Abstract Recent years have seen an upsurge of interest in developing low cost and precise methods for the determination of trace and ultra trace concentrations of persistent organic and inorganic pollutants of carcinogenic effects to human life in various matrices. Thus, the overall work in this thesis can be summarized as follows i. Detailed investigations on the redox behaviour of two organochlorinated pesticides namely alachlor and chlorfenvinphos in B-R buffers of pH 2.3-11 using DP-CSV and cyclic voltammetry techniques at hanging mercury drop electrode (HMDE), Pt and Au working electrodes were carried out in an attempt to develop a low cost and precise DP-CSV procedures for the determination of the tested pesticide. Thus, a sensitive and selective DP-CSV method was developed for the analysis of each pesticide at the optimum experimental conditions. The validation and application of the developed methods were determined by the analysis of the pesticides in water, sediment and food samples and compared successfully with the standard GC-MS. ii. Developing a precise and selective DP-CSV method for the analysis of ultra trace concentration of antimony (III) in complicated matrices. The method was based upon the accumulation of the antimony (III) – HTTA complex at the HMDE, followed by the stripping voltammetric measurements of the resulting cathodic current (ip, c) at -0.18 and -1.32 V vs. Ag/AgCl electrode. The plot of the ip, c versus antimony (III) concentrations was linear over a wide range of concentration (8.20 x 10-9- 1.07 x 10-7 mol L-1). The method was applied for the analysis of antimony (III) and (V) in various samples and compared successfully with the data obtained via the standard ICP-MS method. The DP-CSV technique provides good sensitivity, selectivity, reproducibility and low limit of detection and quantification for the analytes under investigation.