________________________________________ * Author for correspondence; E-mail: khdijajabar@gmail.com Int. J. Chem. Sci.: 14(3), 2016, 1385-1404 ISSN 0972-768X www.sadgurupublications.com A NEW FLOW INJECTION AND SEQUENTIAL INJECTION SYSTEMS WITH SPECTROPHOTOMETRIC DETECTIONS FOR DETERMINATION MAGNESIUM ION KHDEEJA JABBAR ALI * and FATIMA FAHIM ABD Chemistry Department, Education for Girls Faculty, Kufa University, NAJAF, IRAQ ABSTRACT This research includes the design flow injection and sequential injection systems for determining magnesium ion containing valve is designed locally. The FIA and SIA systems based on the reaction of magnesium with Eriochrome Black T at pH (9-10.5) with an absorption maximum at 520 nm. Various parameters (physical and chemical) affecting the determination have been investigated such as flow rate, reaction coil, volume of reagent (Eriochrome Black T), volume of sample, concentration of Eriochrome Black T. The calibration curve was prepared and the dispersion coefficient, reproducibility, interferences and application were studied. Two methods, flow injection and sequential injection analysis were compared for determination of magnesium by Eriochrome Black T. The linear range was (1-15 mg/L), (0.05-15 mg/L) at sampling rate of 120, 100 sample per hour, the detection limits (0.0221 mg/L), (0.0096 mg/L) for FIA and SIA, respectively. Relative standard deviations for (15 mg/L), n = 3 were found (0.0823% for FIA and 0.1221% for SIA). Dispersion coefficient was also measured for the two methods. Key words: Flow injection, Sequential injection, Eriochrome black T, Magnesium. INTRODUCTION Mg(II) ions have indispensable roles in many vital biological events 1,2 . The relationship of magnesium deficiency and diabetes mellitus has generated discussion in the medical field in the past 10 years 3 . In addition, Mg(II) is involved in a series of metabolism processes in the human body, including the formation of bones and cells. The daily requirement of Mg(II) for an adult is 350 mg for a male and 300 mg for a female. Magnesium deficiency will result in muscle sag and poor stamina 4 , so the determination of magnesium in foods and drinking waters is very important. Magnesium is the eighth most abundant element in the crust of the Earth. The