Development of fast Fourier transformations with continuous cyclic voltammetry at an Au microelectrode and its application for the sub nano-molar monitoring of methyl morphine trace amounts

Abstract

In this work, a new highly sensitive and fast method for monitoring methyl morphine in flow-injection systems is introduced. Mathematical methods such as signal integration and fast Fourier transformation used with continuous cyclic voltammetry. It should be stressed that this technique is simple, precise, accurate, time saving and economical. The effects of various parameters on the sensitivity of the detection system were examined. Eventually, it was concluded that the best condition was obtained within the pH value of 2.1, scan rate value of 80 V/s, accumulation potential of 400 mV and accumulation time of 0.4 s. In addition, a special mathematical based numerical method is used for the calculation of the analyte signal and noise reduction. Where, the electrode response was calculated based on the partial and total charge exchanges on the electrode surface, after the background current subtraction from that of noise. In order to increase sensitivity of the method, the currents were integrated over a selected range of potential (including oxidation and reduction of the Au surface electrode), of the recorded CVs. The resulted signal was calculated based on changes in the charge in the CVs. The potential waveform, consisting of two potential steps for electrochemical cleaning, a step for accumulation and a potential ramp for current measurement, was applied to an Au disk microelectrode continuously. In detail, the noteworthy advantages which this method illustrates in comparison with the other reported methods are the following; no oxygen removal is required from the test solution, a sub-nano molar detection limit and the fast determination of any such compound in a wide variety of chromatographic methods. Calibration curve is linear over the concentration range of 0.02–1.1 μM (5.98 × 10 3–329.2 × 10 3 pg/ml) ( r = 0.997) with a detection limit and a quantitation limit of 0.008 μM (2.39 × 10 3 pg/ml) and 0.01 μM (2.99 × 10 3 pg/ml), respectively. Consequently, the method illustrates the requisite accuracy, sensitivity, precision and selectivity to assay methyl morphine in its tablets.