GC/IR gas chromatography/infrared

ECNIMS electron capture negative ionization mass GC-IR gas chromatography-infrared... 

Wilkins CL. Directly-Linked Gas Chromatography-Infrared-Mass Spectrometry (GC/ IR/MS). Published Online 15 AUG 2006. 

We discussed the fundamentals of mass spectrometry in Chapter 10 and infrared spectrometry in Chapter 8. The quadrupole mass spectrometer and the Fourier transform infrared spectrometer have been adapted to and used with GC equipment as detectors with great success. Gas chromatography-mass spectrometry (GC-MS) and gas chromatography-infrared spectrometry (GC-IR) are very powerful tools for qualitative analysis in GC because not only do they give retention time information, but, due to their inherent speed, they are also able to measure and record the mass spectrum or infrared (IR) spectrum of the individual sample components as they elute from the GC column. It is like taking a photograph of each component as it elutes. See Figure 12.14. Coupled with the computer banks of mass and IR spectra, a component s identity is an easy chore for such a detector. It seems the only real... 

Today, there are many so-called hyphenated methods with IR. These methods include gas chromatography-infrared (GC-IR) where the IR spectra are taken from materials as they are evolved through the column. Related to this are high-performance liquid chromatography-infrared (HPLC-IR), thermogravimetry-infrared (TG-IR), and multispec-tral infrared (MS-IR). 

The analytical data in the OCAD is derived from four different techniques. These are nuclear magnetic resonance spectroscopy (NMR), infrared spectroscopy (IR), gas chromatography/mass spectrometry (GC/MS), and gas chromatography retention indices (GC(RI)). With a few exceptions, the OCAD contains only data of compounds that are listed in the schedules of the CWC and their derivatives of BSTFA and dimercaptotoluene. 

ASTM Standard E 1642-94, Standard Practice for General Techniques of Gas Chromatography Infrared (GC/IR) Analysis, American Society for Testing and Material, Philadelphia, February 1995. 

Gas chromatography-infrared spectrometry (GC-IR) combines the separating power of GC with the nondestructive identification capabilities of IR spectometry. 

Infrared spectroscopy has been. combined with various other analytical techniques. Gas chromatography-infrared spectroscopy (GC-IR) allows the identification of the components eluting froiti a gas chromatograph. GC-IR has certain advantages over, say, gas chromatography-mass spectrometry (GC-MS). While GC-MS is able to distinguish easily between compounds of different mass, it is unable to differentiate structural isomers of the same molecular mass. By comparison, GC-IR can easily distinguish such isomers. 

GC-IR-MS Gas chromatography-infrared detection-mass spectral detection ... 

Gas chromatography-infrared (GC-IR) spectroscopy is an appropriate technique for drug analysis as it can be used for isomer separation or contaminant detection. Amphetamines are one class of drug that have been successfully differentiated by using GC-IR spectroscopy. Amphetamines are structurally similar molecules that can be easily mis-identified. Although such similar compounds cannot be differentiated by their mass spectra, there are prominent differences... 

Several analytical tools coupled to mass spectrometers as GC-MS (gas chromatography) and LC-MS (liquid chromatography), including ICP-MS (inductively coupled argon plasma), SCF-MS (supercritical fluid), NMR-MS (nuclear magnetic resonance), and IR-MS (infrared-MS), are routinely used to determine the phenolic acids. With the development of soft ionization techniques, fast atom bombardment (FAB) [19] and plasma desorption (PD) [20], followed by the electrospray ionization (ESI) [21], have been used for phenolic acid analyses. 

Spectrometers are routinely attached to computers that can search for matches between the spectrum of an unknown and a library of known spectra. As with mass spectrometry, gas chromatographs can be attached to IR spectrometers and spectra can be determined as the individual components of a mixture elute from a column. As noted in Section 15.2, this technique is called gas chromatography/infrared spectroscopy, or GC/IR. 

The wide range of spectroscopic techniques such as UV, infrared (IR), Gas Chromatography-Mass Spectroscopy (GC-MS), Liquid Chromatography-Mass spectra (LC-MS), Nuclear Magnetic Resonance (NMR), and mass spectra (MS) form the backbone of modem stmctural elucidation studies as mentioned in the Figure 8.2. Prior to the availability of such advanced techniques, ambiguities existed in the determination of stmctures of bioactive compounds. The process of spectroscopic determination should be closely allied to familiarity with the scientific literature. If the compound has not been described, it may be very similar to reported compounds and that may assist in the interpretation of data for the unknown. In this regard, an awareness of the coextractives from the plant may also be of value to determine the stmctures. 

Table 4 lists the specifications set by Du Pont, the largest U.S. producer of DMF (4). Water in DMF is deterrnined either by Kad Fischer titration or by gas chromatography. The chromatographic method is more rehable at lower levels of water (<500 ppm) (4). DMF purity is deterrnined by gc. For specialized laboratory appHcations, conductivity measurements have been used as an indication of purity (27). DMF in water can be measured by refractive index, hydrolysis to DMA followed by titration of the Hberated amine, or, most conveniendy, by infrared analysis. A band at 1087 cm is used for the ir analysis. 

Ref. 277 unless otherwise noted gc = gas chromatography hplc = high pressure Hquid chromatography ir = infrared spectroscopy uv = ultraviolet spectroscopy glc = ga sliquid chromatography eia = enzyme immunoassay vis = visible spectroscopy. 

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