Electrochemical characterization of cationic surfactants’ adsorption on a disturbed n-alkanethiolate self-assembled monolayer-modified polycrystalline gold electrode

The adsorption of cetyltrimethylammonium bromide (CTAB) on disturbed n-alkanethiolate self-assembled monolayers (SAMs) was investigated by electrochemical methods with potassium ferricyanide [K₃Fe(CN)₆] as a probe. Compared with the completely restrained signal at ordinary compact n-alkanethiolate SAMs, the electrochemical response of K₃Fe(CN)₆ at the disturbed n-alkanethiolate SAMs was partly restored and became progressively reversible in the presence of increasing concentrations of CTAB, which was employed to characterize the adsorption of cationic surfactants on hydrophobic SAMs. The effect of CTAB concentration on electrochemical impedance spectroscopy (EIS) plots indicated that CTAB experienced two different types of adsorptive behavior at the disturbed n-alkanethiolate SAMs: monomer adsorption at low concentrations below 1×10^–6 M and monolayer adsorption at CTAB concentrations above 1×10^–5 M. The adsorption of a series of cationic surfactants with similar structures to CTAB on disturbed n-alkanethiolate SAMs was also explored. These surfactants had similar adsorptive behavior and showed nearly linear adsorption characteristics with the length of their hydrophobic tails.     

Direct Potentiometric Study of Cationic and Nonionic Surfactants in Disinfectants and Personal Care Products by New Surfactant Sensor Based on 1,3-Dihexadecyl−1H-benzo[d]imidazol−3-ium

A novel, simple, low-cost, and user-friendly potentiometric surfactant sensor based on the new 1,3-dihexadecyl−1H-benzo[d]imidazol−3-ium-tetraphenylborate (DHBI–TPB) ion-pair for the detection of cationic surfactants in personal care products and disinfectants is presented here. The new cationic surfactant DHBI-Br was successfully synthesized and characterized by nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) spectrometry, liquid chromatography–mass spectrometry (LC–MS) and elemental analysis and was further employed for DHBI–TPB ion-pair preparation. The sensor gave excellent response characteristics for CTAB, CPC and Hyamine with a Nernstian slope (57.1 to 59.1 mV/decade) whereas the lowest limit of detection (LOD) value was measured for CTAB (0.3 × 10⁻⁶ M). The sensor exhibited a fast dynamic response to dodecyl sulfate (DDS) and TPB. High sensor performances stayed intact regardless of the employment of inorganic and organic cations and in a broad pH range (2−11). Titration of cationic and etoxylated (EO)-nonionic surfactant (NSs) (in Ba²⁺) mixtures with TPB revealed the first inflexion point for a cationic surfactant and the second for an EO-nonionic surfactant. The increased concentration of EO-nonionic surfactants and the number of EO groups had a negative influence on titration curves and signal change. The sensor was successfully applied for the quantification of technical-grade cationic surfactants and in 12 personal care products and disinfectants. The results showed good agreement with the measurements obtained by a commercial surfactant sensor and by a two-phase titration. A good recovery for the standard addition method (98–102%) was observed.     

Potentiometric Surfactant Sensor Based on 1,3-Dihexadecyl-1H-benzo[d]imidazol-3-ium for Anionic Surfactants in Detergents and Household Care Products

A 1,3-dihexadecyl-1H-benzo[d]imidazol-3-ium-tetraphenylborate (DHBI-TPB) ion-pair implemented in DHBI-TPB surfactant sensor was used for the potentiometric quantification of anionic surfactants in detergents and commercial household care products. The DHBI-TPB ion-pair was characterized by FTIR spectroscopy and computational analysis which revealed a crucial contribution of the C–H∙∙∙π contacts for the optimal complex formation. The DHBI-TPB sensor potentiometric response showed excellent analytical properties and Nernstian slope for SDS (60.1 mV/decade) with LOD 3.2 × 10⁻⁷ M; and DBS (58.4 mV/decade) with LOD 6.1 × 10⁻⁷ M was obtained. The sensor possesses exceptional resistance to different organic and inorganic interferences in broad pH (2–10) range. DMIC used as a titrant demonstrated superior analytical performances for potentiometric titrations of SDS, compared to other tested cationic surfactants (DMIC > CTAB > CPC > Hyamine 1622). The combination of DHBI-TPB sensor and DMIC was successfully employed to perform titrations of the highly soluble alkane sulfonate homologues. Nonionic surfactants (increased concentration and number of EO groups) had a negative impact on anionic surfactant titration curves and a signal change. The DHBI-TPB sensor was effectively employed for the determination of technical grade anionic surfactants presenting the recoveries from 99.5 to 101.3%. The sensor was applied on twelve powered samples as well as liquid-gel and handwashing home care detergents containing anionic surfactants. The obtained results showed good agreement compared to the outcomes measured by ISE surfactant sensor and a two-phase titration method. The developed DHBI-TPB surfactant sensor could be used for quality control in industry and has great potential in environmental monitoring.     

Effect of surfactants on the voltammetric response and determination of an antihypertensive drug

The effect of adding surface-active agents to electrolytes containing terazosin, an antihypertensive drug, on the voltammetric response of glassy carbon electrode was studied. The current signal due to the oxidation process was a function of the amount of terazosin, pH of the medium, type of surfactant, and accumulation time at the electrode surface. Two surfactants were used, an anionic type, sodium dodecyl sulfate (SDS) and a cationic type, cetyl trimethyl ammonium bromide (CTAB). Addition of SDS to the terazosin-containing electrolyte was found to enhance the oxidation current signal while CTAB showed an opposite effect. Beside the interfacial interaction of the surfactant with the electrode surface in reference to the bias applied potential and the charge of surfactant, terazosin-surfactant interaction in the electrolytic solution was found to be critical to the magnitude of current signal. Addition of SDS to terazosin-containing buffer solution resulted in a decrease in the drug absorption spectrum both in the ultra-violet and visible (UV-vis) regions. Moreover, NMR measurements showed considerable chemical shifts for the aromatic protons of the quinazolinyl moiety of the terazosin in presence of SDS. The affected aromatic protons are positioned next to the interacting protonated amino-group of the terazosin with the charged sulfonate-group of SDS. On the other hand, addition of CTAB did not cause noticeable changes both to the UV-vis and NMR spectra of the drug. The use of SDS in the electrochemical determination of terazosin using linear sweep voltammetry and differential pulse voltammetry at solid glassy carbon electrode enhanced the detection limit from 6.00 × 10⁻⁷ mol L⁻¹ in absence of surfactant to 4.58 × 10⁻⁹ mol L⁻¹ when present. The validity of using this method in the determination of drug active ingredient in urine samples and tablet formulations was also demonstrated.     

Voltammetric behavior of benzo[a]pyrene at boron-doped diamond electrode: a study of its determination by adsorptive transfer stripping voltammetry based on the enhancement effect of anionic surfactant, sodium dodecylsulfate

Benzo[a]pyrene (BaP), a member of the polycyclic aromatic hydrocarbon (PAH) class, is one of the most potent PAH carcinogens. The electrochemical oxidation of BaP was first studied by cyclic voltammetry at the boron-doped diamond electrode in non-aqueous solvent (dimethylsulphoxide with lithium perchlorate). The compound was irreversibly oxidized in a single step at high positive potential, resulting in the well-resolved formation of a couple with a reduction and re-oxidation wave at much lower potentials. Special attention was given to the use of adsorptive stripping voltammetry together with a medium exchange procedure in aqueous and aqueous/surfactant solutions over the pH range of 2.0-8.0. The technique in aqueous solutions had little value in practice because of too small oxidation peak current. This problem was solved when surfactants were added into the sample solution, by which the oxidation peak currents of BaP were found enhanced dramatically. The employed surfactants were sodium dodecylsulfate (anionic, SDS), cetyltrimethylammonium bromide (cationic, CTAB) and Tween 80 (non-ionic). Using square-wave stripping mode, the compound yielded a well-defined voltammetric response in Britton-Robinson buffer, pH 2.0 containing 2.5 × 10⁻⁴ M SDS at +1.07 V (vs. Ag/AgCl) (after 120 s accumulation at +0.10 V). The process could be used to determine BaP in the concentration range of 16-200 nM (4.04-50.46 ng mL⁻¹), with a detection limit of 2.86 nM (0.72 ng mL⁻¹). This method was also applied to determine BaP in model water sample prepared by adding its different concentrations into tap water.     

The reduction of hexanitrocobaltate(III) ion in the presence of hexadecyltrimethylammonium bromide

The influence of cationic surfactant hexadecyltrimethylammonium bromide (CTAB) on the kinetics of the spontaneous reduction of the analytically important compound, sodium hexanitrocobaltate(III), was studied. The spontaneous reduction was monitored spectrophotometrically at pH 2 and 5 and at concentrations of CTAB from 1 × 10⁻⁵ to 5 × 10⁻⁴ M. The mechanism of this process was described using two consecutive first-order reactions. A decrease in the rate constant for reduction at pH 5 in solutions containing CTAB in concentrations of 5.6 × 10⁻⁵ M (critical micelle concentration) compared with its rate in an aqueous solution was observed. These effects could be explained by electrostatic and hydrophobic/hydrophilic interactions between the micellar pseudophase and the hexanitrocobaltate(III) ion. The article is published in the original.     

Enhanced reduction and determination of trace thyroxine at carbon paste electrode in the presence of trace cetyltrimethylammonium bromide.

The electrochemical response of thyroxine (T4) at a carbon paste electrode (CPE) in the presence of cetyltrimethylammonium bromide (CTAB) was investigated. It gave a well-defined oxidation peak at 0.80 V and a sensitive reduction peak at 0.40 V. Compared with the indiscernible signal in the absence of CTAB, the reduction current of T4 at CPE was greatly enhanced in the presence of CTAB, due to the interactions between T4, CTAB and the hydrophobic electrode surface. The electrode process of T4 was explored by cyclic voltammetry and chronocoulometry. The effect of surfactants on the reduction reaction proved that bromide ions (Br(-)) in CTAB might form special ion complexes with T4 via a special interaction with the iodine atoms on T4, which would activate the reduction of T4. The sensitive and selective reduction of T4 in this system was applied to the determination of T4 in drugs; a detection limit of 6.5 x 10(-9) M was obtained (sigma= 3).     

Electrochemical behavior of phenol at acetylene black-dihexadecyl hydrogen phosphate composite modified glassy carbon electrode in the presence of cetyltrimethylammonium bromide

The electrochemical response of phenol at acetylene black (AB)-dihexadecyl hydrogen phosphate (DHP) composite modified glassy carbon electrode in the presence of cetyltrimethylammonium bromide (CTAB) was investigated. In this system, a sensitive oxidation peak at 0.62 V (SCE) was obtained. The electrode process and the influence of CTAB on the oxidation of phenol were explored by chronocoulometry and linear sweep voltammetry (LSV). Experimental conditions for the determination of phenol were optimized. In the range of 5.0 × 10⁻⁷ to 1.2 × 10⁻⁵ M, the phenol concentration was linear with the oxidation peak current and the detection limit was found to be 1.0 × 10⁻⁷ M for 3 min accumulation. The method was applied for the determination of phenol in lake water and the results were satisfactory. Published in Russian in Elektrokhimiya, 2008, Vol. 44, No. 2, pp. 222–229. The text was submitted by the authors in English.     

Non-extraction flow injection determination of cationic surfactants using eriochrome black-T

A new, rapid, sensitive, non-extraction batch, and flow injection spectrophotometric method for the determination of cationic surfactants (CSs) such as cetyltrimethyl ammonium bromide (CTAB), tetra-n-butyl ammonium chloride (TBAC) and cetylpyridinium chloride (CPC) is proposed. The method is based on the interaction of cationic surfactants with eriochrome black-T to form an ion-association complex. This complex has strong absorbance at 708 nm. The effects of chemical parameters and FIA variables on the determination of cationic surfactants were studied in detail, especially for CTAB. Under optimum conditions, the two linear calibration ranges of the method are 3.0 × 10⁻⁶ to 5.0 × 10⁻³ mol L⁻¹ CTAB, CPB and DTAB for the batch spectrophotometric method and 2.0 × 10⁻⁶ to 2.0 × 10⁻⁴ mol L⁻¹ CTAB, CPB and TBC for the flow injection spectrophotometric method. The sample throughput was 35 ± 5 samples h⁻¹ at room temperature. The relative standard deviations for 10 replicates of analysis of (2.0, 0.6 and 0.2) × 10⁻⁴ mol L⁻¹ CTAB were 1.2, 1.3, and 0.8%, respectively. In addition, the influence of potential interfering substances on the determination of cationic surfactants was studied. The proposed method is simple and rapid, using no toxic organic solvents. It was applied to the determination of trace CS in industrial wastewater with satisfactory results.     

Determination of Thiophosphamide in Aqueous Solutions by Cathodic Stripping Voltammetry at a Silver Electrode

It was demonstrated that thiophosphamide can be determined in aqueous solutions by cathodic stripping voltammetry at a silver electrode. The determination conditions were found. The detection limit for thiophosphamide in the Britton buffer solution (pH 11.2) was 5 × 10^–4M (relative standard deviation 5%), and the upper boundary of the analytical range was 3 × 10^–3M (relative standard deviation 1.5%) for a time of electroaccumulation of 5 min.     

Highly Sensitive Determination of Tenofovir in Pharmaceutical Formulations and Patients Urine—Comparative Electroanalytical Studies Using Different Sensing Methods

This paper discusses the electrochemical behavior of antiviral drug Tenofovir (TFV) and its possible applicability towards electroanalytical determination with diverse detection strategies using square-wave voltammetry. Namely, oxidation processes were investigated using glassy carbon electrode with graphene oxide surface modification (GO/GCE), while the reduction processes, related to the studied analyte, were analyzed at a renewable silver amalgam electrode (Hg(Ag)FE). Scanning electron microscopy imaging confirmed the successful deposition of GO at the electrode surface. Catalytic properties of graphene oxide were exposed while being compared with those of bare GCE. The resultant modification of GCE with GO enhanced the electroactive surface area by 50% in comparison to the bare one. At both electrodes, i.e., GO/GCE and Hg(Ag)FE, the TFV response was used to examine and optimize the influence of square-wave excitation parameters, i.e., square wave frequency, step potential and amplitude, and supporting electrolyte composition and its pH. Broad selectivity studies were performed with miscellaneous interfering agents influence, including ascorbic acid, selected saccharides and aminoacids, metal ions, non-opioid analgesic metamizole, non-steroidal anti-inflammatory drug omeprazole, and several drugs used along with TFV treatment. The linear concentration range for TFV determination at GO/GCE and Hg(Ag)FE was found to be 0.3–30.0 µmol L^–1 and 0.5–7.0 µmol L^–1, respectively. The lowest LOD was calculated for GO/GCE and was equal to 48.6 nmol L^–1. The developed procedure was used to detect TFV in pharmaceutical formulations and patient urine samples and has referenced utilization in HPLC studies.     

Spectrofluorimetric Assay of Cationic Surfactants by Fluorescence Quenching of 9-Anthracenecarboxylic Acid

A new simple, selective and sensitive fluorescence quenching method was developed to determine cationic surfactants with the 9-anthracenecarboxylic acid (ACA). The fluorescence intensity of ACA was decreased by addition of trace amounts of cationic surfactants. Under optimum conditions, the ratio of fluorescence intensity in the absence and presence of cationic surfactants was proportional to the concentration of cationic surfactants over the range of 0.3–4.5 × 10⁻⁵ mol L⁻¹ for cetylpyridinium chloride (CPC) and 0.4–6.0 × 10⁻⁵ mol L⁻¹ for cetyl trimethyl-ammonium bromide (CTAB). The detection limits are 1.0 × 10⁻⁶ mol L⁻¹ for CPC and 1.2 × 10⁻⁶ mol L⁻¹ for CTAB, respectively. Based on this approach, this paper presents a new quantitative method for cationic surfactants assay.     

Electrochemical Sensing of Pb2+ and Cd2+ Ions with the Use of Electrode Modified with Carbon-Covered Halloysite and Carbon Nanotubes

A novel voltammetric method for the sensitive and selective determination of cadmium and lead ions using screen-printed carbon electrodes (SPCEs) modified with carbon-deposited natural halloysite (C_Hal) and multi-walled carbon nanotubes (MWCNTs) was developed. The electrochemical properties of the proposed sensor were investigated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), while the morphology and structure were established by scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). A two-factorial central composite design (CCD) was employed to select the composition of the nanocomposite modifying the electrode surface. The optimal measuring parameters of differential pulse anodic stripping voltammetry (DPASV) used for quantitative analysis were established with the Nelder–Mead simplex method. In the analytical investigation of Cd(II) and Pb(II) ions by DPASV, the MWCNTs/C_Hal/Nafion/SPCE exhibited a linear response in the concentration range of 0.1–10.0 µmol L⁻¹ (for both ions) with a detection limit of 0.0051 and 0.0106 µmol L⁻¹ for Pb(II) and Cd(II), respectively. The proposed sensor was successfully applied for the determination of metal ions in different natural water and honey samples with recovery values of 96.4–101.6%.     

Nanostructured platinum as an electrocatalyst for the electrooxidation of formic acid

Nanostructured platinum prepared by the chemical reduction of hexachloroplatinic acid dissolved in aqueous domains of the liquid crystalline phases of oligoethylene oxide surfactants, was examined as an electrocatalyst for the electrooxidation of formic acid. The electrocatalytic properties of the catalyst combining highly specific surface areas and a periodic mesoporous nanostructure were accessed in sulfuric acid solution containing 0.5 mol dm⁻³ formic acid using cyclic voltammetry (CV) and chronoamperometry. The electrocatalytic activity of the material at 60 °C, is characterised by a mass activity of 8.6 A g⁻¹ and a specific surface area activity of 26 μA cm⁻² at 0.376 V (vs. RHE). The resistance to CO poisoning was found to depend upon electrode potential. At hydrogen adsorption potentials, the material is easily poisoned, while the material shows high resistance to CO poisoning at potentials positive of the hydrogen region. These facts suggest that the decomposition of HCOOH on the mesoporous platinum is likely to proceed through a dual-path mechanism and the high surface area material is a potential electocatalyst towards the electrooxidation of small organic molecules.     

Interfacial Properties,Wettability Alteration and Emulsification Properties of an Organic Alkali–Surface Active Ionic Liquid System: Implications for Enhanced Oil Recovery

Combinatory flooding techniques evolved over the years to mitigate various limitations associated with unitary flooding techniques and to enhance their performance as well. This study investigates the potential of a combination of 1-hexadecyl-3-methyl imidazolium bromide (C₁₆mimBr) and monoethanolamine (ETA) as an alkali–surfactant (AS) formulation for enhanced oil recovery. The study is conducted comparative to a conventional combination of cetyltrimethylammonium bromide (CTAB) and sodium metaborate (NaBO₂). The study confirmed that C₁₆mimBr and CTAB have similar aggregation behaviors and surface activities. The ETA–C₁₆mimBr system proved to be compatible with brine containing an appreciable concentration of divalent cations. Studies on interfacial properties showed that the ETA–C₁₆mimBr system exhibited an improved IFT reduction capability better than the NaBO₂–CTAB system, attaining an ultra-low IFT of 7.6 × 10⁻³ mN/m. The IFT reduction performance of the ETA–C₁₆mimBr system was improved in the presence of salt, attaining an ultra-low IFT of 2.3 × 10⁻³ mN/m. The system also maintained an ultra-low IFT even in high salinity conditions of 15 wt% NaCl concentration. Synergism was evident for the ETA–C₁₆mimBr system also in altering the carbonate rock surface, while the wetting power of CTAB was not improved by the addition of NaBO₂. Both the ETA–C₁₆mimBr and NaBO₂–CTAB systems proved to form stable emulsions even at elevated temperatures. This study, therefore, reveals that a combination of surface-active ionic liquid and organic alkali has excellent potential in enhancing the oil recovery in carbonate reservoirs at high salinity, high-temperature conditions in carbonate formations.     

Linear sweep voltammetry of 9-β- -ribofuranosyluric acid 5′-monophosphate in aqueous and micellar media

Linear sweep voltammetric behaviour of 9-β- -ribofuranosyluric acid 5′-monophosphate (UA-9R-5′-P) has been studied in phosphate buffers of pH 3.0 and 7.0 at the pyrolytic graphite electrode in aqueous and micellar media. At pH 3.0 in the presence of non-ionic and anionic surfactants, UA-9R-5′-P exhibited a single well-defined 2e, 2H⁺ oxidation peak, whereas in the presence of cationic surfactant (CTAB) the oxidation peak I_a showed a tendency to split into two peaks indicating that the 2e, 2H⁺ oxidation of UA-9R-5′-P in peak I_a reaction occurs in two 1e steps. The effect of cationic surfactant at pH 3.0 is explained on the basis of hydrophobic penetration of cationic species in cationic micelles. The products of electrode reaction in micellar medium were found as alloxan, urea and ribosyl phosphate at pH 3.0 and ribose, allantoin and 5-hydroxyhydantoin 5-carboxamide at pH 7.0 and were similar to those observed in aqueous media.     

Determination of Ammonium by Stripping Voltammetry

The behavior of ammonium ions at amalgam electrodes was studied by cyclic and stripping voltammetry. It was found that the oxidation peak of an ammonium hydride amalgam can be used as the analytical signal. Conditions were selected for the determination of ammonium ions in aqueous solutions at a mercury film electrode by stripping voltammetry using potassium chloride as the supporting electrolyte. The determination limit for ammonium ions was found to be 2 × 10^–7M (0.004 mg/L). The procedure was tested in river waters of the Ob' basin and in the atmospheric air.     

Electrochemical Study of Iodide in the Presence of Barbituric Acid: Application to the Catalytic Determination of Barbituric Acid

Electrochemical oxidation of iodide has been studied in the presence of barbituric acid using cyclic voltammetry and controlled-potential coulometry. The results indicate that the barbituric acid participating in the halogenation reaction converts to an iodo derivative of the parent compound. Moreover, the results are indicative of the suitability of iodide as a mediator for the determination of barbituric acid in aqueous solutions. The quasicatalytic peak current is linearly dependent on the barbituric acid concentration. The calibration graph is parabolic, with two linear sections of 6.0 × 10^–5–1.0 × 10^–3and 1.0 × 10^–3–1.0 × 10^–2M. The relative standard deviation for ten determinations of 2.0 × 10^–4M barbituric acid is 2.1%, and the detection limit of the method is 3.97 × 10^–5M.     

Voltammetry and electrochemical stripping analysis for antimony in aqueous and nonaqueous media after extraction

Cyclic voltammetry of antimony was studied in aqueous media (HCl-LiCl) and in nonaqueous media after extraction with 20% tri-n-butylphosphate in toluene, with a rotating glassy carbon disc electrode. Reduction of antimony to the element in aqueous media is nearly reversible, but irreversible in nonaqueous media. Anodic stripping voltammetric and chronopotentiometric determinations were also studied in nonaqueous media; methanol and LiCI, NH₄SCN or NH₄NO₃, were used as base electrolytes. In nonaqueous media, antimony can be determined down to concentrations of 1O⁻⁸ M by stripping voltammetry, and lO⁻⁷ M by stripping chronopotentiometry. Electrochemical stripping determinations of 10⁻⁶ M antimony(III) were not affected by Co²⁺, Ni²⁺, Cd²⁺, Zn²⁺ or As³⁺ (5 · 10⁻³ M), ag⁺ (4 · 10⁺⁴ M in stripping voltammetry or 10⁻³ M in stripping chronopotentiometry), Hg²⁺ (5 · 10⁻⁴M), Pb²⁺ (3 · 10⁻⁴ M), Cu²⁺ (1.5 · 10⁻⁴ M)Sn²⁺ and Sn⁴⁺ (7 · 10⁻⁴ M), Fe³⁺ (4 · 10⁻⁴ M), Au³⁺ (5 · 10⁻⁵ M) and Bi³⁺ (1.5 · 10⁻⁵ M). Thestripping chronopotentiometric determination showed better selectivity.     

Determination of 4-methylbenzilidene camphor in sunscreen by square wave voltammetry in media of cationic surfactant

The voltammetric behavior of 4-methylbenzelidene camphor (MBC) was studied by square wave voltammetry (SWV) using mercury electrode. The experimental condition that provided the highest peak current with the best reduction signal definition of MBC was found in Britton-Robinson buffer and cationic surfactants, cetyltrimethylammoniun bromide (CTABr). A single peak of MBC reduction was observed at − 1.21 V versus Ag/AgCl. The developed methodology was applied for determination of MBC in commercial sunscreen SPF 15, 20 and 30 and for the simultaneous determination when other protection agents were associated, such as benzophenone-3 (BENZO) and octyl methoxycinammate (OMC). Both methodologies had shown good determination values for the analyzed samples. The calculated detection limit was 2.99 × 10^− 9 mol L^− 1 and the quantification limit was 9.98 × 10^− 9 mol L^− 1.