Environmental Risk Assessment of Polyhexamethyleneguanidine Phosphate by Soil Adsorption/Desorption Coefficient

Abstract

This study was performed to determine the adsorption-desorption characteristics of polyhexame- thyleneguanidine phosphate in three different soil types of textural classification. Adsorption and desorption studies is important for prediction their fate and generating essential information on the mobility of chemicals and their distribution in the soil, water and air of our biosphere. The detection limit of the test substance quantified by a spectroscopic method using Eosin indicator was 0.25 g/mL. The reproducibility μμ μ of analytical method was confirmed by the preliminary test. The concentrations of polyhexamethyleneguanidine phosphate in aqueous solution were 1.36 ± 0.09, 2.45 ± 0.01, and 4.25 ± 0.05 g/mL by a spectroscopic μμ μ method using Eosin indicator. The adsorption percents of polyhexamethylenequanidine phosphate in soil were greater than 95.2% for all three test soils. The desorption percents from the adsorbed soil were less than 4.5, 4.7 and 4.7%. Therefore, the adsorption coefficients (K) were greater than 110, 111 and 116. The adsorption coeffi- cient calculated as a function of the organic carbon content (Koc) of the test soils were greater than 9,181, 11,100, and 8,942, respectively. Therefore, the test substance, polyhexamethylenequanidine phosphate could be concluded as medium or high adsorption (>25%) and poorly desorption (<75%) in soil media. Therefore, this chemical is likely to be retained in soil media and may not pose a risk in the aquatic environment.