GC/MS Vs.
LC/MS: Which Is Really The “Gold Standard”?
1.
Gas
Chromatography/Mass Spectrometry x2 (GC/MS/MS).
Gas chromatography separates drugs based on how easy they evaporate.
Unfortunately, drugs of abuse do not evaporate. Samples must initially be
altered chemically before analysis. Once the drugs are chemically altered,
GC/MS/MS produces what amounts to 100 or more “peaks” in the production of
information. “Peaks” are then compared to a computerized list of compounds with
a corresponding mass. The resulting comparison measures mass and the mass is
then compared with figures on a look up table. This is an area for potential
major errors in the testing process. Positive results are often reported in
cases where the probability of the presence of a specific drug is 40% or less.
On top of this, GC/MS/MS machines are certified and checked using a LC/MS/MS
machine.
2.
Liquid
Chromatography/Mass Spectrometry x2 (LC/MS/MS).
Liquid chromatography separates drugs and introduces them into a mass
spectrometer. The sample first passes through a mass filter which only allows
the drug being tested for to pass through. The drug is then broken down in an
argon gas stream. The fragments of any drug present then pass into a second mass
filter and are measured. No sample pretreatment is required, removing one of the
problematic steps in the GC/MS/MS method. Only when drugs of abuse are present
are compounds noted by the instrument. No compound matching is needed. The
results obtained through this method are 99.9% accurate.
So, back to the question: GC/MS/MS vs. LC/MS/MS…Which technology is really the
“Gold Standard”?
Gas chromatography separates drugs based on how easy they evaporate.
Unfortunately some substances, such as drugs of abuse, do not evaporate!
However, Liquid chromatography separates drugs and introduces them in to the
mass spectrometer. The sample first passes through a mass filter, which allows
only the drugs being tested for to pass through. The drug is then broken apart
with an argon gas stream. The fragments of the drug present then pass into a
second mass filter and are then measured. No sample pretreatment necessary,
which is a problematic step in gas chromatography. Only when drugs of abuse are
present, are compounds noted. No compound matching required, as in gas
chromatography. The results are 99.9% accurate. Therefore…..
Liquid Chromatography is the true “Gold Standard”!
