A Novel Voltametric Measurements of Beta Blocker Drug Propranolol on Glassy Carbon Electrode Modified with Carbon Black Nanoparticles

A new voltametric method for highly sensitive propranolol (PROP) determination was developed. A glassy carbon electrode modified with a hybrid material made of carbon black (CB) and Nafion was used as the working electrode. The preconcentration potential and time were optimized (550 mV and 15 s), as well as the supporting electrolyte (0.1 mol L−1 H2SO4). For 15 s preconcentration time, linearity was achieved in the range 0.5–3.5 μmol L−1 and for 120 s in 0.02–0.14 μmol L−1. Based on the conducted calibration (120 s preconcentration time) limit of detection (LOD) was calculated and was equal to 7 nmol L−1. To verify the usefulness of the developed method, propranolol determination was carried out in real samples (tablets and freeze-dried urine). Recoveries were calculated and were in the range 92–102%, suggesting that the method might be considered as accurate. The repeatability of the signal expressed as relative standard deviation (RSD) was equal to 1.5% (n = 9, PROP concentration 2.5 µmol L−1). The obtained results proved that the developed method for propranolol determination might be successfully applied in routine laboratory practice.

Nimesulide Determination on Carbon Black-Nafion Modified Glassy Carbon Electrode by Means of Adsorptive Stripping Voltammetry

Adsorptive Stripping Voltammetric method for Nimesulide (NIM) determination was developed. As a working electrode, glassy carbon electrode (GCE) modified with carbon black and Nafion (CB-Nafion GCE) was used. All measurements were carried out in 0.1 M acetate buffer (pH 4.6). Conducted experiments allowed to optimize differential pulse voltammetry (DPV) instrumental parameters: sampling and waiting time ts = tw = 10 ms, step potential Es = 4 mV, and pulse amplitude ΔE = 50 mV. The best results were obtained for preconcentration potential and time equal to 400 mV and 20 s, respectively. Limit of detection was calculated and was equal to 0.14 µM for 20-s preconcentration time and 0.06 µM for 40-s preconcentration time. In order to prove the applicability of the developed method, concentration of nimesulide in pharmaceutical products was determined. Calculated recoveries were in the range 94–99%, which indicates that the method might be assumed as accurate. Coefficient of variation was equal to 5.0% (n = 7, NIM concentration 1 µM) Obtained results of NIM determination were in good agreement with the content declared by producers.

On-Line Preconcentration and Simultaneous Determination of Cu and Mn in Water Samples Using a Minicolumn Packed with Sisal Fiber by MIP OES

An on-line preconcentration system for the simultaneous determination of Copper (Cu) and manganese (Mn) in water samples was developed and coupled to a microwave-induced plasma optical emission spectrometer (MIP OES). The flow injection system was designed with a minicolumn packed with sisal fiber (Agave sisalana). A multivariate experimental design was performed to evaluate the influence of pH, preconcentration time, and eluent concentration. Optimal conditions for sample preparation were pH 5.5, preconcentration time was 90 s, and HCl 0.5 mol L−1 was the eluent. The main figures of merit were detection limits 3.7 and 9.0 µg L−1 for Cu and Mn, respectively. Precision was expressed as a relative standard deviation better than 10%. Accuracy was evaluated via spiked recovery assays with recoveries between 75–125%. The enrichment factor was 30 for both analytes. These results were adequate for water samples analysis for monitoring purposes. The preconcentration system was coupled and synchronized with the MIP OES nebulizer to allow simultaneous determination of Cu and Mn as a novel sample introduction strategy. The sampling rate was 20 samples/h. Sisal fiber resulted an economical biosorbent for trace element preconcentration without extra derivatization steps and with an awfully time of use without replacement complying with the principles of green analytical methods.

Immobilization of Pseudomonas aeruginosa static biomass on eggshell powder for on-line preconcentration and determination of Cr (VI)

In the present work, a novel continuous flow system (CFS) is developed for the preconcentration and determination of Cr (VI) using Pseudomonas aeruginosa static biomass immobilized onto an effective and low-cost solid support of powdered eggshells. A mini glass column packed with the immobilized biosorbent is incorporated in a CFS for the preconcentration and determination of Cr (VI) from aqueous solutions. The method is based on preconcentration, washing and elution steps followed by colorimetric detection with 1,5-diphenyl carbazide in sulphuric acid. The effects of several variables such as pH, retention time, flow rate, eluent concentration and loaded volume are studied. Under optimal conditions, the CFS method has a linear range between 10 and 100 μg L-1 and a detection limit of 6.25 μg L-1 for the determination of Cr (VI). The sampling frequency is 10 samples per hour with a preconcentration time of 5 mins. Furthermore, after washing with a 0.1 M buffer (pH 3.0), the activity of the biosorbent is regenerated and remained comparable for more than 200 cycles. Scanning electron microscopy reveals a successful immobilization of biomass on eggshells powder and precipitation of Cr (VI) on the bacterial cell surface. The proposed method proves highly sensitive and could be suitable for the determination of Cr (VI) at an ultra-trace level.

A Simple, Fast, and Inexpensive Simultaneous Determination of Trace Bismuth(III) and Lead(II) in Water Samples by Adsorptive Stripping Voltammetry

A simple, fast, and inexpensive voltammetric method for the simultaneous determination of trace bismuth(III) and lead(II) using (Hg(Ag)FE) as a working electrode was optimized. For adsorptive stripping voltammetric determination of Bi(III) and Pb(II) in a single scan, the cupferron was applied as a complexing agent. Experimental conditions under which these elements can be simultaneously detected include 0.1 mol L−1 acetate buffer (pH = 4.6), 1 × 10−4 mol L−1 cupferron, accumulation potential −0.05 V, and accumulation time 30 s. The experiments were performed without deaeration of the solutions. The calibration graph was linear from 2 × 10−9 mol L−1 to 1 × 10−7 mol L−1 for the simultaneous presence of bismuth and lead. The detection limits for preconcentration time of 30 s were 6.7 × 10−10 mol L−1 and 8.8 × 10−10 mol L−1 for bismuth and lead, respectively. The application of this procedure was tested by analyzing certified reference material (SPS-WW1 Wastewater) and Lake Zemborzyce water (eastern areas of Poland).

Voltammetric Determination of Codeine on Glassy Carbon Electrode Modified with Nafion/MWCNTs

A glassy carbon electrode modified with a Nafion/MWCNTs composite is shown to enable the determination of codeine using differential pulse voltammetry in phosphate buffer of pH 3.0. At a preconcentration time of 15 s, the calibration graph is linear in the 0.5 µM (0.15 mg·L−1) to 15 µM (4.5 mg·L−1) concentration range with a correlation coefficient of 0.998. The detection limit at a preconcentration time of 120 s is as low as 4.5 μg·L−1. The repeatability of the method at a 0.6 μg·L−1concentration level, expressed as the RSD, is 3.7% (forn=5). The method was successfully applied and validated by analyzing codeine in drug, human plasma, and urine samples.

Sensitive quantification of trace zinc in water samples by adsorptive stripping voltammetry

A simple and sensitive adsorptive stripping voltammetry method was developed for determination of Zn using N-nitrozo-N-phenylhydroxylamine (cupferron) as a selective complexing agent. This complex absorbed on the hanging mercury drop electrode and created a sensitive peak current. The peak current and concentration of zinc accorded with a linear relationship in the range of 0.85–320 ng mL−1. The influence of pH and the nature of supporting electrolytes, concentration of ligand, preconcentration time and applied potential were investigated. The relative standard deviation at a concentration level of 50 ng mL−1 was 1.8%. The method was applied to the determination of zinc in city, river and mineral water samples, with satisfactory results.

Sensitive and fast determination of papaverine by adsorptive stripping voltammetry on renewable mercury film electrode

The renewable mercury film electrode, applied for the determination of papaverine traces using differential pulse adsorptive stripping voltammetry (DP AdSV) is presented. The calibration graph obtained for papaverine is linear from 1.25 nM (0.42 µg L−1) to 95 nM (32.2 µg L−1) for a preconcentration time of 60 s, with correlation coefficient of 0.998. For the renewable mercury electrode (Hg(Ag)FE) with a surface area of 9.1 mm2 the detection limit for a preconcentration time of 60 s is 0.7 nM (0.24 µg L−1). The repeatability of the method at a concentration level of the analyte as low as 17 µg L−1, expressed as RSD is 3.3% (n=5). The proposed method was successfully applied and validated by studying the recovery of papaverine from drugs, urine and synthetic solution.

Detection of trace cobalt ions in in vivo plant cells using a voltammetric interlocking system

This experiment was conducted to establish a system for detecting trace cobalt ions in water and plant tissues using a voltammetric in vivo sensor. Cyclic and stripping voltammetry was devised from hand-made, macro-type implantable three-electrode systems. The results reached micro and nano working ranges at 100 sec accumulation time. The statistical detection limit (S/N) was attained at 6.0 ng L–1. For the in vivo application, direct assay of cobalt ions was carried out in Eichhornia crassipes (EC) deep tissue in real time with a preconcentration time of 100 s. Interfaced techniques can be interlocked with other control systems.

Development of Highly Sensitive Compact Chemical Sensor System Employing a Microcantilever Array and a Thermal Preconcentrator

The authors developed a highly sensitive compact chemical sensor system employing a polymer-coated microcantilever sensor array and a thermal preconcentrator with an airpump. The theory, design, structure, fabrication, and experiment results are reported here. This sensor system had 1) sub-ppb detection limit enhanced by a carbon-fiber filled preconcentrator with an air pump and 2) analysis function by thermal desorption of the adsorbed VOCs in the preconcentrator and multiple cantilevers (acting as mass sensors) with different polymers. Eight silicon microcantilevers in one silicon chip fabricated by Micro Electro Mechanical Systems (MEMS) technology were driven by a PZT actuator plate mounted in the package, and four of them were wire bonded. Using the 4th vibration mode (resonant frequency: 764 kHz) of a polybutadiene (2.52 µm thick)-coated cantilever, the sensitivity was 514 Hz/ppm for toluene and 850 Hz/ppm for p-xylene with a 5 min preconcentration time. The estimated detection limit of the sensor system was 0.6ppb for toluene and 0.4ppb for p-xylene with a 5 min preconcentration time, which was good enough for application to environmental monitoring. Separate detection of the mixed toluene and p-xylene was achieved as different time peaks. The authors also estimate the concentration of mixed acetone and 1-propanol by the method of the fitting of two Gaussian curves model.