Ion-probe

Field ion microscopy is one of the older techniques to involve ions and yet it remains the only means available for viewing individual atoms on a surface directly. Since an extensive literature exists, the subject will not be considered here except to mention some recent papers on surface diffusion and atomic interactions, cluster formation, the imaging atom-probe microscope, and reviews in the fields of metallurgy and surface chemistry.  

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Ion probes. Determining the level of ions in solution also helps to control corrosion. An increase in concentration of specific ions can contribute to scale formation, which can lead to a corrosion-related failure. Ion-selective elec trode measurements can be included, just as pH measurements can, along with other more typical corrosion measurements. Especially in a complete monitoring system, this can add information about the effect of these ions on the material of interest at the process plant conditions. 

The urease is incorporated into a polyacrylamide gel which is allowed to set on the bulb of the glass electrode and may be held in position by nylon gauze. Preferably, the urease can be chemically immobilised on to bovine serum albumin or even on to nylon. When the electrode is inserted into a solution containing urea, ammonium ions are produced, diffuse through the gel and cause a response by the ammonium ion probe ... 

Kiyose K, Kojima H, Urano Y et al (2006) Development of a ratiometric fluorescent zinc ion probe in near-infrared region, based on tricarbo-cyanine chromophore. J Am Chem Soc 128 6548-6549... 

Ion Probe Magnesium Isotopic Measurements of Allende Inclusions... 

Since the IM-20 had not previously been used for high precision isotopic measurements and since previous isotopic measurements with other ion microprobes [24,25] were characterized by percent level relative errors, we carried out an extensive series of Mg isotopic analyses of terrestrial samples. Terrestrial standards were especially emphasized prior to the study of meteoritic samples, but were also periodically interspersed with later meteoritic analyses as a check on the performance of the ion probe. Terrestrial standards included Ceylon spinel (MgAl204), Madagascar hibonite (CaA112019), a suite of olivines (Fo 100 to Fo 5) used in... 

It is clear from figure 6 that the terrestrial data do not cluster about a single point but instead lie along a line of slope 0.5 on the three-isotope diagram, indicating isotopic variation due to mass-dependent fractionation. Since mass fractionation effects in Mg have not been observed in terrestrial materials [30,31], this distribution of observed isotope ratios must be due to fractionation in the ion probe. The physical process which produces the... 

The fit of the data to the correlation line indicates that the relative yields of 27Al and s ifg secondary ions are constant over the compositional range anorthite 100 to anorthite 50. The slope of the line, O.S1, reflects the higher sensitivity of the ion probe for Mg, and is used to convert measured secondary ion ratios to elemental ratios. 

Mg = 0.5 1.1%0). Note that the slope of the isochron is 8 percent greater here than in our previous publications (excepting [12]) due to a recently discovered error in the ion probe calibration of Mg abundance sensitivity. All of the isochrons discussed in this paper reflect this change. Similar data showing the same linear correlation for other Allende inclusions have been reported in [6,23,24,25]. 

A common feature of anorthite crystals in Allende Type B inclusions is large variations (up to a factor of -v 5) in Mg content on a scale of 10 to 50 pm. (Mg variability and its correlation with Na content and cathodoluminescence color are discussed extensively in [12].) Guided by cathodoluminescence micrographs, we used the microscopic spatial resolution of the ion-probe to measure the Mg isotopic composition at several points with distinct 27Al/24Mg ratios within individual crystals from TS-21 and TS-23. Data from each individual crystal define an... 

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