The effect of pH on the characteristics of the methyl red solution as a gamma-ray dosimeter

Abstract

The effect of the pH on the color change characteristics of the methyl red solution, when exposed by gamma radiation, is the main objective of this study. The colorwas characterized using a UV-Visible spectrophotometer and a digital photography camera. The used irradiator source is 60Co with doses varied from 5-100 kGy and a dose rate of 5.5 kGy/h. The color stability was studied by observing the effects of the storage conditions of the solution: temperature, light, and humidity. The original methyl red solution at pH 6.3 has a red color and gives a radiochromic phenomenon with a change of color from red to dark red for a dose of 5-20 kGy, then the color fades and turns colorless gradually at a dose of 25-100 kGy. On the other hand, for a methyl red solution of pH 7.1 before irradiation has a yellow color, turns to dark yellow at doses of 5-25 kGy, then the color fades and becomes colorless at a dose 40 kGy. The color of the methyl red solution at pH 7.1 is more stable against storage light conditions compared to pH 6.3. These results suggest that this methyl red solution can be used as a gamma-ray dosimeter in the dose range of 5-40 kGy.