GC/MS is the abbrevation for the combination of the analysis methods gas chromatography and mass spectrometry. The substances, whose retention time (time of sample injection up to the detection of the single substance) gives already qualitative information to the kind of the substance, are divided by bombardment with electrons or methane ions into characteristic fragments, which are dependent on the molecular structure and thus permit a clear identification of the substance (via spectrum libraries). GC/MS is a specific and very sensitive analysis method which allows still the provement of substance quantities below 0.1 ng. Thus an uptake of medicines and drugs as well as their metabolites are clearly visible in blood, urine and other materials after a longer time period, see also hair analysis.
The signal intensity of characteristic substance fragments in the MS (Single Ion Mode) permittes the quantitative determination with very high sensitivity after calibration with solutions of known content (or addition of deuterated standard amounts of the substance).
Recent developments of the method are GC/MS/MS, LC/MS/MS and LC/MS/TOF, reducing the detection sensitivity by a factor of 2-3. The use of liquid chromatography (LC) particular enables the detection of substances with higher molecular weight, which otherwise decompose in the GC and thus are not detectable.
