Laurie Caron – Summary of articles
During my graduate studies in natural products chemistry at the University of Quebec at Chicoutimi (UQAC), I had the opportunity to publish a few articles related to the topic of my research. Today, I present the first of them, it deals with a new method for analysis of volatile compounds from plant material:
“Volatile compounds in the foliage of balsam fir Analyzed by static headspace gas chromatography (HS-GC): An example of the spruce budworm defoliation effect in the boreal forest of Quebec, Canada” published in the journal Michrochemical in 2013.
Using the traditional method of analysis by GC-MS analysis of volatile compounds during my study would have been a tedious process of manipulation in the laboratory. This method requires a first step of extracting the compounds of interest and then the analysis of them. Having so many samples to analyze for my research (about 200 for this component) the development of this method by HS-GC (Static Headspace Gas Chromatography) was necessary. My Master Degree was already divided into three separate components analysis and just by itself, it could have been the sole object of my memory.
The HS-GC method differs from the one normally used (by GC-MS) by eliminating the step of extracting the volatile compounds and the addition of a step of preheating the sample. This preheating allows volatile compounds to break free of the initial matrix and concentrate in the headspace of the bottle containing the sample. Then, the principles of analysis of the compounds are the same as gas chromatography, they are explained in a post previously done by my colleague: Analyses by GC – Part I. Principles of separation.
The HS-GC method has saved me a lot of time and ultimately, get a reliable analysis. For my study, the interest compounds were monoterpenes and sesquiterpenes. They are a major part of essential oils and known to be the defense of the plants. These are already well known and listed in the litterature and several databases, it was possible for me to easily identify each compound present in my samples by their retention index.
The difficulty in applying the method lay in finding the right amount of sample to include in the bottles and then the proper warm-up time so that the GC column would not get saturated by volatiles. Once these are found, it was necessary to make sure that the method could provide more than an alternative to quickly identify the volatile compounds in a plant sample, but also be able to quantify these compounds.
For quantification of specific molecules such as β–phellandrene (monoterpene), an internal standard (geraniol) and a commercial standard (for the preparation of a calibration curve) were used. Furthermore, to ensure the stability of the method, each sample was prepared and analyzed in triplicate. The injection of a single sample several times could not be done due to the preheating step of the samples. Similar results have been obtained, it suggest that the method seems to be as reliable as those traditionally used.
In addition, some preliminary results of my research on the influence of spruce budworm (SBW) (Choristoneura fumiferana Clemens) on the chemical composition of balsam fir have also been included in this article. These data demonstrated that among other defoliation, this conifer needles in the wild had an impact on the production of the defensive compounds (monoterpenes, sesquiterpenes, etc). In connection with these results, the hypothesis that an increased production of β–phellandrene (monoterpene) by fir needles during severe defoliation in the period of June was also raised.