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CSI: Chemistry - Cool Science Instruments in Marine Chemistry

June 14, 2021

You’ve probably heard of a marine biologist, but did you know about marine chemists? Catch a glimpse into some of the amazing technology that chemists at the Northeast Fisheries Science Center have used to investigate marine environments.

image shows three panels arranged left to right and from background to foreground. All three panels show scientists working in front of laboratory equipment. At the top the panel is labeled CSI Chemistry: Cool Science Instruments in Marine Chemistry.
 image shows two panels side by side. At the top, the panel is labeled 1960s–1970s. The panel on the left is a black and white image of a scientist standing in front of a lab table with various vials and beakers and two electronic instruments. The panel on the right shows a scientist looking down on a benchtop instrument.
1960s instrumentation to perform titration procedures on seawater. Most likely these titrations were used to measure the dissolved oxygen and alkalinity of seawater samples.

Our investigation begins with an early technique used to determine how much oxygen was present in samples of seawater. A Winkler Titration technique requires the careful addition of chemical compounds and strong acids to a seawater sample to measure the amount of dissolved oxygen in it. The amount of oxygen in seawater is a balance between oxygen produced through photosynthesis and that being consumed by fish and bacteria. Today we have electronic instruments that can measure dissolved oxygen without using a Winkler Titration technique. But we can’t forget the early techniques that led the way to today’s Cool Science Instruments.

Learn more about dissolved oxygen and a low oxygen condition called “hypoxia”.

image shows two panels side by side. At the top, the panel is labeled 1980s to 1990s. The panel to the left shows a scientist in a lab coat and gloves placing sample vials in a machine. The panel on the right shows the same scientist standing in front of a large instrument and an early desktop computer.
Images from the 1990s show a marine chemist at our Sandy Hook, New Jersey lab preparing samples for the mass spectrometer instrument.

In the 1980s and 1990s, instruments were becoming more and more advanced as the computer technology, microchip availability, and sensitivity of sensors increased. In this—and more recent—eras, various instruments were used to measure harmful contaminants that might be present in fish, or to determine a chemical fingerprint of a fish stock. This gave ecologists clues into migration patterns and population structures. These computerized instruments were more capable than humans when it came to distinguishing analytical results. Let’s continue our investigation into some of these Cool Science Instruments.

Image shows two panels side by side. At the top, the panel is labeled 1990s to 2000s. The first panel shows a chemist in a lab coat holding a tray of samples and standing in front of a white and red computerized instrument. The image is labeled ‘atomic absorption’. The second panel shows a different chemist in a lab coat using a small electronic instrument inside of a laboratory fume hood. The image is labeled ‘high performance liquid chromatograph’.
Atomic absorption spectrometry instrument and a high performance liquid chromatograph instrument from the 2000s. On the right, a chemist is injecting fish extract into the instrument to remove lipids and other interfering substances from organic contaminants like PCBs.

Ever wonder how scientists can identify what chemical components are present in a substance? Well, our scientists investigate the presence and quantities of harmful chemicals in samples of fish and other marine organisms using Cool Science Instruments such as the atomic absorption spectrometer and the high performance liquid chromatograph. Different atoms absorb and give off different wavelengths of light when they are excited. The spectrometer can measure the chemical makeup of a substance by comparing these wavelengths to a known library of values. These values tell the scientists what elements are present. The chromatography can separate a substance into its various chemical components by forcing the sample through an absorbent material under pressure. This instrument is a faster, newer generation of liquid chromatography and is used for removing lipids (fats) and other interfering compounds from the extracts of fish tissues containing organic contaminants such as polychlorinated biphenyls, called PCBs for short.

Find out more: What are PCBs?

Image shows two panels side by side. The panel on the left shows an elaborate instrument of numerous glass vials, rubber tubing, and stainless steel.It is labeled Soxhlet extraction. The panel on the right shows a different instrument with a computerized component and a plastic sample carousel.  It is labeled accelerated solvent extraction.
Soxhlet extraction device and an accelerated solvent extraction system used to extract chemical contaminants in fish tissues.

The instruments that our scientists use to separate contaminants from fish tissues are becoming more advanced as time goes on, but some of them still have roots in the past. Soxhlets have been around since 1879. They are named for Franz von Soxhlet, the German agricultural chemist who invented the first one. They are used to extract compounds from a solid sample. Scientists still use the same technique, albeit with a more complex apparatus. Rather than a single Soxhlet extractor, they now use multiple extractors to process more samples at once. Unfortunately, this process can take many hours. A more modern instrument, seen on the right side of the panel, uses heat and pressure to extract organic contaminants in fish tissues and gets the job done in less time. Whether relying on proven century old techniques or using modern computerized technology, these extractors are definitely two Cool Science Instruments.

 Panel has two images, one at the upper left and another at the lower right. The panel is labeled gas chromatography. The image at top  left shows a scientist in a lab coat sitting in front of an instrument. The scientist is holding a spool of copper tube. The image is labeled 2000s single quadrupole mass spectrometer. The image at lower  right shows a computerized instrument on a benchtop.The image is labeled 2020s triple quadrupole mass spectrometer.
Top right, one of our chemists showing how to change a gas chromatographic column. The two images show two generations of gas chromatography mass spectrometers used to identify microplastics found in the marine environment.

If you have ever watched any movies or television shows about police investigations, you have probably heard the words mass spectrometer. There’s a reason for that: It is a very useful instrument for identifying different compounds in a substance. At our science center, researchers use these instruments to learn about microplastics in marine environments, sea birds, sea turtles, fish, and dolphins. Unfortunately, the plastics from our daily lives have found their way into the marine environment and could cause problems for marine life and humans. These instruments rely on two techniques to identify the “usual suspects.” The gas chromatography separates a sample into its component parts and the mass spectrometer then analyzes and identifies each component. So the next time you are watching a show, and hear the words “mass spec,” you can tell your friends how marine chemists use these same instruments to investigate the ocean. 

Learn More: What are microplastics?

The panel has one image, labeled direct mercury analyzer. It shows a blue and white scientific instrument sitting on a table top.
Direct mercury analyzer used to measure mercury in fish tissues.

Careful sample preparation is key to getting accurate results from any of the instruments in an analytical laboratory. Often this sample preparation involves using strong acids or dangerous chemicals. The scientists  who do this work are specially trained to handle these materials safely. One modern instrument that doesn’t require dangerous sample preparation is the direct mercury analyzer. Mercury is a naturally occurring metal that is liquid at room temperature and has been used in various industries for hundreds of years. Mercury is dangerous if eaten, and in some marine environments can be found in the bodies of fish and other marine organisms. This instrument allows marine chemists to investigate the levels of mercury in fish and work to protect us from its harmful effects. Samples are analyzed in less than 10 minutes.

Learn more: Finding mercury in the water.