Expert: Peter L. - 2/11/2010

Question
can you explain what is a GC/MS test for Meth and how it works?

Answer
John,

From Wikipedia:

Gas chromatography-mass spectrometry (GC-MS) is a method that combines the features of gas-liquid chromatography and mass spectrometry to identify different substances within a test sample.

The GC-MS has been widely heralded as a "gold standard" for forensic substance identification because it is used to perform a specific test. A specific test positively identifies the actual presence of a particular substance in a given sample. A non-specific test merely indicates that a substance falls into a category of substances. Although a non-specific test could statistically suggest the identity of the substance, this could lead to false positive identification.

From Oregon State University:

The GC separates chemicals based on their volatility, or ease with which they evaporate into a gas. It is similar to a running race where a group of people begin at the starting line, but as the race proceeds, the runners separate based on their speed. The chemicals in the mixture separate based on their volatility. In general, small molecules travel more quickly than larger molecules.

And lastly my comments:

There seem to be a number of cases where a false positive test for methamphetamine is possible.  Any of a number of amphetamines may give a false positive.  Other prescription drugs can also cause false positives, to my knowledge. Make sure you inform whoever is administering the screen regarding anything you take.