Scanning SIMS

In the scanning (or microprobe) mode the image is measured sequentially point-bypoint. Because the lateral resolution of the element mapping in scanning SIMS is dependent solely on the primary beam diameter, LMISs are usually used. Beam diameters down to 50 nm with high currents of 1 nA can be reached. 

The oxygen ion beam diameter is limited to 0.5 pm by the duoplasmatron source used. For mapping electropositive elements this drawback must be tolerated because of the chemical enhancement effect. 

The counting time for one pixel, and the number of pixels, determine the measurement time for one image. For low concentrations of the elements of interest the Pois- 

Reduction of the measurement time for element distributions is possible by simultaneous detection of several masses. This can be achieved only by use of a magnetic sector field spectrometer with Mattauch-Herzog geometry [3.49] (Fig. 3.20) and parallel detection of up to five masses by mechanically adjusted electron multipliers. 

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Fig. 3.23. Scanning SIMS image of the carbide structure of a high-speed steel [3.52]. In the V distribution different phases (MC and M2C) are visible. The Al distribution shows the shell struc-...

Figure 12. Lateral distribution of F negative secondary ion intensity measured by scanning SIMS of the same SA-PFECA-ODTMAC (1 1 1) mixed monolayer as that shown in Fig. 10. 

Monitoring mode Full scan, SIM Full scan, SIM, product ion scan Full scan, SIM Full range spectrum Full scan, SIM, product ion scan... 

Denison, P., Jones, F.R., Brown, A., Humphrey. P. and Paul, A.J. (1988b). Scanning SIMS fractography of CFRP. In Interfaces in Polymer. Ceramic and Metal Matrix Composites (H. Ishida ed.), Elsevier. New York, pp. 239-248. 

Interaction of phosphate solutions with goethite may lead to surface precipitation of phosphates if the concentration of P in solution exceeds the mineral solubility (Jo-nasson et al., 1988). A combined Auger, XPS, scanning SIMS and electron diffraction study showed that after 90 days at 60 °C, crystals of griphite (an Fe hydroxy phosphate) precipitated out of a phosphate solution onto crystals of goethite (Martin et al., 1988). 

There are basically three variations of the SIMS experiment. Static SIM.S is used for elemental analysis of sub-monolayers on surfaces. Although SIMS is basically a destructive technique, static conditions maintain the surface integrity during the lime scale of the experiment. Dynamic SIMS is used to obtain compositional information as a function of depth below the surface, nic dynamic SIMS experiment takes advantage of the destructive nature of SIMS to oblain information on various layers of materials. Imaging SIMS. also called scanning SIMS, is used to provide spatial images of surfaces. 

Extraction, SEC or SPE Cl8 Column ArHjO + O.OSMFA B ACN + 0.05M FA (0.002M ammonium formate) (Gradient) ESI, positive Single/Triple quadrupole Scan, SIM and daughter scan MC-LR,-RR,-YR NR NR 2001 [127]... 

Denison P, Jones FR, Brown A, Humphrey P, Paul AJ, Scanning SIMS spectography of cfrp, Ishida H ed., Interfaces in Polymer, Geramic and Metal Matrix Gomposites, 239-248, 1988. Hearn MJ, Briggs D, ToF-SIMS studies of carbon fiber surfaces and carbon fiber composite fracture surfaces. Surface Interface Analysis, 17(7), 421 et seq, 1991. 

Oven temperature is at 40 C for 1 min, then temperature gradient of 5 C/min to lOO C and 20°C/min to 280°C. Injection port temperature is at 260°C, and the sample is injected in spfitless mode. Injection port should be equipped with 0.75-mm SPME finer. Transfer fine temperature should be kept at 280°C, and the ion source should be at 240 C carrier gas (He) flow is at 0.8 mL/ min. The sample should be analyzed in scan/SIM mode. Scan range m/z 33-233 should be used with a scanning speed of 6.6 scans/s and threshold 50. K needed, the scan... 

To overcome matrix-related problems, the simplest quantification can be performed with a standard adcfition method and spiking the analyzed wine with a known concentration of TCA. The linearity range of the method should be satisfactory between 5 and 5000 ng/L. Typical scan/SIM chromatogram of red wine spiked with TCA together with its SIM spectrum is shown at Figure 24.5. Alternatively, TCA may be analyzed using GC x GC-TOF-MS system in a configuration described in the section devoted to the analysis of trichothecenes. 

FIGURE 24.5 Chromatogram (selected part) of red wine spiked with 500 ng/L of 2,4,6-trichloroanisole obtained after SPME extraction and simultaneous scan/SIM acquisition on a GC/MS system (7890A/5975C MSD, Agilent Technologies). (A) Total ion current (TIC) of scan run (rn/z = 33-233) (B) TIC of SIM run (m/z = 195,197,210) (C) ion abundances in SIM mass spectrum. Peak of 2,4,6-trichloroanisole on chromatogram B marked with an arrow. 

Acquisition Full-scan SIM FuU-scan SIM Full-scan SIM Full scan... 

Hutter et al detected chemical phases using classification-ANNs on de-noised scanning-SIMS images. Analogously, Tyler ° applied different multivariate statistical techniques (PCA, factor analysis, ANNs and mixture models) to explore spectral images. 

SLAN Target Qualifier SCAN SIM Target Qualifier ... 

Table 5.6 compares some of the tools currently in use. Since charged particles (electrons/ions), used in AES, SIMS and ISS, can be collected by electromagnetic fields into finely focused beams (1 fim to 5 nm), microanalyses are possible with such techniques (micro-AES, scanning SIMS, ion microanalysis). 

Amelia Peterson et al, University Wisconsin, Prof Josh Coon group, published first results on the implementation of an EI/CI interface on a hybrid Orbitrap system for ultra-high resolution GC-MS using a GC-Quadrupole-Orbitrap configuration for full scan, SIM, MS/MS and SRM (selected reaction monitoring) at the ASMS conference. 

Effective ion acquisition time typically in milliseconds, maximized by using a selected ion monitoring scan (-> SIM, MID, SRM)... 

The QIT has a commercial mass range typically from 50-2000 Th, although some manufacturers provide two or three mass ranges up to 4000 Th. Scan rates vary from 500 Th/s to 27,000 Th/s and allow for resolution specifications of up to 5000. The typical mass accuracy is 50 ppm to 100 ppm at m/z 1000. Detection limits can be at the attomole level. Scan modes include the full scan, SIM, SRM, rapid high sensitivity and high resolution, and MS". Some QITs have a high charge capacity, which has increased the sensitivity by 10-fold. See Table 9.A in the Appendix. 

Full-scan and selected ion monitoring (SIM) represent at least 95% of the MS analysis performed today. Full-scan analysis has always offered three benefits (1) selectivity based on m/z detection, (2) universal detection across a wide operating range and (3) library searches (spectral comparison) for confirmation of identity. Since the source of the data for SIM is the same as for full scan, SIM offers no solutions to interference problems. The primary advantage of SIM has always been its improved signal-to-noise ratio (S/N) versus full scan and its interpretation simplicity (ion ratios). 

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