437 Journal of Basic & Applied Sciences, 2012, 8, 437-443 ISSN: 1814-8085 / E-ISSN: 1927-5129/12 © 2012 Lifescience Global Dosimetric Characteristics of Aqueous Solutions of Sandalfix Red Dye for Gamma Dosimetry Taqmeem Hussain 1,* , Muhammad Shahbaz 2 , Inam-ul-Haq 3 , Hashim Farooq 3 , Nasir Amin 1 and Yasir Jamil 3 1 Department of Physics, GC University, Faisalabad, Punjab, Pakistan 2 Punjab Institute of Nuclear Medicine (PINUM), Faisalabad, Punjab, Pakistan 3 Department of Physics, University of Agriculture, Faisalabad, Punjab, Pakistan Abstract: Gamma dosimetric behavior of the aqueous solutions of the Sandalfix Red (C.I. Reactive Red 195A) dye was studied. The sample solutions of two chemical natures i.e., Acidic and Alkaline; were irradiated by Co 60 -source in the range 0-100kGy. The “Control samples” were kept un-irradiated and also chemically neutral. The dosimetry was done in three phases i.e., Low, Intermediate and High, ranging from 100-1000Gy, 1-10kGy and 10-100kGy respectively. The found values of the “!max” and the molar extinction coefficient “"” of the dye were 565nm and 0.19!10 4 dm 3 mol -1 cm -1 respectively. The absorbance (A) of the aqueous solutions was studied at the absorption band maxima (!max). It was hence found that the aqueous solutions of the Sandalfix Red C4BLN dye were able to be used as passive dosimeters in the range 10-100 kGy i.e., the sample solutions have shown radioactive exponential behavior of response in the “Intermediate and High dosimetry”. However, a linear response was shown by the sample solutions in the “Low dosimetry”. Keywords: Chemical dosimeters, Sandalfix Red C4BLN dye, dosimetry, optical density (OD), radiolytic bleaching. 1. INTRODUCTION It is an established fact that the ionizing radiations can cause chemical and physical changes in the exposed material [1-5]. The knowledge about the amount of gamma energy absorbed in the matter is known as radiation chemistry. In radiation chemistry, a quantitative estimation of the absorbed energy deals with its branch known as “Dosimetry” and the system employed to do this job is known as a “Dosimeter” [2- 5]. Amount of energy absorbed from the gamma radiation with respect to the chemical changes produced in the system on exposure to the radiation is called “Chemical dosimetry”, which requires calibration in order to use as dosimeter and is, therefore, termed as secondary dosimeter (passive dosimeter) [6]. The verification of the Sandalfix Red C4BLN to be used for dosimetric calculations within the gamma radiation dose range 0-1kGy was already reported [3] as this dye obeys the Beer’s Law but in the present study the absorbed dose range was increased from 0- 100kGy in order to observe the change in the ! max and the dosimetric response of the dye with respect to the absorbed doses. The application range depends on the concentration of the dye and the solvents used [7]. Bleaching of the dye in aqueous solutions by the *Address corresponding to this author at the Department of Physics, GC University, Faisalabad, Punjab, Pakistan; E-mail: relyables@yahoo.com ionizing radiations is a known fact now and is still an active research area for many researchers of the present era to produce dosimeters which should be inexpensive, easy to handle and have the capacity to work within the high dose ranges [8]. This bleaching property of the chosen dye makes the aqueous solutions of the dye able to be used for dye-dosimetry, since the decomposition of the dye depends linearly upon the amount of dose absorbed [6, 9]. 2. MATERIALS & METHODS Aqueous solutions of Sandalfix Red C4BLN (Color Index: Reactive Red 195A, MW= 1033.5 amu) were prepared. The sample solutions of concentration 1g/L of the dye weighted by electrical balance (Sartorius Ag Gottingen BL2105, Germany) and dissolved in one liter demineralized water. The stock solution was set at pH 7.0 measured by pH-meter (Hanna 8417). Two concentrations of the dye solutions were prepared such as C 1 =968 mol/L and C 2 =484 mol /L. The solutions of pH 1, 2, 3, 4, 5 and 6 in the present study were termed as “Acidic Samples” and those of pH 8, 9, 10, 11, 12, 13 and 14 were termed as “Alkaline Samples” while solution of pH 7, which were kept chemically neutral and un-irradiated, were termed as “Control samples”. The pH of the samples was raised and lowered using sodium hydroxide (NaOH) and hydrochloric acid (HCl) respectively. The prepared samples were preserved at room temperature (30 o C). The dye has absorption band maxima i.e., ! max =565nm