripping voltammetry was described. Pb and Cd were accumulated in acetate buffer pH 4 at a potential of ?1.4 V (vs. Ag/AgCl electrode) for 120 s followed by a DPASV scan from ?1.2 to ?0.2 V. Under optimum conditions the calibration curves were linear in the range of 4.8×10^?9–5.0×10^?5 and 5.0×10^?9–5×10^?5 mol L^?1 for Pb and Cd, respectively. Detection limits were 1.8×10^?9 and 1.2×10^?9 mol L^?1 for Pb and Cd, respectively. Different parameters and conditions, such as membrane ingredients, accumulation time, potential and pH value were optimized. A study of interfering substances was also performed. A significant increase in current was achieved at the modified electrode in comparison with the bare glassy carbon electrode. The validation of the proposed method was made by Pb and Cd determination in the certified reference material Groundwater CRM 610 (BCR, Community Bureau of Reference, Brussels, Belgium). The electrode was successfully applied for determination of Pb and Cd in river water with a high content of organic contaminants without any pretreatment.     

Palladium Particles‐Impregnated Natural Phosphate Electrodes for Electrochemical Determination of Mercury in Ambient Water Samples

We present here a simple procedure for the determination of mercury(II) using differential pulse anodic stripping voltammetry (DPASV) at palladium particles‐impregnated natural phosphate modified carbon paste electrodes (Pd‐NP‐CPE). The surface of modified electrode was characterized using SEM, infrared spectroscopy, X‐ray diffraction and electrochemical analysis. All experimental variables involved in the voltammetric stripping method were optimized. The detection limit was found to be 4.99×10^?8 mol L^?1 (S/N=3) that is not different to the permitted value for Hg(II) in water reported by the Environmental Protection Agency (EPA). The proposed electrode exhibits good applicability for monitoring Hg(II) in tap and wastewater.     

Stripping Analysis of Trace Arsenic Based on the MnOx/AuNPs Composite Film Modified Electrode in Alkaline Media

A simple, rapid fabricated and sensitive modified electrode for detection of As(III) in alkaline media was proposed. The modified electrode was prepared by co‐electrodeposition of manganese oxides (MnO_x) and gold nanoparticles (AuNPs) on the glassy carbon electrode (GCE) with cyclic voltammetry. Linear sweep anodic stripping voltammetry (LS‐ASV) was employed for the determination of arsenic (III) without interference from Cu(II), Hg(II), and other coexisting metal ions. A lower detection limit of 0.057 µg L^?1 (S/N=3) were obtained with a accumulation time of 200 s. The proposed method was successfully applied to determine arsenic (III) in real water samples with satisfactory recoveries.     

Determination of Thallium at A Silver‐Gold Alloy Electrode by Voltammetric Methods in Plant Material and Bottom Sediment Containing Cd and Pb

The applicability of the subtractive anodic stripping voltammetry (SASV) using the square‐wave mode at the silver‐gold alloy electrode has been studied for thallium determination in the presence of large amount of lead and cadmium in natural samples. 10 mmol L^?1 perchloric acid was found as the most suitable supporting electrolyte for determination in synthetic solutions. The thallium peak was separated about 200 mV from Cd+Pb peak. Diethylenetriaminepentaacetic acid addition was necessary to determine thallium at the silver‐gold alloy electrode in digested plant and sediment. The determination limit was equal to 1.4 μg L^?1. The method was validated by the inter‐method comparison (ICP‐MS).     

Nafion‐Coated Bismuth Film Electrodes for the Determination of Trace Lead and Cadmium in Herbal Medicines by Anodic Stripping Voltammetry

A novel analytical procedure for the determination of Pb(II) and Cd(II) in herbal medicines by differential pulse anodic stripping voltammetry (DPASV) on Nafion‐coated bismuth film electrode (NCBFE) was proposed and experimentally validated. Various experimental parameters, which influenced the response of the NCBFE to these metals in real samples, were optimized. The results showed that there were well‐defined peaks of Pb and Cd in herb samples at deposition potential of ?1.2 V and deposition time of 300 s. The analytical performance of the NCBFE was evaluated in the presence of dissolved oxygen, with the determination limits of 0.35 µg·L^?1 for Pb and 0.72 µg·L^?1 for Cd and recoveries of 87.8% –105.4% for Pb and 89.5% –108.5% for Cd obtained from different samples. The Pb and Cd concentrations in the studied samples have been also determined by graphite furnace atomic absorption spectrometry (GFAAS), suggesting that there was a satisfactory agreement between the two techniques, with relative errors lower than 6.5% in all cases. The great advantages of the proposed method over the spectroscopic method were characterized by its simplicity, selectivity and short analysis time, simultaneous analysis of different metals and cost‐efficiency.     

Automated Determination of Cu(II), Pb(II), Cd(II) and Zn(II) in Environmental Samples by Square Wave Voltammetry Exploiting Sequential Injection Analysis and Screen Printed Electrodes

This paper describes the development of a methodology for quantification of Cu(II), Pb(II), Cd(II) and Zn(II) in waters and sediments by anodic stripping voltammetry (ASV) automated by Sequential Injection Analysis (SIA) using a graphite screen printed sensor modified with mercury. Determinations were made by standard addition automated by the SIA system. The limits of detection and quantification were, respectively, 1.3 and 4.3 µg L^?1 for Cu(II), 1.4 and 4.6 µg L^?1 for Pb(II), 0.6 and 1.8 µg L^?1 for Cd(II) and 4.2 and 14 µg L^?1 for Zn(II). These limits were obtained for a sample volume of 1000 µL, flow rate of 10 µL s^?1 (during the deposition step), and utilizing 3 flow reversals (volume of reversion=950 µL), totalizing a deposition time of 315 s. The potentiostat worked synchronically with the SIA system applying the conditioning potential of ?0.1 V vs. pseudo reference of Ag (100 s), deposition potential of ?1.0 V for Cu(II), Pb(II) and Cd(II) or ?1,3 V for Zn(II), square wave frequency of 100 Hz, potential step of 6 mV and pulse height of 40 mV. For quantification of Zn(II) in sediment extracts, deposition of Ga⁰ on the working electrode was necessary to avoid the formation of intermetallic between Zn⁰ and Cu⁰. The accuracy of the method was assessed by spike and recovery experiments in water samples which resulted recovery rates near 100 % of the spiked concentrations. Recoveries of concentrations in the certified sediment sample CRM‐701 undergoing the three steps sequential extraction procedure of BCR varied from 71.7 % for Zn(II) in the acetic acid extract to 112.4 % for Cu(II) in the oxidisable fraction, confirming that the standard addition approach corrected the matrix effects in the complex samples of sediment extracts.     

A Simple and Sensitive Method for the Detection of Trace Pb(II) and Cd(II) based on Nafion‐coated Antimony Film Electrode

Nafion‐coated antimony film electrode (NCAFE) was prepared in situ by simultaneously plated antimony with analytes, and applied to the determination of trace Pb(II) and Cd(II) in non‐deaerated solutions by differential pulse anodic stripping voltammetry (DPASV). Various experimental parameters, which influenced the response of the NCAFE to those metals, were thoroughly optimized and discussed. The results indicated that the sensitivity and resistance to surfactants at the NCAFE were remarkably improved with relative to the antimony film electrode (AFE). In the presence of 5 mg·L^?1 gelatin, the peak heights at the NCAFE showed 4‐fold enhancement for Pb and a 9‐fold enhancement for Cd over a bare AFE. Reproducibility of the sensor was satisfactory, and the relative standard deviations were 4.8% for 20 μg·L^?1 Pb and 3.2% for 25 μg·L^?1 Cd (n=15) with preconcentration time of 180 s. The determination limits (S/N=3) of this sensor were determined to be 0.15 μg·L^?1 for Pb and 0.30 μg·L^?1 for Cd with accumulation time of 300 s. The NCAFE was successfully applied to determining Pb(II) and Cd(II) in vegetable and water samples with satisfactory results.     

Simultaneous determination of Cd, Pb, Cu, Sb, Bi, Se, Zn, Mn, Ni, Co and Fe in water samples by differential pulse stripping voltammetry at a hanging mercury drop electrode

A highly sensitive and selective voltammetric procedure is described for the simultaneous determination of eleven elements (Cd, Pb, Cu, Sb, Bi, Se, Zn, Mn, Ni, Co and Fe) in water samples. Firstly, differential pulse anodic stripping voltammetry (DPASV) with a hanging mercury drop electrode (HMDE) is used for the direct simultaneous determination of Cd, Pb, Cu, Sb and Bi in 0.1 M HCI solution (pH = 1) containing 2 M NaCl. Then, differential pulse cathodic stripping voltammetry (DPCSV) is used for the determination of Se in the same solution. Zn is subsequently determined by DPASV after raising the pH of the same solution to pH 4. Next, the pH of the medium is raised to pH 8.5 by adding NH3/NH4Cl buffer solution for the determination of Mn by DPASV. Ni and Co are determined in the same solution by differential pulse adsorptive stripping voltammetry (DPAdSV) after adding DMG (1 x 10(-4) M). Finally, 1 x 10(-5) M 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) is added to the solution for the determination of Fe by DPAdSV. The optimal conditions are described. Relative standard deviations and relative errors are calculated for the eleven elements at three different concentration levels. The lower detection limits for the investigated elements range from 1.11 x 10(-10) to 1.05 x 10(-9)M, depending on the element determined. The proposed analysis scheme was applied for the determination of these eleven elements in some ground water samples.     

Square-Wave Anodic Stripping Voltammetry (SWASV) for the Determination of Ecotoxic Metals,Using a Bismuth-Film Electrode

This article reviews the use of square wave anodic stripping voltammetry for the simultaneous determination of ecotoxic metals (Pb, Cd, Cu, and Zn) on a bismuth-film (BiFE) electrode. The BiFE was prepared in situ on a glassy-carbon electrode (GCE) from the 0.1 mol L^?1 acetate buffer solution (pH 4.5) containing 200 µg L^?1 of bismuth (III). The addition of hydrogen peroxide to the electroanalytical cell proved beneficial for the interference-free determination of Cu (II) together with zinc, lead, and cadmium, using the BiFE. The experimental variables were investigated and optimized with the view to apply this type of voltammetric sensor to real samples containing traces of these metals. The performance characteristics, such as reproducibility, decision limit (CC_a), detection capability (CC_β), sensitivity, and accuracy indicated that the method holds promise for trace Cu²⁺, Pb²⁺, Cd²⁺, and Zn²⁺ levels by employment of Hg-free GCE with SWASV. CCa, and CCβ were calculated according to the Commission Decision of 12 August 2002 (2002/657/EC). Linearity was observed in the range 20–280 µg L^?1 for zinc, 10–100 µg L^?1 for lead, 10–80 µg L^?1 for copper, and 5–50 µg L^?1 for cadmium. Using the optimized conditions, the stripping performance of the BiFE was characterized by low limits of detection (LOD). Finally, the method was successfully applied in real as well as in certified reference water samples.