What does GC-MS interference mean?
If a clear mass spectral fragmentation pattern. cannot be obtained the specimen is reported as Invalid:GC/MS Interference. This does. not mean the donor has intentionally tampered with his specimen, although that is a possibility. The sample is reported as Invalid to urge a second collection of the donor.
Which is an advantage of GC-MS?
One of the major advantages of GC-MS compared to LC-MS is the high reproducibility of generated mass spectra using EI. The electron impact ionization process, used in GC-MS, is a hard ionization that results in the production of very reproducible mass spectra from one instrument to another.
What is the application of GC-MS?
GC-MS can be used for the bioanalysis of body fluids to detect narcotics, barbiturates, alcohols, and drugs such as anticonvulsants, anesthetics, antihistamines, sedative hypnotics, and anti-epileptic drugs. It is also useful in detecting pollutants and metabolites in serum and in fatty acid profiling in microbes.
When would you use LC-MS over GC-MS?
LC is a separation performed in the liquid phase and is generally used for larger more polar molecules which are incompatible with GC. When a mass spectrometer is used as a detector, you have LCMS. There really are significant differences, but in terms of which one is best, it simply depends on the application.
How accurate is GC-MS drug testing?
Only if both portions of the divided specimen show up positive is it considered a positive result by the testing lab. The accuracy of the initial drug screen, the immunoassay test, ranges between 92% – 98%. The accuracy of the GC/MS confirmatory test is virtually 100% from a scientific standpoint.
What happens when the GC is combined with the MS?
Furthermore, the researcher can determine the quantities (concentrations) of each of the components. Figure 3 represents a three-dimensional graph generated when the GC is combined with the MS. Try to visualize how the chromatogram combines with the mass spectrum to produce this image.
How is the GC-MS used to identify unknown chemicals?
The computer on our GC-MS has a library of spectra that can be used to identify an unknown chemical in the sample mixture. The library compares the mass spectrum from a sample component and compares it to mass spectra in the library. It reports a list of likely identifications along with the statistical probability of the match.
What does each cycle of ranges in GC-MS represent?
Each cycle of ranges is referred to as a scan. The computer records a graph for each scan. The x-axis represents the M/Z ratios. The y-axis represents the signal intensity (abundance) for each of the fragments detected during the scan.
Which is the main principle of separation in GC?
In GC the main principle of separation is partition. 1. A gaseous mobile phase flows continuously through the column which is coated with a liquid stationary phase. 2. The sample is introduced into the heated injection port where it is vaporized and carried in to the column. 3.