Quantitative analysis differential method

Many analytical techniques are in use for the qualitative and quantitative evaluation of monomers and oligomers extracted from PA6 (GC, differential refrac-tometry, IR, PC, SEC, HPLC, RPLC, etc.). FTIR has been used for quantitative analysis of caprolactam oligomer content (extract %) in polyamide-6 [113], The method, which involves a 3h extraction in boiling methanol, is suitable for process control and plant environment. Kolnaar [114] has used FTIR characterisation of fractional extracts with pentane, hexane, and heptane of HDPE for blow moulding applications. Vinyl acetate in packaging film has similarly been determined by quantitative FUR. 

Total flavonoid content. Quantitative analysis of flavonoids depends on the objective of the study. Colorimetric estimation of total flavonoid content is measured by the aluminum chloride colorimetric assay (Jia and others 1999 Chang and others 2002). The total flavonoid content measured in this way is normally expressed in equivalent values of a standard flavonoid, often catechin or quercetin equivalents. Not all subgroups of flavonoids can be quantified by colorimetric methods however, total anthocyanin content is determined using the pH-differentiation method (Boyles and others 1993). 

Difficulties are encountered in the qualitative and quantitative analysis of carbohydrate mixtures because of the structural and chemical similarity of many of these compounds, particularly with respect to the stereoisomers of a particular carbohydrate. As a consequence, many chemical methods of analysis are unable to differentiate between different carbohydrates. Analytical specificity may be improved by the preliminary separation of the components of the mixture using a chromatographic technique prior to quantitation and techniques such as gas-liquid and liquid chromatography are particularly useful. However, the availability of purified preparations of many enzymes primarily involved in carbohydrate metabolism has resulted in the development of many relatively simple methods of analysis which have the required specificity and high sensitivity and use less toxic reagents. 

Vibrational Spectroscopy [Infrared (mid-IR, NIR), Raman]. In contrast to X-ray powder diffraction, which probes the orderly arrangement of molecules in the crystal lattice, vibration spectroscopy probes differences in the influence of the solid state on the molecular spectroscopy. As a result, there is often a severe overlap of the majority of the spectra for different forms of the pharmaceutical. Sometimes complete resolution of the vibrational modes of a particular functional group suffices to differentiate the solid-state form and allows direct quantification. In other instances, particularly with near-infrared (NIR) spectroscopy, the overlap of spectral features results in the need to rely on more sophisticated approaches for quantification. Of the spectroscopic methods which have been shown to be useful for quantitative analysis, vibrational (mid-IR absorption, Raman scattering, and NIR) spectroscopy is perhaps the most amenable to routine, on-line, off-line, and quality-control quantitation. 

SP-2401" and 3% SP-2250. ° Detectors used by EPA standards procedures, include photoionization (PID)," electron capture (ECD)," Eourier transform infrared spectrometry (PTIR), " and mass spectrometry detectors (MSD)." ° Method 8061 employs an ECD, so identification of the phthalate esters should be supported by al least one additional qualitative technique. This method also describes the use of an additional column (14% cyanopropyl phenyl polysiloxane) and dual ECD analysis, which fulfills the above mentioned requirement. Among MSDs, most of the procedures employ electron impact (El) ionization, but chemical ionization (CI) ° is also employed. In all MSD methods, except 1625, quantitative analysis is performed using internal standard techniques with a single characteristic m/z- Method 1625 is an isotope dilution procedure. The use of a FTIR detector (method 8410) allows the identification of specific isomers that are not differentiated using GC-MSD. 

Methods for quantitative analysis of Co indude flame and graphite-furnace atomic absorption spectrometry (AAS e.g., Welz and Sperling 1999), inductively coupled plasma emission spectrometry (ICP-AES e.g., Schramel 1994), neutron activation analysis (NAA e.g., Versieck etal. 1978), ion chromatography (e.g., Haerdi 1989), and electrochemical methods such as adsorption differential pulse voltammetry (ADPV e.g., Ostapczuk etal. 1983, Wang 1994). Older photometric methods are described in the literature (e.g.. Burger 1973). For a comparative study of the most commonly employed methods in the analysis of biological materials, see Miller-Ihli and Wolf (1986) and Angerer and Schaller... 

Dixon, J. B. 1966. Quantitative analysis of kaolinite and gibbsite in soils by differential thermal and selective dissolution methods. Clays and Clay Minerals 14, no. 1 83-89. doi 10.1346/CCMN.1966.0140107. 

Differential Thermal Analysis (DTA). A method for the identification and approximate quantitative determination of minerals. In the ceramic industry, DTA is particularly applied to the study of clays. The basis of this technique is the observation, by means of a thermocouple, of the temperatures of endothermic and/or exothermic reactions that take place when a test sample is heated at a specified rate in the differential method, one junction of the thermocouple is buried in the test sample and the other junction is buried in an inert material (calcined AI2O3) that is heated at the same rate as the test sample. In the DTA of a clay, the major effect is the endotherm resulting from the evolution of the water of... 

This method of differentiation has been tested on many carbonate and magnesia minerals. In certain cases, the magnesitic or dolomitic nature of the mineral was recognized, although it had been wrongly classified from its crystal habit. The diagnosis from the diphenylcarbazide reaction always agreed with that deduced from the quantitative analysis carried out later. 

The major reason why GC is not generally used for qualitative analysis is that it cannot differentiate or identify indisputably the structure of the molecule. Therefore, it is necessary to perform additional tests on the separated peak to ascertain its fnnctionality and elemental composition. Many books and articles are available regarding microanalysis, so this method is not extensively reviewed here. Usually it is necessary to trap the peak, then perform whatever specific microanalysis techniques are necessary to confirm the identity of the peak. Several commercial instruments are available for elemental analysis (usually carbon, hydrogen, sulfur, and halogens), or by GC (see Reference 17). These instruments usually require 0.1-3 mg of sample and often employ trapping systems for quantitative analysis. 

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