Activities and Events
An algorithm to solve them all (almost)
Alexis St-Gelais, M. Sc., chimiste – Activities and events
PhytoChemia has always been proud to provide the essential oils community with GC-FID results obtained from a dual-column system – just as it is done in academia. This powerful approach is able to solve most coelutions and reach a high level of detail in analyses in an efficient and precise fashion, and is one of our hallmarks.
While there are numerous advantages to this technique, the downside to this was, up to now, data-dense reports that needed time and training to be properly read. Calculations are needed to solve coelutions, and we have for a good while now been working on an automated approach to this challenge.
After months of hard work and testing, we finally have a working solution. The algorithm munches through all the data to provide you with a clean, single column of results, termed consolidated results. Therefore, all GC profile reports will henceforth have a modified Analysis summary table.
The new essential oils reports will have a summary table that looks as follows:
There already was a summary table previously, but it listed results from both our DB-5 and DB-Wax columns, with annotations to indicate coelutions and repeated percentages. With the new format, the algorithm sorts through all coelutions and solves them whenever possible. There remains a few rare cases where solving is not possible (e. g. very often, β-phellandrene and 1,8-cineole coelute together on both columns, so there is no efficient way to assign an individual percentage value to each). In those circumstances, a notation using the [ ] symbols will still be in use. Overall, though, the solving algorithm and the two-columns system is able to process over 90% of coelutions to get clean numbers out.
Take note that our reports still feature an “annex” section, set after a blank page, which presents the reader with both chromatograms images and a full data table. This second table does not change, and still lists all coelutions on all used columns as before. It allows advanced users to make their own calculations/verifications if needed.
Hydrosols, CO2 extracts, absolutes and cannabis terpenes
For other aromatic material, the analysis summary table will feature two different result columns, as follows:
The first column lists physical units of concentration (e. g. mg/g, mg/L, and so on). These take advantage of the solving algorithm, but also of a clever correction factor system for GC-FID published in 2016 by Cachet et al. This combination allows us to provide near-quantitative data for all compounds screened, after solving coelutions – a very powerful feature. This gives a much better idea of the concentration of volatiles in the matrix (CO2 and absolutes contain several non-volatile compounds and percentages are not fully representative of the composition).
The second column gives a percent breakdown for each volatile constituent against the total volatiles. In other words, the % column does not take into account the non-volatile fraction, just the relative importance of each volatile compared to the whole volatile fraction (in the case of cannabis, anything coming out before phytol). For CO2 extracts and absolutes, these percentages will be equivalent to those shown in our previous reports.
These changes will reflect in both our PDF reports, as well as in the CSV files we can provide upon request.