Prisma

Van der Schaaf, T.W. 1996. PRISMA A Risk Management Tool Based on Incident Analysis, International Conference and Workshop on Process Safety Management and Inherently Safer Processes, Center for Chemical Process Safety of the American Institute of Chemical Engineers, New York. 

Base Character Syrup Syrup Prisma containing 2H 0, m.p. 36-40 (e rr.). Anhydrcnis... 

Bydioohlorlde Crystal 11 oa Prlactfl in Prisma In Prisms in varty... 

Sz. Nyiredy, K. Dallenhach-Toelke and O. Sticher, The PRISMA optimization system in planar chromatography , /. Planar Chromatogr. 1 336-342 (1988). 

Nicol sches Prisma. Nicol prism, nie, adv. never. 

The PRISMA model is a system for the optimization of two- to five-eomponent mobile phases, developed by Nyiredy et al. to simplify the optimization proeess in different planar and column chromatographic systems [66]. This model for the seleetion of solvents and optimization of the mobile phase was developed first for TEC and high-performanee liquid ehromatography (HPLC) [38,67]. 

FIGURE 4.11 The PRISMA model. (Adapted from Siouffi, A.-M. and Abbou, M., Optimization of the mobile phase, in Planar Chromatography, A Retrospective View for the Third Millennium, Nyiredy, Sz., Ed., Springer Scientific, Budapest, 2001, chap. 3. With permission.)... 

Horizontal and vertical correlations of hR values of nonpolar compounds and the selectivity points at different levels of the solvent strength using samrated TLC systems were given by Nyiredy et al. [18,67] applying the PRISMA model ... 

Mobile phase optimization by the PRISMA system follows the steps [20,38,66,69,70] ... 

Investigation of the chromatographic system using the PRISMA model... 

Morita et al. [69] optimized the mobile phase composition using the PRISMA model for rapid and economic determination of synthetic red pigments in cosmetics and medicines. The PRISMA model has been effective in combination with a super modihed simplex method for fadhtating optimization of the mobile phase in high performance thin layer chromatography (HPTLC). 

Pelander et al. [71] studied the retardation behavior of cyanobacterial hepato-toxins in the irregular part of the PRISMA model for TLC at 16 selectivity points. The mobile phase combination and the area of the triangular plane were selected in the preassay. The retardation of all the toxins followed the relation for ftRp. The cyanobacterial hepatotoxins behaved predictably in the selected systems in the irregular part of the PRISMA model. 

Cimpoiu et al. [72] made a comparative study of the use of the Simplex and PRISMA methods for optimization of the mobile phase used for the separation of a group of drugs (1,4-benzodiazepines). They showed that the optimum mobile phase compositions by using the two methods were very similar, and in the case of polar compounds the composition of the mobile phase could be modified more precisely with the Simplex method than with the PRISMA. 

Pelander et al. [81] developed a computer program for optimization of the mobile phase composition in TLC. They used the desirability function technique combined with the PRISMA model to enhance the quahty of TLC separation. They apphed the statistical models for prediction of retardation and band broadening at different mobile phase compositions they obtained using the PRISMA method the optimum mobile phase mixtures and a good separation for cyanobacterial hepatotoxins on a normal phase TLC plate and for phenolic compound on reversed-phase layers. 

On the basis of Snyder s system for characterization of solvents the PRISMA method for mobile phase optimization has been developed. This system enables the optimization of solvent strength and mobile phase selectivity and also the transfer of the optimized mobile phase to different planar chromatographic techniques, in our case the PLC. 

Procedures used vary from trial-and-error methods to more sophisticated approaches including the window diagram, the simplex method, the PRISMA method, chemometric method, or computer-assisted methods. Many of these procedures were originally developed for HPLC and were apphed to TLC with appropriate changes in methodology. In the majority of the procedures, a set of solvents is selected as components of the mobile phase and one of the mentioned procedures is then used to optimize their relative proportions. Chemometric methods make possible to choose the minimum number of chromatographic systems needed to perform the best separation. 

For practical purposes, it is most suited to combine the analyst s practice with computer assistance, in this context the PRISMA model being very efficient. 

Figure 7.14 The PRISMA Bobile phase optiaization model showing M the construction of the prism and the selection of selectivity points (Reproduced with permission from ref. 170. Copyright Marcel Dekker, Inc.) ...

An important difference between the statistical mixture design techniques popular in HPLC and the PRISMA model is that the former yields a computed optimum solvent composition id>ile the latter relies on a structured trial and error approach, which is readily adaptable to TLC. Solvent changes and re-equilibration in HPLC can be quite time consuming, so that it becomes attractive to ainimize the number of experiments, while for TLC, experiments can be performed in parallel and time constraints are less significant. Changes in solvent strength are also more rapidly adjusted empirically within the PRISMA model when theoretical considerations are found inadequate or require modification due to differences in the experimental approach. 

The PRISMA model was developed by Nyiredy for solvent optimization in TLC and HPLC [142,168-171]. The PRISMA model consists of three parts the selection of the chromatographic system, optimization of the selected mobile phases, and the selection of the development method. Since silica is the most widely used stationary phase in TLC, the optimization procedure always starts with this phase, although the method is equally applicable to all chemically bonded phases in the normal or reversed-phase mode. For the selection of suitable solvents the first experiments are carried out on TLC plates in unsaturated... 

The optimization of the solvent strength by varying the selectivity points has to be carried out until at least a beginning separation is obtained. At this point the third part of the PRISMA iK>del can be used to select the appropriate development mode. If an Increase in efficiency is required to improve the overall resolution of the sample then forced-flow linear... 

PRISMA Prevention and Recovery Information System for Monitoring and Analysis... 

The last requirement, i.e. if all (root)cause areas are included, was used to retrieve three pro-active methods indicating safety risks. All three methods address the entire socio-technical system (technical, human and organizational). These three methods are used to construct a new pro-active method of indicating safety risks, which includes the benefits and addresses the limitations of these three existing methods. The three methods evaluated are MORT, Johnson (Johnson, 1980), TRIPOD, Hudson (Hudson et al., 1991), and PRISMA, van der Schaaf (Schaaf van der, 1992). 

From this analysis it appears that a huge discrepancy exists between deviations prior to accidents, that can be found in normal operation and the pro-active safety indicators and methods in current use. The re-occurring indirect safety related deviations that are the dominant class of events causing accidents are therefore defined as the precursors for accidents, as stated in Chapter 1. Furthermore, from Table 5 it can be concluded that a clear link between risk reduction and the normal way of working is not explicitly present in one of the three methods. Finally, the feasibility of methods (except PRISMA) needs some attention additional expert knowledge is often necessary to apply the method. The focus of the method indicating safety risks developed in this thesis will lie especially on these three criteria. 

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