Mixed Analyte Performance Evaluation

Samples from international laboratory proficiency test exercises were also analysed, these included five soils from the Mixed Analyte Performance Evaluation Programme (MAPEP), USA Department of Energy, Idaho Falls, Idaho, (MaS21, 23, 24, 25 and 26) and one soil from the Institutde Radioprotection et de Sflrete Nucleaire (IRSN), Le Visenet, Cedex, France, (113SL300). 

These results obtained from the analyses of industrial blends proved that the identification of the constituents of the different surfactant blends in the FIA-MS and MS-MS mode can be performed successfully in a time-saving manner only using the product ion scan carried out in mixture analysis mode. The applicability of positive ionisation either using FIA-MS for screening and MS-MS for the identification of these surfactants was evaluated after the blends examined before were mixed resulting in a complex surfactant mixture (cf. Fig. 2.5.7(a)). Identification of selected mixture constituents known to belong to the different blends used for mixture composition was performed by applying the whole spectrum of analytical techniques provided by MS-MS such as product ion, parent ion and/or neutral loss scans. 

Initial Test of Matrix Effects Assay matrices are typically the most troublesome component in LBA. There should be careful consideration of this variable during method validation. Two types of tests are used to address the two major concerns surrounding matrix effects. These are performed in consideration of (1) whether there is a matrix difference between the standards and anticipated study samples that impacts the relative accuracy of an assay and (2) whether there are inter-individual or disease-specific differences in matrix in the target patient population. Two types of tests are used to evaluate such matrix effects spike recovery, where known amounts of analyte are mixed ( spiked ) into characterized matrix, and parallelism in patient samples. However, limited availability of patient samples may prevent the latter testing during the method feasibility phase. 

Potentiometric titrations may be also performed in the flow injection mode. This is attractive because small amounts of sample are needed, the time of determination is short, and the results for low concentration are reliable. Besides, the potentiometric signal depends linearly on the concentration of the analyte, enabling determination in a broad concentration range. There are several types of such titration, e.g., a fixed sample volume is mixed with a titrant solution of constant concentration. The width of the potentiometric signal, measured on the time scale as At, is proportional to the logarithm of the analyte concentration. The quantitative evaluation is based on a calibration graph. The important factors are the linear range of determination and the time constant of the potentiometric detector. The latter must be compatible to the flow rate of the solution in the system. 

The pressure drop in a fluted mixing section can be calculated for a Newtonian fluid. The first theoretical analysis was performed by Tadmor and Klein [51]. Their final equation for the pressure drop contains five dimensionless numbers, which makes determination of the effect of certain design variables rather indirect. A non-iso-thermal and non-Newtonian analysis was performed by Lindt et al. [52]. This analysis requires numerical techniques to solve the equations. Therefore, this analysis can only be used if one develops the computer software to perform the calculations. A simpler analysis was made by the author [53], leading to closed form analytical solutions from which the effect of the most important design variables can be easily evaluated. 

Thus, in order to evaluate the enantiopurity of the Michael product 14a obtained during the optimization of the catalyst A (Scheme 5), the purification of the analytical quantities of the crude 14a from its diastereomer and residual p-ketoester 12a was performed by semipreparative normal phase HPLC using achiral silica-based column ( -hexanes/lPA, Zorbax Rx-SIL column). This purification provided partial separation, and the pure fractions containing major diastereomer (i.e., 14a) along with some mixed fractions containing both diastereomers were collected. Remarkably, the first collected fraction contained highly enantiopure 14a (99% ee). 

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