Ultratrace elements transport

The phytotoxic actions of rubidium mostly affect the transportation of substances in the xylan (Zornoza and Carpona 1996). In order to prevent excessive amounts of rubidium in plant tissues, these authors proposed an increase in the content of potassium, manganese and boron in the soil solution, because of the known antagonism of these elements towards rubidium. Young, growing plants or parts of plants are extremely rubidium-rich and accumulate this element like most other macro, trace and ultratrace elements (Angelow 1994, Wyttenbach et al. 1995). The toxicity of rubidium in plants is low, and essentially unknown. 

Active transport - the accumulation within, or the extrusion from, a cell of an element in opposition to a concentration gradient. Active transport is saturable, is energy dependent and involves a carrier protein that usually is quite specific for an element. The mechanisms of absorption for the various ultratrace elements are given in Table 1 this table also lists the known transport and storage vehicles for these elements. 

Table 1 Absorption, transport, and storage characteristics of the ultratrace elements...

For the determination of traces and ultratraces of Hg, As, Se, Te, As, and Bi, the formation of the volatile mercury vapor or of the volatile hydrides of the other respective elements is often used. This allows a high sampling efficiency to be achieved and accordingly a high power of detection. The absorption measurement is often performed in a quartz cuvette. Hg, for instance, can be reduced to the metal and then transported with a carrier gas into the cuvette. No heating is required for the absorption measurement. The other elements are reduced to the volatile hydrides, which are then transported with a carrier-gas flow (argon or nitro-... 

Laser ablation ICP-MS is used for direct analysis of the elemental and isotopic composition of solid samples. Photons from the laser system are focused into a high peak power energy pulse that interacts with the sample. As a result of this interaction, small particles, atoms and ions are removed from the topmost atomic layers forming a laser-induced aerosol above the sample surface. The aerosol is then transported by an inert gas stream to the ICP-MS. After vaporization, atomization and ionization of the particles in the ICP, quadrupole, magnetic sector field or time-of-flight mass filters are used for mass separation. Because of the properties of the laser systems available today, bulk analysis with low spatial resolution (>100 p-m) as well as local analysis with high spatial resolution (<20 p.m) are possible. Since only small sample amounts are ablated per laser shot, a high sensitivity analytical detection system is a prerequisite for trace and ultratrace analysis. 

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