Spectrophotometric studies of the reaction between 3-(2-hydroxy-4 and 5-substituted-1-phenylazo)-1,2,4-triazoles and manganese(II) and its applications for microdetermination of manganese(II) in real samples INTRODUCTION However a surplus of manganese in a biological system may damage the nervous system, manganese is a biologically important microelement. Many biological processes, for example photosynthesis, respiration, and transport of substances in plants take place with the participation of manganese. The methods usually used for manganese determination are based on oxidation of Mn(II) to Mn(VII) by heating in presence of oxidizing agents followed by the spectrophotmetric detection of Abdalla M.Khedr*, Mohamed Gaber Chemistry Department, Faculty of Science, Tanta University, Fax: +20 40 3350804, P.O. Box-31527, Tanta, (EGYPT) E-mail: abkhedr2001@yahoo.com. Received: 8 th May, 2008 ; Accepted: 13 th May, 2008 permanganate anion. For spectrophotometric determi- nation of manganese both inorganic [1] and organic [2,3] reagents have been used. These methods based on the color reaction between manganese and organic com- plex-forming reagents are more advantageous. But the known existing methods are often complicated and re- quire oxidation and heating [1] , involve creating exact reaction conditions, and are frequently characterized by poor sensitivity. Therefore, there is need to develop new analytical procedures for manganese determina- tion which do not have these disadvantages. Recently, KEYWORDS Triazole azodyes; Metal complexes; Manganese(II) determination. ABSTRACT Manganese(II) reacts with 3-(2-hydroxy-4 and 5-substituted-1-phenylazo)- 1,2,4-triazoles to produce a purple violet chelates in aqueous media con- taining 40 % (v/v) methanol. The article included an extensive study of the optimum conditions that are essential for the spectrophotometric determi- nation of trace amounts of manganese(II) based on its chelates formation with the azodyes under interest. The molecular structures of the formed complexes were found to be 1:1 and 1:2 (Mn 2+ :HL). The colored dye- manganese complexes showed absorption maxima at 510, 535, 460, 480, 520, and 500 nm. Beer  s law is valid over manganese(II) concentrations up 27.47, 71.42, 54.94, 54.94, 54.94 and 49.44  g of Mn(II) per 10 ml, with molar absorptivities of 3.9810 4 , 1.5710 4 , 0.2010 4 , 0.1010 4 , 0.1010 4 and 0.5310 4 l mol 1 cm 1 using HL 1 -HL 6 , respectively. A notable advantage of the investigated method is that the determination of Mn(II) is possible in the presence of many cations and anions. The method has been applied to the determination of manganese in pharmaceutical formulations with reli- able analytical results. Some solid complexes were prepared and subjected to different spectroscopic and analytical techniques as well as thermal analysis in order to investigate the mode of interaction between the azo compounds and Mn(II) ion.  2008 Trade Science Inc. - INDIA Full Paper ICAIJ, 3(3), 2008 [175-181] An Indian Journal Trade Science Inc. Volume 3 Issue 3 September 2008 Inorganic CHEMISTRY