The chromatographic properties of organophosphorus chemicals can present difficulties during analysis. Commonly, a mass spectrometer is used for qualitative and quantitative analysis for drugs of abuse. Spectra for the swab and cocaine reference standard and the peak table showing a match for cocaine are inset in the figure.
As compounds are separated and leave the gas chromatograph column, those compounds are destroyed by the attached detector. Large transferable EI-mass spectral libraries exist and are available for library searching of acquired spectra from any instrument . Briefly, GC is widely available and used for qualitative and quantitative drug analysis.
The ions have unique molecular weights which can be represented in a mass spectrum like Figure 5, below. The sample is instantly vaporized by heat inside the injector port and sent into the column for the gas chromatograph via carrier gas.
One of the main benefits of using chemical ionization is that a mass fragment closely corresponding to the molecular weight of the analyte of interest is produced. From this spectrum, one can select a prominent product ion which can be the product ion for the chosen precursor ion. The computer program will then compare the different types of ions that are present to a library of spectrums.
SRM is highly specific and virtually eliminates matrix background. 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.
Full-scan mass detection is an untargeted approach and is capable of potentially detecting all compounds in the sample which is advantageous for broad spectrum drug screening. Computers can also simultaneously correlate more data such as the retention times identified by GCto more accurately relate certain data.
These compounds are normally not present but appear in individuals suffering with metabolic disorders. Collisions with the make up gas at the expanding supersonic jet reduce the internal vibrational and rotational energy of the analyte molecules, hence reducing the degree of fragmentation caused by the electrons during the ionization process.
InElectronic Associates, Inc. The advantages of SIM are that the detection limit is lower since the instrument is only looking at a small number of fragments e.
An inert gas such as Nitrogen N2 is bubbled through the water; this is known as purging or sparging. Ideally, the process of separation causes different chemical compounds to leave the column at separate times for proper identification. Essentially though, the format, design and footprint of GC—MS systems have changed little since the s.
In such matrices, isobutane or ammonia, which have higher proton affinities, are preferred as reagent gases. It involves identifying an acid metabolite of tetrahyhydrocannabinol THCthe active ingredient in marijuana, in urine samples by employing derivatization in the sample preparation.
This process of destruction creates signals that are detected and then interpreted by a computer attached to the detector.
The alkyl methylphosphonochloridates RO Me P O Cl are also toxic, but less so, and can be converted to the corresponding phosphonofluoridates. The molecular fragmentation pattern is dependent upon the electron energy applied to the system, typically 70 eV electron Volts.
This is done by comparing the relative concentrations among the atomic masses in the generated spectrum.Document Title: Forensic Drug Identification by Gas Chromatography – Infrared Spectroscopy. Author(s): Robert Shipman, Trisha Conti, Tara Tighe, Eric Buel.
Most forensic laboratories routinely employ Gas Chromatography/ Mass Spectrometry (GC/MS) as.
Although gas chromatography/mass spectrometry (GS/MS) is recognized Substances with identical mass spec tra. Qualitative identification by mass Mechanism of interferences for gas chromatography/mass spectrometry analysis of urine for drugs of abuse.
Gas chromatography-mass spectrometry. Gas chromatography-mass spectrometry (GC-MS) is an important technique for qualitative and quantitative analysis of food contaminants and residues. approach and is capable of potentially detecting all compounds in the sample which is advantageous for broad spectrum drug screening.
Identification of. Fulton G.
Kitson, in Gas Chromatography and Mass Spectrometry (Second Edition), GC/MS is the synergistic combination of two powerful microanalytical techniques. The gas chromatograph separates the components of a mixture in time, and the mass spectrometer provides information that aids in the structural identification of each component.
The gas chromatograph/mass spectrometer is known as the best resource to prove the identification of a chemical substance, such as a drug, because of the mass chromatographs that act like a fingerprint of a chemical substance.
Attorney Kevin Leckerman describes Drug Identification Methods and explains the basics of gas chromatography. For Mass Spectrometry details, call ()Download