Matrix mist

B. Spraying. Spraying matrix solution to the surface of the sample deposits a fine distribution of matrix mists on the surface. A homogeneous thin film of crystallized matrix layer is formed after solvent evaporation. This approach results in smaller crystal sizes (typically around 20 pm that is comparable with... 

Copper like vanadium has a separate OSHA standard for dust and fumes resulting in some confusion for the industrial hygienist in selecting collection media. The 0.2 mg Cu/cu m fume standard is one-fifth the dust standard. The distinction between fumes and mist is somewhat ambiguous. Both methods for copper use nitric acid wet ashing however, S-186 uses an analyte matrix of hydrochloric acid for AAS aspiration. 

Thermal Pretreatment. In this stage the analyte is separated from the interfering matrix components. Biological samples decompose to carbon and produce lots of soot and smoke. Inorganic compounds distill, sublime, or decompose to mist. If these processes take place at the same time as the atomization of the analyte, the measurement of the absorption signal would be impossible. 

Interferences caused by desolvation are related to differences in volatility between the matrix and analyte, and are noticed as a change of the analyte concentration in the aerosol mist during desolvation. 

Since in SIMS imaging experiments only the top layer is sampled, the matrix layer shonld not be too thick and the analytes have to be able to migrate to the top surface layer. This combination is critical for a snccessful ME-SIMS experiment and therefore the ESD conditions have to be optimized carefully, in order to produce a fine mist of matrix droplets so the matrix arrives onto the sample surface in a wet environment. 

Although fog, mist, and snow samples require matrix-specific sample collection and sample preparation steps, the resulting aqueous solutions are very similar to rain and may therefore be analyzed using methods developed for rain samples. However, matrix-specific methods and applications are also available [7,73,76]. 

Two special requirements for the effective use of structured packing are efTiciem mist eliminators and uniform iiquid distribution. Kean et al. (1991) recommend a vane type eliminator with a 3- to 4-in. mesh pad face to minimize carry-over. A simple wire-mesh mist eliminator is not considered adequate at the high gas velocities employed with structured packing. They also recommend that a high-efficiency drip-type distributor be used with typical matrix dimensions of 4 in. by 4 in. and the peripheral drip points iocated no more than 2 in. from the wall. The distributor must be installed as close as possible to the packing to ensure good distribution and minimize carry-over. 

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