Suppose you have a weak lot of lavender. Linalyl acetate is only twenty-five per cent, below the range the market accepts.
There is a fix: buy pure linalyl acetate and add it until the figure looks good.
The analysis afterwards will look perfect.
Why GC/MS cannot catch it
Gas chromatography separates compounds by volatility; mass spectrometry identifies them by how they break apart. Both operations look at molecular structure.
A synthetic linalyl acetate molecule is structurally identical to a linalyl acetate molecule extracted from the plant. Same formula, same mass, same fragmentation. The machine has no way of telling them apart.
This is a fundamental limit of the method, not a fault of the instrument or the operator.
Four indirect signs
Not being able to catch it directly does not mean there are no clues.
Ratios that are too good. Natural raw materials vary. A sample in which every main component falls right in the middle of the ideal range, year after year, is suspicious rather than reassuring.
Unusually poor trace components. Whoever adds a pure compound adds only the compounds listed in the standard. The dozens of trace compounds nobody checks are not added, so the overall picture becomes poorer than the natural version.
Isomers in the wrong ratio. Many components exist in two isomeric forms. Plants make them in a fairly stable ratio; industrial synthesis gives a different one. An ordinary GC/MS usually cannot separate the two isomers, but a specialised column can — that is the subject of the next lesson.
A total above a reasonable threshold. If the total of identified components reaches ninety-nine per cent, ask questions. Natural raw materials almost always have a part lying below the identification threshold.
What this says about every analysis you are handed
A full GC/MS analysis covers layers one and two, described in the previous two lessons. That is real value, and not small.
It does not cover this layer. If a lot has had a pure component added somewhere in the supply chain, the analysis will look normal and neither seller nor buyer will know.
A seller who claims their method catches everything either does not understand the method, or understands it and chooses not to say.
The next two lessons cover the two analyses that really can tell natural from synthetic, and why very few places carry them out.