Analysis IR

Analytical Procedures. Standard methods for analysis of food-grade adipic acid are described ia the Food Chemicals Codex (see Refs, ia Table 8). Classical methods are used for assay (titration), trace metals (As, heavy metals as Pb), and total ash. Water is determined by Kad-Fisher titration of a methanol solution of the acid. Determination of color ia methanol solution (APHA, Hazen equivalent, max. 10), as well as iron and other metals, are also described elsewhere (175). Other analyses frequendy are required for resia-grade acid. For example, hydrolyzable nitrogen (NH, amides, nitriles, etc) is determined by distillation of ammonia from an alkaline solution. Reducible nitrogen (nitrates and nitroorganics) may then be determined by adding DeVarda s alloy and continuing the distillation. Hydrocarbon oil contaminants may be determined by ir analysis of halocarbon extracts of alkaline solutions of the acid. 

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. 

Alfin Catalysts. Alfin catalysts (44,45) give polyisoprenes of high /ram-1,4 microstmcture (46). For example, a typical Alfin catalyst gives polyisoprene of 52% /ram-1,4, 27% cis-1,4, 16% 3,4, and 5% 1,2 content (ir analysis) (46). One type of Alfin catalyst consists of aHylsodium, sodium isopropoxide, and sodium chloride (47,48). Because of the mixed microstmcture polyisoprene produced, Alfin catalysts are not used commercially. 

The keto-enol tautomerism of 1,2-benzisoxazoles has been examined and the existence of either form can be postulated on the basis of reactivity. IR analysis on the solid indicates the exclusive existence of the enol form, while in CHCI3 solution both appear to be present (71DIS(B)4483). 

This is a destructive method in which the resin is ground and pelleted as a KBr disc and analysed by FT-IR analysis. This method works best for systems where disdnct ftinctional group transformations (C=0, C-OH, C=C, etc) are expected. No special equipment is needed. 

Aqueous GPC can also be semiprepped in manner just like nonaqueous GPC. In this case one must consider carefully the buffers, salts, and biocides used in the eluant. If the fractions are destined for nuclear magnetic resonance experiments it will be imperative to either reduce the salt concentration in the eluant or remove salt after the initial fractionation. Likewise, if the collected samples are destined for infrared (IR) analysis, it is important to choose salts and buffers that have good IR transparency in the wavenumber ranges of interest. 

IR analysis can also be used quantitatively to determine the EO-PO ratio [12]. Using mixtures of polyethylene glycol and polypropyene glycol as calibration standards, the ratio of two absorbances, one due to the methyl group of the PO unit (e.g., the C-H stretch band at 2975 cm ) and one due to the methylene group (e.g., the C-H stretch band at 2870 cm ), are plotted against percent of PO content. The ratio of the same two absorbances taken from the IR spectrum of a poloxamer may then be used to determine its percent of PO content by interpolation. 

We reacted 2 first with bromine in chloroform at 10 C. iH NMR studies have revealed that the reaction mixture was very complex and consisted of six products. This mixture was submitted to silica gel column chromatography. Careful repeated chromatography followed by fractional crystallization allowed us to isolate ten products (Scheme 3). IR analysis indicated that a hydroxyl group was incorporated in compounds lfi-19. Therefore, we assume that these products have been formed by partial hydrolysis of compounds lfl-14. Structural determination of compounds lfl-19 revealed that the barrelene skeleton was rearranged completely. 

The effect of oxidative irradiation on mechanical properties on the foams of E-plastomers has been investigated. In this study, stress relaxation and dynamic rheological experiments are used to probe the effects of oxidative irradiation on the stmcture and final properties of these polymeric foams. Experiments conducted on irradiated E-plastomer (octene comonomer) foams of two different densities reveal significantly different behavior. Gamma irradiation of the lighter foam causes stmctural degradation due to chain scission reactions. This is manifested in faster stress-relaxation rates and lower values of elastic modulus and gel fraction in the irradiated samples. The incorporation of O2 into the polymer backbone, verified by IR analysis, conftrms the hypothesis of... 

Blends of enzymatically synthesized poly(bisphenol-A) and poly(p-r-butylphenol) with poly(e-CL) were examined. FT-IR analysis showed the expected strong intermolecular hydrogen-bonding interaction between the phenolic polymer with poly(e-CL). A single 7 was observed for the blend, and the value increased as a function of the polymer content, indicating their good miscibility in the amorphous state. In the blend of enzymatically synthesized poly(4,4 -oxybisphenol) with poly(e-CL), both polymers were miscible in the amorphous phase also. The crystallinity of poly(e-CL) decreased by poly(4,4 -oxybisphenol). 

In agreement with the results from the characterization, the SCR activity of VOx/Zr02 also depends only on the V-content, not on the method used for catalyst preparation. The marked increase in SCR activity with the V-content shows that only specific vanadium configurations are active. Although we assess the V=0 modes associated with these active configurations, IR analysis did not specify the structure of active polyoxoanions. 

OS 49] [R 17] [R 26] [P 36] At almost quantitative conversion, yields of 90% of two (in a first run) unidentified products and of 10% N,N -diethylurea were reported, accompanied by small amoimts of the mono-product [38], AH products no longer contained any C=S moiety, hence were somehow attacked via a nucleophilic route. By subsequent MS and IR analysis, the two main products were identified as N,N -diethyl-N-nitrosourea and, probably, N,N -diefhyl-N,N -dinitrosourea. By optimization of the [P 23] procedure, 100% selectivity for the nitration of N,N -diethylurea to N,N -diethylurea was achieved. 

For the purpose of IR analysis, in order to establish the nature of the polymer matrix, the sample is pressed... 

To assure consistency and speed in multidisciplinary structure analysis of low-MW compounds involving various techniques (IR, NMR, MS, etc.) most industrial laboratories use a Standard Operating Procedure (SOP). In such schemes IR analysis is frequently used as a cheap filter for a quick starting control and as a means for verification. As IR detects only structural units identification of an unknown compound on the basis of IR is difficult. Mass spectrometry is used as the prime identification tool and is especially important in the determination of the exact mass and gross formulae. While structural prognostication on the basis of MS is difficult for the non-expert, a posteriori interpretation is quite feasible. H NMR is both easy and cheap, however requires greater sample quantities than either... 

In off-line extraction the extracted analytes are collected and isolated independently from any subsequent analytical technique, which is to be employed next. For example, the extracted analyte can be collected in a solvent or on a solid sorbent. The choice of the collection method affects the possibilities for further analysis. The extracts may be used for final direct measurements (i.e. without further separation), e.g. UV and IR analysis. More usually, however, extraction is a pre-separation technique for chromatography, either off-line (the most common mode of SEE) or on-line (e.g. SFE-GC, SFE-LC-FTTR, etc.). The solvents used in extraction may affect subsequent chromatography. 

General techniques of qualitative IR analysis and the identification of material by IR absorption spectroscopy are described in ASTM E 1252 and ASTM E 204, respectively. The theoretical aspects of FTIR spectroscopy and analysis have been described in many books [106,107] and reviews [108]. Coates [109] has reviewed sampling methods for IR spectroscopy. 

As reported by Nelissen [58], unreacted carbodi-imides (Stabaxol I, P and P100), used as hydrolysis stabilisers in e.g. polyesters, are readily detected by IR analysis on the basis of the —N=C=N—absorption at 2140 cm 1, but without further discrimination within... 

In conclusion, IR analysis of polymer/additive extracts before chromatographic separation takes advantage mainly of straightforward transmission measurements. Without separation it is often possible to make class assignments (e.g. in the reported examples on plasticisers and carbodiimide hydrolysis stabilisers) it may eventually be necessary to use multivariate techniques. Infrared detection of chromatographic effluents is dealt with in Chapter 7. 

The minute sample sizes allowed in SFE-SFC analysis (typically 0.5 mg cf. the approximate weight of 30 mg for a single pellet), which is several orders of magnitude smaller than the sample weights used in GC, HPLC or IR analysis (5-10g), allows us to perform additive dispersion studies on a pellet-to-pellet basis [106]. 

There is a need for increased chromatography-FTIR sensitivity to extend IR analysis to trace mixture components. GC-FTIR-MS was prospected as the method of choice for volatile complex mixture analysis [167]. HPLC-FT1R, SFC-FTIR and TLC-FTIR are not as sensitive as GC-FTIR, but are more appropriate for analyses involving nonvolatile mixture components. Although GC-FTIR is one of the most developed and practised techniques which combine chromatography (GC, SFC, HPLC, SEC, TLC) and FUR, it does not find wide use for polymer/additive analysis, in contrast to HPLC-FTIR. 

Standard practices for GC-IR analysis have been described (ASTM E 1642-94). Griffiths [200] has discussed GC-FTIR designs. Sample preparation methods for hyphenated infrared techniques, in particular GC-FTIR, have been reported [201]. The technique has been reviewed repeatedly [167,183,201-204] a monograph [205] has appeared. 

Figure 7.35 HPLC(SEC)-UV-MS-NMR-IR analysis applied to polymer additives. After Wilson [664]. Reprinted with permission from I.D. Wilson, Analytical Chemistry, 72, 534-542A. Copyright (2000) American Chemical Society...

Both a pneumatic heated nozzle system [487] and an ultrasonic nozzle/vacuum system [699] have been described for removing the troublesome solvent in order to simplify IR analysis. The former system (LC Transform ) has been commercialised [700], and allows full use of the mid-IR spectral range by providing analyte films free from solvent interference. The evaporative... 

When considering libraries of spectra for identification purposes, the effect of sample preparation on spectral characteristics is also important. Two FUR sampling methods have been adopted for IR analysis of TLC eluates in the presence of a stationary phase, namely DRIFTS [741] and PAS [742], of comparable sensitivity. It is to be noted that in situ TLC-PA-FTIR and TLC-DRIFT spectra bear little resemblance to KBr disc or DR spectra [743,744]. This hinders spectral interpretation by fingerprinting. For unambiguous identification, the use of a reference library consisting of TLC-FTIR spectra of adsorbed species is necessary. 

---