Farhad Nakhostin Allaf - Department of Chemistry, University of Mohaghegh Ardabili, Ardabil, Iran
Habibollah Eskandari - Department of Chemistry, University of Mohaghegh Ardabili, Ardabil, Iran

Orange II (sodium4-[2-(2-oxonaphthalen-1-ylidene)hydrazinyl]benzenesulfonate ) is an azo dye which has many applications in light emitting diodes (OLEDs), inks, soaps, wood preservation, textile and leather industry, hair dyeing, cosmetics, and foodstuffs [1]. Many countries, however, have regulated the use of Orange II in foodstuffs because it poses a risk to human health as carcinogenic, and reduces the number of red blood cells, accompanied by the lowering of hemoglobin and packed cell volume [2]. Hence, the determination of low concentrations of Orange II is a primary need.In this work, a new magnetic sorbent, magnetite/nickel hydroxide is introduced for a typical enrichment-electrochemical determination. After sorption of Orange II, the nickel hydroxide content of the sorbent (containing Orange II) was dissolved in a low volume of acetic acid/acetate buffer (pH equal to 3.6) and then was analyzed by differential pulse voltammetry (DPV) when Orange II is electrochemically oxidized on MWCNT-COOH modified platinum disk microelectrode. The magnetic sorbent and surface of the modified electrode were characterized by different methods including XPS, SEM, VSM, EDX and XRD. Under optimum condition of enrichment and detection, calibration curve was constructed that showed two linear ranges of 0.5-10 and 60-300 nmol L-1. The relative standard deviation and recovery for determination of Orange II (5 nmol L-1) were 4.1 and 105.0 as percent, respectively. Limit of detection for the Orange II determination method was also evaluated (0.3 nmol L-1). The method was applied for the determination of Orange II in various environmental water samples. This approach showed advantages on simplicity, sensitivity and selectivity of Orange II determination when was compared with the other analytical methods