The effect of Crosslinking Temperature on the Swelling Degree of Citric Acid-Agarose Gel for Diffusive layer of DGT
Digwanggi Arum Tazkiyatu An-Nufuus, Barlah Rumhayati, Qonita Fardiyah, Diah Mardiana, Ulfa Andayani, Layta Dinira

Department of chemistry
Faculty of mathematics and natural sciences
Brawijaya University

Abstract

Diffusive gradient in thin films (DGT) technique is a diffusive passive sampling technique which is combined in situ analyte uptake, contaminants filtration, and pre concentration in a single way. Probe of DGT consists of a filter, diffusive layer, and a binding layer sequentially. Agarose has been used for the diffusive layer of DGT with big pore size inducing high swelling degree. Addition of crosslinker, such as citric acid, for agarose-diffusive layer can reduce the swelling degree. The aim of this research was to study the effect of temperature of crosslinking of citric acid and agarose on the swelling degree of the diffusive gel. Agarose diffusive layer was prepared by mixing 1.5% agarose solution with the addition of 0.75% citric acid solution. The mixture was casted in an oven at temperature of 25, 40, 50, 70 Celsius degree. The formed gel then was soaked in water, NaCl 0.1 M, pH 4, 5, 6, 7, and 8 for 1, 2, 3 and 24 hours. The mass of gel was weighted before and after soaking. Swelling degree is the ratio between the final mass and the initial mass. Results shows that the swelling degree of agarose-citric acid diffusive gel was stable at 3 hours. The diffusive layer showed stable swelling degree at crosslinking temperature of 400 C. The diffusive layer was not swelling out in the media of NaCl 0.1 M.

Keywords: citric acid, diffusive layer, agarose, DGT, swelling

Topic: Analytical Chemistry