Irradiation times, optimization

De Ruiter et al. [4] observed that photochemical decomposition by ultraviolet irradiation of dansyl derivatives of chlorinated phenolic compounds in methanol-water mixtures led to the formation of highly fluorescent dansyl-OH and dansyl-OH3 species. The optimal irradiation time was 5.5s. This reaction was utilised in a post-column photochemical reactor in the high performance liquid chromatography determination of highly chlorinated phenols in river water. The method calibration curve (for dansylated pentachlorophenol) was linear over three orders of magnitude. 

Having obtained a rough estimate of the irradiation time, the time dependence of labeling of the receptor should be measured directly. The optimal photolysis time (e.g. Fig. 4.2), determined by the incorporation of label or by photoinactivation (see below), will be used in many labeling and control experiments, and it is important that it be reproducible. For the results to be useful the sample must be irradiated at a fixed point relative to the lamp. For example, if a long arc is used, the intensity varies both with the distance from the center of the lamp and with the position along the... 

Optimization of Irradiation Times. By far the greatest usage of the calculational model has been to study the optimization of irradiation times. This is a multi-dimensional problem of great complexity which has as its motivation the proper utilization of very expensive facilties and a very valuable inventory of intermediate products, mainly the mixtures of curium isotopes. The problem does not lend itself to a complete solution however, various simplifying approximations can be applied to the problem to explore the interacting parameters. 

C12 substituted complex exhibits optimal efficiency. After a short induction period the H2 generation rate establishes itself at 60 ml/hour/liter solution. In view of the small concentration of sensitizer employed (5 X 10 5M) this rate is astonishingly high. The quantum yield of H2 production in this cyclic water decomposition system approaches 5% and may be readily improved by optimizing further the catalyst. The H2 production rate does not decrease even after 50 h of irradiation time, the turnover numbers for the Ru complex being far over 1000. 

The reaction was conducted under solvent-free conditions in a domestic MW oven using four different kinds of solid support (silica gel, acidic alumina, mont-morillonite K-10, and zeolite HY). The best results (77-94%) were obtained with silica gel and an optimized irradiation time of 2 min. In the absence of a solid support, under neat conditions, the products were obtained in low yields and the results were not reproducible. 

UF of sugarcane juice and BSA solutions modified membranes showed more resistance to fouling and a higher rejection than unmodified membranes relatively high monomer concentration (40 g/1) at medium irradiation times (1.5-3 min) were among the optimal modification conditions to reduce membrane fouling (Susanto et al. 2007)... 

As mentioned above, the initial photoconversion of the provitamin (1) into the previtamin (171) (Scheme VII) is followed by a facile interconversion of the previtamin with tachysterol (173), and to a lesser extent with lumisterol (172) and the starting provitamin. These secondary interconversions are difficult to avoid as the ultraviolet absorption spec-trxim of the previtamin completely overlaps that of the starting (1). Optimization of previtamin formation can be attained by short irradiation times at low temperature (55), by operating at a wavelength close to 295 nm (i) and by a second irradiation in the presence of a triplet sensitizer which will catalyze a more favorable ratio of previtamin to tachysterol to be formed (52). If the photolysis is carried out on a... 

The choice of optimal reaction condition will depend both on the nature of the photoaffinity label and the immunoglobulin chain that is to be labeled. Thus, DNP reacts predominantly with the light chain of protein 460 and requires a larger concentration of DNP-AD and a longer irradiation time than the reaction of DNP-Nz, which reacts predominantly with the heavy chain. The considerations for a choice of reaction conditions are complex and will differ for each protein. The reader is referred to references"" for the conditions employed with protein 460. 

The other difference concerns penetration depth. As EB radiation is attenuated by all matter, penetration depth is a function of electron energy and density, e.g., at 300 kV the useful penetration depth at a density of 1 g/cm is 0.35 mm [264], In a clear layer of nonabsorbent polymers the penetration depth of UV radiation may increase with the absorbed irradiation energy (i.e., irradiation time) [265]. With low concentration of the photoinitiation, optimal wavelength, and sufficient irradiation time, coatings with a thickness of more than 1 mm can be cured. 

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