Method transfer success factors

Sukhan has used PTAB cationic micelles to enhance the CL reaction of 4-diethylaminophthalohydrazide with oxygen and Co(II) in the presence of fluorescein as sensitizer [48], This enhancement is mainly due to electron-excited energy transfer from the donor (4-diethylaminophthalohydrazide) to the acceptor (fluorescein). The addition of fluorescein combined with the presence of PTAB reduces the detection limit of Co(II) by a factor of 6. The method was successfully applied in the determination of Co in tap water samples. 

The smooth and efficient method transfer between the two platforms will remain important within the transition period between UHPLC and HPLC. The column dimension, particle size, stationary phase chemistry, mobile phase flow rate and gradient profile, dwell volume, injection volume, and data acquisition are key factors to be carefully evaluated to ensure improved or maintained performance of transferred methods. Other factors including regulatory requirements should also be considered for a successful method transfer to quality control labs. The extra-column volume effects such as increased retention factors and decreased efficiency and high pressure effects (e.g., frictional heating and changes in retention factors) should be considered when various methods are compared and transferred. 

Gamson et a/.t49) have successfully used the. /-factor method to correlate their experimental results for heat and mass transfer between a bed of granular solids and a gas stream. 

To develop robust methods, you have to keep in mind that simple methods are preferable. Also, if you have a chromatographic background, then the factors affecting CE precision (and to a lesser extent accuracy) are widely different to HPLC, which is currently the predominantly employed technique for drug assay. There is no general preference for the choice between techniques CE, LC, or other. The choice should be made on a scientific basis, supported by the relative merits of the techniques for the specific problem and factors such as the experience of the method-developing scientist. Robust CE methods have been successfully transferred to relatively inexperienced QC and Contract Research Organisation (CRO) labs. 

The method of linear solvation energy (LSER), based on the Kamlet-Taft multiparameter scale (10) has been successfully exploited to study retention in LC. The LSER approach, when applied to phase-transfer processes, correlates a general solute property (SP), such as logarithmic capacity factor, with parameters of the solute and both the mobile and stationary phases ... 

In our opinion, this development was facilitated mainly by two key factors the technical progress of all analytical methods, particularly in the fields of NMR spectroscopy and X-ray diffractometry, and the plenty of structural data meanwhile available for metal complexes of model compounds of carbohydrates. The basic research on the structural chemistry of the latter complexes followed by a transfer of the thereby gained knowledge in stability and regioselectivity of metal coordination into reducing carbohydrates has proved to be very successful. By this way, the improvement of existing and the development of new applications of metal complexes of carbohydrates, which provide a cheap and renewable feedstock, is merely a matter of time. 

The essential parameters which determine the electrochemical process are the electron affinity of the neutral compound, which correlates with the energy of the LUMO, the energies of interaction with the solvent and counterions, the electron-electron repulsion energies and stereochemical factors. A precondition for an electrochemical study is that the chemical reaction which may occur, e.g. with the solvent, is much slower than the electron transfer process, and that the electrochemical reaction is reversible 66). Correlation of half-wave potentials with the energies of Huckel LUMO s has been one of the early successes of the Huckel model 8>2°.67-88>. The power of the electrochemical method in the study of polycyclic anions has been demonstrated recently 69a). Studies on reactions occurring during electrochemical reductions report reductive alkylations of polycyclic systems and their mechanism 70,69b). 

The application of the z-transform and of the coherence theory to the study of displacement chromatography were initially presented by Helfferich [35] and later described in detail by Helfferich and Klein [9]. These methods were used by Frenz and Horvath [14]. The coherence theory assumes local equilibrium between the mobile and the stationary phase gleets the influence of the mass transfer resistances and of axial dispersion (i.e., it uses the ideal model) and assumes also that the separation factors for all successive pairs of components of the system are constant. With these assumptions and using a nonlinear transform of the variables, the so-called li-transform, it is possible to derive a simple set of algebraic equations through which the displacement process can be described. In these critical publications, Helfferich [9,35] and Frenz and Horvath [14] used a convention that is opposite to ours regarding the definition of the elution order of the feed components. In this section as in the corresponding subsection of Chapter 4, we will assume with them that the most retained solute (i.e., the displacer) is component 1 and that component n is the least retained feed component, so that... 

Generally, if robustness is designed into the method development process, the methods should transfer more readily. The successful performance of a test method may be sensitive to the setting of some operational parameters. In robustness testing, a variety of parameters are evaluated to determine the extent to which they can be varied without affecting the performance of the method. In an HPLC experiment, the following representative parameters (factors) may be evaluated ... 

Successful apphcations of SLMs are possible due to their advantages compared to other separation methods. The main advantages of SLMs are the small amounts of organic phase and extractant (carrier) used, one-step mass transfer, the possibility of achieving high separation factors, concentration of extracted compound(s) during separation, and low separation costs. 

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