Simple and sensitive voltammetric and HPLC methods were developed for the determination of the three azo dyes (Acid Orange 7, Acid Orange 10 and Acid Orange 12). Optimization of various experimental conditions for quantitative determination of dyes is described. The voltammetric method for determination of trace amounts of dyes is carried out by differential pulse-adsorptive cathodic stripping voltammetry (DP-AdCSV) technique at a hanging mercury drop electrode (HMDE). The effects of different parameters that influence the (DP-AdCSV) response are described. These parameters include pH, accumulation potential, accumulation time, pulse amplitude, scan rate, drop size and interference by other ions. The calibration graphs for the determination of the studied dyes were linear in the range 0.004-0.105 ppm, 0.009-0.180 ppm and 0.007-0.140 ppm with detection limit of 0.002 ppm, 0.005 ppm and 0.004 ppm and relative standard deviation of 1.96%, 2.10% and 2.15% for Acid Orange 7, Acid Orange 10 and Acid Orange 12 respectively. The HPLC method for the determination of dyes using optimum conditions is carried out. The wavelengths of maximum absorbance were 477nm for Acid Orange 10, 485nm for Acid Orange 7 and Acid Orange 12. Retention times were found to be 2.8 min, 4.8 min, and 3.1min for Acid Orange 7, Acid Orange 10 and Acid Orange 12 respectively. Calibration graphs for the determination of the studied dyes were linear in the range 0.05-4.0 ppm, 0.10-4.0 ppm and 0.10-4.0 ppm with relative standard deviation of 3.8%, 4.1% and 4.2% and detection limit of 0.03, 0.05 and 0.05 ppm for Acid Orange 7, Acid Orange 10 and Acid Orange 12 respectively. The Reducing degradation kinetics of the studied dyes by zero-valent iron in aqueous-solutions were studied. Effective degradation was achieved with rate constants of 0.004, 0.002 and 0.003 mmol/L.min, and half-lives of 10 min 22 min and 17min for Acid Orange 7, Acid Orange 10 and Acid Orange 12 respectively.