Water analysis – Semi-volatiles
SVOCs in watercourses
The universal use of pharmaceuticals and personal care products (PPCPs) results in the continual presence in the environment of a large number of semi-volatile organic compounds (SVOCs), even though individual compounds may not be especially persistent. Low concentrations of such SVOCs have been detected in a range of environmental media, including surface water, groundwater, marine water, drinking water, soils and sediments.
There is now a significant body of evidence supporting the theory that exposure to low doses of certain SVOCs at several key stages of development can influence patterns of growth in a range of organisms, including humans. Furthermore, it is thought that low doses can result in effects that would not necessarily be predicted from their effects at high doses.
The lack of information on amounts of SVOCs in water and their possible ecological effects has led to debate about the need to monitor them in (and remove them from) waste water.
|Endocrine-disrupting chemicals (EDCs) || |
A wide range of substances, both natural and man-made, are thought to disrupt the action of hormone receptors in humans.
These include dioxin and dioxin-like compounds, polychlorinated biphenyls (PCBs), brominated flame retardants, pesticides, and components of plastics such as bisphenol A (BPA) and phthalates.
At low doses, EDCs are believed to be linked to adverse effects in humans, including cancer, obesity, type 2 diabetes, low semen quality and genital malformations.
As a result, EDCs are of ongoing interest to the analytical chemist, and the focus of much current research.
This is a relatively new and highly complex field, with many unanswered questions, including:
- What are the sources of SVOCs found in the environment?
- What are the most important routes of exposure?
- How are levels affected by environmental factors?
- At what point do SVOC levels start to present a hazard?
- What are the mechanisms of action resulting in ecological effects?
Thermal desorption–gas chromatography (TD–GC) has a role to play in answering some of these questions, by providing detailed information on the identity and abundance of individual chemicals.
What Markes can offer
Detecting SVOCs in water falls into two broad areas:
- Short-term monitoring – At the site of an ongoing pollution event, rapid sampling and analysis is paramount, and best addressed by sorptive extraction. This can be done by sampling analytes onto a HiSorb probe, which is then directly desorbed in an empty TD tube, with subsequent analysis by TD–GC–MS. HiSorb sampling is now fully automated on the Centri sampling and preconcentration system.
- Long-term monitoring – Here the emphasis is on collecting the largest possible quantities of compounds, to even-out daily variations and to obtain maximum possible sensitivity. Semi-permeable membrane devices (SPMDs) are typically deployed in a watercourse for several weeks, and in conjunction with analysis by GC×GC–TOF MS are a powerful technique for detecting a range of compounds at varying concentrations.