Infrared spectrophotometric method

Mynka et al. reported a method for the infrared spectrophotometric identification and the determination of acetylcholine in the presence of other esters in pharmaceuticals [3]. Acetylcholine was determined at the maximum absorbance of 1755 cm-1. Beer s law was obeyed in the concentration range 1-10 pg/mL, and the relative standard deviation was less than 2.7%. Results obtained were reported to be reliable and reproducible. 

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Infrared Spectrophotometric Method for Determination of Acetone Content of Pentaerythritol trinitrate , NOTS 1877, NAVORD 5649 (1958) 5a) A.R. Lawrence AJ. Matuszko, JPhysChem 65,1903 (1961) CA 56, 5483 (1962)... 

More recently, Eggers and Humphrey [28] have reported on the application of gel permeation chromatography to monitor epoxy resin molecular distributions and curing. The preparation given describes an infrared spectrophotometric method to follow curing. 

Accepted methods of the first type comprise the hide-power method [77], the refrac-tometric method, and various visible, ultraviolet, and infrared spectrometric methods. Accepted methods of the second type include comparative methods such as the Stiasny-Orth method [78,79] and its modifications, all these being gravimetric methods largely obsolete today due to the lack of reliability consequent to coprecipitation of some carbohydrates together with the phenolic material of the tannin extract and to the results being expressed in an absolute value which is never reportable to a percentage of useful material in the extract, the Lemme [80] sodium bisulfite backtitration method, the ultraviolet spectrophotometric molybdate ion method [77,81], and infrared spectrophotometric methods [82]. 

Szonyi et al. (1962) have described a differential infrared spectrophotometric method for the determination of trans unsaturation in fats. The method utiUzes absorption at 965 cm which is due to C—H out-of-plane deformation vibrations of trans unsaturated compounds. The method is rapid, accurate, and directly appUc-able to the determination of trans unsaturation in triglycerides. It is applicable to samples which contain low concentrations of trans acids (down to 2%) and also to samples with fatty acids of mixed chain length. The absorptivities used in the calculations for this method are those established by Shreve et al. (19506). 

J. Carol, Report on Infrared Spectrophotometric Methods for Drugs. Infrared Spectra of Various Pharmaceuticals, J. Assoc. Offic. Agr. Chemists 38, 638-643, 1955. 

Infrared Spectrophotometry. The isotope effect on the vibrational spectmm of D2O makes infrared spectrophotometry the method of choice for deuterium analysis. It is as rapid as mass spectrometry, does not suffer from memory effects, and requites less expensive laboratory equipment. Measurement at either the O—H fundamental vibration at 2.94 p.m (O—H) or 3.82 p.m (O—D) can be used. This method is equally appticable to low concentrations of D2O in H2O, or the reverse (86,87). Absorption in the near infrared can also be used (88,89) and this procedure is particularly useful (see Infrared and raman spectroscopy Spectroscopy). The D/H ratio in the nonexchangeable positions in organic compounds can be determined by a combination of exchange and spectrophotometric methods (90). 

ASTM D 2124-99. Standard Test Method for Analysis of Components in Poly(Vinyl Chloride) Compounds Using an Infrared Spectrophotometric Technique, Annual Book of ASTM Standards, ASTM, West Conshohocken, PA (1999), Vol. 08-01. 

Pentazocine is identified according to USP XX by use of infrared or ultraviolet spectrophotometric methods. In the first a dispersion in KBr of the dried drug exhibits maxima only at the same wavelengths as a similar preparation of USP Pentazocine Reference Standard. In the ultraviolet method a 1 in 12,500 solution of pentazocine in 0.01 N HC1 exhibits maxima and minima at the same wavelengths as reference standard. Calculated absorbances at 2 8 nm of dried drug and standard do not differ by more than 3.0 % (3). 

Following successful recovery of peptide/protein molecule from the microspheres, a simple spectrophotometric method does not always allow discrimination between the monomeric protein form and its aggregates. However, HPLC might separate these species and thus provides more accurate qualitative data [96], But HPLC cannot quantify exclusively the amount of active protein antigen, as is the case with ELISA techniques [97], Nowadays, Fourier transform infrared (FTIR) spectroscopy has become a popular, noninvasive method, as it is able to characterize the secondary structure of entrapped proteins [26, 95, 98-101], Only recently, the integrity of their primary structure was evaluated, thanks to a new matrix-assisted laser... 

Spectrophotometric methods [22-26], where applicable, have the advantage of allowing a sample to be studied under reaction conditions. Ultraviolet, visible, or infrared spectra can be taken at elevated temperatures and pressures [27]. If a reaction is so fast that sampling is not practical, a pump-around loop with spectrophotometric cell can be hooked to the reactor or, even better, a probe can... 

Often the enthalpy of reaction is obtained by measuring the equilibrium constant of an acid-base reaction over a range of temperatures. If In K is plotted versus l/T. the slope will be equal to -AH/R. Thus various experimental methods have been devised to measure the equilibrium constant by spectrophotometric methods. Any absorption which differs between one of the reactants (either acid or base) and the acid-base adduct is a potential source of information on the magnitude of the equilibrium constant since it gives the concentration of two of the three species involved in the equilibrium directly and the third indirectly from a knowledge of the stoichiometry of the reaction. For example, consider the extensively studied reaction between organic carbonyl compounds and iodine. The infrared carbonyl absorption is shifted in frequency in the adduct with respect to the free carbonyl compound. Thus the equilibrium mixture exhibits two absorption bands in the carbonyl region of the spectrum (Fig. 9.1) and the relative concentrations of the free carbonyl and the adduct can be obtained.3- Alternatively, one can observe the absorption of the iodine molecule, U, in... 

Spectrophotometric Methods 8.6.1 Calorimetric Determinations 8.6.2 Ultraviolet Determinations 8.6.3 Fluorimetric Analysis 8.6.4 Infrared Determinations 8.6.5 Circular Dichroism Determination... 

Nowadays, spectrophotometry is regarded as an instrumental technique, based on the measurement of the absorption of electromagnetic radiation in the ultraviolet (UV, 200-380 nm), visible (VIS, 380-780 nm), and near infrared region. Inorganic analysis uses UV-VIS spectrophotometry. The UV region is used mostly in the analysis of organic compounds. Irrespective of their usefulness in quantitative analysis, spectrophotometric methods have also been utilized in fundamental studies. They are applied, for example, in the determination of the composition of chemical compounds, dissociation constants of acids and bases, or stability constants of complex compounds. 

Several direct spectrophotometric methods are used for the sulphur dioxide measurement, including non-dispersive infrared absorption, ultraviolet absorption, molecular resonance fluorescence and second-derivative spectrophotometry. 

The radiation absorption and transmission characteristics of polymers can be used to identify polymer types. The basic principle of spectrophotometric methods of analysis is to provide an energy source (such as infrared radiation, IR) to which a sample is exposed, and to convert to some measure a response that is characteristic of the moiecuies. This response is, most often, absorption of a fraction of the incident tight. 

In 1965, Wayland and Weiss published infrared spectra of 33 antibiotics not included in the earlier collections in the same journal (Hayden et al., 1962 Sammul et al, 1964). These antibiotics are listed in Table 16.8. Unterman (1965) has published a survey on spectrophotometric methods for antibiotic determination in the ultraviolet and infrared regions. 

Blinn and Gunther (1963) have reviewed the use of infrared and ultraviolet spectrophotometry in the field of pesticide residue chemistry. Spectrophotometric measurements offer several unique advantages to the analytical chemist the radiation which is absorbed is characteristic of the material doing the absorbing the degree of absorption of radiation is directly proportional to the concentration of the material in solution and spectrophotometric methods are usually essentially nondestructive to the absorbing material and therefore allow recovery for further scrutiny by other types of instrumentation when applicable. 

ASTM D2124-99el Standard Test Method for Analysis of Components in Poly(Vinyl Chloride) Compounds Using an Infrared Spectrophotometric Technique... 

Among techniques employed in paint analysis, spectrophotometric methods (infrared (IR), Raman, and UV-visible), chromatography (both gas and liquid). X-ray diffraction and fluorescence, atomic spectrometry, nuclear magnetic resonance, and pyrolysis are the most useful and provide more selective or more sensitive information than the classical procedures about the main components of paints. In the following sections the main merits and applications of these techniques will be described. 

The study of the reaction AIBN with various additives is difficult because the stmctirre of its molecules is syrmnetrical, weak signals in the infrared (IR) and nuclear magnetic resonance (NMR) are, it does not make decisions abont the reaction, especially, at its initial stage. To study the kinetics of the azo initiator decomposition, most ofterr, the spectrophotometric method are used [7]. 

The remaining methods of analysis addressed in this chapter are instrumental methods of analysis. The first group of these to be addressed are spectrophotometric methods based on the absorption and anission of photons of electromagnetic radiation including visible light, ultraviolet radiation, and infrared radiation. 

Generally, methods are based on solvent extraction of the additive followed by analysis for the extracted additive by a suitable physical technique such as visible spectrophotometry of the coupled antioxidant, redox spectrophotometric methods, ultraviolet spectroscopy, infrared spectroscopy, gas chromatography, thin-layer chromatography or column chromatography. In general, direct chemical methods of analysis have not foimd favour. These include potentiometric titration with standard sodium isopropoxide in pyridine medium or reaction of the antioxidant with excess standard potassium bromide-potassium bromate (ie. free bromine) and estimation of the unused bromine by addition of potassium iodide and determination of the iodine produced by titration with sodium thiosulphate to the starch end-point. ... 

G. Duyckaerts, Differential Infrared Spectrophotometric Analysis, Bull. soc. roy. sci. Liege 21, 7-17, 1952. The differential spectrophotometric method of Hiskey CA 44, 1844c 45, 2814a) is applied to infrared analysis. Errors in analysis of... 

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