Detection of species

Hintelmann H, Evans RD. 1997. Application of stable isotopes in environmental tracer studies — measurement of monomethyhnercury (CKjEg ) by isotope dilution ICP-MS and detection of species transformation. Fresenius J Anal Chem 358 378-385. 

A modification of the RDC design, based on the ring-disk arrangement of the RDE [36], incorporated an arc electrode [37,38] deposited on the surface of the membrane around the untreated area. This facilitated the electrochemical detection of species reacting at the interface at short times following the reaction. This method was used to study the solvent extraction of cupric ions, which were detected by reduction to copper metal at the arc electrode. The resulting current flow was related to the interfacial flux at the membrane. 

The use of non-inert and chemically modified electrodes and other strategies for the detection of species that are difficult to analyze with the normal electrode materials have been reviewed.55 Photosensitization prior to amperometric detection is another tactic that has proved useful for the analysis of substances that are normally considered to be electrochemically inert.56 The use of pulsed amperometry has recently been reviewed.57... 

CO insertion reactions. The catalytic hydrogenation mechanism presented was based on detection of species 64 and HC1 during hydrogenation of ethylene, Eq. (92). Species 65 then catalyzes the reaction by pathways outlined in Eq. (5). 

The mass spectrum of CTC, shown in Figure 14 (42), is characterized by a reasonably intense molecular ion at m/e 478 with the concomitant isotope peak at P+2 representing one chlorine atom in the ring system. Although it has been suggested that this chlorine atom be employed as a tracer via the isotope ratio for detection of species containing... 

More recently, studies concerning cluster ion formation from solid or deeply cooled liquid alcohols [120-122] have gained new interest. [123,124] Low-temperature fast atom bombardment (LT-FAB) of frozen aqueous solutions of metal salts provides a source of abundant hydrated metal ions. [125-127] Organic molecules can also be detected from their frozen solutions. [128] Such LT-FAB applications are particularly interesting when enabling the detection of species that would otherwise not be accessible by mass spectrometry, because they are either extremely air- and/or water-sensitive [129,130] as the phosphaoxetane intermediate of the Wittig reaction [131] or insoluble in standard FAB matrices. [106,132]... 

When applied to electron-transfer reactions, this kinetic isotope effect technique can provide information on the real reaction pathway leading to the formation of the product. Frequently, spectroscopic detection of species or identification of products is indicative of radical intermediates. The formation of the intermediates could simply be a blind step. 

Time-resolved laser experiments make possible the detection of species with short lifetimes [1-6]. Usually, such experiments are carried out under normal conditions and a quick enough snapshot can capture the intermediate in action. A different philosophy is to prolong the lifetime of the reactive species by generating it in an inert environment at low temperature. Matrix isolation... 

One inherent problem with NMR is the relatively low sensitivity of the technique. Thus, for a reasonable S N/collection time, it is necessary to use solutions of 10-100 mM, which is well above the concentrations (often <1 mM) used in catalytic experiments. As a result, species present in the catalytic solution can sometimes be different at the higher concentrations used for NMR measurements. However, for reactions involving H2, the use of P-H2 circumvents these problems and detection of species at very low concentrations is possible (chapters 1, 6 and 9). 

Dinkel, A., Njoroge, E.M., Zimmermann, A., Walz, M., Zeyhle, E., Elmahdi, I.E., Mackenstedt, U. and Romig, T. (2004) A PCR system for detection of species and genotypes of the Echinococcus granulosus-comp ex, with reference to the epidemiological situation in eastern Africa. International journal for Parasitology 34, 645-653. 

All the previously described, unique triple-quadmpole scans—SRM/MRM, precursor ion, and neutral loss—filter out a significant amount of background noise, allowing for detection of species present at very low levels. 

Studies have been made towards connecting low-selectivity anion-selective electrodes to chromatographic columns, using the column to separate the ions and the ISE to detect them. For instance [30], a CWE has been reported for the detection of species such as carboxylic acids, sugar phosphates and nucleotides from mixtures which had been passed through an anion-exchange column. 

Direct in situ detection of species (e.g., ion selective electrodes and electron spectrometry)... 

FIGURE 1 Proteomics pipeline used for the identification, characterization, and detection of species-specific peptide biomarkers for fish authentication purposes. 

Fluorescence detection of species is analogous to the pure absorption measurements discussed above, except that the emission from the excited-state species produced by the absorption is monitored rather than the amount of absorbed radiation. This is inherently a more sensitive method... 

Technetium(II) complexes are paramagnetic with the d5 low-spin configuration. A characteristic feature is the considerable number of mixed-valence halide clusters containing Tc in oxidation states of +1.5 to + 3. This area has been reviewed (42). For convenience, all complexes, except those of [Tc2]6+, are treated together here. EPR spectroscopy is particularly useful in both the detection of species in this oxidation state and the study of exchange reactions in solution. The nuclear spin of "Tc (1 = f) results in spectra of 10 lines with superimposed hyperfine splitting. The d5 low-spin system is treated as a d1 system in the hole formalism (40). 

In addition to receptor-type proteins, bilayer lipid membranes (BLMs) have been investigated for the detection of species of biochemical interest [221, 231,232]. The lipid film can be used alone, or chemical receptor agents can be incorporated into the membrane to enhance selectivity for inorganic ions or organic compounds/ions. Responses for BLM-coated devices are related to the mass loading of the analyte in/on the lipid film and to changes in interfacial conditions, e.g., elastic and viscous coupling effects [53,221-223]. 

The problem with Raman spectroscopy is the low intensity of the Raman lines, which permits easy detection of species only in concentrated solutions. Fortunately, the availability of lasers, which are intense sources of monochromatic light, is stimulating further applications of this powerful technique, which is noted for the lack of ambiguity with which it can report on the species in an electrolytic solution. Devices that distinguish a low-intensity signal from noise also help. 

The methods of generation of the radical and of analysis of different types of kinetic data have been referred to. Optical detection of species was made, primarily of the parent dimer itself or of certain products referred to later. 

Duarte, G.F., Rosado, A.S., Seldin, L., de Araujo, W. and van Elsas, J.D. (2001) Analysis of bacterial community structure in sulfurous-oil-containing soils and detection of species carrying dibenzothiophene desulfurization (dsz) genes. Applied and Environmental Microbiology, 67, 1052-1062. 

---