Band 30, Heft 1

No abstract available

No abstract available

The liquid chromatography-electrospray ionization tandem mass spectrometry method was developed for determination of clenbuterol residues in liver tissue as a regulatory matrix for the control of clenbuterol abuse as an anabolic. To investigate the level of clenbuterol residues during the withdrawal period, male food-producing pigs were exposed to subchronic repeat oral administration of a clenbuterol growth-promoting dose for 28 days. The analytical procedure showed acceptable validation results for all liver spiked samples analyzed and proved to be useful as a quantification and confirmation method in supporting regulatory enforcement programs of clenbuterol misuse monitoring. The highest level of clenbuterol in the liver of treated animals was recorded on day 0 of treatment cessation (21.58±14.29 ng/g), followed by 6.59±3.11 ng/g on day 3, 0.83±0.27 ng/g on day 7, and 0.44±0.08 ng/g on day 14 of withdrawal. At the end of the study period (day 35), the concentration of clenbuterol was below the method limit of detection (<0.1 ng/g).

The simultaneous spectral prediction of levamisole (LEV) and triclabendazole (TRI) in combined veterinary formulation was performed by the new chemometric methods, artificial neural network (ANN) and principal component analysis-artificial neural network (PCA-ANN). Despite the overlapping spectra of LEV and TRI in the same wavelength region, the proposed methods do not use any separation procedure for the analysis of the related compounds. Good precision and accuracy were observed for the applications of the proposed artificial neural network models to an independent binary mixture set consisting of the active compounds. These methods were successfully applied for the chemometric quantitation of a veterinary formulation of LEV and TRI.

An electrochemical investigation of hydroxyflavone, HF; 3-hydroxyflavone, 3-HF; 6-hydroxyflavone, 6-HF; and 3,6-dihydroxyflavone, 3,6-DHF oxidation on a glassy carbon (GC) electrode was carried out using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrochemical oxidation is a complex process, which proceeds in a cascade mechanism, related to the hydroxyl groups of HF, 3-HF, 6-HF, and 3,6-DHF molecules. The hydroxyl group is the first to be oxidized by a one- or two-electron and one- or two-proton irreversible or quasi-reversible oxidation-reduction reaction, followed by an irreversible oxidation reaction due to the hydroxyl groups. The electron and proton oxidation process at the first peak led to the formation of the corresponding quinone, which is an electrochemically active and unstable species, as evidenced by the dependence of the cyclic voltammogram profile on the applied scan rate, in agreement with the electrochemical and then chemical mechanism.

In this article, the investigation of electrochemical determination of guanine(GU) by 1-phenyl-3-methyl-4-(2-furoyl)-5-pyrazolone (HPMαFP) modified glassy carbon electrode (HPMαFP/GCE) in Aciclovir Dispersible Tablets solution was reported. The direct electrochemical behavior of GU was carefully studied in pH 5.5 phosphate buffer solution. Cyclic voltammogram results indicated that a well-defined irreversible redox peak was obtained with the formal potential of 0.92 V. The electrochemical parameter such as the electron transfer number (n) was calculated as 2. The HPMαFP modified electrode showed good electrocatalytic ability to GU. The concentration linear equation is as follows: iP (μA)=4.3767C (μmol l -1 )+9.51332 with the detection limit of 1.2×10 -7  mol/l.

In this study, square-wave adsorptive stripping voltammetry (SWAdSV) and differential pulse adsorptive stripping voltammetry (DPAdSV) were used for determination of ezetimibe (EZE) in the presence of 0.1  m K 2 HPO 4 –Na 2 B 4 O 7 (1:1) supporting electrolyte. The well-defined peaks for SWAdSV were observed at accumulation time of 15 s, accumulation potential of -0.80 V, frequency of 15 Hz, pulse amplitude of 25 mV, potential increment of 4 mV. For DPAdSV, accumulation time of 15 s, accumulation potential of -0.85 mV, scan rate of 20 mV/s and pulse amplitude of 50 mV were found as the best apparatus parameters. EZE gave rise to a single voltammetric peak in the potential interval from -1236 to -1252 mV for SWAdSV and interval from -1190 to -1210 mV for DPAdSV. The developed methods were validated according to the ICH guideline and were found to be linear, sensitive, specific, precise and accurate. The linearity ranges of EZE for SWAdSV and DPAdSV are 33–596 ng/ml and 66–400 ng/ml, respectively. The developed method was applied successfully for the determination of EZE in tablet dosage form.

In this study, electrochemical behavior of phytohormone abscisic acid (ABA) at the bismuth-film electrode (BiFE) has been investigated using square-wave cathodic stripping voltammetry. BiFE was prepared ex situ on a supporting pencil-lead graphite electrode. ABA yielded a well-defined voltammetric response in phosphate buffer, pH 3.0 at -1.08 V (vs. Ag/AgCl) (a pre-concentration step being carried out at a fixed potential of -0.80 V for 120 s). The process could be used to determine ABA concentrations in the range 0.756–15.08 μ m , with a detection limit of 0.209 μ m (55.24 ng/ml). As an example, the practical applicability of pencil-lead BiFE was tested with the measurement of ABA in seed samples of maize plant ( Zea mays L.).

The electrochemical properties of thiourea (TU) were investigated in pH range 2.0–12.0 by cyclic and square-wave voltammetry. The compound was irreversibly oxidized at a pencil graphite electrode in one or two oxidation steps which are pH-dependent. Based on the voltammetric peak for the second oxidation process of TU in phosphate buffer at pH 12.0, a square-wave voltammetric method was proposed for the determination of the compound in the range 6.3–30μ m , with a detection limit of 1.29μ m . The applicability to direct assays of wastewaters was also tested.