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A novel voltammetric method for the determination of trifluralin is proposed based on a composit of carbon paste and copper nanowire as a sensitive sensor. The presence of copper nanowire in the composite film enhance the conductivity and as a result increased the electron transfer rate constant and so the current will increase. The composite exhibits a promising higher electrocatalytic activity towards the oxidation of trifluralin in pH 4.0 aqueous solution. The reduction peak currents of trifluralin increased remarkably and the reduction peak potential shifted positively at the nanostructuring electrode, compared with that at a bare CPE which show the enhanced effect of nanowire. The support electrolyte to provide a more defined and intense peak current for trifluraline determination was 0.05 mol L phosphate buffer at pH 4.0. The fast Fourier transform square wave voltammetry was used as a new electrochemical technique in flow injection system to abtain more sensitivity by application of discrete fast Fourier transform method by background subtraction and two-dimensional integration of the electrode response over a selected potential range and time window, the signal-to-noise ratio has significantly increased and made the sensivity to be higher than other methods. The effective parameters such as frequency, amplitude, and pH were optimized to get the best sensitivity. As a result, the sensor showed a valuable response in linear concentration range of 100-0.02 nmol L with a (limit of detection) LOD of 0.008 nmol L and (limit of quantification) LOQ of 0.15 nmol L for trifluralin. A good recovery was obtained for assay spiked urine samples and a good quantification of trifluralin was achieved in soil samples. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the optimization of instrumental and solution parameters for determination of tamoxifen in urine and plasma and formulation by fast Fourier transform square wave voltammetry (SWV) using a gold microelectrode in flow-injection system. The samples are subjected by the same buffer solution and are injected in the flow-injection apparatus. By applying a novel square wave voltammetry method to perform as a sensitive method the voltamograms are recorded. The method used for determination of tamoxifen by measuring the changes in admittance voltammogram of a gold ultramicroelectrode (in 0.05molL−1 H3PO4 solution) caused by adsorption of the tamoxifen on the electrode surface. The best sensitivity was achieved using a frequency of 600Hz and a medium composed of 0.05molL−1 phosphate buffers at pH 2.0. The best performance was obtained with the pH value of 2, pulse amplitude 25mV, frequency 600Hz, accumulation potential of −100mV and accumulation time of 0.5s. Furthermore, signal-to-noise ratio has 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. Calibration plots are given for solutions containing 1.0×10−11 to 3.0×10−6 molL−1 of tamoxifen. The detection limit is calculated to be 3.0×10−12 molL−1 (∼2pgmL−1). The relative standard deviation at concentration 2.0×10−8 M is 6.1% for five reported measurements. [Copyright &y& Elsevier]

This study illustrates a novel method for fast monitoring of tetracycline in flow-injection systems. The fast Fourier transformation, along with continuous cyclic voltammetry (FFTCV) at a gold microelectrode in a flowing solution system, was used for the determination of tetracycline in its pharmaceutical formulation. The benefit of the developed technique is that it is 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. Three considerable advantages are demonstrated by this method, which other methods do not possess. Firstly, there is no requirement for oxygen removal from the test solution; secondly, a picomolar detection limit is gained; and, finally, rapid determination of any such compound in a broad range of chromatographic methods. As a result, the method was found to be linear over the concentration range of 16-440 pg/mL (r = 0.9962), with a limit of detection and quantitation of 4.5 and 16 pg/mL, respectively. Furthermore, the technique shows the requisite accuracy, sensitivity, precision, and selectivity to assay tetracycline in capsules. [ABSTRACT FROM AUTHOR]