Interaction between Humic Acid and p-Arsanilic Acid Using Fluorescence Quenching Approach

P-arsanilic acid(p-ASA),as a kind of organoarsenic feed additive,has been widely used in poultry and swine breeding.However,it has caused the arsenic pollution around the farm.Currently data shows humic acid(HA)is closely to the migration and transformation of p-ASA.Therefore,the interaction between p-ASA and HA was investigated by using the method of fluorescence quenching titration.The association constant changed from2.74 to 4.88 L·mol-1at a p H varying from 5 to 9 and reached the maximum at p H 7.In addition,log K varied from4.15 to 5.02 L·mol-1when the temperature increased from 15℃to 35℃.The log K increased with an increase in the concentration of HA.The dominant mechanism between p-ASA and HA is static quenching.The primary interaction force was likely the hydrogen bond,and the binding behavior occurred on the As-O stretch of p-ASA and the carboxylic acid C=O stretch of HA.The results showed that dissolved organic matters could affect the fate and biogeochemical cycling of organoarsenic pharmaceuticals in aquatic ecosystems.

Interaction between Humic Acid and p-Arsanilic Acid Using Fluorescence Quenching Approach

P-arsanilic acid (p-ASA),as a kind of organoarsenic feed additive,has been widely used in poultry and swine breeding.However,it has caused the arsenic pollution around the farm.Currently data shows humic acid (HA) is closely to the migration and transformation of p-ASA.Therefore,the interaction between p-ASA and HA was investigated by using the method of fluorescence quenching titration.The association constant changed from 2.74 to 4.88 L·mol-1 at a pH varying from 5 to 9 and reached the maximum at pH 7.In addition,logK varied from 4.15 to 5.02 L·mol-1 when the temperature increased from 15 ℃ to 35 ℃.The logK increased with an increase in the concentration of HA.The dominant mechanism between p-ASA and HA is static quenching.The primary interaction force was likely the hydrogen bond,and the binding behavior occurred on the As-O stretch of p-ASA and the carboxylic acid C =O stretch of HA.The results showed that dissolved organic matters could affect the fate and biogeochemical cycling of organoarsenic pharmaceuticals in aquatic ecosystems.