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Looking for plastics

For years, scientists have looked for a way to eradicate the problem of the immortal plastic that

continues to plague land and water alike, but to remove plastic we must find it first. Researchers

have found a solution to this problem and are currently using a simple technique to look for the

presence of plastics in organisms.

Organisms were originally checked for plastics using three methods- lavage, necropsy and

endoscopy. However, using lavage to look for plastics in a specimen would often result in insufficient sampling of gastrointestinal contents unless done repeatedly. The use of necropsy to follow out this investigation would mean the usage of beached dead specimens, resulting in inconclusive answers due to unknown causes of death. Endoscopy would take simply too much time and resources and

would be inaccurate as the whole organism couldn’t be searched. They later came up with a much

more reliable technique.

First, the organism is thoroughly cleaned and sanitized, a process that involves several regents and heating and drying in an oven. Once the specimen is ready, the preen oil is extracted from the

uropygial glands using a swab and the presence of three common plasticizers- Dimethyl phthalate, dibutyl phthalate and bis(2-ethylhexyl)-pthalate are tested. A plasticizer is usually added to several plastic materials to increase its plasticity, decrease its viscosity and make it more flexible. These are the most common plasticizers as they are found in many of the plastics that often end up in marine environments. It is essential to use apparatus that has never been touched by plastic during this experiment.

The extract is then transferred to a round-bottom flask where it is tested for the presence of the

plasticizers. The extract is first analysed by capillary GC to determine the concentration of analytes, this is usually performed using a Varian 3800 gas chromatograph, controlled by Galaxy

chromatography software. Then the identity of individual phthalate compounds are confirmed using GC‐MS analyses on a Thermoquest/Finnigan DSQ‐Plus benchtop mass spectrometer fitted with a direct capillary inlet and an on‐column injector. 

The most important observations are based on retention times and full scan mass spectra compared to reference standards of the three phthalates mentioned above. The compound identifications are confirmed by standard co-injection. Many phthalate esters in use share a common property and hence, in the mass spectrometer, these compounds undergo rearrangement to yield a mass spectrum overtaken by the 149 ion. The exception, dimethyl phthalate, yields the ion 163. Selected ion monitoring mode is then used as it is sensitive and distinctive enough to detect the very low

levels of phthalate in the samples.

The test can be done with dead and alive specimens. Once done, the results can be displayed in the form of a graph to show just how plastic influences the animals in that specific area and how

common it is.


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