Filtering and Polarization

This method can also be used to analyse soil samples. For instance, fenpropi-morph, which is a non-polar pesticide with good UV sensitivity but poor selectivity, has, after treatment, been determined in soil samples (31). In this example, an amount of soil was extracted overnight with acetonitrile this was then poured into a Buchner filter and rinsed with the same solvent. The acetonitrile solution was concentrated and, prior to LC analysis, the extract was diluted with water and 100 p.1 were then injected into the LC system. 

Impingers and bubblers. Figure 8.5, containing liquids have been used extensively for collecting high boiling, reactive or polar substances that cannot be quantitatively recovered from solid sorbents [8,72]. They are most frequently used as personal sampling systems and in combination with filters and various... 

Mobile phase compositions for this experiment are polar methanol-water mixtures in the ratios 90/10, 80/20, and 70/30 by volume. The stationary phase is C18. Prepare 200 mL of each mobile phase and then filter and degas each through 0.45-/./m filters with the aid of a vacuum (instructor will demonstrate). Slowly pour each (so as to avoid reaeration by splashing) into individual mobile phase reservoirs that are labeled appropriately. 

This method is very useful for separating amino acids found in food samples. The most effective matrix for separation is an absorbent cellulose-based filter paper. A very effective mobile phase is 70% isopropyl alcohol in water. Although the 20 amino acids are chemically very similar, they may be successfully separated by this method. Amino acids interact with the stationary phase to different extents, thus moving at different speeds. Chemical differences among amino acids that determine migration speed include molecular weight, charge, and polarity. 

Pitfalls in steady-state fluorescence measurements inner filter effects and polarization effects... 

Figure 2.12 Photographs of polymer crystalline structures a) optical photograph of PP resin using polarizing light and filters, and b) electron micrograph of sPS resin (courtesy of Robert C. Cieslinski of The Dow Chemical Company)...

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