Quantitative analysis 584 INDEX

The refractive index detector, in general, is a choice of last resort and is used for those applications where, for one reason or another, all other detectors are inappropriate or impractical. However, the detector has one particular area of application for which it is unique and that is in the separation and analysis of polymers. In general, for those polymers that contain more than six monomer units, the refractive index is directly proportional to the concentration of the polymer and is practically independent of the molecular weight. Thus, a quantitative analysis of a polymer mixture can be obtained by the simple normalization of the peak areas in the chromatogram, there being no need for the use of individual response factors. Some typical specifications for the refractive index detector are as follows ... 

Analysis procedures can be additionally classified into procedures that involve physical properties, wet chemical analysis procedures, and instrumental chemical analysis procedures. Analysis using physical properties involves no chemical reactions and at times relatively simple devices (although possibly computerized) to facilitate the measurement. Physical properties are especially useful for identification, but may also be useful for quantitative analysis in cases where the value of a property, such as specific gravity or refractive index (Chapter 15), varies with the quantity of an analyte in a mixture. 

Recent developments and prospects of these methods have been discussed in a chapter by Schneider et al. (2001). It was underlined that these methods are widely applied for the characterization of crystalline materials (phase identification, quantitative analysis, determination of structure imperfections, crystal structure determination and analysis of 3D microstructural properties). Phase identification was traditionally based on a comparison of observed data with interplanar spacings and relative intensities (d and T) listed for crystalline materials. More recent search-match procedures, based on digitized patterns, and Powder Diffraction File (International Centre for Diffraction Data, USA.) containing powder data for hundreds of thousands substances may result in a fast efficient qualitative analysis. The determination of the amounts of different phases present in a multi-component sample (quantitative analysis) is based on the so-called Rietveld method. Procedures for pattern indexing, structure solution and refinement of structure model are based on the same method. 

Elemental composition Cu 57.47%, C 5.43%, H 0.91%, 0 36.18%. Both malachite and azurite may be identified by x-ray analysis and analyzed qualitatively using physical properties such as refractive index and density. For quantitative analysis, the compound may he digested in nitric acid and analyzed for copper by various instrumental methods (see Copper.)... 

The reaction between ammonia and methyl halides has been studied by using ab initio quantum-chemical methods.90 An examination of the stationary points in the reaction potential surface leads to a possible new interpretation of the detailed mechanism of this reaction in different media, hr the gas phase, the product is predicted to be a strongly hydrogen-bonded complex of alkylammonium and halide ions, in contrast to the observed formation of the free ions from reaction hr a polar solvent. Another research group has also studied the reaction between ammonia and methyl chloride.91 A quantitative analysis was made of the changes induced on the potential-energy surface by solvation and static uniform electric fields, with the help of different indexes. The indexes reveal that external perturbations yield transition states which are both electronically and structurally advanced as compared to the transition state in the gas phase. 

FTIR reflectance and transmission spectroscopy is used for analysis of thin films. Nevertheless, due to the high absorptivities of mid-IR bands, the film thickness must be limited (up to 100 pm, depending on the specific bands chosen) in order to perform an accurate qualitative analysis. Other IR methods, such as attenuated total reflectance (ATR) and photoacoustic methods provide IR spectra of thick material, because they penetrate a very thin layer at the surface of a sample. However, is important to point out that the effective pathlength for the ATR and the photo-acoustic methods depends on the refractive index and thermal diffusivity, respectively. Therefore, the use of these techniques for the quantitative analysis of non-homo-geneous materials can be difficult. 

A second index of biocompatibility was the quantitative analysis of cell growth inhibition, again on mouse fibroblast L929 cells, induced by the liquid components of the adhesive system and water extracts of two solid crosslinked materials. Table IV is a summary of the percent inhibition of cell growth (percent ICG). The mean protein values at 4 °C have been subtracted from the mean protein values (five test samples) at 37 °C for each treatment condition. The percent inhibition of cell growth (percent ICG) is shown for each treatment condition. The precision of the assay is approximately 10%. 

The application of refractive index and differential viscometer detection in SEC has been discussed by a number of authors [66-68]. Lew et al. presented the quantitative analysis of polyolefins by high-temperature SEC and dual refractive index-viscosity detection [69]. They applied a systematic approach for multidetector operation, assessed the effect of branching on the SEC calibration curve, and used a signal averaging procedure to better define intrinsic viscosity as a function of retention volume. The combination of SEC with refractive index, UV, and viscosity detectors was used to determine molar mass and functionality of polytetrahydrofuran simultaneously [70]. Long chain branching in EPDM copolymers by SEC-viscometry was analyzed by Chiantore et al. [71]. 

Analysis of Drugs in Preparations HPLC has found widespread use for the quantitative analysis of drugs in preparations of pharmaceutical and illicit manufacture. Drug concentrations are generally high enough to allow dissolution of the sample (tablet, powder, ointment, etc.) in a suitable solvent followed by injection. Ultraviolet-visible, fluorescence, or refractive index detection is normally used. 

The overall sensitivity of the detector appears to be very similar to that of the refractive index detector with about the same linearity. However, the most important characteristic of this detector is not its propensity for accurate quantitative analysis but its proficiency in providing molecular weight data for extremely large molecules. 

Kinetic resolution of racemic compounds is by far the most common transformation catalyzed by lipases, in which the enzyme discriminates between the two enantiomeric constituents of a racemic mixture. It is important to note that the maximum yield of a kinetic resolution is restricted to 50% for each enantiomer based on the starting material. The prochiral route and transformations involving meso compounds, the meso-trkk, have the advantage of potentially obtaining a 100% yield of pure enantiomer. A theoretical quantitative analysis of the kinetics involved in the biocatalytic processes described above has been developed. - The enantiomeric ratio ( ), an index of enantioselectivity, can be calculated from the extent of conversion and the corresponding enantiomeric excess (ee) values of either the product or the remaining substrate. The results reveal that for an irreversible process. 

Digital computers are being increasingly applied to infrared problems (L17). They can be used to obtain accurate spectra by correcting for known instrumental distortions (C26) and for resolution of overlapping bands. The corrected spectra can be filed to provide an index of fine structure for both qualitative and quantitative analysis. Although infrared spectroscopy at present is primarily a tool for structural and qualitative analysis, the increasing availability of computer facilities for complex correction procedures may make more widespread quantitative analysis possible. 

The introduction of GC as an analytical technique has had a profound impact on both qualitative and quantitative analysis of organic compounds. Identification of compounds by GC can be accomplished by their retention times on the column as compared to known reference standards, by inference from sample treatment prior to chromatography, " or by the concept of retention index. " The latter method and tables of retention indices " with associated conditions have been reported. " Although qualitative data and analytical techniques for identification of compounds are well-established " and relative retention data for over 600 substances also have been published, " the main utility of GC undoubtedly lies in its powerful combination of separation and quantitative capabilities. Use in quantitative analysis involves the implementation of two techniques being performed concurrently, i.e., separation of components and subsequent quantitative measurement. 

This method for defining detector linearity is satisfactory up to a point and ensures a minimum linearity from the detector and, consequently, an acceptable quantitative accuracy. However, the specification is significantly looser than that given above, and it is not possible to correct for any nonlinearity that may exist, as there is no correction factor provided that is equivalent to the response index. It is strongly advised that the response index should be determined for any detector that is to be used for quantitative analysis. In most cases, r need only be measured once, unless the detector undergoes some catastrophic event that is liable to distort its response, in which case, r may need to be checked again. 

Selectivity and Specificity. Selectivity and specificity are the ability to which an analytical method can measure and quantify the analyte precisely with or without interferents. These can be checked quantitatively by measuring the selectivity index Aan/Aint, where Aan is the sensitivity of the method and, 4lnl is the sensitivity of the analyte with or without interferents. Any major differences would be an indication of negative effect by interferents and must be checked against a sample without interferents. If the interfent is too great for accurate quantitative analysis an alternative method must be used. 

Generally, for a qualitative analysis of heterogeneous samples the results will hardly be influenced by this phenomenon. For quantitative analysis, however, the effect must be taken into account. By using another reflection element, for example, germanium with a higher refractive index (4.0 instead of 2.4 for ZnSe), the gradient would be much smaller (about one-third), because of the lower penetration depth under these experimental conditions. 

As noted above, the A(NTE)/ (AChE) ratio can be used as a convenient index of the probable neuropathic potential of the compound [3,26,40,55,57,58] We firstly used a QSAR approach for quantitative analysis structure - NTE selectivity and obtained equations describing dependence of neuropathic potential of O-phosphorylated oximes I-IV on the hydrophobicity and steric properties of the studied compounds. 

For the quantitative analysis of the light scattering data the concentration CpEc(X) of the PECs and their refractive index increment i pec(X) in dependence on the mixing ratio X must be known. In the case of polyanion solutions as starting ones, cP,c(X) is given by the expression... 

Oil industry has a long history of application of NMR spectroscopy for characterization of crude oils, products and oil fractions. The methodology has been mainly ID proton- or carbon-detected experiments. Quantitative NMR and NMR experiments have been used in estimation of aromatic, olefin, naphtene and paraffin proportions in the samples. ° A more detailed characterization has been obtained using various ID carbon-detected experiments, like GASPE, CSE, QUAT and DEPT to obtain quantitative CH sub-spectra. " The goal of characterization of the oil fractions and quantification of certain structural features has been to find correlation between these features and the product properties (e.g. viscosity index, pour point). Due to environmental concerns oil companies are nowadays more interested in development of lubricant base oils that have low aromatic and olefin contents. Hydrogenation of unsaturated components also improves the stability of the base oils, which is an important property for the end-product. Quantitative analysis of a saturated oil fraction with NMR is a major challenge. When the oil fraction contains only aliphatic compounds, the spectrum width that contains the resonances narrows to ca. 1 ppm in the NMR spectrum and ca. 50 ppm in NMR spectrum. This causes excessive... 

There are several performance tests for the return of motor function. One of the most often used is the Sciatic Function Index (SFT) derived by de Medinaceli et al. (1982) from a series of measurements of the walking gait of the rat. This index has been modified by Bain et al. (1989) for analysis of foot prints after peroneal nerve injury, and is known as the Peroneal Function Index (PFI). We and others have found that the quantitative analysis of toespread and of print length is more reliable indicator of recovery from peroneal nerve crush than is the PFI (Hare et al., 1993 Strand et al., 1993b). 

NB differing values in Merck Index (4.35), Foye (9.25), Connors et al. (9.8 at 18 C 10.2 at 16.5 C). There is confusion here between pKi, and pKa values, especially die Merck value. The value of 5.93 comes from Medwick T, Kaplan G, Weyer LG, Measurement of acidity and equilibria in glacial acetic acid widi the glass calomel electrode system, /. Pharm. Sci., 58,308-313 (1969) see also Bases (nonaqueous titrations). This value is mainly relevant to quantitative analysis by nonaqueous titration. 

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