Absorbancy index

The specific absorption (or extinction) coefficient Es (sometimes termed absorbancy index) may be defined as the absorption per unit thickness (path length) and unit concentration. 

Measurements taken at wave lengths near 740 m/i and 860 are also uncertain, because of the abrupt changes in refractive index associated with such absorption bands. Instrumental inadequacies magnify the anomalous refractive-index effects associated with these bands. As a practical method, most laboratories determine an absorbancy-index curve similar to that shown in Fig. 2, which, thereafter, is used for correcting measurements (made against water in the reference cell) to the colorless sucrose standard. This curve is actually also a calibration of the instrument, and, as the two effects may not always be applicable, occasional anomalies may be encountered. 

A color unit based on the absorbancy curve of a standard, white sugar was proposed by Peters and Phelps.3 This particular sugar had an absorbancy index at 560 mg of 0.00485. It was not intended that the white sugar... 

The term absorptivity is synonymous with extinction coefficient, absorbancy index, and specific extinction (Browning 1967). 

Reagent Solvent Wavelength (mil) Molar absorbancy index (1 cm) Reference... 

The results of enzymatic determinations of ceruloplasmin are often expressed in arbitrary units, and the values judged in the light of a series of results obtained in normal subjects by the same method. Expression of the enzyme activity in milligrams of ceruloplasmin per unit volume of serum is also possible. The relation between oxidase activity and the amount of ceruloplasmin in serum can be determined by measuring in parallel samples of sera both the oxidase activity and the change of optical density at 610 mix before and after the addition of ascorbic acid or cyanide. On the basis of the known absorbancy index, the ceruloplasmin concentration can be calculated (see Section 2.2.1) and the relation between it and the enzyme activity determined. Alternatively, purified human ceruloplasmin can be used for standardization of the enzymatic method. The ceruloplasmin content of the purified preparation can be determined colorimetrically or, in the case of a highly purified preparation, by nitrogen analysis. Predetermined increments of ceruloplasmin can then be added to aliquots of a selected serum. It is convenient to select a serum with relatively low ceruloplasmin level to start with. Serum of a patient with Wilson s disease, some of whom have no measurable amount of enzyme activity, would be ideal for the purpose however, Walshe (W5) has recently found an inhibitor in these sera. 

A Absorptivity (c is concentration in g L-1) A be k Extinction coefficient, Absorbancy Index... 

Absorptivity (a) Extinction coefficient, absorbancy index, absorbing index ... 

Microgram amounts of TcOj can be ascertained by measuring the absorbance of the colored complex, formed with toluene-3,4-dithiol in 2.1 M HCl, after extraction into carbon tetrachloride. One hour must be allowed for the development of the color. ITie molar absorbance index at 410 nm is 1.1-10" mole -1-cm. Beer s law is followed over the range of 1.1 to 16.1 pg Tc/ml. Because many cations interfere, an initial separation of technetium is necessary [73]. The same complex was used for the determination of technetium in uranium fission element alloys after separation of Tc by distillation from sulphuric acid [74j. I hc complex formation of technetium, rhenium, and molybdenum with toluene-3,4-dithiol and its analytical application have been studied in detail [71]. 

A method was developed to ascertain technetium in the range of pg/ml by reduction of TcO to Tc(IV) with 1,5-diphcnylcarbohydrazidc and subsequent complexa-tion of Tc(lV) with the reagent. The absorbance was measured at 520 nm after extrae-tion of the complex in carbon tetrachloride. The molar absorbance index was found to be 4.86 lO mole 1 cm [80]. 

A Tc(VI) species was reported to be prepared in aqueous solution by reduction of 1.82 mM TCO4 with 0.015 M N2H4 in 0.7 M OH . ITie reddish-brown product absorbed in the visible region at 500 nm with an absorbance index of about 200... 

Molar absorptivity e = Ajbc Molar absorbancy index, molar extinction coefficient, molar absorption coefficient... 

The sensitivity of a GC/FTIR system depends on the type of interface and the molar absorbance index of the analyte. Comparative studies of the three interfaces have shown that the highest sensitivity is achieved with the DD interface. In general, the limit of detection (LOD) of the hght-pipe GC/FTIR is about 10 ng on-column, while, the LODs of the DD/FTIR and MI/FTIR are 35 and 100 pg, respectively. In practice, the LODs of analytes in real samples are of the order of 0.5-25 ng on-column. To enhance the sensitivity of detection, additional clean-up and preconcentration methods are applied, such as head-space sampling, purge and trap, solid-phase extraction, and solid-phase micro-extraction. It would also be possible to achieve improved sensitivity by modifications of other parts of the analytical procedure, such as the use of large-volume sampling methods. 

Absorptivity, absorbance index, absorption cor i-cient the proportionality constant e, in Beer s law for light absorption A = elc, where A is absorbance, / the length of the light path, and c the concentration. If concentration is expressed on a molar basis, e becomes the molar absorptivity, molar absorption coefficient or molar extinction coefficient, i.e. e = A/lc, where I is the length of the light path in cm, and c is the molar concentration. 

Reactions were followed at wavelengths appropriate to the various reactants or products. Molar absorbancies at the wavelengths used are listed in Table 1 or in the text. In some cases, the molar absorbancy index was observed to change slightly immediately upon addition of acid. In such cases, a corrected absorbancy index for the reactant was obtained by extrapolating the observed absorbancy measurements back to zero time. 

Absorbanz (Extinktion) absorbance index/absorptivity Absorptionsindex absorbed dose (Gy)... 

Amino Acid 3- 1-Letter Letter Side chain polarity Side chain charge (pH 7.4) Hydropathy Absorbance index kmax(nm) max (xlO ... 

A spectrophotometric test for purity may be made by measuring the optical density at 260 m/i, the wavelength of the absorption maximum of nucleic acid and thus of the phages. Extraneous nucleic acid will increase the absorbency index per particle (see Sec. IV, 6). A correction must be made for light scattering. 

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