Pulsed Amperometric Method Research Articles

Use of ion chromatographic pulsed amperometric method (IC-PAD) for measuring aqueous sulfide in synthetic and real domestic wastewater

Sulfide detection in domestic wastewater is widely demanded, as sulfide induces odour nuisance and wastewater assets corrosion. However, traditional sulfide detection methods are usually plagued by the limited detection range or interference from impurities. To address these constraints, this study improved the ion chromatographic pulsed amperometric method (IC-PAD) and tested its validity for use in domestic wastewater. Prior to sulfide detection, sulfide-containing sample collection usually requires the use of sulfide antioxidant buffers (SAOB) to minimize sulfide loss. Different sample matrixes require different SAOB recipes, which increases complexity and uncertainty when measuring different environmental samples. Therefore, this study also developed a more convenient and generic sample collection method without the addition of SAOB. The results indicated that the proposed SAOB-free sample collection method could minimize the sulfide loss during sample collection. The IC-PAD method showed a wide linear detection range up to 10 mg-S/L. The detection limit was 3 μg-S/L. Matrix effect studies showed that 1 g/L glucose, formate, acetate, methanol, ethanol, propionate, butyrate, lactate, or sulfate had no evident interference on sulfide measurement. However, 5 mM phosphate buffer led to interference, but reducing the KOH eluent concentration from 62 to 30 mM avoid this interference. Wolfe's vitamin mixture and Wolfe's modified mineral mixture could cause diminutive interference equivalent to 2.53 ± 1.32 μg-S/L sulfide. Moreover, the interference caused by chloride indicated that the IC-PAD method is more applicable for measuring sulfide in low-chloride wastewater. To this end, the IC-PAD method showed high accuracy and precision in the real domestic wastewater samples with chloride concentration of 68 mg/L. The recovery was higher than 97% and the relative standard deviation (RSD) was lower than 1.2%. This study demonstrated the potential use of IC-PAD method for measuring sulfide in real domestic wastewater and possible interference from the solution matrix to be considered.

Flow-Injection Amperometric Determination of Tacrine based on Ion Transfer across a Water–Plasticized Polymeric Membrane Interface

A flow-injection pulse amperometric method for determining tacrine, based onion transfer across a plasticized poly(vinyl chloride) (PVC) membrane, was developed. Afour-electrode potentiostat with ohmic drop compensation was used, while a flow-throughcell incorporated the four electrodes and the membrane, which containedtetrabutylammonium tetraphenylborate. The influence of the applied potential and of theflow-injection variables on the determination of tacrine was studied. In the selectedconditions, a linear relationship between peak height and tacrine concentration was foundup to 4x10-5M tacrine. The detection limit was 1x10-7M. Good repeatability was obtained.Some common ions and pharmaceutical excipients did not interfere.

Flow-injection pulse amperometric detection based on ion transfer across a water-plasticized polymeric membrane interface for the determination of imipramine

A flow-injection pulse amperometric method for determining imipramine, based on ion transfer across a plasticized poly(vinyl chloride) (PVC) membrane, was developed. A four-electrode potentiostat with ohmic drop compensation was used, while a flow-through cell incorporated the four electrodes and the membrane, which contained tetrabutylammonium tetraphenylborate. The influence of the applied potential, the flow-injection variables and of the pH on the determination of imipramine was studied. In the selected conditions, a linear relationship between current peak height and imipramine concentration over a range of 1 × 10 −6 to 8 × 10 −5 M imipramine was found. Good repeatability and between-day reproducibility were obtained. No interference was observed on the part of some common ions and pharmaceutical excipients. The method proposed was applied satisfactorily to the determination of imipramine in pharmaceuticals and human serum.

Flow-injection pulse amperometric detection based on ion transfer across a water-plasticized polymeric membrane interface for the determination of verapamil

A flow-injection pulse amperometric method for determining verapamil, based on ion transfer across a plasticized poly(vinyl chloride) (PVC) membrane, was developed. A four-electrode potentiostat with ohmic drop compensation was used, while a flow-through cell incorporated the four-electrode and the membrane, which contained tetraphenylpyridinium tetraphenylborate. The influence of the applied potential and of the flow-injection variables on the determination of verapamil was studied. In the selected conditions, a linear relationship between current peak height and verapamil concentration over a range of 5 × 10 −6 to 1 × 10 −4 M verapamil was found. Good repeatability and between-day reproducibility were obtained. Some common ions and pharmaceutical excipients did not interfere. The method proposed has been applied satisfactorily to the determination of verapamil in pharmaceuticals and human urine.

Determination of Cr(VI) Using a Pulse Amperometric Method with an Ionophore‐Immobilized Membrane Electrode

AbstractA pulse amperometric method for the determination of Cr(VI) in aqueous solution has been investigated with an ionophore‐immobilized membrane electrode. The double potential step chronoamperometry was applied to measure the current for the facilitated transfer of Cr(VI) by the membrane with N,N,N′,N′‐tetrakis(3‐aminopropyl)‐1,4‐butanediamine (DABAm4) coated on a silver electrode. The current responses were stably detected by the pulse amperometry while voltage pulses, ΔE=−240 mV, of short duration of 50 ms were employed at the interval of 5 s. In the range of 1.65–81.3 μM, Cr(VI) in water could be selectively determined in the presence of various interfering anions below 100 μM without removal of Cr(VI) from the interferences using an ion exchange column.

A Novel Electrochemical Microsensor for Nitric Oxide Based on Electropolymerized Film ofo-Aminobenzaldehyde-ethylene-diamine Nickel

A novel electrochemical microsensor for nitric oxide (NO) is described. The microsensor, which is based on an electropolymerized film ofo-aminobenzaldehyde-ethylene-diamine nickel [Ni(ABED)] and Nafion, shows a low detection limit, high selectivity and sensitivity to NO determination. The oxidation current (measured by differential pulse amperometric method) is linear with NO concentration ranging from 1.0×10−8to 1.0×10−6mol/L with a calculated detection limit, at a signal-to-noise ratio of three, equal to 5.0×10−9mol/L and a linear coefficient of 0.9921. Some endogenous electroactive substances in biological tissues, such as ascorbate, dopamine, 5-hydroxytryptamine, cysteine and nitrite do not interfere with NO determination at the concentrations higher than those in biological systems. The microsensor should be promising for in vivo measurement of NO. The mechanism of the response of the microsensor to NO is preliminary studied.

A New Ultramicrosensor for Nitric Oxide Based on Electropolymerized Film of Nickel Salen

A new amperometric ultramicrosensor for the determination of nitric oxide (NO) is described. The ultramicrosensor, which is based on an electropolymerized film of ethylenebis(salicylideneiminate) nickel [Ni(salen)] and Nafion, shows a low detection limit, high selectivity and sensitivity to NO determination. The oxidation current (measured by a differential pulse amperometric method) is linear with NO concentration ranging from 1.0x10−8 to 4.0x10−6 mol/L with a calculated detection limit, at a signal to noise ratio of three, equal to 5.0x10−9 mol/L. Some endogenous electroactive substances in biological tissues, such as dopamine, 5-HT and nitrite do not interfere with NO determination at the concentrations higher than those in biological systems. The ultramicrosensor could be employed for in vivo measurements of NO. The mechanism of the response of the ultramicrosensor to NO is also studied.

Improved ruggedness for membrane-based amperometric sensors using a pulsed amperometric method.

This paper introduces a new approach to the use of membrane-based amperometric sensors which is expected to improve the ruggedness of these sensors significantly relative to the steady-state method in common use. In this new method, the fixed-voltage source used with the conventional steady-state method is replaced by a pulsed-voltage source. Unlike the fixed-source approach, which yields steady-state currents corresponding to large differences between analyte concentrations inside and outside the isolating membrane, the pulsed-source approach permits measurement of currents corresponding to near-equilibrium conditions between solutions inside and outside the membrane. Because the measured currents correspond to near-equilibrium conditions, results are expected to be virtually independent of variables that affect rates of mass transport to and across the membrane. The new approach is evaluated using the "oxygen electrode" as a model system. Results obtained using the new method are compared with results obtained using the conventional steady-state option as well as a coulometric approach described recently. The reproducibility of the pulsed amperometric approach and the scatter of data about least-squares calibration lines are an order of magnitude or more better than for the conventional steady-state option. As expected, the pulsed amperometric method is 40-100-fold less dependent on changes in membrane thickness, stirring rate, and temperature than the conventional steady-state option.

A nitric oxide sensor using reduction current.

Nitric oxide (NO) has a wide range of biologic activity. Methods commonly used for the detection of biologically derived NO are indirect and measure only the amount of NO released during an interval of time. An electrochemical method available is capable of being direct and continuous but is subject to interference. The recent explosion of scientific research into NO activity requires better methods of NO detection. This article reports a new NO electrochemical sensing method and sensor design. The tip of the sensor is covered with a hydrophobic membrane and contains an internal electrolyte. Platinum is used for the working and counter electrodes and silver/silver bromide (Ag/AgBr) for the reference electrode. The components of the internal electrolyte are potassium bromide and sulfuric acid. The NO that diffuses to the working electrode is first oxidized to NO+; the NO+ is reduced to NO; and the reduction current is determined. An integrated pulsed amperometric method is used to achieve the redox of NO and the measurement and integration of the reduction current. The results show that the NO sensor is sensitive and has a rapid response and less interference.