Homogeneous mode

This is the preferred mode with cuvettes it is still however necessary to correct for radial dilution effects. 

For a constant (centrifuge) speed operation equation (8.4) is applied. In the gradient mode (centrifuge speed increasing with time in order to speed up the analysis) cois replaced by an expression relating centrifuge speed with time. 

The light cut off by particles in the light beam is related to the concentration by the equation  

Kamack s equation is applied with the assumption that the attenuation is proportional to the product of the extinetion coefficient and the cross-sectional area of the particles in the beam i.e. ln(/(//) is replaced by the optical density D where  

The data are then converted to a mass distribution by summating the product of AT) and d, . 

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Several centrifugal cuvet photocentrifuges are commercially available. These instruments use the same theoiy as the disc photocentrifuges but are hmited in operation to the homogeneous mode of operation. 

Table 8.6 Centrifuge particle size analysis, homogeneous mode with...

Photocentrifuges are available in both disc and cuvette configuration. The former are normally used in the line-start mode and the latter in the homogeneous mode. The line-start mode has a much higher resolution... 

Other published solutions state that the amount of light cut off is proportional to particle volume [34,35] for line-start and to particle surface for homogeneous mode. 

Thus water as a solvent not only has the advantage of being a mobile support and simultaneously actually immobilizing the catalyst while retaining the homogeneous mode of reaction but, in particular, has positive effects on the environmental aspects of hydroformylation [33]. 

Fig. 2. Reverse phase HPLC of GAs. Column 250 x 5 mm i.d. 5 p,m ODS Hypersil Mobile phase 40 min, 40-90% gradient of methanol in 0.5 % aqueous acetic acid. Flow rate 1 ml min". Detector radioactivity monitor operating in homogeneous mode [66,67]. Sample ca. lOOOOdpm of each GA. [Crozier, unpublished data].

Fig. 12. HPLC-RC analysis of the metabolism of radiolabelled lAA conjugates by leaf discs from wild-type and RolB tobacco plants. After a 24 h metabolism period leaf discs were extracts with methanol and ca. 10 000 dpm aliquots were analysed by reverse phase HPLC-RC with column and flow rate, as in Fig. 6. Mobile phase 25 min, 10-60% gradient of methanol in 1% aqueous acetic acid. Detector radioactivity monitor operating in homogeneous mode [66,67]. Traces illustrate [ CJIAGluc metabolism by (A) wildBtype and (B) RolB leaf discs [ HJlAInos metabolism by (C) wildBtype and (D) RolB leaf discs [ C]IAAsp metabolism by (E) wildBtype and (F) RolB leaf discs [117],...

The discharge transition from filamentary to diffuse mode in atmospheric air has been analyzed (Jozef Sherman, 2005) in the system shown in Fig. 4-100. The transition can lead not only to the dififirse mode but also into another non-homogeneous mode where the filaments are more numerous and less intense. 

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