Abstarct: In this study a new simple, sensitive and selective catalytic-kinetic-spectrophotometric method for the determination of trace amounts of oxalate is proposed. The method is baxsed on the catalytic effect of oxalate on the oxidation of crystal violet by dichromate in acidic media. The reaction was followed by measuring the decrease in absorbance of crystal violet at 630 nm (λmax of crystal violet in acidic solution). The dependence of sensitivity on the reaction variables was studied and discussed. Under the optimum conditions a fixed time procedure was used to obtain a linear calibration curve in the ranges of 0.20-5.5 of oxalate. The calculated detection limit was 0.050 µg ml-1. The standard deviations for ten replicate determinations of 0.40, 1.8 and 2.5.µg ml-1 of oxalate were 7/1%, 3/7% and 1/77%, respectively. The effect of the presence of various species, commonly associated with real samples was also investigated. The proposed method has been successfully applied for the determination of oxalate in spinach and spiked water samples. In this study, N, N - Bis (naphtiliden imino) diethyltriamin bonded on polystyrene has been used as a new chelating sorbent for the on–line preconcentration and determination of Co )II( by flame atomic absorption spectrometry using a flow injection manifold. Cobalt (II) can be quantitatively retained on adsorbent filled in a minicolumn at pH=7.0. The elution of cobalt with HCl 2.0 M from the sorbent is quantitative. The effect of various chemical and instrumental variables on the preconcentration and determination of cobalt (II) has been investigated. Under the optimum conditions, for 10 ml of sample solution the calibration graf was linear in the range of 0.001-0.08. The 3 limit of detections were 0.78 and 0.29 ngml-1 using 10 and 20 ml of sample solution, respectively. A preconcentration factor of 110 can be achieved for 10 ml of sample solution. The relation standard deviations for 10 replicate determination of 0.007 and 0.030 μgml-1 of cobalt (II) were 0.0020. The method has been applied to the determinate of cobalt in tap water, spring water and sodium chloride solution with satisfactory results (%Recovery91- 107).