Differential Pulse Stripping Voltammetric Determination Of Complex Systems Of Organic Pharmaceuticals

The application of electrochemistry methods for determination of organic pesticide residues and pharmaceuticals has been developed. And the combination of electrochemistry with chemometrics can be used to solve some problems, which are countered in spectrum resolution. One of the current requirements in analytical chemistry is to detect and quantify smaller amounts of chemical contaminants in samples of diverse natures, with low cost and time consumption. Hence selective, sensitive and rapid methods of analysis, using rapidly available and conventional instrumentation, must be developed.The work is divided into five parts.Chapter oneOne of the current requirements in analytical chemistry is to detect and quantify smaller amounts of chemical contaminants in samples of diverse natures, with low cost and time consumption. Hence selective, sensitive, rapid and inexpensive methods of analysis, using rapidly available and conventional instrumentation, must be developed. In part one, it is described and reviewed the application of chemometrics in the determination of organic pesticide residues. Organic pesticide residues can be analyzed by these techniques in the environment successfully. Application of chemometrics in organic pesticide residues analysis during recent twenty years is reviewed with 135 references. Optimization of experiment conditions, multivariate calibration method, artificial neural network and signal smooth have been described in details.Chapter twoA differential pulse stripping voltammetry method (DPSV) is proposed for the determination of pendimethalin, dinoseb and sodium 5-nitroguaiacolate at a hanging mercury drop electrode (HMDE). The voltammagrams of these three compounds overlap strongly, and it is difficult to determine the compounds individually from their mixtures. Quantitative analysis for each of the pesticide compounds in a mixture has been investigated with the aid of chemometrics and the prediction performance of the different methods such as classical least squares (CLS), principal component regression (PCR) and partial least squares (PLS) was compared. A set of synthetic mixtures of the three compounds was analysed by using the proposed methods, and it was found that the lowest relative prediction error (RPE) was achieved with the DPLS procedure. The proposed method was also applied to several vegetable samples and water samples spiked with known amounts of the pesticides with satisfactory results.Chapter threeVoltammetric behaviour of three herbicides, cyanazine, simetryn and dipropetryn was investigated, and a method was developed for the simultaneous determination of these compounds. This was based on their anodic voltammetric behaviour at hanging mercury drop electrode. It was found that by applying the differential pulse stripping voltammertric (DPSV) method in the presence of Britton-Robison buffer, the three compounds have well defined voltammetric reduction waves with peak potentials at -1043, -1062 and -1011 mV, respectively. For each compound, a linear calibration was obtained in the concentration range of 0.01～0.08μg mL^-1. Serious overlapping of individual voltammetric peaks was observed for the mixtures of these three compounds, and to facilitate the resolution of these complex voltammograms, different calibration models were investigated based on three different chemometrics methods, viz., classical least squares (CLS), principal component regression (PCR) and partial least squares (PLS). The best results were obtained with the PLS method, and the developed method was then applied to the analysis of the pesticide in field samples with similar satisfactory results.Chapter fourEther pesticides are widely used in agriculture and their properties provide numerous benefits in terms of production and quality increase. Their presence in water and food poses a potential hazard to human health, and fast, reliable and economically viable methods are required for their detection in the environment and in agro-food products. As shown in this section, multivariate calibration in general and principal component regression (PCR) in particular allow the determination of ether pesticides by differential pulse stripping voltammetry (DPSV) method despite the overlap between their voltammetric bands. The analytical performance of the prediction models was characterized with the use of various figures of merit, and the best results were obtained with the radial basis function artificial neural network (RBF-ANN) method, which was adopted as the parameter to be minimized. The proposed method is quite fast as a result of the decreased analysis times.Chapter fiveA differential pulse stripping voltammetry method for the determination of metoclopramide in Chinese traditional medicines was developed. The electrochemical behavior and voltammetric parameters of Metoclopramide at a glass carbon electrode were investigated and evaluated. In the pH=3.29 B-R buffer solution, Metoclopramide has a sensitive irreversible reductive peak. The electrode reaction is an irreversible process according to the differential pulse stripping voltammetry graph. We could deduce that the peak was obtained from absorption. Under the optimal condition the peak current was linear with its concentration in the range of 1.2～2.5μg mL^-1. The detection limit was 0.28μg mL^-1. It was applied to the determination of metoclopramide in Chinese traditional medicines with satisfactory results.