Polycyclic aromatic hydrocarbons (PAHs) are found worldwide and are emitted from a number of sources including fossil fuel, coal and shale oil derivatives, coke production, and burning wood for home heating, generally arising from incomplete combustion. Surface water supplies, such as water in ponds may be used for recreational purposes or become a drinking water source. Characterization of PAHs and their concentration is of interest in maintaining public health.
PAH measurement in water should be accurate, precise, and sensitive enough to measure low concentrations. Method EN 16691 is a recently developed method that uses solid-phase extraction to isolate organic compounds from 1 L of water using a divinylbenzene (DVB) solid phase extraction disk. PAHs are eluted from the disk with dichloromethane and dried to remove water before evaporation, solvent exchange into toluene, and introduction into GC–MS. The method specifies the use of the whole water sample, ensuring that any analyte adsorbed on the particulate matter will be extracted along with the water sample. Disks are a particularly well suited SPE format for samples containing particulates because the increased surface area does not become clogged with particulate as easily as a cartridge format might, even for larger water samples, such as 1 L. In addition, the particulates are rinsed with solvent at the same time as the bottle is rinsed in an automated system (SPE-DEX® 4790), including compounds adsorbed on the particulate surfaces in the extraction process.
The recoveries of a suite of PAH compounds spiked into a pond water sample using this methodology are shown in Table I. A slow flow rate through the disk (25 mL/min) is specified in the method and excellent recoveries are shown in the full application note. However, the flow rate through a disk does not need to be limited in the same way as a cartridge for good equilibrium. The recoveries shown in Table I result from extraction at full speed (approximately 100 mL/min). Recoveries of the surrogate compounds is very good ensuring the method is operating properly. The recoveries of spiked compounds from the matrix is excellent.
The performance of the SPE-DEX 4790, using Atlantic DVB disks for the extraction of PAHs was shown to comply with method requirements and provided excellent recoveries of the full suite of PAH analytes.
(1) Application Note AN1101606_01, available from www.horizontechinc.com.
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