Development a New Method for the Determination of Chloropromazine in Trace Amounts by Fast Fourier Continuous Cyclic Voltammetry at an Au Microelectrode in a Flowing System

In this study a new technique has been developed for the determination of chloropromazine in flow‐injection systems. The technique, named fast Fourier transformation continuous cyclic voltammetry (FFTCV), basically illustrates the benefits of sensitivity, selectivity, simplicity and low detection limit. It is also important to refer to the positive points, presented only by the use of this technique. Firstly, it is no longer necessary to remove the oxygen from the test solution. Furthermore, the quick determination of any such compound in many chromatographic methods is possible. Thirdly, the corresponding detection limit is of sub‐nanomolar level. Additionally, a special computer based numerical method is also introduced for the calculation of the analyte signal and noise reduction. The electrode response was calculated in accordance with the partial and total charge exchanges on the electrode surface, after the background current subtraction from that of noise. The integration range of currents was set for all the potential scan ranges, including oxidation and reduction of Au surface electrode, to obtain a sensitive determination. The performed experiments aimed at measuring the effects of different parameters on the method sensitivity. In the end of these measurements, it was concluded that the method was linear for the concentration range of 0.32–31900 pg/mL (r = 0.996) with a limit of detection and quantitation 0.1 and 0.32 pg/mL, respectively. For the achievement of these optimum results, the parameter values were set to 100 V/s for the scan rate, 0.4 s for accumulation time, 800 mV for accumulation potential and 2 for the pH.     

Subsecond FFT‐adsorptive Voltammetric Technique as a Novel Method for Subnano Level Monitoring of Piroxicam in its Tablets and Bulk Form at Au Microelectrode in Flowing Solutions

Abstract

In this work a novel method for the determination of piroxicam in flow‐injection systems has been developed. A system using fast Fourier transform continuous cyclic voltammetry (FFTCV), at a gold microelectrode in flowing solution, was used for determining piroxicam in its pharmaceutical formulations. The developed technique is very simple, precise, accurate, time saving, and economical, compared to all of the previously reported methods. The effects of various parameters on the sensitivity of the method were investigated. The best performance was obtained with a pH value of 2, scan rate value of 40 V/s, accumulation potential of (400) mV, and accumulation time of 0.4 s. The proposed method has some advantages over other reported methods, such as, no need for the removal of oxygen from the test solution, a picomolar detection limit, and finally that the method is fast enough for the determination of any such compound, in a wide variety of chromatographic methods. To obtain a sensitive determination, the integration range of currents was set for all the potential scan ranges, including oxidation and reduction of the Au surface electrode, while performing the measurements. The potential waveform, consisting of the potential steps for cleaning, accumulation, and potential ramp of analyte, was applied on an Au disk microelectrode (with a 12.5 µm in radius) in a continuous way. The method was linear over the concentration range of 1.5–364000 pg/ml (r=0.998) with a limit of detection and quantitation of 0.33 and 1.5 pg/ml, respectively. The method has the requisite accuracy, sensitivity, precision, and selectivity to assay piroxicam in tablets.     

Fast Fourier Transform Continuous Cyclic Voltammetry Development as a Highly Sensitive Detection System for Ultra Trace Monitoring of Thiamine

Abstract

In this work, a highly sensitive method for the fast monitoring of thiamine hydrocholoride in flow‐injection systems has been developed. The fast Fourier transform continuous cyclic voltammetry (FFCV) in flowing solution as a detection system was applied for the very fast monitoring of thiamine in its pharmaceutical formulations. This technique is very simple, precise, accurate, time‐saving and economical, compared to all previous reported methods. The effects of various parameters on the sensitivity of the detection system were considered. The best condition was obtained within the pH value of 2, and scan rate value of 25 V s^?1, accumulation potential of ?400 mV, and accumulation time of 0.6 s. The proposed method has some advantages over other reported methods such as, there is no need for the removal of oxygen from the test solution, has a sub‐nanomolar detection limit, and finally the method is fast enough for the determination of any such compound, in a wide variety of chromatographic methods. This research also introduces a special computer‐based numerical method, for the calculation of the analyte signal and noise reduction. The electrode response was calculated based on partial and total charge exchanges on the electrode surface after subtracting the background current from that of noise. To obtain a sensitive determination, the integration range of currents was set for all the potential scan ranges, including oxidation and reduction of the Au surface electrode, while performing the measurements. The potential waveform, consisting of the potential steps for cleaning, accumulation and potential ramp of analyte, was applied on an Au disk microelectrode (12.5 µm in radius) in a continuous way. The detection limit of the method for thiamine was 1.0×10^?12 M. The relative standard deviation of the method at 1.0×10^?8 M was 2.2% for 8 runs.     

Fast Monitoring of Nano‐Molar Level of Gentamycin by Fast Fourier Transform Continuous Cyclic Voltammetry in Flowing Solution

Abstract

A novel method for the determination of gentamycin in flow‐injection systems has been developed in this work. The principal advantages of this method are that it is rapid, simple, and possesses low detection limit. Some investigations were also done to find the effects of various parameters on the sensitivity of the proposed method. The conditions producing the performance were the pH value of 2, the scan rate value of 350 V/s, accumulation potential of (100 mV), and accumulation time of 0.9 s. Some of the advantages of the proposed method are: the removal of oxygen from the test solution is not required anymore, the detection limit of the method is sub‐nanomolar, and finally, the method is fast enough for determination of such compounds, in a wide variety of chromatographic methods. We also introduce a special computer‐based numerical method for calculation of the analyte signal and noise reduction. After subtracting the background current from noise, the electrode response was calculated, based on partial and total charge exchanges at the electrode surface. The integration range of currents was set for all the potential scan ranges, including oxidation and reduction of the Au surface electrode, to obtain a sensitive determination. The waveform potential was continuously applied on an Au disk microelectrode (12.5 µm in radius). Detention limit of the method for gentamycin was found to be 1.0×10^?9 M. For 10 runs, the relative standard deviation of the method at 1.0×10^?7 M was 2.1%.     

Nonelectroactive recognition: Monitoring of perphenazine by its subsecond adsorption on an Au microelectrode by the fast fourier transform continuous cyclic voltammetric technique (FFTCCV)

A novel method for determining perphenazine in flow-injection systems has been developed in this work. The method was successfully applied for fast determination of perphenazine in its pharmaceutical formulations. Being very simple, precise, accurate, time-saving, and economical, this method has many advantages compared to all of the previously reported methods. Some investigations were also performed to find the effects of various parameters on the sensitivity of the proposed method. The conditions responsible for the performance were a pH value of 2, a scan rate value of 30 V/s, an accumulation potential of 500 mV, and an accumulation time of 0.8 s. Some of the advantages of the proposed method are as follows: the removal of oxygen from the test solution is not required anymore, the detection limit of the method is subnanomolar, and finally, the method is fast enough to determine such compounds in a wide variety of chromatographic methods. We also introduce a special computer-based numerical method to calculate the analyte signal and noise reduction. After subtraction of the background current from noise, the electrode response was calculated based on partial and total charge exchanges at the electrode surface. The integration range of currents was set for all the potential scan ranges, including oxidation and reduction of the Au surface electrode, to obtain a sensitive determination. The waveform potential was continuously applied on an Au disk microelectrode (a radius of 12.5 μm). The detention limit of the method for perphenazine was 15 pg/ml. For eight runs, the relative standard deviation of the method at 1.1 × 10⁻⁸ M was 2.1%. Published in Russian in Elektrokhimiya, 2008, Vol. 44, No. 9, pp. 1093–1102. The text was submitted by the authors in English.     

A novel method for fast determination of vitamin B6 by fast continuous cyclic voltammetry

In this work a novel method for the determination of Vitamin B6 in flow-injection systems has been developed. The fast Fourier transform continuous cyclic voltammetry (FFTCV) at gold microelectrode in flowing solution system was used for determination of Vitamin B6. This method is rapid, simple and highly sensitive procedures allowing the determination of Vitamin B6 in pharmaceutical analysis. The effects of various parameters on the sensitivity of the method were investigated. The best performance was obtained with the pH value of 2, scan rate value of 30 V/s, accumulation potential of 200 mV and accumulation time of 0.3 s. The proposed method has some advantages over other reported methods such as, no need for the removal of oxygen from the test solution, a sub-nanomolar detection limit, and finally the method is fast enough for the determination of any such compound, in a wide variety of chromatographic methods. To obtain a sensitive determination, the integration range of currents was set for all the potential scan ranges, including oxidation and reduction of the Au surface electrode, while performing the measurements. The potential waveform, consisting of the potential steps for cleaning, accumulation and potential ramp of analyte, was applied on an Au disk microelectrode (12.5 μm in radius) in a continuous way. The detection limit of the method for Vitamin B6 was 2.8 pg/ml. The relative standard deviation of the method at 2.1% was 8 runs. Published in Russian in Elektrokhimiya, 2008, Vol. 44, No. 2, pp. 173–181. The text was submitted by the authors in English.     

Use of the differential pulse cathodic adsorptive stripping voltammetric method for the simultaneous determination of trace amounts of cadmium and zinc

A selective and sensitive method for the determination of cadmium and zinc is presented. The method is based on the adsorptive accumulation of the complexes of Cd(II) and Zn(II) ions with 4-amiono-5-methyl-2.4-dihydro-3H-1,2,4-triazol-3-tion (MMTT) onto hanging mercury drop electrode (HMDE), followed by the reduction of the adsorbed species using a voltammetric scan using differential pulse modulation. The ligand concentration, pH, potential and time of accumulation, scan rate, and pulse height were optimized. Under the optimized conditions, a linear calibration curve was obtained for the concentration of Cd(II) and Zn(II) in the range of 5–450 and 5–850 ng/mL, respectively, with a detection limit of 1.7 ng/mL Cd(II) and 1.3 ng/mL Zn(II). The ability of the method was evaluated by analysis of cadmium and zinc in water and alloy samples The text was submitted by the authors in English.     

Catalytic adsorptive stripping voltammetry determination of ultra trace amount of tungsten using factorial design for optimization

A highly sensitive procedure is presented for the determination of ultra-trace concentration of tungsten by catalytic adsorptive stripping voltammetry. The method is based on adsorptive accumulation of the tungsten-pyrocatechol violet complex onto a hanging mercury drop electrode, followed by reduction of the adsorbed species by voltammetric scan using differential pulse modulation. The reduction current is enhanced catalytically by chlorate. The influence of variables was completely studied by factorial design analysis. Optimum analytical conditions for the determination of tungsten were established. Tungsten can be determined in the range 0.06–12.0 ng/mL with a limit of detection of 0.02 ng/mL. The influence of potentially interfering ions on the determination of tungsten was studied. The procedure was applied to the determination of tungsten in one sandwich polyoxometalate and some synthetic samples similar to alloy compounds with satisfactory results.     

Selective and non-selective determination of heavy metal ions in flowing solutions by fast stripping cyclic voltammetry.

A simple and fast stripping voltammetric detection method has been designed for selective and non-selective measurements of heavy metal ions in a flow-injection system. A special computer numerical method is introduced for calculating the analyte signal and noise reduction, where the signal is calculated based on the partial and total charge exchange at electrode surface. For a selective determination, the currents are integrated in the range of the oxidation and reduction of the analyte. For non-selective measurements, the integration range is set for the whole potential scan range (including oxidation and reduction of the Au surface). The time for stripping has been shown to be less than 300 ms. The main advantages of the detection method are as follows: first, removal of oxygen from the measured solution is not required; second, it is sufficiently fast for the determination of heavy metal ions in various chromatographic analysis methods. The limit of detection for tested ions was between 3 x 10(-9) and 6 x 10(-10) M, and the relative standard deviation at 50 ppb Pb2+ was 4.7% for 10 runs.     

Application of Adsorptive Stripping Voltammetry for the Nano‐Level Detection of Tramadol in Biological Fluids and Tablets Using Fast Fourier Transform Continuous Cyclic Voltammetry at an Au Microelectrode in a Flowing System

Abstract

A novel adsorptive fast Fourier transform cyclic voltammetry (AFFTCV) technique for the fast determination of tramadol in flow‐injection systems has been introduced in this work. The potential waveform, consisting of the potential steps for cleaning, stripping, and potential ramp, was continuously applied on an Au disk microelectrode (with a 12.5 µm in radius). The proposed detection method has some advantages, the greatest of which are as follows: first, it is no more necessary to remove oxygen from the analyte solution and second, it is a very fast and appropriate technique for determination of the drug compound in a wide variety of chromatographic analysis methods. The influences of pH of eluent, accumulation potential, sweep rate, and accumulation time on the determination of the tramadol were considered. The method was linear over the concentration range of 1.5–900,000 pg/ml (r=0.9968) with a limit of detection and quantitation 0.32 and 1.5 pg/ml, respectively. The method has the requisite accuracy, sensitivity, precision, and selectivity to assay tramadol in tablets and in biological fluids.     

A novel lable-free electrochemical immunosensor for carcinoembryonic antigen based on gold nanoparticles-thionine-reduced graphene oxide nanocomposite film modified glassy carbon electrode

In this paper, gold nanoparticle-thionine-reduced graphene oxide (GNP-THi-GR) nanocomposites were prepared to design a label-free immunosensor for the sensitive detection of carcinoembryonic antigen (CEA). The nanocomposites with good biocompatibility, excellent redox electrochemical activity and large surface area were coated onto the glassy carbon electrode (GCE) surface and then CEA antibody (anti-CEA) was immobilized on the electrode to construct the immunosensor. The morphologies and electrochemistry of the formed nanocomposites were investigated by using scanning electron microscopy (SEM), ultraviolet-visible (UV-vis) spectrometry, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). CV and differential pulse voltammetry (DPV) studies demonstrated that the formation of antibody-antigen complexes decreased the peak current of THi in the GNP-THi-GR nanocomposites. The decreased currents were proportional to the CEA concentration in the range of 10-500 pg/mL with a detection limit of 4 pg/mL. The proposed method was simple, fast and inexpensive for the determination of CEA at very low levels.     

Determination of Titanium In Quartz and Silica Glass Samples By Adsorptive Stripping voltammetry

ABSTRACT

This article presents a method for determination of titanium in quartz and silica glass samples based on adsorptive stripping voltammetry (AdSV) with mandelic acid. Hanging mercury drop electrode as a working electrode was used. The optimized conditions include: pH 3.3, accumulation potential –0.15 V, accumulation time 90 s, scan rate 10 mV/s, pulse amplitude 25 mV. In case of 5 min accumulation time the obtained detection limit was 6.5×10^-9 mol/L Ti. ET-AAS was applied as a reference method to AdSV measurements. The procedure for decomposition of quartz and silica glass samples applying small amount of acids is described.     

ICP-MS 法直接测定冰芯样品中超痕量镉

采用 ICP- MS法对冰芯样品中超痕量 Cd的直接测定进行了研究。确定了直接测定浓度为 pg/m L 级的 Cd的最佳仪器参数、载气流速、进样速度等与灵敏度之间的关系以及浓度和扫描参数对分析精度的影响。本方法对浓度 5～2 0 0 pg/m L Cd的分析 ,RSD<1 0 % ,回收率在 88%～ 1 0 5%之间 ,检测限为0 .1 5pg/m L     

Determination of Cysteine in the Presence of Copper in Diluted Alkaline Electrolyte by Adsorptive Stripping Voltammetry at the Mercury Film Electrode

Abstract

A stripping method for the determination of cysteine in the presence of copper at the submicromolar concentration levels is described. The method is based on controlled adsorptive accumulation of cysteine at mercury film electrode followed by linear cyclic voltammetry scan measurement of the surface species. Optimum experimental conditions were found to be the use of a 1×10^?3 M NaOH solution, an accumulation potential of ?0.50 V and a scan rate of 200 mV. s^?1. The response of cysteine is linear over the concentration range 0.04–0.20 ppm. For an accumulation time of 15 minutes, the detection limit was found to be 0.9 ppb (7.4×10^?9 M). The more convenient relation to measuring the cysteine in presence of metals, and others amino acids were also investigated. The utility of the method is demonstrated by presence of casein and ATP.     

Selective Determination of Verapamil in Pharmaceutics and Urine Using a Boron‐doped Diamond Electrode Coupled to Flow Injection Analysis with Multiple‐pulse Amperometric Detection

This work presents a simple and low‐cost method for fast and selective determination of Verapamil (VP) in tablets and human urine samples using a boron‐doped diamond working electrode (BDD) coupled to a flow injection analysis system with multiple pulse amperometric detection (FIA‐MPA). The electrochemical behaviour of VP in 0.1 mol L⁻¹ sulfuric acid showed three merged oxidation peaks at around +1.4 V and upon reverse scan, one reduction peak at 0.0 V (vs. Ag/AgCl). The MPA detection was performed applying a sequence of three potential pulses on BDD electrode: (1) at +1.6 V for VP oxidation, (2) at +0.2 V for reduction of the oxidized product and (3) at +0.1 V for cleaning of the working electrode surface. The FIA system was optimized with injection volume of 150 μL and flow rate of 3.5 mL min⁻¹. The method showed a linear range from 0.8 to 40.0 μmol L⁻¹ (R>0.99) with a low limit of detection of 0.16 μmol L⁻¹, good repeatability (RSD<2.2 %; n=10) and sample throughput (45 h⁻¹). Selective determination of VP in urine was performed at+0.2 V due to absence of interference from ascorbic and uric acids in this potential. The addition‐recovery tests in both samples were close to 100 % and the results were similar to an official method.     

Gold nanoparticles/carbon nanotubes/ionic liquid microsized paste electrode for the determination of cortisol and androsterone hormones

A novel nanocomposite electrode material constituted of gold nanoparticles (AuNPs), multi-walled carbon nanotubes (MWCNTs) and n-octylpyridinium hexafluorophosphate (OPPF₆) ionic liquid was prepared and checked for the development of electrochemical (bio)sensing devices. AuNPs/MWCNTs/OPPF₆ paste electrodes with micrometer dimensions (500 μm, i.d.) were constructed and applied to the determination of cortisol and androsterone hormones. Regarding cortisol determination, the microsized paste electrode was used to detect 1-naphtol generated upon addition of 1-naphthyl phosphate as enzyme substrate in the competitive immunoassay between alkaline phosphatase-labelled cortisol and cortisol. Squarewave voltammetry allowed determining the hormone within the 0.1- to 10-ng/mL linear range (r?=?0.990) with a detection limit of 15 pg/mL and a EC₅₀ value of 0.46?±?0.06 ng/mL cortisol. The method was applied to the determination of cortisol in urine and serum samples containing a certified cortisol content. Moreover, a microsized enzyme biosensor prepared by bulk modification of the AuNPs/MWCNTs/OPPF₆ electrode with the enzyme 3α-hydroxysteroid dehydrogenase was used for the determination of androsterone through the amperometric detection of reduced nicotinamide adenine dinucleotide. A calibration plot with a linear range between 0.1 and 120 μg/mL (r?=?0.993) and a limit of detection of 89 ng/mL were obtained. The biosensor was applied to the analysis of human serum spiked with androsterone at the 250 ng/mL concentration level.     

Determination of linuron in water and vegetable samples using stripping voltammetry with a carbon paste electrode

A carbon paste electrode was used for the electrochemical determination of linuron concentrations in water and vegetable extracts. Optimal conditions were established with respect to electrode activation (electrochemical pretreatment), time accumulation, potential accumulation, scan rate, and pH. The limit of detection achieved with a pre-concentration step was 23.0 μg L⁻¹. Recovery measurements in vegetable extract and natural water samples were in the range of 98-103%, indicating that the proposed electrochemical method can be employed to analyze linuron in these matrices. The determination results were in good agreement with HPLC results.     

A Novel Adsorptive Square Wave Voltammetric Method for Pico Molar Monitoring of Lorazepam at Gold Ultra Microelectrode in a Flow Injection System by Application of Fast Fourier Transform Analysis

Abstract

This paper describes development of a new analysis system for determination of lorazepam by a novel square wave voltammetry method to perform a very sensitive method. The method used for determination of lorazepam involves measuring the changes in admittance voltammogram of a gold ultramicroelectrode (in 0.05 M H₃PO₄ solution) caused by adsorption of the lorazepam on the electrode surface. Variation of admittance in the detection process is created by inhibition of oxidation reaction of the electrode surface, by adsorbed lorazepam. Furthermore, signal-to-noise ratio is significantly increased by application of discrete fast Fourier transform (FFT) method, background subtraction, and two-dimensional integration of the electrode response over a selected potential range and time window. Also in this work, some parameters such as SW frequency, eluent pH, and accumulation time were optimized. Calibration plots are given for solutions containing 10^?6–10^?11 M of lorazepam. The detection limit is calculated to be 6.0 × 10^?12 M (～ 2 pg/ml). The relative standard deviation at concentration 3.0 × 10^?8 M is 6.1% for 5 reported measurements.     

Highly Selective Adsorptive Cathodic Stripping Voltammetric Determination of Uranium in the Presence of Pyromellitic Acid

A very sensitive and selective adsorptive cathodic stripping procedure for trace measurement of uranium is presented. The method is based on adsorptive accumulation of the uranium‐pyromellitic acid (benzene‐1,2,4,5‐tetracarboxylic acid) complex onto a hanging mercury drop electrode, followed by reduction of the adsorbed species by voltammetric scan using differential pulse modulation. Influences of effective parameters such as pH, concentration of pyromellitic acid, accumulation potential and accumulation time on the sensitivity were studied. The peak current was proportional to the concentration of U(IV) up to 40 ng mL^?1 with a limit of detection of 0.136 ng mL^?1 with an accumulation time of 120 s. The range of linearity enhanced to 71.4 ng mL^?1and the detection limit improved to 0.058 ng mL^?1with accumulation times of 60 s and 300 s respectively. The relative standard deviation for 10 replicate determination of 4.76 ng mL^?1 U(IV) was equal to 2.7%. The possible interference by major cations and anions are investigated. The method was applied to the determination of uranium in some analytical grade salts, seawater and in synthetic samples corresponding to some uranium alloys with satisfactory results.     

Ultratrace Xanthine Determination in Diluted Alkaline Electrolyte by Adsorptive Stripping Voltammetry at the Mercury Film Electrode

Abstract

A stripping method for the determination of xanthine at the submicromolar concentration level is described. The method is based on controlled adsorptive accumulation of xanthine at a thin-film mercury electrode followed by a linear scan voltammetry measurement of the surface species. Optimum experimental conditions were found to be the use of a 5.0 × 10^?3 M NaOH solution, an accumulation potential of 0.00 V, and a scan rate of 20 mV s^?1. The response of xanthine is linear over the concentration range 20–140 ppb. For an accumulation time of 30 min, the detection limit was found to be 36 ppt (2.3 × 10^?10 M). The more convenient relations for measuring xanthine in the presence of the metals, hypoxanthine, amino acids, and other nitrogenated bases were also investigated. The utility of the method is demonstrated by the presence of xanthine in adenosine-5′-triphosphate or DNA.