Method development and monitoring of Irgarol-1051 and its metabolites by liquid chromatography electrospray tandem mass spectrometry

Abstract

Marine fouling is the growth and settlement of microorganisms, plants and animals on submerged structures such as ship hulls, buoys and oil rig supports. The fouling is a serious problem to shipping industry, as it increases the surface friction of ship hull and hence its movement resistance through water. The subsequent increase in fuel consumption boosts the emission of air pollutants, e.g. sulfur dioxide, nitrogen oxides and carbon monoxide. Fouling also increases the frequency of dry-docking and repairing of vessels. A large amount of toxic wastes are generated during these operations and resources are wasted when remedial measures are applied. Antifouling agents are used to control the fouling of submerged structures. EU (European Union) restricted the use of tributyltin (TBT) antifouling agents in the late 1980s and the IMO (International Maritime Organization) has eventually banned the use of TBT world-wide in 2003. New organic booster biocides were recently introduced as alternatives to TBT. Irgarol 1051 (2-methythio-4-tert-butylamino-6-cyclopropylamino-s-triazine), an algaecide used with copper based antifouling agents, has become one of the most popular TBT replacements and has been the first booster biocide to gain prominence as an environmental contaminant. Various studies have indicated that Irgarol 1051 can undergo chemical, biological and photo degradation with the formation a greater environmental persistence product known as M1 or GS26575 (2-methylthio-4-tert-butylamino-6-amino-s-triazine). Recently, our research group has identified two new Irgarol-related s-triazine species in coastal waters. They are 3-[4-tert-butylamino-6-methylthiol-s-triazin-2-ylamino]-propionaldehyde (M2) and 2-methylthio-4,6-bis-tert-butylamino-s-triazine (M3). Although the occurrence of M2 and M3 in the aquatic environment of Hong Kong has been established, their distribution in other environmental compartments, e.g. sediments, is still unknown. It is interesting to have a better insight into it, as this can further enhance our understanding of the accumulation properties and environmental fate of Irgarol 1051 and its related species in the aquatic ecosystem. In this study, a sensitive, selective and novel method for the detection of Irgarol 1051 and its related compounds in both coastal waters and sediments has been developed. The extraction of these compounds in waters was performed by means of liquid-liquid extraction using dichloromethane. For sediment samples, acetone sonication followed by C18 SPE (solid phase extraction) clean-up was adopted. The resulting extracts were then analyzed by liquid chromatography electrospray tandem mass spectrometry (LC-ESI-MSMS). A perfluorinated carboxylic acid was used as an ion-pairing agent (IPA) for the chromatographic separation. Multiple-reaction-monitoring (MRM) mode was adopted for mass spectrometric detection. The resulting chromatographic performance is superior to previous LC-UV methods using alkylsulfonate as the ion-pairing agent, in terms of the enhancement of resolution and the reduction of analysis time. The analytical protocols were successfully applied to determine s-triazine species in the coastal waters and sediments in various selected spots in Hong Kong. Our results show that Irgarol 1051 and its related compounds are found in both environmental compartments with concentrations up to 76.1 ng L-1 in waters and 3694.0 pg g-1 in sediments. It is also indicates that the s-triazine species can be accumulative in sediments.

Date of Award	2 Oct 2007
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Hon Wah Michael LAM (Supervisor)