oysters, GC-MS/MS, GC-MS, PAH, oil, Thermo ScientificThere are oil and other fuel spills and contamination everywhere. Everyone in the US remembers the tanker that wrecked off the coast of Alaska. Pristine areas were contaminated and much wildlife died. Another one that we remember in the US was in the Gulf of Mexico. An oil rig exploded and let out millions of barrels of oil before some really smart people figured out how to stop it. The US is not the only place this happens. In the North Atlantic there are a lot of oil rigs and full shipping lanes. In the Pacific it is the same. There are even ship wrecks in the Mediterranean. There is a lot of wildlife that we depend on for food that can come into contact with the oil that we use for energy. It contaminates other organisms that do not die right away. PAHs can be metabolized pretty quickly but there are still toxic effects. Oysters, bivalve mollusks, filter and accumulate PAHs from the contaminated water and their food sources. These PAHs may remain in the meat and can be consumed by humans or other predators. Because oysters cannot move they make a good indicator species for contamination and they also need to be tested for contaminants prior to consumption.

This method can be applied to oysters to detect the presence of aliphatic hydrocarbons and PAH contamination from crude oil. From the profile using GC-MS/MS, the method can be used to characterize the source of contamination. The method can give a semi-quantitative indication of whether levels of PAHs exceed safety limits for human consumption of oysters. A liquid extraction of oysters with hexane, followed by a clean-up on a silica-SPE-cartridge is used. The sample is fortified with appropriate labeled internal standards and analyzed by simultaneous GC-MS/MS using a TSQ Quantum XLS. Aliphatic hydrocarbons and PAHs of food safety significance are measured and compared with the profile from crude oil collected from the Gulf of Mexico in late May 2010.

Method performance was established by separate spiking experiments for blank oysters first with a mixture of aliphatic hydrocarbon standards followed by mixture of 16 PAH standards. To evaluate method performance with combined aliphatic hydrocarbons and PAHs, spiking was carried out with NIST 1582 petroleum crude oil. Average recoveries of n-hexadecane to n-tetratricontane ranged from 52-108%. Background contamination and lack of availability of a real blank sample made it impossible to make an accurate estimate of the recoveries of the lower mass PAHs. However average recoveries of the remaining higher mass PAHs [(B(a)P, Chr, B(b)F, B(k)F, B(k)F, B(a)P, B(g,h,i)P, and D(a,h)A] ranged from 65-126%. Identification was confirmed by close agreement of retention times for standards and comparison with scanned spectra, particularly checking for evidence of interferences. Extracted ion chromatograms using m/z 57 and 71 were used for profiling.

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LODs for aliphatic hydrocarbons were estimated to be between 20-100 ng/g hydrocarbon contaminations in oysters in full scan. Background contamination made it impossible to make an accurate estimate of the LODs of the lower mass PAHs (Naph, Ace, Acy, Flu, Ant, Phe, Fln and Pyr). However, LODs of the remaining higher mass PAHs [(B(a)P, Chr, B(b)F, B(k)F, B(k)F, B(a)P, B(g,h,i)P, and D(a,h)A] were between 1-7 ng/g (ppb) PAH and oil contamination of oysters in SRM.

Download method application here; PAH in Oysters