Photometric measurement

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 influence of temperature, solution s pH and other parameters in formation of ionic associate is investigated. As a result, optimal conditions of determination are established pH 4,0 volume of acetate buffer - 0,5 ml volume of 0,1% aqueous solution of CV - 0,3 ml extraction time - 3 minutes. The ratio of aqueous and organic phases is 1 1. Photometric measurement of toluene layer is carried out at = 606,0 nm. The accuracy of procedures checked by the method of additives. 

Water samples showing contamination by phenols are best examined by extracting the phenol into an organic solvent tri-n-butyl phosphate is very suitable for this purpose. Photometric measurements can be carried out on the extract, and the requisite alkaline conditions are achieved by the addition of tetra-n-butylammonium hydroxide. 

Separation techniques may have to be applied if the given sample contains substances which act as interferences (Section 21.10), or, as explained above, if the concentration of the element to be determined in the test solution is too low to give satisfactory absorbance readings. As already indicated (Section 21.10), the separation methods most commonly used in conjunction with flame spectrophotometric methods are solvent extraction (see Chapter 6) and ion exchange (Chapter 7). When a solvent extraction method is used, it may happen that the element to be determined is extracted into an organic solvent, and as discussed above it may be possible to use this solution directly for the flame photometric measurement. 

Fig. 5—4. Analysis by the absorption-edge method. The solid lines are photometric measurements of a photograph of the x-ray intensity as a function of angle. The concentration is calculated from the ratio of these lines extrapolated to the absorption edge. Table 5-4 gives some typical results.

The network is implemented by the participating countries through WHO. Sulfur Dioxide (SO,) and suspended particulate matter (SPN) data are routinely reported from each of the participating countries to WHO for entry into the global data base, which is maintained by the United States Environmental Protection Agency (U.S. EPA) at Research Triangle Park, North Carolina. Methods of collection and analysis varies by country. SPN is reported either as a gravimetric or a photometric (transmittance or reflectance) measurement converted to mass units. Since the accuracy of the conversion of the photometric measurement to mass units is... 

In sitn quantitation The absorption photometric measurements in reflectance were made at a wavelength X = 590 run (Fig. 2). 

In situ quantitation The photometric measurement in reflectance was carried out at X = 525 nm (Fig. IB). In order to ensure that the zone coloration had stabilized, scanning was not commenced iintil ca. 30 min after the dipping process. The detection limit for sugars was of the order of 25 ng substance per chromatogram zone. 

Subcase b2 This case, called the paired f-test , is often done when two test procedures, such as methods A and B, are applied to the same samples, for instance when validating a proposed procedure with respect to the accepted one. In practicular, an official content uniformity" 5 assay might prescribe a photometric measurement (extract the active principle from a tablet... 

In situ quantitation The absorption photometric measurement in reflectance was performed at A = 490nm, the fluorimetric analysis at Ae,c = 436nm and Afi > 560 nm (Fig. 1). 

So far, we have discussed monomacrocyclic intra-annular acids, but bimacrocyclic concave benzoic acids [74a]-[74c] and [75] have also been synthesized and their acidities determined at 25°C by photometric measurements in ethanol (Wangnick, 1991). Table 17 compares the (ethanol) values. No general trend could be found for the acidity of concave benzoic acids [74] and [75]. While [75] with 3,5-disubstituted outer phenyl rings was slightly more acidic than benzoic or acetic acid, [74] with 2,6-disubstituted outer phenyl rings was much less acidic than the non-macrocyclic analogues. 

As a test of reproducibility of spot printing and staining, a 10 spot by 10 row array (100 spots total) were printed on three slides. All slides were stained in a single staining run, using the same secondary detection chemistry with DAB as a chromogen. While DAB cannot provide accurate photometric measurements, it can provide relative comparisons from one spot to another on the same slide. When the stained control slides were analyzed in this... 

The experimental device for photometric measurements is shown schematically in Fig. 7. The device includes a measuring box (1) in which a mobile platform (2) is situated with two windows (3), into which plates (3 ) are inserted, each plate having 9 holes with paper matrixes. 

Photometric measurements of colouring in the AChE-biotests after biochemical hydrolysis of acetylthiocholine may be made by using any... 

Photometric measurements provide the basis for the majority of quantitative methods in biochemistry and are related to the amount of radiation absorbed rather than the nature of such radiation. This relationship is expressed in two experimental laws, which provide the mathematical basis for such quantitative methods. 

A discussion on steady state fluorescent monitoring necessitates a distinction between spectroscopic and photometric measurements. The former involves a grating-based spectrofluorometer where full spectrum excitation and emission multivariate spectra are acquired. In contrast a filter photometer involves optical elements (e.g., optical Alters) to isolate excitation and emission bands thereby resulting in a univariate output emission response. 

A-nitrosomethylurea and other carcinogens Food products incubated with nitrite under simulated gastric conditions Column chromatography NBP derivatisation Photometric Measuring alkylating activity [10]... 

Applicability of analytical Photometric measurement Well suited for any type... 

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