Ion-extraction analysis

Figure 4.2 Residual ion-extract analysis of PCBs cleaned with co-solvent HFE-7100/SA24 and with azeotrope HFE-71DA. Copyright 2000, 3M Co., reproduced with permission.)...

EDS compositional analysis with a focused 2nm electron beam of the FEG-TEM in the central part of mother cluster on the Ar-irradiated AuAg sample, gives an Au/ Ag ratio (measured at AuL and AgL) of 1.4 + 0.1, whereas the same ratio measured on the satellite clusters is 2.3+0.8. Similar ratios have been found from EDS analysis on AuAg sample irradiated with He, Ne, or Kr ions. EDS analysis reveals therefore a preferential extraction of Au atoms from the original cluster and this selective dealloying process is independent of the particular system investigated (we obtained similar results for Ne-irradiated AuCu cluster, as previously reported). 

The main complication with this technique is that the mass transfer analysis is nontrivial. For example, the change of velocity as a function of the distance down the jet was not taken into account in modeling the system. The LJRR has been used to study the diffusivities of benzene and toluene in water [41] and cupric ion extraction [42,49]. 

M. L. Aleksandrov, L. N. Gall, V. N. Krasnov, V. I. Nikolaev, V. A. Pavlenko and V. A. Shkurov, Ion extraction from solutions at atmospheric pressure a method for mass spectrometric analysis of bioorganic substances, DoklAkadNaukSSSR, 277, 379 383 (1984) (in Russian). 

This field is therefore at an exciting stage. Ion-selective electrodes have a proven track record in terms of clinical and biomedical analysis, with a well-developed theory and a solid history of fundamental research and practical applications. With novel directions in achieving extremely low detection limits and instrumental control of the ion extraction process this field has the opportunity to give rise to many new bioana-lytical measurement tools that may be truly useful in practical chemical analysis. 

Analysis of terrestrial samples demonstrated that the tuning of the ion extraction system, and consequently the amount of instrumental mass fractionation, was very sensitive to charge build-up on the sample, the position of the primary beam relative to the spectrometer optic axis, and the position of the sample relative to the extraction lens. To optimize reproducible tuning of the extraction system from sample to sample, we developed the following criteria (1) resistance of the sample (Au-coated) to ground less than 106 fi (2) alignment of the primary beam to within 10 pm using... 

Figure 30. Mass analysis of ions extracted from a CF4/O2 discharge using a silicon target extraction electrode. (Reproduced with permission...

Quantitative results were produced for each compound on the basis of internal standard method calculations. A three-point calibration curve was generated for each compound by using peak areas of a quantitation ion extracted from the mass spectrum of the compound. The ion was selected on the basis of it being a uniquely characteristic mass of the compound. The use of extracted ion quantitation produces more accurate results than total ion-current quantitation in cases in which two or more components are not completely resolved chromatographically. This situation is generally the case in complex mixture analysis. The quantitation ions selected for each of the compounds in the mix are listed in the box. 

The secondary Ion extraction optics should Include an Immersion lens above the sample surface to maximize secondary Ion transmission from the sample surface to the mass spectrometer. An electrostatic analyzer should again be used to filter out high-energy neutral particles and photons from the secondary Ion beam. Energy analysis of the secondary Ions Is generally not necessary, but can be used to vary the amount of fragmentation observed In the mass spectrum (9). 

The secondary ion extraction optics and ion energy filter is of commercial design (Kratos). Also incorporated in the analysis chamber is a scanning electron gun having a... 

E. Sugiyama, A. Hara, and K. Uemura, A quantitative analysis of serum sulfatide by matrix-assisted laser desorption ionization time-of-flight mass spectrometry with delayed ion extraction, Anal. Biochem., 274 (1999) 90-97. 

Marshall, A. G. (2002). Improved ion extraction from a linear octopole ion trap SIM ION analysis and experimental... 

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