SEATTLE, WASHINGTON—To measure for the presence of oil in seafood, NOAA's scientists in the gulf region use a team of 10 "expert sniffers" trained to detect the distinctive smell. The same samples are sent to scientists here at the Northwest Fisheries Science Center who prepare them for chemical analysis for polycyclic aromatic hydrocarbons (PAHs) using a 3-day cleaning, drying, and preparatory step. NOAA research chemist Daryle Boyd showed ScienceInsider frozen samples of red snapper and shrimp kept in glass jars in a freezer.
To ensure accurate results, the samples are marked "just with numbers and species" so the scientists analyzing them don't know where they came from or the results of the sniff test, explained Boyd. She worked alone late in the afternoon Wednesday to insert about a dozen samples in metal test tubes into a machine called a solvent extractor. ("Most people here are early birds, coming in 5, 6 a.m.," said Boyd, who wore Crocs, jean shorts, and latex gloves as she worked.)
The extractor uses 100°F (38°C) and 2000 psi of pressure to separate contaminants from the seafood tissues; subsequent steps separate PAHs from fats, proteins, and other natural compounds. NOAA scientists have recently cut the time for sample preparation and analysis from 4.5 days to 3 days---2 days of which include "no lunch," Boyd said.
After preparation, the samples are put through a state-of-the-art gas chromatography-mass spectroscopy machine run by a team including NOAA research chemist Catherine Sloan. That machine plots peaks on a connected computer, and scientists try to identify the 28 PAHs in oil they are looking for.
"The labs down [in the gulf] are not well-equipped to do this," said NOAA's Walton Dickhoff. But Sloan says she is helping train scientists to get up to speed on the sophisticated procedure, via "many e-mails from people who want to know how to do this" and some visitors to her team's windowless, humming facility.
For more on the gulf oil spill, see our full coverage.