What can cause GC-MS interference?
Drugs that produce similar high molecular-weight mass fragment ions could potentially interfere if they have similar GC retention times and if inappropriate ions are selected for monitoring. The conversion of one drug to another by the GC/MS instrument itself is a particularly insidious problem.
What does GC-MS interference mean?
Gas Chromatography/Mass Spectroscopy
RE: GC/MS Interference. Urine samples submitted for drug testing are first screened by immuno assay. Any sample. that provides a positive response on the screen is considered a suspect positive and. submitted to Gas Chromatography/Mass Spectroscopy (GC/MS) for confirmation.
What are the limitations of GC-MS?
However, GC–MS suffers from two major limitations: First, only a relatively small range of volatile, thermally stable compounds are amenable for analysis, and second, EI mass spectra suffer from a frequent absence or weakness of the molecular ions.
Can GC-MS resolve enantiomers?
Using chiral (cyclodextrin) and non-chiral (DB-17) GC columns we show that these enantiomer pairs can be baseline resolved – depending on the derivative/GC column combination – and that any single acetal/TFA combination can resolve the majority of enantiomers in a single run.
Can GC-MS be wrong?
Periodically, GC/MS tests can have false-positive results. Such results could have clinical implications for physicians.
Why is GC-MS better than LC-MS?
The only difference is that LC-MS uses a solvent as its mobile phase, while GC-MS uses inert gases (like helium) in the same capacity. 3. GC-MS is the preferred standard for forensic identification, and it is also the preferred machine in terms of costs and operation.
Why is GC-MS better than GC FID?
Good selectivity, linearity and higher upper values of the working range are the main advantages of SPME-GC-FID versus low bottom values of working ranges, better sensitivity and lower limits of detection and quantification of SPME-GC-MS.
How can we separate enantiomers?
You can separate the enantiomers from racemic mixtures by (a) mechanical separation, (b) reaction with enzymes, (c) formation of diastereomers, and (d) chromatography. If the enantiomers are solids, you can use tweezers to separate the crystals based on their shapes (rather labour intensive!).
What are the limitations of gas chromatography mass spectrometry (GS/MS)?
Although gas chromatography/mass spectrometry (GS/MS) is recognized as the definitive procedure for confirming positive immunoassay screening results of urine for drugs of abuse, targeted GC/MS analysis does have limitations. False negative results can occur when interfering drugs are present at high relative concentrations.
Can we eliminate matrix residues injected into GC/MS systems?
Different matrix cleanup protocols have been studied but could not eliminate matrix residues injected into a GC/MS system. Matrix can cause quantitation interference, lower response (higher LOQ), and/or bad peak shape resulting in poor data quality.
How to control system suitability of GC/MS metabolomics?
Quality control of system suitability of GC/MS metabolomics using a mixture of reference compounds: FAMEs, methoximation and low-boiling compounds Fig. 2a) Relative intensities of the grid of fatty acid methyl esters (FAME) with C08 to C30 fatty acyl carbon lengths.
What is a matrix effect in GC-MS?
Many problems observed in GC-MS data acquisition quality are due to matrix effects, or contaminations that build up in liners and ultimately in the begin of the column. Open in a separate window Figure 6 Quality control flowchart overview for reference compound mixture and pooled samples