Investigative Approach for Sample Preparation

In more recently introduced equipment, the calcination and loading of the catalyst samples can be performed under shallow-bed conditions. For example, the equipment developed by Zhang et al. (51) (Fig. 9) allows a calcination of the powder in a horizontal tube inside a heater at temperatures of up to 1000 K. After loading of the catalyst with probe molecules or reactants, the powder is added to an MAS NMR rotor at the bottom of the equipment, sealed with a rotor cap from a plug rack, and transferred to the NMR spectrometer. As in the case of the former approaches, the samples prepared in the equipment of Zhang et al. 151) can be used for ex situ as well as in situ NMR investigations under batch reaction conditions. Furthermore, this equipment is suitable for ex situ investigations of solid-catalyzed reactions under flow conditions. In this case, the horizontal tube inside the heater is used as a fixed-bed reactor. 

Supercritical fluid extraction (SFE) is a new and promising technique for sample preparation. Because SFE is so new, and there are so many control parameters available to the scientist, it can be difficult to know how to proceed when developing an SFE method. This paper discusses two samples and describes a systematic approach for evaluating SFE extraction parameters for methods development. The effects of modifiers are investigated. 

Grimes et al., 1998 Reinisch et al, 2000 Wikoff et at, 2000). Likewise, advances in electron cryomicroscopy and image reconstruction techniques allow time-resolved investigations of structural transitions associated with capsid assembly and maturation (Conway et al., 2001 Lawton et al, 1997). These developments have been paralleled by refinements in the molecular approaches used for sample preparation, with the result that synthesis of assembly intermediates and end products has become routine for many viruses. 

The main analyser chamber contains a spectrometer and ports for different excitation sources. The preparation chamber is needed for sample preparation e.g. cleavage). The electrolyte components are allowed to react with the interface in the adsorption chamber, where temperature control is used to stabilise the interface-adsorbate interaction. Water, halogen and alkali species are allowed to interact with electrode material to investigate structure and potential distribution of the electrochemical double layer (Sass, 1983 Bange et al, 1987 Sass et al., 1990). laegermann (1996) gives a comprehensive review of the semicondnctor/electrolyte interface within the vacnnm science approach. 

TEM approaches. The scope of this chapter prevents an in-depth description of standard TEM techniques or specific 3D reconstruction methodologies. Instead we concentrate on providing an appropriate conceptual framework, together with appropriate references to more in-depth sources, combined with selected practical tips and protocols for sample preparation methods routinely used within our laboratory. The existence of several National Institutes of Health regional facilities whose charge is to provide expertise, instrumentation, and practical guidance for TEM 3D reconstruction means that the techniques described in this chapter should be widely accessible to individual investigators. 

In contrast to nntargeted metabolomics, which aims to separate and identify as many compounds as possible, class-specific nontargeted metabolomics is focnsed on a group of chemically related compounds, aiming to find previonsly unknown metabolites belonging to that class. By this approach, the sample preparation step may be optimized for the class of investigated componnds, resnlting in both a preconcentration and reduced matrix effect. 

---