SICM

Figure Bl.19.40. The scanning ion-conductance microscope (SICM) scans a micropipette over the contours of a surface, keepmg the electrical conductance tlirough the tip of the micropipette constant by adjusting the vertical height of the probe. (Taken from [211], figure 1.)...

The sensitivity of GC-MS can be increased still further by selective ion current monitoring (SICM) whereby only a limited number of characteristic ions in the mass spectrum of the compound are monitored. Therefore the time for which each ion is monitored, and hence the sensitivity, is increased so that the amount of an identifiable GA is reduced to 10 T 4 g. As in mass fragmentometry, sufficient ions must be monitored for an identification to be made. 

Quantitation. Combined GC-SICM has been used mainly for quantitation. For a particular GA the absolute intensity of a characteristic ion in its mass spectrum is related to the amount of GA present, using standards to calibrate the instrument. Frydman et al. (35) used this "external standard method" to measure the levels of a number of GAs throughout the development of pea seeds. An alternative and preferable approach employs... 

Other local probe techniques to be discussed, of an electrochemical nature, which rely on much of the same instrumental technology, are scanning electrochemical microscopy (SECM) and scanning ion conductance microscopy (SICM). 

Scanning micropipette microscopy (SMM) Scanning micropipette molecule microscopy (SMMM) Scanning ion conductance microscopy (SICM)... 

AHFS Drug Information 2(MK). Bethesda. MD. American Society <4 Hculth-Sy.sicm Pharmacists. 2IKKI p. 3275. 

The mth order SICm is defined in a normalized form of the information content to delete the influence of graph size ... 

The mth order BICm is deflned in a normalized form as the SICm index, but taking into account the number of edges and their multiplicity. 

The apparatus involved in this method is related to that of SICM, except that the micropipette is blocked by a permeable polymer plug, and connected to the inlet of a differentially pumped quadrupole mass spectrometer... 

Data Sy.sicms. Modern XPS instruments have nearly all components under computer control. Thus, electron guns, ion guns, valves, lens voltages, sample position. and analyzer parameters are all selected by the computer. Currenl software on XPS instruments al-... 

Rice, D., and Barone. S. (2000). Critical periods of vulnerability for the developing nerx ous sy.sicm Evidence from hum.ins and animal models. Environ. Health Perspect. 10K(Suppl 3). 511-533. 

---