Configuration selection techniques

Several configurations for the sensor are possible. An especially viable alternative would seem to be the competitive displacement of fluorescent label. Since this is an equilibrium, fouling or contamination of the surface should not alter the absolute result. Krull et al (75) have reported the reproducible immobilisation of a stable phospholipid membrane containing fluorophore in this context. Concurrent fluorescence polarisation measurements can offer the possibility of multidimensional analysis (76) and are in any case experiencing a rejuvenation of interest as a highly selective technique, when the effective molecular weight of the antibody is increased relative to the antigen, by immobilisation on a latex or metal particle (77)... 

Having grown site — 1, site n can be selected by the usual configurational bias technique out of a set of k trial positions according to Eq. (14). 

As with most Cl schemes of that period, the construction of the Hamiltonian matrix and its direct diagonalization effectively limited the size of calculations to a few thousand determinants. One possible strategy for extending the capability of this type of calculation is to introduce some sort of selection criterion for the A -particle functions, and to leave out those that do not contribute appreciably. Such methods had been developed within the framework of multireference Cl (MR-CI) calculations, and Hess, Peyerimhoff, and coworkers (Hess et al. 1982) extended this to the case of spin-orbit interactions. Their procedure was based on performing a configuration-selected non-relativistic MR-CI, followed by extrapolation to zero threshold. This technique may be applied in a one-step scheme, where selection criteria are introduced not only for the correlating many-particle states, but also for those that couple to the reference space via spin-orbit interaction. The size of the calculation that has to be performed in the double group may thereby be reduced. The errors introduced by these selection procedures appear to be small. 

Pyrolysis is carried out either outside or inside the identification instrument. In the outside mode, the thermal degradation is carried out by a pyroprobe connected to the injection port of a GC using a selected technique - time-programmed or flash pyrolysis. GC-separated individual pyrolysates can be identified with different equipment connected to the GC, e.g., Py-GC-MS, Py-GC-FTIR or Py-GC-AED (atomic emission detector). Advances in Py-GC and the different configurations can be summarised as follows ... 

The third alternative is a more robust, sensitive and specialized fonn of the first, in that only hydrogen nuclei indirectly spin-spin coupled to in a specific molecular configuration are imaged. In achieving selectivity, the technique exploits the much wider chemical shift dispersion of compared to H. The metliod involves cyclic transfer from selected H nuclei to indirectly spin-spin coupled C nuclei and back according to the sequence... 

A hanging electrolyte drop has also been applied to determine ionic species in solution using differential-pulse-stripping voltammetry procedures [69]. Particular emphasis was given to assessing the selectivity and sensitivity of the method. The technique of current-scan polarography has also been applied in the study of electron-transfer [70] and coupled electron-transfer-ion-transfer [71,72] reactions at the ITIES in this configuration. 

Classical LLEs have also been replaced by membrane extractions such as SLM (supported liquid membrane extraction), MMLLE (microporous membrane liquid-liquid extraction) and MESI (membrane extraction with a sorbent interface). All of these techniques use a nonporous membrane, involving partitioning of the analytes [499]. SLM is a sample handling technique which can be used for selective extraction of a particular class of compounds from complex (aqueous) matrices [500]. Membrane extraction with a sorbent interface (MESI) is suitable for VOC analysis (e.g. in a MESI- xGC-TCD configuration) [501,502]. 

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