Ex situ analysis

Unfortunately, only thin films of about 20 nanometers in thickness could be obtained with Gel4 An ex situ analysis was difficult, because of experimental limitations, but XPS clearly showed that elemental Ge was also obtained, besides... 

Based on electrochemical experiments combined with ex situ analysis by AES, LEED, and RHEED, Wang et al. (2001) suggested the formation of a (2 x 2) (2CO + O) adlayer on Ru(OOOl) at = 0.2 V in CO-samrated HCIO4, similar to the phase formed in UHV after CO adsorption on a (2 x 2)0-covered surface [Schiffer et al., 1997]. Erom the total charge density transferred after a potential step to 1.05 V in a CO-free electrolyte, they concluded that only 60% of the CO content in such an adlayer can be oxidized under these conditions [Wang et al., 2001]. 

The recently developed ex situ analysis of electrode ad-layers by thermal desorption mass spectroscopy has been demonstrated to be a powerful tool for the study of adsorbates [13, 14],... 

Prior to the introduction of ion-selective electrode techniques, in situ monitoring of free copper (II) in seawater was not possible due to the practical limitations of existing techniques (e.g., ligand competition and bacterial reactions). Ex situ analysis of free copper (II) is prone to experimental error, as the removal of seawater from the ocean can lead to speciation of copper (II). Potentially, a copper (II) ion electrode is capable of rapid in situ monitoring of environmental free copper (II). Unfortunately, copper (II) has not been used widely for the analysis of seawater due to chloride interference that is alleged to render the copper nonfunctional in this matrix [288]. 

A closer examination by ex situ analysis using NMR or gas chromatography illustrates that intrazeolite reaction mixtures can get complex. For example photooxygenation of 1-pentene leads to three major carbonyl products plus a mixture of saturated aldehydes (valeraldehyde, propionaldehyde, butyraldehyde, acetaldehyde)38 (Fig. 33). Ethyl vinyl ketone and 2-pentenal arise from addition of the hydroperoxy radical to the two different ends of the allylic radical (Fig. 33). The ketone, /i-3-penten-2-one, is formed by intrazeolite isomerization of 1-pentene followed by CT mediated photooxygenation of the 2-pentene isomer. Dioxetane cleavage, epoxide rearrangement, or presumably even Floch cleavage130,131 of the allylic hydroperoxides can lead to the mixture of saturated aldehydes. 

The primary methods for analysis were usually gravimetric, thermal, and spectroscopic in nature but not necessarily correlated with in situ analysis (XPS, AFM, TEM, etc.) or ex situ analysis of surface-bound polymers by de-grafting (NMR, MW, polydispersity, etc.). Colloidal stability and homogeneity of the grafting process is a primary concern. A range of these systems were analogous to what has been done in solution and in bulk and should be thoroughly examined in terms of chemistry on flat substrate surfaces. Several examples follow. 

In the present study, we report new results on in-situ near-normal external reflection FTIR on the monolayers containing both reactive and inactive moieties to adsorption of ions. Unlike the conventional ex-situ analysis, it was capable of observing suppressing effects of mixed monolayer surfaces to ion adsorption. 

Various approaches have been described in the literature for the characterization of carbon-supported metal catalysts. The catalysts are usually analyzed before and after (postmortem) their electrochemical operation with conventional ex situ techniques such as x-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive x-ray analysis (EDX), x-ray photoelectron spectroscopy (XPS), and x-ray absorption spectroscopy (XAS). Although ex situ analysis provides an important starting point in catalyst characterization, one must keep in mind that significant morphological changes may occur under the operational conditions. It is thus vitally important... 

The advantages of the radiolysis/EPR method for studying mechanisms of zeolite catalysis are due to the sensitivity and structural specificity of EPR, surpassing that of other in situ spectroscopies, such as FTIR and NMR, and the ability to identify products at low temperature. It is often the case that at high temperatures needed to evolve products from the zeolite for ex situ analysis, a... 

Surface deconstruction has been discovered on single-crystalline electrodes in contact with electrolytes with the help of different experimental methods. These were the combination of cyclic voltammetry with ex situ analysis after... 

The experimental yield of H2 is lower than expected for complete PH3 decomposition [9]. Up to about 250 C, H2 partial pressures followed those expected for decomposition of PH3 into PH2. Up to about 550 C, H2 partial pressures increased but did not reach those expected for decomposition into P4 [11, figure 8]. The apparently lower PH3 decomposition derived from ex-situ observations indicates equilibrium reactions which lead to reformation of PH3 during ex-situ analysis [9 to 11 ]. Because P4 is thermodynamically more stable than PH3, PH or PH2 must be the sources of PH3 reformation [11]. 

A wide range of techniques and methods have been used to measure fractal structure in environmental systems. Which approach is appropriate in given circumstances depends on whether an in-situ measurement is required or whether the samples may be taken for ex-situ analysis, on the size of the materials one is analysing and on their optical and mechanical properties. 

Table 3.2 Relative composition and processing variables, along with high-throughput (HT) in situ and low-throughput (LT) ex situ analysis techniques available...

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