UV-absorptivity coefficient

Figure 4. Relationship between UV-absorptivity coefficient (280 nm) and non-UV absorbing mass in chain extended HPL.

Vodacek, A., Hoge, F., Swift, R.N., Yungei, J.K., Peltzer, E.T., and Blough, N.V. (1995) The use of in situ and airborne fluorescence measurements to determine UV absorption coefficients and DOC concentrations in surface waters. Limnol. Oceanogr. 40, 411-415. 

Studies of polymers such as polymethylemethacrylate (PMMA), polyethylenetherephthalate (PET) and polytetrafluoroethylene (PTFE) revealed that the chemical surface changes depend considerably on the laser fluence, the nature of the environment surrounding the polymer during the treatments and the UV absorption coefficient of the polymer (6.7.81. It was found that the Ablative... 

In Figure 2 the UV absorption coefficient of PCL samples appears to be a linear function of each active species... 

In Figure 3 the effect of activator concentration on the UV absorption coefficient of our polymer samples, at constant [I], is given. Almost parallel lines, well joined to the interpolated values on the equimolar concentration line, have been found. 

Fig. 7.13.21 shows a cross section of a thermoelectric infrared sensor. This structure has potentially low cost because of its high compatibility with the widely used SiCMOS ICs [4], To improve sensitivity, the sensor uses a swastika pattern with a curved beam and a gold-black absorber with good IR absorptivity so as to attain a UV absorption coefficient of 90% or larger. 

Refractive index detectors can also be used. Their main advantage is that they can used for compounds with small to no UV absorption coefficients. They are, however, much less sensitive than UV detectors for the majority of compounds encountered as natural products. These detectors are generally more difficult to set up to obtain a stable baseline. They are best used with isocratic mobile phases such as those used in size-exclusion chromatography. 

The higher molecular weight species show a higher UV absorption coefficient. This discrete absorption coefficient makes analysis difficult. 

Different pitches have different GPC calibration curves and each sample should be used to define its own /elution volume relationship. A quantitative evaluation performed on the CPTI sample shows a higher UV absorption coefficient for high MW species. This quantum nature of the absorption coefficient makes the definition of a continuous relationship between absorption coefficient and MW difficult. 

Hydrodynamic sizes of the BIS-series samples were also monitored by SEC-LALLS. Figure 7 shows the chromatograms of both IMC and PAAM samples that had been pre-purified by dialysis. Since the UV absorption coefficient varied with the dichromate-to-PAAM ratio (Table 3), it was impossible to assign an absolute concentration for each fraction of the eluted polymer. However, the relative sizes of the IMC samples may still be recognized from the normalized UV absorption elution curves. 

The reproducibility of the IMC process was also examined by observing the sizes of four replicate IMC samples. The normalized SEC-LALLS chromatograms of the four samples were nearly identical (Figure 8). The percentage deviation for the peak position, apparent M measured at the peak position, and average apparent size (calculated assiaming all fractions had the same UV absorption coefficient) were 0.5, 4.0 and 2.5, respectively at a 95% C.I. 

Using PAS, the influence of SC constituents such as water, lipids, and hydrophilic substances on UV light absorption have been investigated. The data reveal that upon hydration of SC, there is a decrease of UV absorption coefficient by about 20%. Lipids were not shown to have any direct effect on UV absorption by SC. Further, the data suggest that the hydrophilic substances of SC were protected in situ by polar lipids enmeshed within the structure of SC. 

Additive UV absorption coefficient before solvent extraction UV absorption coefficient after solvent extraction... 

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