Here are just a few examples of laboratory instruments used by ECOGIG scientists to analyze the wide variety of samples that they collect from the Gulf of Mexico. Some of these can be packed up and taken onboard a research ship, while others need to remain in a laboratory on land.
A gas chromatograph is an instrument used for measuring the compounds in a gas. A gas sample is injected into the instrument, and it passes through a column with a compound that slows gases down very selectively. The gases emerge from the column at defined intervals and are measured by a flame-based detector. In Dr. Tracy Villareal's lab (ECOGIG), gas chromatographs are used to measure nitrogen fixation. The same enzyme that converts nitrogen gas to ammonium also converts acetylene to ethylene. Dr. Villareal's lab injects a sample with acetylene and then measures the resulting ethylene.
The ANTEK detector with gas chromatography is used to detect nitric oxide. NOx gas (nitric oxide plus nitrogen dioxide) is converted to nitric oxide in an acidic heated solution. The nitric oxide is detected through a chemiluminscent detector. Nitrite is measured on a separate instrument and then subtracted from the nitric oxide value to get the nitrate concentration of the samples.
The gas chromatograph with an electron capture detector measures nitrous oxide (N2O) in water column. Identifying sources and sinks of N2O can help researchers identify nitrogen cycling processes in marine systems, particularly where changes in dissolved oxygen can lead to changes in the nitrogen cycling pathways (i.e., nitrification versus denitrification).
Mass spectrometry is an analytical technique that separates chemical species into ions and sorts the ions based on their mass to charge ratio. Mass spectrometry is used in many different fields and is applied to pure samples as well as complex mixtures.
A Membrane Inlet Mass Spectrometer (MIMS) has a specifically designed inlet system that allows it to analyze water samples. This inlet is hooked up to a mass spectrometer that analyzes stable isotopes such as 18O and 15N gases.
The Los Gatos is a cavity ring down mass spectrometer which connects to the underway system of the ship to measure surface water methane and carbon dioxide so that ECOGIG scientists can measure the flux of greenhouse gases from the ocean to the atmosphere.
Gas chromatograph-mass spectrometer
The Pegasus GCxGC-ToF-MS, or a comprehensive gas chromatograph coupled with a time of flight mass spectrometer, is a really advanced GC-MS (gas chromatograph-mass spectrometer) which is the workhorse of an organic geochemistry lab. A GC-MS is an instrument that separates out the constituents of a sample, either gas or liquid, along a really long column (the Pegasus has a 60 meter (180ft!) long column!) based on boiling points. At the end of the column, the separated out constituents enter into the mass spectrometer. There, an ion beam shatters the compound into smaller mass fragments, which serve as a fingerprint for that particular compound. In the Pegasus GCxGC, there is a second column which is connected to the first column which allows scientists to separate out compounds in their samples to an even finer degree. The time-of-flight portion of the mass spectrometer refers to the way in which the mass spectrometer determines the size of the ions flying towards it-- based on how long it takes them to fly down the meter long flight tube. This allows scientists to look as very large compounds, up to 1000 Daltons in size, which is much larger than what traditional mass spectrometers can detect. ECOGIG is currently using this instrument to look at hydrocarbons present in surface waters and sediments in the Gulf of Mexico.
Imaging flow cytometer
This system uses powerful lasers and multiple detectors to examine small particles in the sea. Many cells contain distinctive pigments that produce light of a specific wavelength when illuminated by a single wavelength laser beam. The instrument causes the cells in the sample to stream by the detectors one at a time. It records the wavelength of light emitted, the amount of light and takes a picture of each cell. From this information, we can identify very small cells that are very challenging to identify and count in the microscope. This type of system first went to sea on an ECOGIG research cruise.
Sulfate reduction rig
Sediment is incubated with 35S (35 sulfur - a radioactive isotopic form of sulfur) and then this reaction is stopped with the addition of ZnAc (zinc acetate). The sediment is digested with hot chromous acid using the sulfur reduction distillation rig in order to recover the 35S which was trapped as ZnS (zinc sulfide). The amount of sulfur recovered is compared to the amount of methane oxidation measured on a separate instrument, as sulfate reduction and methane oxidation processes by bacteria in the sediment are often (but not always) linked.