Submitted to: Journal of Agriculture and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/2007
Publication Date: 4/25/2007
Citation: Shelver, W.L., Kamp, L.M., Church, J.L., Rubio, F.M. 2007. The measurement of triclosan in water using a magnetic particle enzyme immunoassay. Journal of Agriculture and Food Chemistry 55:3758-3763.
Interpretive Summary: This paper describes a new technique for measuring the amount of the antibacterial, triclosan, in water samples such as drinking water, raw sewage or treated sewage. Triclosan is incorporated into a number of cosmetic and household products commonly used throughout the world. The new technique is capable of measuring the triclosan content of a large number of samples much faster than previous methods. As a result, the new method is suitable for wide applications to making sure water supplies contain only small amounts of this contaminant.
Technical Abstract: A sensitive magnetic particle-based immunoassay to determine triclosan (5-chloro-2-(2,4-dichlorophenoxy)phenol) in drinking water and wastewater was developed. Rabbit antiserum was produced by immunizing the rabbit with 6-(5-chloro-2-(2,4-dichlorophenoxy)phenoxy)hexanoic acid-keyhole limpet hemocyanin. Horse radish peroxidase was conjugated with 4-(3-bromo-4-(2,4-dibromophenoxy)phenoxy butyric acid via N-hydroxysuccinimide (NHS) and 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide (EDC). The triclosan antibody was coupled to magnetic particles via NHS/EDC reaction. The antibodies were able to recognize some structurally related polybrominated biphenyl ethers but did not recognize various common pollutants that were less similar to the hapten. The ELISA could detect triclosan at 20 ppt and its metabolite, methyl-triclosan, at 15 ppt. Water samples were prepared to contain 25% methanol and spiked with 62.5, 125, 250, and 500 ppt and analyzed directly without any sample extraction or pre-concentration. The results showed that recoveries were greater than 80% and the % CV was less than 10% demonstrating the assay was both accurate and precise. Application of the triclosan ELISA to water treatment plants (WWTP) showed that tap water at various purification stages had low concentrations of triclosan (< 20 ppt) and required an increased sample size for appropriate detection and measurement. Application of ELISA to the wastewater treatment plants demonstrated high concentrations of triclosan (in general, >3000 ppt in water entering the WWTP) with the levels decreasing as the water proceeded through the processing plant (<500 ppt at outflow sewage). The ELISA assay was shown to be equivalent to the more specific GC-MS assay on a number of wastewater treatment samples with a high degree of correlation, with the exception of a few samples with very high triclosan concentrations. Measurement of methyl triclosan (in WWTP) using GC-MS demonstrated the levels of this compound to be low. In summary, a rapid, sensitive, accurate, and precise magnetic particle-based immunoassay has been developed for triclosan analysis, which can serve as a cost-effective monitoring tool for various water samples.