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Impurities, organic identification

Infrared absorption spectra can be employed for the identification of pure compounds or for the detection and identification of impurities. Most of the applications are concerned with organic compounds, primarily because water, the chief solvent for inorganic compounds, absorbs strongly beyond 1.5//m. Moreover, inorganic compounds often have broad absorption bands, whereas organic substances may give rise to numerous narrower bands. [Pg.743]

The testing of impnrities in active pharmacentical ingredients has become an important initiative on the part of both federal and private organizations. Franolic and coworkers [113] describe the utilization of PLC (stationary phase — silica gel and mobile phase — dichloromethane-acetonitrile-acetone (4 1 1, v/v)) for the isolation and characterization of impurities in hydrochlorothiazide (diuretic drug). This drug is utilized individually or in combination with other dmgs for the treatment of hypertension. The unknown impurity band was scraped off the plate and extracted in acetonitrile. The solution was filtered and used for LC/MS and NMR analysis. The proposed procedure enabled the identification of a new, previonsly nnknown impurity. It was characterized as a 2 1 hydrochlorothiazide-formaldehyde adduct of the parent drug substance. [Pg.227]

Most early publications on bacterial polysaccharides were concerned with impure products and poorly-described organisms. Many more recent papers are of limited value also, due to low yields, lack of characterization of products and arbitrary interpretations of data. Low yields of methylated polysaccharides may be due to degradation of the bacterial polysaccharide during methylation, or to degradation of the hydrolytic products of the methylated polysaccharide (to form methyl levulinate, etc.46). The great importance of (a) complete methylation of polysaccharide products prior to structural determination by hydrolysis and (6) quantitative identification of the hydrolytic products, has been emphasized previously. Other difficulties in end group analysis have been discussed recently.7... [Pg.222]

Identification and structural analysis of organic compounds. Determination of trace impurities in a wide range of inorganic materials (spark source mass spectrometry). [Pg.426]

So you have a mass spectrum of an organic compound in your hands. How should you start the process of identification By this time it is very useful to have all available information on the sample. Any information may be relevant (method of synthesis and isolation, the nature of precursors and solvents, the presence of impurities, etc.). Sometimes even knowing what was synthesized in the same flask earlier may be of crucial importance for the final decision. [Pg.152]

The concurrent identification and quantification of organic impurities is a principal use of liquid chromatography in the pharmaceutical industry. However, the application of liquid chromatography to this task highlights a weakness of this technique when compared to gas chromatography specifically, the lack of a universal detector. Great strides have been made to create detectors and hyphenated techniques to address these problems. However, multiple detectors and analytical procedures may be necessary to accurately and specifically identify and quantify the impurities in complex systems. [Pg.363]

ICH Q3 A(R) [8] provides a clear guidance for the control of the organic impurities. Table 1.1 describes the hmits or thresholds for the reporting, identification, and qualification of the impurities based on the maximum daily dose of the drug substance administered per day. [Pg.6]

However, care must be exercised in using molecular sieves for drying organic liquids. Appreciable amounts of impurities were formed when samples of acetone, 1,1,1-trichloroethane and methyl-r-butyl ether were dried in the liquid phase by contact with molecular sieves 4A (Connett Lab.Practice 21 545 1972). Other, less reactive types of sieves may be more suitable but, in general, it seems desirable to make a preliminary test to establish that no unwanted reaction takes place. For the principles of synthesis and identification see R. Szostak Molecular Sieves, Chapman Hall, London 1988, and for structure, synthesis and properties see R.Szostak Handbook of Molecular Sieves, Chapman Hall 1992. [Pg.29]

The more advanced instrumental methods of analysis, including GC, for the detection and identification of expls are presented (Ref 90) Pyrolysis of expls in tandem with GC/MS was used for the identification of contaminant expls in the environment (Ref 108). Isomer vapor impurities of TNT were characterized by GC-electron capture detector and mass spectrometry (Ref 61). Volatile impurities in TNT and Comp B were analyzed using a GC/MS the GC was equipped with electron capture and flame ionization detectors (Ref 79). The vapors evolved from mines, TNT, acetone, toluene, cyclohexanone and an organosilicon, were analyzed by GC/MS (Ref 78). Red water produced by the sellite purification of crude TNT was analyzed by GC/MS for potentially useful organic compds, 2,4-dinitrotoluene, 3- and 4-sulfonic acids (Ref 124). Various reports were surveyed to determine which methods, including GC/MS, are potential candidates for detection of traces of TNT vapors emitted from land mines factors influencing transportability of TNT vapors thru soil to soil/air interface are dis-... [Pg.783]

This study evaluated the impurity profile of untreated water from a textile plant in Portugal [35]. The organic material was concentrated by extraction from 11 of water into dichloromethane and HPLC-NMR and HPLC-MS experiments were carried out using a reverse-phase separation with an acetonitrile/ D2O gradient elution with H NMR spectroscopic observation at 600 MHz. For the HPLC-NMR studies, the samples were further fractionated into two pools according to their HPLC retention times. The HPLC-NMR studies were carried out in the stop-flow mode and the combination of NMR and MS results yielded the identification or tentative identification of 14 compounds, comprising mainly surfactants, anthraquinone dyes and nonylphenol-related molecules. [Pg.62]

Impurities. Of course, the presence of impurities in a sample will have a dramatic effect on the XRD characteristics. Zeolite preparations, as synthesized, can contain both organic and inorganic impurities. After washing and calcination, many impurities become amorphous, and the resulting XRD powder pattern will clearly show changes from the as-synthesized material. Some impurities, however, are stable to calcination and can make identification and characterization of the material (especially a new material) rather difficult. This is particularly true for cases where only a small number of samples, prepared in a narrow synthesis regime, are available for XRD examination. Common impurities found in zeolite preparations are the stable silicates, quartz and cristobalite. [Pg.295]

The initial gradient analysis (such as shown in Fig. 12) does not guarantee that the sample will be eluted from the column or be separated from other components of the mixture. For example, the sample may be bound irreversibly to the column, precipitated by the organic solvent, obscured by the solvent peaks in the breakthrough volume, or obscured by peaks from buffer or solvent impurities present in the gradient run. For these reasons it is essential that the initial gradient analysis be followed by some identification procedure to confirm that the sample of interest has in fact been eluted satisfactorily. Some widely used procedures are the following ... [Pg.71]


See other pages where Impurities, organic identification is mentioned: [Pg.136]    [Pg.6]    [Pg.113]    [Pg.277]    [Pg.336]    [Pg.141]    [Pg.13]    [Pg.223]    [Pg.311]    [Pg.315]    [Pg.345]    [Pg.173]    [Pg.714]    [Pg.527]    [Pg.157]    [Pg.261]    [Pg.274]    [Pg.274]    [Pg.292]    [Pg.92]    [Pg.53]    [Pg.126]    [Pg.310]    [Pg.458]    [Pg.375]    [Pg.181]    [Pg.784]    [Pg.277]    [Pg.124]    [Pg.130]    [Pg.27]    [Pg.509]    [Pg.436]    [Pg.216]   
See also in sourсe #XX -- [ Pg.363 ]




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Impurities, identification

Impurities, organic

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