• Rein, Arno
• Gosewinkel, Ulrich Bay
• Smith, Kilian E. C.
• Mayer, Philipp
• Heringa, Mb

Abstract

Achieving well-defined and constant dissolved concentrations of hydrophobic compounds is <br/>challenging due to volatilization or sorptive losses. With passive dosing, continual partitioning <br/>into the test medium of compound(s) loaded in a polymer compensates for losses, and provides <br/>defined and constant dissolved concentrations. Passive dosing can be used for studying biotransformation/ <br/>degradation. Here, the polymer HOC reservoir also compensates for losses due <br/>to the bio-transformation/degradation process itself. Furthermore, a large mass of test compound <br/>is introduced so that compound turnover is significant even at low dissolved concentrations thus <br/>facilitating measurement of the relevant endpoint (e.g., metabolic products in biotransformation <br/>or growth in biodegradation). This study details two applications of passive dosing for studying <br/>bio-transformation/degradation. A format has been developed to study the biodegradation of <br/>phenanthrene and fluoranthene by the bacterial strain EPA 505, allowing degradation rates to be <br/>quantified at defined freely dissolved concentrations from mg/L down to ng/L levels. Passive dosing <br/>was also applied for quantifying the mutagenicity of benzo(a)pyrene metabolites produced <br/>after activation by the liver S9 mix in the in vitro Ames II assay. Compared to the case with spiking, <br/>responses from passive dosing were shifted by a factor 100-1000 to lower concentrations, <br/>and were also more reproducible between repeated tests. This difference in apparent sensitivity <br/>cannot solely be explained by partitioning, and is due to slow dissolution kinetics as well as massdepletion <br/>of the spiked benzo(a)pyrene. Therefore, passive dosing is a useful tool for the study of <br/>hydrophobic compound bio-transformation/degradation at well-defined dissolved concentrations <br/>down to very low levels. Important advantages include studying process kinetics at precisely <br/>defined dissolved concentrations and allowing increased compound turnover even at constant <br/>and low concentrations. <br/> <br/>

Topics

• impedance spectroscopy
• compound
• polymer
• activation
• additive manufacturing