Anyone who is beginning to dive deep into essential oils will soon come across the term GC-MS. The first thing that someone will find confusing is the fact that these terms are often spoken about as if they are the same thing. GC stands for gas chromatography, while MS refers to mass spectrometry. While typically spoken about synonymously, they are actually two completely separate pieces of equipment. Here we will take a look at what this equipment does in the essential oil industry.
On a basic level, these machines are simply used to determine the quality of an essential oil. Each of these is used in conjunction to draw conclusions regarding the quality of essential oils differently. Although these are the most common tools used for this purpose there are others and they can also determine factors about quality with their results.1
Chemistry strives to accurately quantify data that directly relates to the properties of a given substance. In this pursuit, the data will often show the exact amount of different ingredients within the substance being examined. The complexity of this process grows significantly when the substance being examined has more ingredients.
One of the reasons that this process is complicated is the fact that, among all the other ingredients, the scientist will have to isolate the one they want to study. GC was developed by a scientist who wanted to study the pigments in plants. This scientist specifically wanted to know more about chlorophyll. The name of this tool came from the fact that he was working with substances of color – the name was taken from a Greek word that means color.
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This tool, when studying individual compounds of a substance, is used to separate those compounds so that they can be examined independently from the others. Essential oils typically have dozens and even sometimes hundreds of individual molecules and this makes this tool especially useful to help determine the quality of each essential oil. Another useful aspect of this tool is the fact that it cannot only separate the different substances but it can do it in a reasonable amount of time.
This process relies on the individual molecules that are gaseous in nature. Many of the molecules in essential oils are volatile and will quickly change to gas. For this reason, this type of tool is a perfect choice when studying the individual elements of any essential oil. The thing that is necessary to understand the tool is the fact that it separates the molecules so that they can be released and studied. Even so, this tool does not give any information about the individual compounds – it only separates them.2
One of the reasons why these two tools are often spoken about interchangeably is the fact that if a scientist were to only have the gas chromatography tool then they would be able to separate the individual components but they would have no way of examining them. This is why they need a mass spectrometer to gather information from those separated molecules.
The scientists will use the GC to separate the compounds and then they will use the MS to examine them. There is more than one type of possible detector that can be used for these. There are the GC-MS which is commonly used but there’s also the GC-FID. FID is a flame ionization detector. There is also an electron capture detector and a thermal conductivity detector. In some rare situations, there are others that are used for specific purposes such as when studying the aroma of perfumes and wines.
GC-MS is considered the most complex detector when compared to others like the FID. When a compound is analyzed with the detector it will be exposed to a strong electrical current which creates fragments that are electrically charged. Gas is then used to carry those fragments over magnets thereby creating magnetic fields. This allows the fragment to be attracted to the detector where it can then be neutralized.
When larger amounts of fragments reach the detector it produces a more intense signal. The heavier fragments will cross the magnets and this allows their atomic mass to be known. The detector does a complete analysis. As the magnetic field isolates, the detector will scan the fragments for their atomic masses multiple times per second.
It is important to understand that when a scientist refers to a compound reaching the detector there are actually trillions of molecules that are doing so simultaneously. The fragmentation of these molecules doesn’t occur in a random way. There are some bonds that can be broken more easily than others. Through this process, the weaker fragments will be more produced and this can be examined. This gives relative amounts and allows scientists to figure this information out.
The software compares what information it gathers along with references already compared, to produce a statistical analysis. This makes MS one of the most powerful tools when identifying compounds for essential oils. When other types of examinations fail to identify different molecules within the essential oil, it can typically resolve that problem.3
There Are Some Pitfalls
One of the primary pitfalls of this system is the fact that different compounds can have very similar mass. This means when compared to the database of existing information it could be misconstrued. There are also times when a particular molecule is not part of an existing database. This type of information is thought to never be totally complete and that means there’s always the possibility of coming across a molecule that hasn’t been previously identified.
MS is by far a great tool for finding the compounds in an essential oil. It gives scientists lots of information on the precise structure of those molecules. Like any tool, however, it has its limitations and chemists need to use it with caution.
Determining The Proportions Of A Compound
When scientists try to quantify the proportion of a compound they use a calibration based on target molecules. When you want to get this information then you can compare different concentrations of an essential oil and then inject each of those concentrations into the GC instrument. This is considered the most reliable way to quantitate compound concentrations accurately.
The process of doing this in the essential oils industry is considered to be a daunting one. This is because there are so many different molecules that have to be separated. Another problem is the fact that many of those molecules are not pure. To do this the electronic output of a detector is used to examine the peak in the sample being used. It is from this that the percentage format is needed.
GC-MS Can Help Lab Scientist Confirm Botanical Sources
Often it is important to identify the actual sources that the essential oil is coming from. Using these tests scientist can identify many volatile constituents. As well, they can also determine their respective proportions. All of this information and data can be used to confirm the origin from which the oil came. Other data that can be gathered from this include determining other ingredients used in the oil.
Often the data gathered from this can even be used to determine the geographic origins of the samples that are being tested. The information gathered from the compounds are compared to a database on specific plant markers found in expected variations of the different essential oils. Using the analysis of GC-MS tests the scientist can identify different volatile compounds in the oil, they can confirm the botanical source, they can identify contaminants, and they can compare other essential oils to determine the overall quality.
Some of the things that this analysis cannot provide include whether or not pesticides have been used. It also lacks the ability to analyze compounds that are not volatile. When it comes to examining single compounds it isn’t able to determine whether it is synthetic or natural. Finally, and unfortunately, this analysis has no way to determine if the oil smells good or not.
This type of analysis gives a great amount of data that is very useful. That said, it does not tell everything about the essential oil that might want to be known. The GC technology is used to separate the different compounds and the MS is used to gather data from those individual components. It is the best tool for examining volatile compounds. It is also a very useful tool for determining the amounts of compounds within the essential oil.
The GC-MS technology is considered a cornerstone for analyzing essential oils. If you want to see GC-MS technology at work, a MONQ personal diffuser like Mountain Blend is a great choice!
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