Amperometric L‐cysteine Sensor Using a Gold Electrode Modified with Thiolated Catechol

A thiolated catechol (CA) consisting of 1,6‐Hexanedithiol (HDT) and CA was modified on a gold (Au) electrode to obtain an amperometric L‐cysteine sensor with detection limit of 60.6 nM. The preparation of thiolated CA was conducted via a thiol addition between HDT and electro‐oxidized CA (EOCA). Briefly, the thiol addition reaction was accomplished by potential cycling of HDT/Au electrode in 0.1 M phosphate buffer (PB, pH 7.2) containing CA, and an EOCA‐HDT/Au electrode was produced. The obtained EOCA‐HDT/Au electrode exhibits a pair of well‐defined redox peaks (at 0.22/0.10 V) of o‐quinone moiety, which effectively mediates the oxidation of L‐cysteine in a 0.1 M PB (pH 7.2), with an over‐potential decrease by ca. 0.12 V (versus bare Au electrode). Electrochemical quartz crystal microbalance, cyclic voltammetry and surface‐enhanced Raman spectra were used to study relevant processes and/or film properties. The amperometric L‐cysteine sensor has good anti‐interferent ability and reproducibility. It also has acceptable recovery for detection of L‐cysteine in urine samples.     

Gold Electrode Modified with Self‐Assembled Monolayer of Cysteamine‐Functionalized MWCNT and Its Application in Simultaneous Determination of Dopamine and Uric Acid

The voltammetric behavior of dopamine (DA) and uric acid (UA) on a gold electrode modified with self‐assembled monolayer (SAM) of cysteamine (CA) conjugated with functionalized multiwalled carbon nanotubes (MWCNTs) was investigated. The film modifier of functionalized SAM was characterized by means of scanning electron microscopy (SEM) and also, electrochemical impedance spectroscopy (EIS) using para‐hydroquinone (PHQ) as a redox probe. For the binary mixture of DA and UA, the voltammetric signals of these two compounds can be well separated from each other, allowing simultaneous determination of DA and UA. The effect of various experimental parameters on the voltammetric responses of DA and UA was investigated. The detection limit in differential pulse voltammetric determinations was obtained as 0.02 µM and 0.1 µM for DA and UA, respectively. The prepared modified electrode indicated a stable behavior and the presence of surface COOH groups of the functionalized MWCNT avoided the passivation of the electrode surface during the electrode processes. The proposed method was successfully applied for the determination of DA and UA in urine samples with satisfactory results. The response of the gold electrode modified with MWCNT‐functionalized SAM method toward DA, UA, and ascorbic acid (AA) oxidation was compared with the response of the modified electrode prepared by the direct casting of MWCNT.     

Development of Nonenzymatic Benzoic Acid Detection on PdSn/GCE/Vulcan XC‐72R Prepared via Polyol Method

In this study a PdSn based sensor was developed for the determination of benzoic acid (BA) in foods. A carbon (Vulcan XC‐72R) supported PdSn catalyst was prepared via polyol method and its surface electronic and chemical properties were investigated by advanced surface analytical techniques such as scanning electron microscopy (SEM), X‐ray diffraction spectroscopy (XRD), X‐ray Photoelectron Spectroscopy (XPS), temperature‐programmed reduction with H₂ (TPR‐H₂) and transmission electron microscopy (TEM). Electrochemical measurements were performed by employing cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques on PdSn/GCE/Vulcan XC‐72R electrode. The developed sensor showed a wide linear range up to 10 mM with a 0.77 μM low limit of detection (LOD) as well as high stability. Further experiments were performed on food samples containing BA to achieve real sample measurements. For real sample measurements, PdSn/GCE/Vulcan XC‐72R electrode was used for the determination of BA in different kinds of samples such as mayonnaise, ketchup and carbonated beverages.     

Enhanced Electrocatalytic Activity of Ni‐CNT Nanocomposites for Simultaneous Determination of Epinephrine and Dopamine

A promising electrochemical sensor based nickel‐carbon nanotube (Ni‐CNT) modified on glassy carbon (GC) electrode had been developed and the properties of the modified electrode were characterized by multispectroscopic analysis. The fabricated sensor (GC/Ni‐CNT) electrode was utilized to determine the catecholamines such as epinephrine and dopamine simultaneously. Differential pulse voltammetry and amperometry were used to verify the electrochemical behavior of the studied compounds. The GC/Ni‐CNT based amperometric sensor showed a wide linear range and low detection limit with high analytical sensitivity of 8.31 and 6.61 μA μM^?1 for EP and DA, respectively which demonstrates better characteristics compared to other electrodes reported in the literature. Further, no significant change in amperometric current response was observed in presence of biological interference species such as glucose, cysteine, citric acid, uric acid and ascorbic acid in the detection of EP and DA. The utility of this GC/Ni‐CNT electrode was well established for the determination of EP and DA in human urine samples.     

Selective Electrochemical Determination of Dopamine with Molecularly Imprinted Poly(Carbazole‐co‐Aniline) Electrode Decorated with Gold Nanoparticles

Dopamine (DA) is a significant neurotransmitter in the central nervous system, coexisting with uric acid (UA) and ascorbic acid (AA). UA and AA are easily oxidizable compounds having potentials close to that of DA for electrochemical analysis, resulting in overlapping voltammetric response. In this work, a novel molecularly imprinted (MI) electrochemical sensor was proposed for selective determination of DA (in the presence of up to 80‐fold excess of UA and AA), relying on gold nanoparticles (Au_nano)‐decorated glassy carbon (GC) electrode coated with poly(carbazole (Cz)‐co‐aniline (ANI)) copolymer film incorporating DA as template (DA imprinted‐GC/P(Cz‐co‐ANI)‐Au_nano electrode, DA‐MIP‐Au_nano electrode). The DA recognizing sensor electrode showed great electroactivity for analyte oxidation in 0.2 mol L^?1 pH 7 phosphate buffer. Square wave voltammetry (SWV) was performed within 10^?4–10^?5 mol L^?1 of DA, of which the oxidation peak potential was observed at 0.16 V. The limit of detection (LOD) and limit of quantification (LOQ) were 2.0×10^?6 and 6.7×10^?6 mol L^?1, respectively. Binary and ternary synthetic mixtures of DA‐UA, DA‐AA and DA‐UA‐AA yielded excellent recoveries for DA. Additionally, DA was quantitatively recovered from a real sample of bovine serum spiked with DA, and determined in concentrated dopamine injection solution. The developed SWV method was statistically validated against a literature potentiodynamic method using a caffeic acid modified‐GC electrode.     

Electrochemical Characterization of Gold 6‐Amino‐2‐mercaptobenzothiazole Self‐Assembled Monolayer for Dopamine Detection in Pharmaceutical Samples

A new sensor, gold‐6‐amino‐2‐mercaptobenzothiazole (6A2MBT), was fabricated via a self‐assembly procedure. Electrochemical properties of the monolayer were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The modified electrode showed excellent antifouling property against the oxidation products of DA, allowed us to construct a dynamic calibration curve with two linear parts, 1.00×10^?6 to 3.72×10^?4 and 3.72×10^?4 to 6.42×10^?4 M DA, with correlation coefficients of 0.997 and 0.992 and a detection limit of 1.57×10^?7 M DA by using differential pulse voltammetry (DPV), respectively. Finally, the performance of the Au‐6A2MBT modified electrode was successfully tested for electrochemical detection of DA in a pharmaceutical sample.     

Gold Nanoparticles‐β‐Cyclodextrin‐Chitosan‐Graphene Modified Glassy Carbon Electrode for Ultrasensitive Detection of Dopamine and Uric Acid

The nanocomposite (denoted as GR‐AuNPs‐CD‐CS) of graphene (GR), gold nanoparticles (AuNPs), chitosan (CS) and β‐cyclodextrin (β‐CD) was prepared to modify a glassy carbon electrode. The as‐modified electrode was explored for the ultrasensitive detection of dopamine (DA) and uric acid (UA). The modified electrode demonstrated linearly increased current response in the concentration range of 0.1–120 µm for DA and 0.05–70 µm for UA, with so far the best detection limit for DA and UA. Good stability and repeatability were further demonstrated for the as‐made sensor.     

Selective Detection of Dopamine in Presence of Ascorbic Acid by Use of Glassy‐Carbon Electrode Modified with Amino‐β‐Cyclodextrin and Carbon Nanotubes

A glassy carbon electrode modified with per‐6‐amino‐β‐cyclodextrin (β‐CDNH₂) and functionalized single‐walled carbon nanotubes (SWCNT‐COOH) was elaborated. This structure was investigated for the detection of dopamine acid (DA) in presence of ascorbic acid (AA). The sensor behavior was studied by cyclic voltammetry, square wave voltammetry and electrochemical impedance spectroscopy. The analysis results show that the electrode modification with CD derivative improves the sensitivity and selectivity of the DA recognition; the electrochemical response was further improved by introduction of SWCNT‐COOH. The sensor shows good and reversible linear response toward DA within the concentration range of 7×10^?7–10^?4 M with a detection limit of 5×10^?7 M.     

Efficient Electrocatalytic Detection of Epinephrine at Gold Electrodes Modified with Self‐Assembled Metallo‐Octacarboxyphthalocyanine Complexes

Electrocatalysis of epinephrine at gold electrode pre‐modified with the self‐assembled monolayer of cysteamine and subsequently integrated with novel metallo‐octacarboxyphthalocyanine (MOCPc where M=Fe, Co and Mn) complexes (Au‐Cys‐MOCPc) was investigated. The electrodes showed response to the presence of epinephrine. The oxidation peak potential (E_p/V vs. Ag|AgCl, sat'd KCl) and charge transfer resistance (R_ct (kΩ)) in epinephrine solution depend markedly on the central metal of the phthalocyanine cores: Au‐Cys‐FeOCPck_ch=4.1×10⁷ M^?1 s^?1) which is higher than that of the Au‐cys‐CoOCPc or Au‐cys‐MnOCPc electrode. Mechanism, recognizing the mediation of the electrocatalytic process by the central M(II)/M(III) redox processes was proposed. Epinephrine electro‐oxidation at the Au‐cys‐FeOCPc electrode was studied in more details for the response characteristics. The diffusion coefficient of epinephrine was evaluated as (2.62±0.23)×10^?9 cm² s^?1. It was established that Au‐Cys‐FeOCPc is suitable for sensitive determination of epinephrine in physiological pH (7.40) conditions showing linear concentration range of up to 300 nM, with excellent sensitivity (0.53±0.01 nA nM^?1), and very low limits of detection (13.8 nM) and quantification (45.8 nM). The peak separation between ascorbic acid and epinephrine is large enough (190 mV) to permit simultaneous determination of both epinephrine and ascorbic acid in physiological pH 7.4 conditions using the Au‐cys‐FeOCPc electrode. Au‐cys‐FeOCPc electrode was successfully used for the determination of epinephrine in epinephrine hydrochloric acid injection with recovery of ca. 98.4%.     

Voltammetric Study of Methylene Blue at Thiol SAMs‐Modified Gold Electrodes

The voltammetric behavior of methylene blue (MB) at thiol self‐assembled monolayers modified gold electrodes (SAMs/Au) has been investigated. MB exhibited a redox peak at about ?0.35 V (vs.SCE) in alkaline solution at bare gold electrodes. When the gold electrodes were modified with thiol SAMs, the peak grew due to the accumulation of MB at SAMs. With the solution pH rising, more MB was accumulated, hence the peak height increased, which differed from that at bare gold electrodes. The electrode process at SAMs/Au featured the characteristics of adsorption and/or electrode reaction controlled. The enhancing action of glutathione monolayer (GSH SAM), 3‐mercaptopropionic acid monolayer (3MPA SAM) and other thiol SAMs was compared. Among these, GSH SAM made the MB peak increase more. At GSH SAM/Au, the peak height varied linearly with MB concentration over the range of 2 μM to 400 μM. So this can be developed for the determination of MB and studies concerned. The accumulation behavior caused by GSH SAM and native fish sperm dsDNA was compared. The interaction between DNA and MB was also discussed under this condition.     

A Sensitive Electrochemical Sensor for Voltammetric Determination of Ganciclovir Based on Au‐ZnS Nanocomposite

An electrode modified with ZnS and gold nanoparticles (Au‐ZnS NPs) is introduced for highly sensitive voltammetric determination of ganciclovir (GCV). Surface structure and topography of the modified electrode was studied by SEM, EDX and XRD techniques. Electrochemical oxidation of GCV was investigated by cyclic (CV) and square wave voltammetry (SWV) in Briton‐Robinson buffer solution (pH 1.5). The results showed that electrochemical oxidation of GCV at the Au‐ZnS modified glassy carbon electrode (GCE) is irreversible and exhibited diffusion controlled electrode process over the pH range from 1.0 to 6.0. The oxidation potential peak and pH relationship showed that electrons and protons were transferred simultaneously over the electrochemical oxidation process. Using the proposed sensor, the linear calibration curves were obtained in the ranges of 0.04–1.50 μM and 1.5–70.0 μM with detection limit of 0.01 μM GCV by SWV technique. The modified electrode was successfully applied as a sensitive, reproducible and repeatable sensor for determination of the trace amount of GCV in human serum, urine and cymevene vials. Reasonable results were obtained from comparing the measurements of the real samples by the new sensor to high performance liquid chromatography (HPLC) as a standard method.     

A Host‐Guest‐Recognition‐Based Electrochemical Sensor for Sequence‐Specific DNA Detection

We herein constructed a sensor that converts target DNA hybridization‐induced conformational transformation of the probe DNA to electrochemical response based on host‐guest recognition and nanoparticle label. In the sensor, the hairpin DNA terminal‐labeled with 4‐((4‐(dimethylamino)phenyl)azo)benzoic acid (dabcyl) and thiol group was immobilized on Au electrode surface as the probe DNA by Au‐S bond, and the CdS nanoparticles surface‐modified with β‐cyclodextrins (CdS‐CDs) were employed as electrochemical signal provider and host‐guest recognition element. Initially, the probe DNA immobilized on electrode kept the stem‐loop configuration, which shielded dabcyl from docking with the CdS‐CDs in solution due to the steric effect. After target hybridization, the probe DNA underwent a significant conformational change, which forced dabcyl away from the electrode. As a result, formerly‐shielded dabcyl became accessible to host‐guest recognition between β‐cyclodextrin (β‐CD) and dabcyl, thus the target hybridization event could be sensitively transduced to electrochemical signal provided by CdS‐CDs. This host‐guest recognition‐based electrochemical sensor has been able to detect as low as picomolar DNA target with excellent differentiation ability for even single mismatch.     

Highly Sensitive and Selective Determination of Dopamine Based on Graphite Nanosheet‐Nafion Composite Film Modified Electrode

A graphite nanosheet (GNS)‐Nafion modified glassy carbon (GC) electrode was prepared and used for highly sensitive and selective determination of dopamine (DA). The GNS‐Nafion/GC electrode displayed excellent electrocatalytic activities towards DA and ascorbic acid (AA). The selective determination of DA was carried out successfully in the presence of AA by differential pulse voltammetry. High sensitivity (3.695 μA μM^?1) and low detection limit (0.02 μM, S/N=3) for the DA detection were obtained. These good properties can be attributed to a large amount of edge plane defects presented on GNSs and the charge‐exclusion and concentration features of Nafion.     

2,2‐Bis(3‐Amino‐4‐hydroxyphenyl)hexafluoropropane Modified Glassy Carbon Electrodes as Selective and Sensitive Voltammetric Sensors. Selective Detection of Dopamine and Uric Acid

2,2‐bis(3‐Amino‐4‐hydroxyphenyl)hexafluoropropane (BAHHFP) was electro‐polymerized oxidatively on glassy carbon by cyclic voltammetry. The activity of the modified electrode towards ascorbic acid (AA), uric acid (UA) and dopamine (DA) was characterized with cyclic voltammetry and differential puls voltammetry (DPV). The findings showed that the electrode modification drastically suppresses the response of AA and shifts it towards more negative potentials. Simultaneously an enhancement of reaction reversibility is seen for DA and UA. Unusual, selective preconcentration features are observed for DA when the polymer‐modified electrode is polarized at negative potential. In a ternary mixture containing the three analytes studied, three baseline resolved peaks are observed in DPV mode. At physiological pH 7.4, after 5 min preconcentration at ?300 mV, peaks positions were ?0.073, 0.131 and 0.280 V (vs. Ag/AgCl) for AA, DA and UA, respectively. Relative selectivities DA/AA and UA/AA were over 4000 : 1 and 700 : 1, respectively. DA response was linear in the range 0.05–3 μM with sensitivity of 138 μA μM^?1 cm^?2 and detection limit (3σ) of 5 nM. Sensitive quantification of UA was possible in acidic solution (pH 1.8). Under such conditions a very sharp peak appeared at 630 mV (DPV). The response was linear in the range 0.5–100 μM with sensitivity of 4.67 μA μM^?1 cm^?2 and detection limit (3σ) of 0.1 μM. Practical utility was illustrated by selective determination of UA in human urine.     

Simultaneous Determination of Ascorbic Acid,Dopamine and Uric Acid Based on Gold Nanoparticles‐PTCA‐Cys Composites Modified Electrodes

In this study, a nanocomposite of 3, 4, 9, 10‐perylenetetracarboxylic acid and L‐cysteine (PTCA‐Cys) with satisfactory water‐solubility and film‐forming ability was prepared and worked as substrate for modifying the glassy carbon electrode. Then, gold nanoparticles (AuNPs) were immobilized to achieve a PTCA‐Cys‐AuNPs modified electrode which provided more reaction positions on the sensor. Scanning electron microscopy, transmission electron microscopy, cyclic voltammetry and different pulse voltammetry were employed to characterize the assembly process of the sensor. The constructed sensor displayed desirable sensitivity, selectivity and stability towards the simultaneous detection of ascorbic acid (AA), dopamine (DA) and uric acid (UA). Under the optimal experimental conditions, the oxidation peaks of AA, DA and UA appeared at 64, 240 and 376 mV, respectively. The corresponding linear response ranges were 3.2–435, 0.04–100 and 0.80–297 μM, and the detection limits were 1.1, 0.010 and 0.27 μM (S/N=3), respectively.     

A Novel Electrochemical Sensor Based on Copper‐based Metal‐Organic Framework for the Determination of Dopamine

A glassy carbon electrode (GCE) modified with a copper‐based metal‐organic framework (MOF) [HKUST‐1, HKUST‐1 = Cu₃(BTC)₂ (BTC = 1,3,5‐benzenetricarboxylicacid)] was developed as a highly sensitive and simple electrochemical sensor for the determination of dopamine (DA). The MOF was prepared by a hydrothermal process, and the morphology and crystal phase of the MOF were characterized by scanning electron microscopy (SEM) and X‐ray diffraction (XRD), respectively. Meanwhile, the electrochemical performance was investigated using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). Under optimized conditions, the modified electrode showed excellent electrocatalytic activity and high selectivity toward DA. The linear response range was from 5.0 × 10⁻⁷ to 1.0 × 10⁻⁴ M and the detection limit was as low as 1.5 × 10⁻⁷ M. Moreover, the electrochemical sensor was used to detect DA in real samples with excellent results. MOF‐based sensors hold great promise for routine sensing applications in the field of electrochemical sensing.     

Immunosensors Based on Layer‐by‐Layer Self‐Assembled Au Colloidal Electrode for the Electrochemical Detection of Antigen

Colloidal Au particles have been deposited on the gold electrode through layer‐by‐layer self‐assembly using cysteamine as cross‐linkers. Self‐assembly of colloidal Au on the gold electrode resulted in an easier attachment of antibody, larger electrode surface and ideal electrode behavior. The redox reactions of [Fe(CN)₆]^4?/[Fe(CN)₆]^3? on the gold surface were blocked due to antibody immobilization, which were investigated by cyclic voltammetry and impedance spectroscopy. The interaction of antigen with grafted antibody recognition layers was carried out by soaking the modified electrode into a phosphate buffer at pH 7.0 with various concentrations of antigen at 37 °C for 30 min. Further, an amplification strategy to use biotin conjugated antibody was introduced for improving the sensitivity of impedance measurements. Thus, the sensor based on this immobilization method exhibits a large linear dynamic range, from 5–400 μg/L for detection of Human IgG. The detection limit is about 0.5 μg/L.     

An Impedimetric Aptasensor Based on a Novel Line‐Pad‐Line Electrode for the Determination of VEGF165

In this work, a novel, simple and label‐free line‐pad‐line electrode (LPLE) biosensor was developed for detection of vascular endothelial growth factor (VEGF₁₆₅). DNA aptamer was used as a recognition element for high specificity to VEGF₁₆₅, and original LPLE as the substrate electrode for high sensitivity of the biosensor. This sensor was prepared by immobilizing anti‐VEGF₁₆₅ aptamers on the LPLE surface through gold‐sulfur (Au?S) bonding. Upon the addition of VEGF₁₆₅, a large target‐induced conformational change in the surface‐immobilized aptamer was generated and caused variations in the interfacial properties,which led to a corresponding increase in the impedance magnitude of the LPLE. Finally, our results demonstrate that the calibration curve for VEGF₁₆₅determination was linear over the range of 0.026‐31.4 fM with a detection limit as low as 0.017 fM.Additionally, our sensor was fabricated on printed circuit board (PCB) with a new electrode construction, and can potentially be implemented with the advantages of simplicity, low‐cost and easy mass production. Besides, considering its desirable sensitivity and specificity, the proposed use of LPLE provided a promising strategy for a wide variety of sensing applications.     

Gold‐Iron Bimetallic Nanoparticles Impregnated Reduced Graphene Oxide Based Nanosensor for Label‐free Detection of Biomarker Related to Non‐alcoholic Fatty Liver Disease

We report for the first time a microwave assisted, one pot, direct, and facile synthesis of monodispersed iron‐gold bimetallic nanoparticles (BNP_Au‐Fe) using glucose as a reducing agent in merely 90 s. The as such synthesized BNP_Au‐Fe were thoroughly characterized using UV‐Vis, XRD, TEM, EDX, elemental mapping, and raman spectroscopy. These BNP_Au‐Fe were further impregnated with reduced graphene oxide (rGO) and coated onto glassy carbon electrode (GCE) to develop a sensor probe for label free electrochemical detection of acetaminophen, which is considered to be a most potent biomarker related to non‐alcoholic fatty liver disease. The sensor probe was systematically characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The BNP_Au‐Fe‐rGO nanocomposite matrix showed the sensing of acetaminophen with a wide dynamic range between 50 and 800 nM with detection limit (DL) of 0.14 nM (±0.05) nM (RSD<4.12 %) that was lower compared to previously reported acetaminophen sensors. To show the practical application of the sensor probe, acetaminophen was detected in human urine samples, which showed the percentage recovery between 86.65 % and 91.32 %. To the best of our knowledge, this is the first report where BNP_Au‐Fe impregnated rGO was used to detect acetaminophen. Interferences due to various molecules such as glucose, serum albumin, glycine, glutamic acid, alanine, citric acid, and ascorbic acid were tested individually and in mixed sample. Long‐term stability of sensor probe was examined which was found to be stable up to 12 weeks. The sensor fabricated using BNP_Au‐Fe‐rGO nanocomposite has many attractive features such as; simplicity, rapidity, and label free detection, hence it could be a method of choice for acetaminophen detection in clinical settings.     

Construction of a Highly Selective and Sensitive La(III) Sensor Based on N‐(2‐Pyridyl)‐N′‐(4‐methoxyphenyl)‐thiourea for Nano Level Monitoring of La(III) Ions

N‐(2‐Pyridyl)‐N′‐(4‐methoxyphenyl)‐thiourea (PMPT) was found to be a suitable neutral ion carrier for the construction of a highly selective and sensitive La(III) membrane sensor. Poly(vinyl chloride) (PVC) based membranes of PMPT with potassium tetrakis (p‐chlorophenyl) borate (KTpClPB) as an anionic excluder and oleic acid (OA), dibutyl phthalate (DBP), benzyl acetate (BA) and o‐nitrophenyloctyl ether (NPOE) as plasticizing solvent mediators were constructed and investigated as La(III) membrane sensors. A membrane composed of PMPT‐PVC‐KTpClPB‐BA with the ratio 8.0 : 35.0 : 3.0 : 54.0 works well over a very wide concentration range (4.0×10^?8 to 1.0×10^?1 M) with a Nernstian slope of 19.6±0.2 mV per decade of activity between pH values of 4.0 and 9.0. The detection limit of the sensor was calculated to be 2.0×10^?8 M (ca. 3.0 ppb). The sensor displays very good discrimination toward La(III) ions with regard to most common metal ions and lanthanide ions. The proposed sensor shows a short response time for whole concentration range (ca. 12 s). For evaluation of the analytical applicability of the La(III) sensor, it was successfully used as an indicator electrode for the titration of La(III) ions with EDTA. It was also applied to the determination of fluoride content of two mouth wash preparation samples and monitoring of La(III) ions in some binary and ternary mixtures.