Extractive monitoring

Applications Applications of UV/VIS spectrophotometry can be found in the areas of extraction monitoring and control, migration and blooming, polymer impregnation, in-polymer analysis, polymer melts, polymer-bound additives, purity determinations, colour body analysis and microscopy. Most samples measured with UV/VIS spectroscopy are in solution. However, in comparison to IR spectroscopy additive analysis in the UV/VIS range plays only a minor role as only a limited class of compounds exhibits specific absorption bands in the UV range with an intensity proportional to the additive concentration. Characteristic UV absorption bands of various common polymer additives are given in Scheirs [24],... 

UV/VIS spectrophotometry can also be used for extraction monitoring on the basis of the chromophore of functional classes and to follow up polymer impregnation with additives in scC02 [81]. 

Figure 10.4 Typical UHPLC trace of isoflavones from a soy protein extract monitored at 260 nm using a Hypersil Gold C18 column (100 x 2.1 mm 1.9 pm Waters, Milford, MA) and a 0.5-mL/min flow rate (9600 psi) of a linear gradient of 0.1 % aq. formic acid versus methanol/acetonitrile(l l). FL = flavone (internal standard), other details in figure and in text. Concentrations of ISOFLAVONE peaks (pM) D = 17.66, GLY = 6.27, G = 26.49, D-Mal = 16.76, GLY-Mal = 3.62, D-Ac = 5.87, G-Mal = 26.70, DE = 3.37, GLYCITEIN = 1.74, G-Ac = 8.33, GE = 4.36.

Figure 5.2.3 depicts the HPLC chromatogram of a tomato peel extract monitored by UV absorbance at 469 nm. The separation was performed on a 150 x 4.6 mm C30 column (ProntoSil, 3 xm, 200 A, Bischoff, Germany) at room temperature and a flow rate of 1 ml/min with a binary mixture of acetone/ water, developed for LC-NMR experiments. The 50-min gradient elution was performed in four steps, i.e. (1) an initial 3 min with 75/25 (v/v) acetone/water, (2) a 24-min gradient to 100% acetone, (3) an isocratic step from 27 45 min with 100% acetone, and (4) a 2-min gradient back to the initial conditions. 

The Separation of a Fermentation Extract Monitored by Differential Detection... 

There are two ways to monitor the concentrations of trace gases in the atmosphere by FT-IR spectrometry. The first is to draw the atmosphere in the region of interest into a long-path gas cell, and the second is to measure the spectrum of the atmosphere in situ. The first approach, which is known as extractive monitoring [1], is covered in this section, and the second, known as open-path FT-IR spectrometry (OP/FT-IR) [2], is covered in Section 22.2. 

One of the most important uses of MALT is calculation of the lines in the spectrum of water vapor. By subtracting the calculated spectrum of water vapor from a measured spectrum measured by extractive monitoring or OP/FT-IR spectrometry, the spectrum of the remaining molecules in the beam may be seen more clearly, and multivariate analytical protocols such as CLS and PLS regression work even better. 

The alternative technique to extractive monitoring is open-path FT-IR spectrometry. In this approach, no gas cell is used to contain the air sample. Instead, the beam is passed through a path (typically, between 100 and 400 m in length) that crosses the... 

Despite all the potential problems of OP/FT-IR spectrometry, remarkably good results have been found. Typical detection limits for the path-integrated concentration are less than 10 ppm-meter. Thus, for a pathlength of 100 m, the detection limits for most pollutants is less than lOOppbv. Detection limits are greater than are obtained by extractive monitoring, but the problems introduced by point sampling are eliminated. 

To ensure disposal water quality is in line with regulatory requirements (usually 40 ppm), the oil content in water is monitored by solvent extraction and infrared spectroscopy. The specification of 40 ppm refers to an oil in water content typically averaged over a one month period. 

Speckle shearing interferometry, or shearography, is a full field optical inspection teclmique that may be used for the nondestructive detection of surface and, sometimes, subsurface defects. Whilst being more sensitive in the detection of surface defects, it may also be considered for pipe inspection and the monitoring of internal conoslon. In contrast, laser ultrasound and other forms of ultrasound, are point by point measurement techniques, so that scanning facilities and significant data processing is required before information on local defects is extracted from any examination of extensive areas [1 - 3]. 

The Analysis of Trihalomethanes in Drinking Water by Liquid Extraction US Environmental Protection Agency, Environmental Monitoring and Support Laboratory, Cincinnati, OH, 9 Sept. 1977. 

Clinical Analysis Clinical, pharmaceutical, and forensic labs make frequent use of gas chromatography for the analysis of drugs. Because the sample s matrix is often incompatible with the GC column, analytes generally must be isolated by extraction. Figure 12.25b shows how gas chromatography can be used in monitoring blood alcohol levels. 

Description of Method. Fluoxetine, whose structure is shown in Figure 12.31a, is another name for the antidepressant drug Prozac. The determination of fluoxetine and its metabolite norfluoxetine. Figure 12.31 b, in serum is an important part of monitoring its therapeutic use. The analysis is complicated by the complex matrix of serum samples. A solid-phase extraction followed by an HPLC analysis using a fluorescence detector provides the necessary selectivity and detection limits. 

Automated analyzers may be used for continuous monitoring of ambient poUutants and EPA has developed continuous procedures (23) as alternatives to the referenced methods. Eor source sampling, EPA has specified extractive sampling trains and analytical methods for poUutants such as SO2 and SO [7446-11-9] sulfuric acid [7664-93-9] mists, NO, mercury [7439-97-6], beryUium [7440-41-7], vinyl chloride, and VOCs (volatile organic compounds). Some EPA New Source Performance Standards requite continuous monitors on specified sources. 

Source sampling of particulates requites isokinetic removal of a composite sample from the stack or vent effluent to determine representative emission rates. Samples are coUected either extractively or using an in-stack filter EPA Method 5 is representative of extractive sampling, EPA Method 17 of in-stack filtration. Other means of source sampling have been used, but they have been largely supplanted by EPA methods. Continuous in-stack monitors of opacity utilize attenuation of radiation across the effluent. Opacity measurements are affected by the particle size, shape, size distribution, refractive index, and the wavelength of the radiation (25,26). 

A iridine traces in aqueous solution can be determined by reaction with 4-(p-nitroben25l)pyridine [1083-48-3] and potassium carbonate [584-08-7]. Quantitative determination is carried out by photometric measurement of the absorption of the blue dye formed (367,368). Alkylating reagents interfere in the determination. A iridine traces in the air can be detected discontinuously by absorption in Folin s reagent (l,2-naphthoquinone-4-sulfonate) [2066-93-5] (369,370) with subsequent chloroform extraction and hplc analysis of the red dye formed (371,372). The detection limit is ca 0.1 ppm. Nitrogen-specific thermal ionisation detectors can be used for continuous monitoring of the ambient air. 

The environmental appHcations of infrared spectrometry are many and varied. Many appHcations at industrial sites are analogous to those for on-line process analysis waste streams and recycling processes can be monitored in the same way. Commercial infrared stack-gas monitors are based on either an extractive probe attached to a long-path gas ceU or an open-path (across stack) configuration (69). Stack plume and flare monitoring can be done externally... 

Quantitative mass spectrometry, also used for pharmaceutical appHcations, involves the use of isotopicaHy labeled internal standards for method calibration and the calculation of percent recoveries (9). Maximum sensitivity is obtained when the mass spectrometer is set to monitor only a few ions, which are characteristic of the target compounds to be quantified, a procedure known as the selected ion monitoring mode (sim). When chlorinated species are to be detected, then two ions from the isotopic envelope can be monitored, and confirmation of the target compound can be based not only on the gc retention time and the mass, but on the ratio of the two ion abundances being close to the theoretically expected value. The spectrometer cycles through the ions in the shortest possible time. This avoids compromising the chromatographic resolution of the gc, because even after extraction the sample contains many compounds in addition to the analyte. To increase sensitivity, some methods use sample concentration techniques. 

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