Infrared spectroscopy identification tests

Infrared spectroscopy can fill some of the current gaps in testing methodology and allow analysts to cope with a wider range of analytical problems (135). Combining MS with infrared (IR) data creates a highly complementary identification system. 

M.T. Soderstrom, H. Bjork, V.M.A. Hakkinen, O. Kostiainen, M.-L. Kuitunen and M. Rautio, Identification of compounds relevant to the chemical weapons convention using selective gas chromatography detectors, gas chromatography/Mass spectrometry and gas chromatography/Fourier transform infrared spectroscopy in an international proficiency test, J. Chromatogr., A742, 191-203 (1996). 

Specific Identity Tests. At least one specific identity test that is capable of distinguishing the drug substance from related compounds must be included. Spectrometric tests are usually used, such as ultraviolet, infrared, nuclear magnetic resonance, and mass spectroscopy. Retention times or factors derived from thin-layer, gas-liquid, and HPLC are also used as identification tests to verify a more specific spectral identity test. 

Identification of a drug substance is the fingerprinting of a drug material. This ensures that the correct material is utilized for biological testing, pharmaceutical investigation, and production. Infrared spectroscopy (Avith KBr pellet or Nujol mull) is commonly used for this purpose. UV spectroscopy Avith the material tested in aqueous or alcoholic solution is a convenient method of identification. 

Fourier transform infrared spectroscopy (FTIR) is a common identification test. Chapter 11 also discusses FTIR applications supporting stability. The Fourier transform enhances sensitivity and greatly reduces the time of the spectroscopic measurement. FTIR is commonly used as an identification test, but has been used qualitatively (e.g., dimethicone). Spectra are compared with a reference spectrum for identification purposes. As an identification test, FTIR is used as a release test rather than a stability test. Additional testing information can be found in USP/NF, General Chapter <851 >. 

Infrared spectra are now widely used in the examination of pharmaceuticals. The sixteenth revision of The Pharmacopoeia of the United States (U.S.P.) and the eleventh edition of the National Formulary (N.F.) have presented identification tests which used infrared spectroscopy, whereas no infrared tests were used in U.S.P. XV or N.F. X. Infrared spectra have attained acceptance in legal considerations and are now given in patent applications as characteristics of antibiotics of unknown structure. In the pharmaceutical industry there are many applications for quantitative infrared analyses in research and development work, pharmacy research, and in various phases of pharmaceutical production. For example, infrared data are used to characterize reaction conditions and yields, to assay the purity of intermediate products, to examine such problems as the stability of a drug in the material in which it is suspended, and to maintain quality control in the chemical production of bulk drugs. A recent review (Papendick et al, 1969) has given many references to fractionation and isolation methods for pharmaceutical analysis, such as the various types of chromatography, electrophoresis, countercurrent distribution, and extraction. The authors presented many references to infrared analyses for a wide variety of compounds (Table 16.1). 

Polymer Testing 96. Conference proceedings. Shawbury, 5th-6th Sept. 1996, paper 6. 57 IDENTIFICATION OF ADDITIVES IN RUBBER AND PLASTIC MATERIALS BY COMBINED LIQUID CHROMATOGRAPHY/INFRARED SPECTROSCOPY Sidwell J... 

The quality control of radiopharmaceuticals labeled with short-lived radionuclides has to rely on indirect methods for the identification of the compound. Direct methods such as nuclear magnetic resonance (NMR) and infrared spectroscopy cannot be used. Some tests, such as measurement of pH and LC-analysis, can be performed before the radiopharmaceutical is released for use. The radiopharmaceutical is mixed with authentic reference substance and if... 

A brief introduction to conventional qualitative and quantitative analysis of water-based polymer dispersions is followed by a demonstration of the use of near-infrared spectroscopy for the rapid identification and determination of water content. Use of the BC AP chemo-metric software package is discussed for library searching to identify unknown tests. It is shown how within a few minutes various polymer dispersions (about 50%) can be identified and their water content determined to a plus or minus 0.2% degree of precision. 5 refs. 

The ability to identify organic compounds is an important skill that is frequently used in the organic laboratory. Although there are several spectroscopic methods and many chemical and physical tests that can be used for identification, the goal of this experiment is to identify an unknown liquid using infrared spectroscopy and a boiling-point determination. Both methods are introduced in this experiment. 

An unequivocable identification of an unknown component is unlikely by the chromatographic process alone. Not the least of the reasons for this is the need for the comparisons of standards, thereby assuming reasonable prior assurance of the possible identity of the unknown. Certainly the more discrete pieces of information obtainable concerning an unknown compound, the easier it will be to obtain confident identification. Microchemical tests such as functional group classification, boiling point, elemental analysis, and derivative information, as well as infrared spectroscopy, coulometry, flame photometry, and ultraviolet (UV)-visible spectroscopy are also useful aids when used in conjunction with gas chromatographic data. 

Prior to the much-vaunted renaissance of the Raman technique with the advent of FT instrumentation or the availability of CCD systems, there were few literature reports on the use of Raman spectroscopy for investigating pharmaceutical systems. The technique has been used to characterize drugs in much the same way that infrared has been used for identification testing. Thus, the infrared (IR) and Raman spectra of Dapsone, used in the treatment of leprosy, have been reported [1]. 

Prior to release from quarantine for use in manufacture, drugs and excipients are subject to identification testing. Generally, this is by infrared spectroscopy, and pharmacopeial standards or pure materials from the regulatory bodies are available for confirmation of identity. However, as a complementary technique, new chemical entities may be registered with regulatory bodies in the United States using Raman data for proof of identity, but, in practice, both infrared and Raman data tend to be submitted for approval. 

Frequently, the identification of an unknown plastic can be made on the basis of simple physical tests such as solubility in solvents, odours produced on ignition, etc. Such tests will be discussed in as much as they provide a simple practical means of identification. In Chapter 6 the principles of infrared spectroscopy and pyrolysis - gas chromatography will be discussed and infrared and pyrograms presented for a wide range... 

There are many types of nylons with a specific gravity ranging from 1.04 to 1.17. All types burn with blue flames and yellow tips and give off a burnt wool or hair odor. Nylon self-extinguishes on removal of the flame. Phenol, m-cresol, and formic acid are the most common solvents. Different types of nylons can be identified by the Fisher-Johns melting-point test (ASTM D 789). Solubility and specific gravity tests are also used to differentiate between the types of nylons. However, infrared spectroscopy is the best method for positive identification. 

The most reliable (time-consuming and costly) identification method is to use infrared spectroscopy measurements to determine the material. The Rapra Collection of Infrared Spectra of Rubbers, Plastics, and Thermoplastic Elastomers can be used to compare the spectrum of a test material to reference spectra. The transmission spectra in this reference are obtained either from cast or molded thin film or in the case of cross-linked materials by pyrolysis of the material in a Pyrex tube. 

Some plasticizer mixes require pretreatment, such as saponification, but in most instances chromatographic separations can be accomplished with the mix. In addition to the usual identification of substances by organochemical analysis, other methods now being used include color tests, physical tests (determinations of boiling point and refractive index), and infrared and ultraviolet spectroscopy. 

Composition of oil/fat. To study the composition of oil/fat it is essential to test the purity of an oil/ fat for adulteration, accidentally or voluntarily. The specific fatty acid in fat can be determined by GC by preparing methyl esters with sodium methoxide. Mass spectrometry coupled to GC (GC-MS) is the most powerful tool for identification of fatty acids separated by GC. Free fatty acids in oil (index of rancidity) can be determined by titration against standard alkali. Infrared (IR) spectroscopy, Raman spectroscopy, and ultraviolet (UV) spectroscopy (200—400 nm) are used to detect isomers (trans and cis) of unsaturated fatty acids and conjugated double bonds. It is important to study saponification value (depict fatty acid chain length), iodine value (give the degree of unsaturation), and hydroxyl value (free fatty acids present in fats). 

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