Electrocatalytic Reduction Of Nitrite Research Articles

A novel and simple electrochemical sensor for electrocatalytic reduction of nitrite and oxidation of phenylhydrazine based on poly (o-anisidine) film using ionic liquid carbon paste electrode

In this study, nitrite electroreduction and phenylhydrazine electrooxidation were investigated on poly(o-anisidine) formed by cyclic voltammetry at the surface of ionic liquid carbon paste electrode. The films were characterized by cyclic voltammetry and scanning electron microscopy (SEM) and were contrasted with poly(o-anisidine) prepared under identical conditions in the absence of ionic liquid in carbon paste electrode. This carbon paste modified electrode exhibits a good electrocatalytic capability (via an EC’ mechanism) for both electrooxidation and electroreduction of some important molecules. The obtained results showed that the catalytic oxidation peak currents of phenylhydrazine and catalytic reduction peak currents of nitrite at the surface of this simple (unfunctionalized) polymeric electrode were linearly dependent on their concentrations. Electrode was successfully applied for determination of nitrite and phenylhydrazine in real samples.

A new Wells-Dawson polyoxometalate-based metal-organic hybrid decorated by the flexible bis-pyridyl-bis-amide ligand

A new Wells-Dawson polyoxometalate-based compound, H[Cu(L) 2 (P 2 W 18 O 62 ) 0.5 ]·~ 3H 2 O ( 1 ) (L = N,N′-bis(3-pyridinecarboxamide)-1,6- hexane), has been hydrothermally synthesized. Compound 1 is a 2D network based on [P 2 W 18 O 62 ] 6 − polyanion and nonparallel 1D Cu(L) 2 polymer chain constructed from two types of bi-nuclear circles alternately arraying with the dihedral angle of 34.75°. Compound 1 represents the first example of 2D Wells-Dawson POM-based compound constructed from the flexible bis-pyridyl-bis-amide ligand. Moreover, the electrochemical behavior, luminescent property and photocatalytic activity of 1 have been investigated. By introducing the N,N′-bis(3-pyridinecarboxamide)-1,6-hexane (L) in Wells-Dawson type polyoxometalate system, a new 2D inorganic–organic hybrid H[Cu(L) 2 (P 2 W 18 O 62 ) 0.5 ]·~ 3H 2 O was obtained, which represents the first example by combining the Wells-Dawson polyoxometalate with the flexible bis-pyridyl-bis-amide ligand. The title compound shows excellent activity in electrocatalytic reduction of nitrite and photocatalytic degradation of MB. ► Flexible bis-pyridyl-bis-amide was first introduced into the Wells-Dawson POM system. ► A new 2D inorganic–organic hybrid was constructed from [P 2 W 18 O 62 ] 6 − and 1D Cu(L) 2 chain. ► The 1D Cu(L) 2 chain is formed by the alternate arrangement of two types of bi-nuclear circles. ► The compound shows excellent electrocatalytic and photocatalytic activities.

Electrochemical detection of nitrite based on the polythionine/carbon nanotube modified electrode

In this paper, thionine was electro-polymerized onto the surface of carbon nanotube (CNT)-modified glassy carbon (GC) to fabricate the polythionine (PTH)/CNT/GC electrode. It was found that the electro-reduction current of nitrite was enhanced greatly at the PTH/CNT/GC electrode. It may be demonstrated that PTH was used as a mediator for electrocatalytic reduction of nitrite, and CNTs as an excellent nanomaterial can improve the electron transfer between the electrode and nitrite. Therefore, based on the synergic effect of PTH and CNTs, the PTH/CNT/GC electrode was employed to detect nitrite, and the high sensitivity of 5.81μAmM−1, and the detection limit of 1.4×10−6M were obtained. Besides, the modified electrode showed an inherent stability, fast response time, and good anti-interference ability. These suggested that the PTH/CNT/GC electrode was favorable and reliable for the detection of nitrite.

Electrocatalytic reduction of nitrite on transition and coinage metals

A systematic comparison of the electrochemical reduction of nitrite at polycrystalline metals has been carried out. In acidic media, solution-phase NO from HNO2 decomposition is converted to N2O by all noble metals in a common potential range for most metals (0.2–0.5V vs. RHE). Transition metals can also convert HNO2 directly to hydrogenated products (NH3OH+, NH4+) at lower potentials, while coinage metals (Ag, Au, Cu) feature a stepwise reduction to NO and N2O, which can be both detected by on-line mass spectrometry. The reduction of nitrite ions in alkaline media never yields gaseous products; the first electron transfer to give adsorbed NO is the rate-determining step for all noble metals. Coinage metals are largely inactive, except for Cu. The selectivity and electrocatalytic trends have been interpreted on the basis of DFT calculations of the metal–NO interaction available in the literature. In agreement with the Sabatier principle, metals with an intermediate affinity to NO are the most reactive and show the lowest tendency to poisoning. Coinage metals are a special case because of their weak NO adsorption and the formation of NO dimers.

Carbon Nanotubes-Doped Glassy Carbon Ceramic Composite Electrode and its Electrocatalytic Reduction of Nitrite

A conductive glassy carbon ceramic composite electrode (GCCE) comprised of multi-walled carbon nanotubes (MWNTs) and glassy carbon microparticles in an organically modified silicate matrix was fabricated using a sol-gel method. The electrode thus prepared exhibits electrocatalytic behavior to the reduction of nitrite and facilitates the detection of nitrite at an applied potential of 0.0 V. A linear range from 2.5×10-5 to 3×10-3 M for the detection of sodium nitrite has been observed at the composite electrode with a sensitivity of 9.6 μA/mM and a detection limit of 9×10-6 M based on a signal-to-noise ratio of 3.

Electrocatalytic reduction of nitrite on tetraruthenated metalloporphyrins/Nafion glassy carbon modified electrode

This paper describes the electrochemical reduction of nitrite ion in neutral aqueous solution mediated by tetraruthenated metalloporphyrins (Co(II), Ni(II) and Zn(II)) electrostatically assembled onto a Nafion film previously adsorbed on glassy carbon or ITO electrodes. Scanning electron microscope (SEM-EDX) and transmission electron microscopy (TEM) results have shown that on ITO electrodes the macrocycles forms multiple layers with a disordered stacking orientation over the Nafion film occupying hydrophobic and hydrophilic sites in the polyelectrolyte. Atomic force microscopy (AFM) results demonstrated that the Nafion film is 35 nm thick and tetraruthenated metalloporphyrins layers 190 nm thick presenting a thin but compacted morphology. Scanning electrochemical microscopy (SECM) images shows that the Co(II) tetraruthenated porphyrins/Nf/GC modified electrode is more electrochemically active than their Ni and Zn analogues. These modified electrodes are able to reduce nitrite at −660 mV showing enhanced reduction current and a decrease in the required overpotential compared to bare glassy carbon electrode. Controlled potential electrolysis experiments verify the production of ammonia, hydrazine and hydroxylamine at potentials where reduction of solvent is plausible demonstrating some selectivity toward the nitrite ion. Rotating disc electrode voltammetry shows that the factor that governs the kinetics of nitrite reduction is the charge propagation in the film.

Polyoxometalates–Directed Assembly of Inorganic–Organic Hybrid Compounds with Copper Multinuclear Nano-cluster Based on Flexible Double Tetrazole-based Thioether

Two new inorganic–organic hybrid compounds constructed from different polyoxometalates (POMs) and copper multinuclear clusters, [Cu(bmte)(H2Mo8O26)0.5]·3H2O (1) and [Cu3(bmte)3(HSiMo12O40)]·H2O (2) (bmte = 1,2-bis(1-methyl-5-mercapto-1,2,3,4-tetrazole)ethane), have been synthesized under hydrothermal conditions with a flexible double tetrazole-based thioether and characterized by IR, TG and single-crystal X-ray diffraction analyses. In compound 1, two bmte ligands chelate two CuI ions with three N atoms to form a binuclear nano-scale subunit [Cu2(bmte)2]2+, then the binuclear CuI subunits are connected by [Mo8O26]4− anions to build a one dimensional (1D) chain. In compound 2, a trinuclear nano-scale subunit [Cu3(bmte)3]3+ constructed from three CuI ions and three bmte ligands has been obtained, and the adjacent trinuclear subunits are linked by [SiMo12O40]4− anions to form a “zipper” 1D chain. The adjacent chains of the title compounds are ultimately extended into 2D layers by hydrogen bonds between bmte and POMs. The structural difference of the two compounds indicates that the POMs play an important structure-directed role on the final networks. In addition, the electrochemical behavior of 2-modified carbon paste electrode (2-CPE) and its electrocatalytic reduction of nitrite have been discussed.

Electrocatalytic reduction of nitrite on a polycrystalline rhodium electrode

This paper addresses the mechanism of the electrochemical reduction of HNO 2 and NO 2 - on polycrystalline rhodium. Intermediates and/or reaction products were detected by means of various (combined) techniques: rotating ring-disk voltammetry (for NH 2OH detection), online electrochemical mass spectrometry (for volatile products) and transfer experiments (for NO ads). In acidic media, HNO 2 depletion due to homogeneous-phase reactions generates dissolved NO: the latter species can be adsorbed at Rh and is reduced to N 2O when 0.3 < E < 0.5 V (vs. RHE), while HNO 2 is reduced in a diffusion-limited wave to mainly NH 3 at potentials preceding hydrogen evolution. In alkaline media, the predominant product for the reduction of NO 2 - when E < 0.2 V is still NH 3, which can poison the electrode via dehydrogenation to NH x ,ads species. For more positive potentials, reduction still occurs via NO ads and stops at NH 2OH for E > 0.3 V. The behavior of Rh is compared to Pt and explained in terms of general properties of these metals. A mechanistic scheme including NO, HNO 2 and NO 2 - is discussed.

Effect of silver nanoelectrode ensembles on the electrocatalytic reduction of NO 2− by zinc phthalocyanine

Ag nanoparticles anchored on mesoporous silica materials with and without zinc phthalocyanine (ZnPc) were prepared (Ag-MPS and Ag-MPS-ZnPc respectively). The morphology, structure and composition of the materials were characterized by transmission electron microscopy, X-ray diffraction, UV/vis diffuse reflectance spectra, and X-ray photoelectron spectroscopy techniques. The new materials were used for electrode modification and the nanoelectrode ensemble (NEE) behavior of Ag-MPS and Ag-MPS-ZnPc materials was semi-quantitatively evaluated by cyclic voltammetry. Further, electrocatalytic reduction of nitrite is demonstrated at these NEE.

As 8W 48O 184] 40−, a new crown-shaped heteropolyanion: Electrochemistry and electrocatalytic properties towards reduction of nitrite

The electrochemical behavior of the new crown-shaped heteropolyanion [As 8W 48O 184] 40− was investigated. Compared to the analogous complex [P 8W 48O 184] 40−, [As 8W 48O 184] 40− displayed a close similar behavior. As previously reported for [P 8W 48O 184] 40−, [As 8W 48O 184] 40− is found to be stable in a large range of pH, roughly from 0 to 8 and found to be slightly more soluble than [P 8W 48O 184] 40−. Comparison between the cyclic voltammetry curves of the two complexes reveals that the potentials of the redox waves of [As 8W 48O 184] 40− are slightly shifted towards the positive values. Contrary to the high dependence of [P 8W 48O 184] 40− to buffer capacity of the supporting electrolyte, interestingly, [As 8W 48O 184] 40− displays less sensitivity. The numerous possibilities for chemical applications opened up by the electrochemistry of this new complex are exemplified here by the good linear relationship between the peak potentials of the redox waves as a function of pH and, by the electrocatalytic reduction of nitrite.

Rational Synthesis, Structure, Magnetism and Electrochemistry of Mixed Iron–Nickel‐Containing Wells–Dawson‐Fragment‐Based Sandwich‐Type Polyoxometalates

AbstractThe compound [Na2(H2O)2Ni2(As2W15O56)2]18–, Ni2As4, was synthesized and structurally characterized for the first time by X‐ray crystallography. This complex reacts with FeIII to form two new mixed‐metal sandwich‐type complexes, [Fe2(H2O)2Ni2(As2W15O56)2]14–, Fe2_Ni2As4, and [Fe(H2O)Ni(H2O)Ni2(As2W15O56)2]15–, FeNi_Ni2As4. In comparison, the synthesis of the previously reported complex [Na2(H2O)2Fe2(As2W15O56)2]16–, Fe2As4, was rationalized and improved, and the incorporation of NiII into the latter compound leads to the new mixed‐metal complex [Ni2(H2O)2Fe2(As2W15O56)2]14–, Ni2_Fe2As4. Complete characterization of these complexes by FTIR, UV/Vis, elemental analysis, magnetic measurements and X‐ray crystallography, wherever possible, clearly defined their electronic and structural properties. These complexes undergo multiple electron‐transfer processes and are effective in the electrocatalytic reduction of nitrite, dioxygen and hydrogen peroxide.(© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2009)

Electrocatalytic Nitrite Reduction to Nitrogen Oxide by a Synthetic Analogue of the Active Site of Cu‐Containing Nitrite Reductase Incorporated in Nafion Film

AbstractThe electrocatalytic reduction of nitrite to NO by [CuMe2bpa(H2O)(ClO4)]+ (1), which is a model for the active site of copper‐containing nitrite reductase, incorporated in Nafion film was investigated. The Cu complex in the Nafion matrix exhibits an intense band at 267 nm and a broad band around 680 nm, assigned to d–d and ligand field transitions, respectively. The 77‐K EPR spectrum of 1 in the Nafion matrix reveals the typical axial signals (g//=2.28, g$\rm{_\perp}$=2.08, A//=13.3 mT) of a tetragonal Cu2+ chromophore. The redox potential, which is related to the Cu+/Cu2+ couple, was −146 mV (ΔE=72 mV) at pH 5.5. The redox reaction of 1 in Nafion was not dependent on pH and was a diffusion‐controlled process. The electronic structure and redox properties of 1 in the negatively charged polymer matrix were almost the same as those in aqueous solution. In the presence of nitrite, an increase in the cathodic current was observed in the cyclic voltammogram of 1 in the Nafion matrix. The current increase was dependent on the nitrite concentration and pH in solution. Upon reaching −400 mV, a linear generation of NO was observed for the 1/Nafion film coated electrode. The relationship between the rate of NO generation and the nitrite concentration in solution was analyzed with the Michaelis–Menten equation, where Vmax=45.1 nM s−1 and Km=15.8 mM at pH 5.5. The Cu complex serves the function of both the catalyst and electron transport in the Nafion matrix. The sensitivity of the electrode was estimated to be 3.23 μA mM−1 in the range of 0.1–0.4 mM nitrite.

2D Rhombus-grid networks constructed from vanadium-substituted Keggin-type polyoxomolybdophosphates and Cd/Zn complex fragments

Two 2D rhombic grid-like organic–inorganic hybrid compounds [{M(2,2′-bpy) 2} 2{PMo 11VO 40}] (M = Cd( 1), Zn( 2); bpy = 2,2′-bipyridine) have been hydrothermally synthesized and characterized by elemental analysis, IR spectroscopy, TG analysis, luminescence spectroscopy, X-ray powder diffraction and single-crystal X-ray diffraction. They are isomorphic and their structures can be considered that the Keggin-heteropolyanion [PMo 11VO 40] 4− are bridged by {M(2,2′-bpy) 2} groups through the O–M–O bridges into a 2D covalent network. It is noteworthy that the adjacent layers stack each other to form 3D supermolecular structure via extended C–H⋯O interaction between Keggin-anions and 2,2′-bpy ligands of different layers. Furthermore, the electrochemical behavior of 1-CPE ( 1-modified carbon paste electrode) and 2-CPE and their electrocatalytic reduction of nitrite were investigated.

Size-dependent electrocatalytic reduction of nitrite at nanostructured films of hollow polyaniline spheres and polyaniline–polystyrene core–shells

Nanostructured films of the conducting polymer polyaniline (PANI) were prepared by its potentiostatic polymerization in the presence of thin polystyrene (PS) nanoparticle templates. Two sizes of PS nanoparticles were used (50 and 100 nm) and electron microscopic analysis showed that core–shell composite films of PANI (PANI–PS 50 and PANI–PS 100) and, following removal of the PS, hollow structures (PANI 50 and PANI 100) were formed due to the growth mechanism of PANI around the PS templates. The electrochemical behaviour of the PANI-modified electrodes was studied by cyclic voltammetry, chronocoulometry and amperometry in the presence of nitrite and it was found that nitrite reduction was enhanced by the nanostructuring of the films. The electrocatalysis was dependent on the size of the template, being more pronounced at 50 nm than at 100 nm. The hollow PANI 50 film was also a better catalyst than PANI–PS 50, whereas for structures based on 100 nm templates, the composite film was better. Such behaviour could be explained in terms of larger surface area and surface concentration of PANI 50 and PANI–PS 50 films on the electrodes and by higher differential capacitance of those films.

Electroreduction of nitrite to nitrogen oxide by a copper-containing nitrite reductase model complex incorporated into collagen film

The electrocatalytic reduction of nitrite to NO by CuMe 2bpaCl 2, which is a model for the active site of copper-containing nitrite reductase, incorporated into collagen film was investigated. The 77-K EPR spectrum of CuMe 2bpaCl 2 in the collagen matrix revealed the typical axial signals ( g // = 2.26, g ⊥ = 2.05, A // = 16.4 mT) of a tetragonal Cu 2+ chromophore. The redox potential, which is related to the Cu +/Cu 2+ couple, was − 63 mV ( ∆E = 72 mV) at pH 5.5. In the presence of nitrite, an increase in the cathodic current was observed in the cyclic voltammogram of CuMe 2bpaCl 2 in the collagen matrix. Upon reaching − 300 mV, a linear generation of NO was observed for the CuMe 2bpaCl 2/collagen film-coated electrode. The relationship between the rate of NO generation and the nitrite concentration in solution was analyzed using the Michaelis–Menten equation, where V max = 3.16 nM s − 1 and K m = 1.1 mM at pH 5.5. The current increase and the reaction rate were dependent on the pH of the solution. The mechanism of nitrite reduction by the copper complex in the collagen matrix was the same mechanism as that of the enzyme in aqueous solution.

Electropolymerization of N-methylaniline in the presence of sodium dodecylsulfate and its application for electrocatalytic reduction of nitrite

Poly(N-methylaniline) (PNMA) films were electrosynthesized on carbon paste electrode by oxidation of N-methylaniline (NMA) in acidic aqueous solution and in the presence of anionic surfactant. The films were characterized by cyclic voltammetry and scanning electron microscopy (SEM) and were contrasted with PNMA prepared under identical conditions in the absence of surfactant. The cyclic voltammograms of the film indicate a good redox behavior. Also, SEM studies show that the presence of the anionic surfactant strongly influences the morphology of the polymer product. This polymeric modified electrode has a very good activity toward the nitrite electroreduction via a EC′ mechanism. The electrocatalytic reduction peak current is linearly dependent on the concentration of nitrite. The good linearity between the electroreduction peak current and the concentration of nitrite makes it possible to determine nitrite concentration accurately in the range of 1 × 10−4 to 1.8 × 10−2 M.

The Fabrication of Structurally Multiordered Polyaniline Films and Their Application in Electrochemical Sensing and Biosensing

AbstractStructurally multiordered thin films composed of conducting polymer polyaniline (PANI) were fabricated on home‐made screen‐printed carbon electrodes (SPEs). Formation of monolayered sulfate‐ or amine‐modified PS templates on bulk polyaniline was assisted by various polyelectrolytes – negatively charged poly(sodium 4‐styrenesulfonate) (PSS) and positively charged poly(diallyldimethylammonium chloride) (PDDA). Additional layers of PANI with controlled thickness were electrodeposited on the templated PANI‐SPEs. Different morphologies of the outermost PANI films were obtained including PS‐PANI core‐shell and PS‐PANI composites. It is shown that the surface charge of PS templates determines different mechanisms of polymer growth, which results in the above structures. The fact that nanostructured PANI films are grown on bulk PANI significantly increases the surface area and enhances the catalytic properties of such films. Removal of template particles by dissolving in toluene resulted in PANI hollow spheres and dimpled, semi‐porous PANI films, respectively. As‐prepared electrodes were used for the electrocatalytic reduction of nitrite. Upon further modifications with horseradish peroxidase, a biosensor was developed which could be used for the amperometric determination of H2O2. In the case of both analytes, catalytic responses were obtained only on multiordered PANI films. Difference in responses have been explained in terms of different morphologies and the different thickness of the outermost layers of PANI.

Synthesis and Electrochemical Properties of a New 1D Organic–Inorganic Hybrid Compound Based on Keggin-Type Heteropolyanions and Isopolyanions Decorated by Transition Metal Fragments

A new chain-like organic–inorganic hybrid compound composed of the heteropolyanions and isopolyanions, [{CuII(2,2′-bpy)}6(MoVMoVI5O22)] [PMoVI12O40] · H2O 1 (bpy = 2,2′-bipyridine) has been hydrothermally synthesized and characterized by elemental analysis, IR spectroscopy, TG analysis, XPS spectrum and single-crystal X-ray diffraction. Crystal data for compound 1: monoclinic, space group P2(1)/c, a = 13.9382(14) A, b = 20.0300(19) A, c = 17.1757(17) A, β = 94.054(2)°, V = 4783.2(8) A3, Z = 2. The Keggin-heteropolyanion [PMo12O40]3− and the Cu-supporting isopolyanion [{Cu(2,2′-bpy)}6(Mo6O22)]3+ building units are bridged through the O–Cu–O bridges into 1D infinite chain. Note that, the [{Cu(2,2′-bpy)}6(Mo6O22)]3+ unit, which contains a rarely reported isopolyanion [Mo6O22]9− decorated by six [Cu(2,2′-bpy)] fragments. Furthermore, the electrochemical behavior of a 1-modified carbon paste electrode (1-CPE) and its electrocatalytic reduction of nitrite were investigated.

Electrocatalytic Reduction of Nitrite by Phosphotungstic Heteropolyanion. Application for Its Simple and Selective Determination

AbstractThree couples of reversible redox peaks of the PW12O403− (PW12) anion, which are composed of two one‐electron and one two‐electron processes occur in the potential range from +0.25 to −0.7 V in aqueous solutions. The electrocatalytic reduction of nitrite has been studied by the first redox couple of the PW12 anion at the surface of a carbon paste electrode. Cyclic voltammetric and chronoamperometric techniques were used to investigate the suitability of PW12 anion as a mediator for nitrite electrocatalytic reduction in aqueous solution with strongly acidic concentration of H2SO4. Results showed that H2SO4 1.00 M is the best medium for this purpose. In the optimum concentration of H2SO4, the electrocatalytic ability about 500 mV can be seen and the homogeneous second‐order rate constant (ks) for nitrite coupled catalytically to PW12 anion was calculated as 2.52×103 M−1 s−1 using the Nicholson–Shain method. According to our voltammetric experiments, the catalytic reduction peak current was linearly dependent on the nitrite concentration and the linearity range obtained was 3×10−5 to 1.00×10−3 M. The detection limit has been found to be 2.82×10−5 M (2σ). This method has been applied as a selective, simple, and precise method for determination of nitrite in real samples.

Voltammetric sensor for nitrite determination based on its electrocatalytic reduction at the surface of p-duroquinone modified carbon paste electrode

A p-duroquinone (tetramethyl-p-benzoquinone) modified carbon paste electrode (DMCPE) was employed to study the electrocatalytic reduction of nitrite in aqueous solutions using cyclic voltammetry (CV), double potential-step chronoamperometry, and differential pulse voltammetry (DPV). It has found that under an optimum condition (pH 1.00), the reduction of nitrite at the surface of DMCPE occurs at a potential of about 660 mV less negative than that of an unmodified carbon paste electrode (CPE). The catalytic rate constant, k′h, based on Andrieux and Saveant theoretical model was calculated as \(k'_h = 4.56 \times 10^{ - 5} \,cm\,s^{ - 1} \) for scan rate 10 mV s-1. Also, the apparent diffusion coefficient, Dapp, was found as 2.5 × 10–10 and 3.61 × 10–5 cm2 s-1for p-duroquinone in carbon paste matrix and nitrite in aqueous buffered solution, respectively. The values for αnα were estimated to be −0.65 and −0.19 for the reduction of nitrite at the surface of DMCPE and CPE, respectively. The electrocatalytic reduction peak currents showed a linear dependence on the nitrite concentration, and a linear analytical curve was obtained in the ranges of 5.0 × 10–5 M to 8.0 × 10–3 M and 6.0 × 10–6 M to 8.0 × 10–4 M of nitrite concentration with CV and DPV methods, respectively. The detection limits (2σ) were determined as 2.5 × 10–5 M and 4.3 × 10–6 M by CV and DPV methods. This method was also applied as a simple, selective and precise method for determination of nitrite in real samples (the weak liquor from the wood and paper factory of Mazandaran province in Iran) by using a standard addition method.