Molar absorptivity calculation

Aqueous solution of a drug (0-10 milli molar) shows a percentage transmission of 50 in a 1 cm cell at 250 run. The molar absorptivity, calculated ... 

The calibration graph at 510 nm is a straight line and Beer s law is obeyed from 0.5 to 5 [xg/ml of boron in the final measured solution (corresponding to 10-110 xg of boron in the aqueous phase). The molar absorptivity, calculated from the slope of the statistical working calibration graph at 510 nm, was 29051/mol/cm. The Sandell sensitivity was 0.011 xgcm2 of boron. The precision of the method for ten replicate determinations was 0.6%. The absorbance of the reagent blank solution at 510 nm was 0.010 d= 0.003 for ten replicate determinations. Therefore, the detection limit was 0.04 xg/ml of boron in the final measured solution. 

The indirect molar absorptivity calculated from the change in absorbance produced by fluoride (F) under the conditions given below in the procedure is 2.7-10 (sp. abs., a = 1.4) at 540 nm. At this wavelength, the difference in the absorbance before and after reaction is greatest (at pH 1). 

Molar absorptivity (Section 13 21) Ameasure of the intensity of a peak usually in UV VIS spectroscopy Molecular dipole moment (Section 1 11) The overall mea sured dipole moment of a molecule It can be calculated as the resultant (or vector sum) of all the individual bond di pole moments... 

The basic principle of most colorimetric measurements consists in comparing under well-defined conditions the colour produced by the substance in unknown amount with the same colour produced by a known amount of the material being determined. The quantitative comparison of these two solutions may, in general, be carried out by one or more of six methods. It is not essential to prepare a series of standards with the spectrophotometer the molar absorption coefficient can be calculated from one measurement of the absorbance or... 

The values of the molar absorption coefficients and e2 can be deduced from measurements of the absorbances of pure solutions of substances 1 and 2. By measuring the absorbance of the mixture at wavelengths Xl and X2, the concentrations of the two components can be calculated. 

The second form is statistically advantageous, but the first is amenable to linearized graphical analysis. It represents the equation of a straight line. A plot of (Y, — Too)-1 versus time will be a straight line with a slope from which k may be calculated k = slope x (Yq - Fx)/tA]o. Note that the bracketed quantity is the difference in y s (in spectrophotometry, the difference in molar absorptivities). Thus, k = slope X (yA - yP) = slope X (eA - p). 

Carotenoid concentration in solution can be calculated taking in consideration the absorption coefficient (Aj ) or molar absorptivity (s) values of the specific carotenoid according to the Beer-Lambert law. The absorption coefficient and e values were determined for many carotenoids and values are available in the literature. These two values are related as shown in Equation 1. The concentration is calculated according to Equation 2. 

Calculate the molar absorptivity of each of. them (in dm3 mol Cm 1 ) atthe wave ... 

This intensity is expressed by the molar absorption coefficient 8 which can be calculated from the (measured) absorbance A, (A = log Iq/I) via the well known equation of Lambert Beer (1.3), wherein c is the concentration (mole/1) and d is the optical path length of the cell (in cm). 

The concentration of a liquid sample contained in an infrared cell of thickness 0.15 pm is 0.5 M. Calculate the molar absorptivity of the sample if the absorbance at a specified wavenumber is 0.300. 

Calculate the transmittance of a solution in a 1.00-cm cuvette given that the absorbance is 0.398. What additional information, if any, would you need to calculate the molar absorptivity of this analyte ... 

T = 0.400. In order to calculate the molar absorptivity, the molarity of the solution would be needed. 

It is important to note that the calculation of the initial concentrations of phenol ( 10-2 mol dm-3) and acetonitrile (possibly 1 mol dm-3) were corrected for the density of the solvent at each temperature. The temperature effect on the molar absorption coefficient (e) was also considered when relating [PhOH] to the absorbance of the O-H free band. This was empirically made by measuring the absorbances (A) of a phenol solution (in the same solvent and with a concentration similar to that used in the equilibrium study) over the experimental temperature range. For each temperature, the Lambert-Beer law [312],... 

It is possible to measure the absorbance of a sample of a known compound at its absorption maximum and to calculate the actual concentration of the compound in the sample using a known value for the molar absorption coefficient (often obtainable from published spectral tables). In Figure 2.2 the absorption spectrum of ADP shows an absorbance of 0.22 at 258 nm. The quoted value for the molar absorption coefficient of ADP at this wavelength is 1.54 X 104 1 mol-1 cm-1 and hence the concentration of ADP in the sample used can be calculated from the Beer-Lambert equation ... 

Concentrations in the region of 0.1 mol 1 1 are often convenient but it obviously depends upon such factors as the amount of substance available, the cost, the solubility, etc. From this stock solution, a series of accurate dilutions are prepared using volumetric glassware and the absorbance of each dilution measured in a 1-cm cuvette at the wavelength of maximum absorbance for the compound. A plot of absorbance against concentration will give an indication of the validity of the Beer-Lambert relationship for the compound and a value for the molar absorption coefficient may be calculated from these individual measurements or from the slope of the linear portion of the graph ... 

If the use of the molar absorption coefficient is inappropriate then it may be sufficient to use a single reference solution of known concentration (known as a standard or calibrator solution) and to compare the test absorbance with that of this standard. The principle of quantitation is exactly the same as before except that the molar absorption coefficient is eliminated from the calculation by measuring the absorbance of both the test and standard solutions at the same wavelength and comparing their absorbance values. 

Alternatively the absorbance of the mixture can be measured at different wavelengths (usually one for each compound present) and, provided that the molar absorption coefficients for each compound at each wavelength are known, the concentration of each compound can be calculated. Procedure 2.2 illustrates such a calculation. 

The enzyme activity in katals per litre may be calculated from the molar absorption coefficient for NADH at 340 nm (6.22 X 103 1 mol-1 cm-1). 

A. The use of the molar absorption coefficient for NADI I to calculate the concentration change (mol... 

The molar absorptivity spectra of species A, B and C have been determined independently. Ma in ABC L in2. m calculates the corresponding concentration profiles of the 3 components using the complete data set from Data ABC. m. They are shown in Figure 4-31. 

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