Ft fH

Spots not distinguishable from background

CHCI,

CCI,

11 5 25

Figure 7 Bottom: chromatogram of a conventional development on 20 cm long silica gel plate with RF values normally considered about optimal. Top: chromatogram of continuous development on 2.5 cm distance from the solvent level and 1.1 cm from the origin on silica gel plate with solvent of lower solvent stength, with RF values less than 0.05. (Reproduced with permission from Perry JA (1979) Solvent strength, selectivity, and continuous development. Journal of Chromatography 165: 117.)

New Berlin, WI, USA). Eluent strength of the mobile phase applied for the chromatograms shown in Figure 6 was 0.40, 0.30 and 0.20 (marked at the top left corner of each plate). The samples (Oil orange, Butter yellow, Sudan green and Sudan III) were spotted on the plate as benzene solutions. The emergence position (atmospheric boundary) of the plate from the chamber was 7.3 cm from the start line (position of the sample spotting) and 7.8 cm from the eluent level (immersion position of the plate in the solvent). An extraordinary increase in selectivity is observed with solvent of the lowest eluent strength (0.20). However, it is necessary to perform the development for a very long time (18 h) to maintain the same relative retentions as when using pure chloroform (0.57 h). A more efficient separation can be obtained by applying continuous development over a very short distance. The two components of the sample (Oil orange and Sudan green) were separated using SB/CD on a silica gel G plate (10 x 10 cm, Camag, New Berlin, WI, USA) for 35 min with pure carbon tetrachloride. The RF values obtained were less than 0.05 (Figure 7 (top)). Evaporation of eluent from the plate was carried out at a position 2.5 cm from eluent level and 1.1 cm from the spotting position. For com parison, Figure 7 (bottom) demonstrates the results of a conventional development on a 20 cm long bed of the same adsorbent with chloroform as the developing solvent, showing RF values of about 0.38 and a development time of 90 min. The resolution obtained by the SB/CD mode is better than continuous mode and the development time is also shorter. Additionally, the spot diameter is very small, which leads to better detection levels.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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