Absorbtivity, molar

Molar absorbtivities from charge-transfer absorption are large (greater that 10.000 LmoF cm"1). 

In addition, positive bias is often introduced as a result of (1) product differences in molar absorbtivity, (2) partitioning of soluble aromatics from the bulk... 

Calculate the concentration of p-nitrophenolate ion produced using molar absorbtivity of 1.78 x lOVM/cm. 

C) This question relates to the Beer Lambert Law, A = ebc where A is absorbance, e is molar absorbtivity, b is the path length, and c is concentration of the sample. This relationship is linear. 

Cu(II) sites in proteins have been classified into three types based on their spectral properties (2). Type I Cu(II) sites are characterized by very high molar absorbtivity values for the visible band near 600 nm... 

Type II Cu(II), or low-blue copper, is less colored at common research concentrations. These systems have received less attention than Type I copper. However, even low-blue cupric copper can possess high molar absorbtivities when compared with simple coordination complexes of Cu(II). The Cu(II) sites in such proteins also yield Azz values normally greater than 140 G, i.e., more like that of low molecular weight square planar Cu(II) complexes (2, 8). The only available crystal structure of a copper protein is that of a low blue protein bovine erythrocyte superoxide dismtuase (9). The two copper atoms in this protein are each coordinated to four histidine nitrogens in an approximate square planar array. 

Stability constants were determined from spectrophotometric titration data treated by molar-ratio method procedures. In all cases only 1 1 complexes were assumed to form. Thus, the molar absorbtivities and the conditional stability constants in Table IV reflect this assumption. 

The process of absorption in chemistry is often treated with Beer s law (after the German scientist August Beer (1825-1863)) rather than considering the imaginary component of the refractive index. The two approaches are equivalent. According to Beer s law, the absorption. A, of a sample is related to the concentration of the absorbing species, the optical path length, and the molar absorbtivity ... 

In some cases, drug substance does not have chromophores with a molar absorbtivity sufficient for accurate quantitation using UV detection. If HPLC with UV detection is used as a basic quantitation technique, then MS detection as a complementary technique is desirable in most cases. LC-MS is essentially preferable in most preformulation assays. High selectivity of the MS detector allows the use of fast gradient HPLC separation methods, which does not require significant development time. Practically in all assays used in preformulation, the quantitation of only drug substance is required and MS detection provides an accurate quantitation. 

Some related structures shown in Scheme 21 have similar UV absorptions and molar absorbtivities (82MI2). 

Dividing AOD by the respective initial radical concentration and the density of the solution p results in the presentation of the kinetic data in units of molar absorbtivity... 

The analytical wavelength is selected to avoid the interference caused by other absorbing substances. Also, there is a need for a molar absorbtivity that causes the change in absorbance during the titration to fall within a convenient range. Often, the chosen wavelength lies well apart from an absorption maximum. 

Note It is advisable to check for Ptl , either by electronic absorption or by the platinum-195 NMR spectrum. The molar absorbtivity at 495 nm, where I Ii" has a maximum with e 1.1 x 10 cm", should not exceed... 

Electronic transitions in the absorption spectra of Pt(II) complexes include ligand-field (LF) and charge-transfer (CT) bands and perhaps 5d-6p transitions e.g., the absorption spectrum of aq [PtCl ] displays well-separated LF and CT transitions with a maximum at 480 nm (molar absorbtivity, e = 15 M cm ) assigned to a triplet LF absorption, two maxima at 394 nm (e = 57) and 337 nm (e = 62) assigned to singlet LF absorption, and intense bands 200-250 nm (e > 10 ) to LMCT transitions ". The luminescence of K lPtCl ] in ice occurs from the lowest LF-triplet state, and the molecular geometry of this excited state (ES) may be (distorted T j) rather than D41, (square planar), which is particularly relevant to the photochemistry of Pt(II) complexes. 

The special criteria of validation for an analytical method are directly related to the characteristics of the analytical method. For UV/Vis spectrometry, the reaction between the analyte and reagent must be fast, reproducible, and quantitative. The solution of the product resulting from the reaction must have at least 10,000 times the value of molar absorbtivity. In this regard, higher values can be obtained by using a polyfunctional reagent (e.g., Arsenazo III). For atomic absorption spectrometry and ICP, reproducibility of the flame and plasma, respectively, are essential for the quality and reliability of the analytical information, as well as for the validation criteria of the method. 

It is frequently desirable to analyse for dehydroascorbic acid and l-ascorbic acid in the same solution. The former has an u.v. absorbance at 220 nm, but with a much smaller molar absorbtivity of 720. Thus any attempt at a direct spectrophotometric determination will be factor of about 20 times less sensitive than for L-ascorbic acid. We will see later that these facts have far reaching consequences in the use of chromatographic techniques for the separation and subsequent detection of L-ascorbic acid and dehydroascorbic acid. 

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