Evaluation of the types of emission systems observed in aqueous media with controlled-release formulations

Three types of release systems have been observed for controlled release formulations (CRF) of biocides in aqueous media. A type I system, which is concentration dependent, can be divided into a IA system whose concentration maximum is dependent upon sample size and degradation, and a IB system whose concentration is dependent upon the solubility of the biocide in the solvent. A type II system, which is time dependent, can be divided into a IIA system whose release rate is dependent upon t1/2 and a IIB system whose emission is zero order or dependent only upon time. A type III system, which is a failure system, can be divided into a IIIA system whose concentration decreases to a nondetectable range as a function of t1/2 and a IIIB system whose decreasing concentration is first order. Equations relating the theoretical life of the CRF to its bioactive life are also presented.