Long pathlength optical cell

No racemization was observed when the electrode potential was scanned only to a value where the dianion is formed. Upon formation of the tetraanion, subsequent chemical reactions were found. With a slightly different electrolyte salt (Mc4NBF4 instead of BU4NF6), reversibility without racemization was found even up to the tetraanion formation. Further examples include the spectroelectrochemistry of vitamin D2 [139], which has been studied with a long pathlength cell similar to the design described by Zak et al. [44]. Optical rotary dispersion and CD of optically active polybithiophene that has been electropolymerized in a cholesteric electrolyte have been studied [140]. The optical rotation of this chiral polymer could be controlled via the electrode potential. 

Geometry of optical pathway as parallel as possible within the cell, otherwise problems with long pathlength close to bottom (however, above a necessary stirrer in the cell). 

Transfer optics The interface of the IR beam with the sample, especially in a classified hazardous environment, can be a major challenge. Gas samples are not too difficult, although it is important to pay attention to the corrosivity of the gases, relative to the windows and any internal optics, as with a folded pathlength cell. Liquids offer different challenges. For on-line applications, users prefer to minimize the use of valves, bypass streams and auxiliary pumps, especially over long distances between the stream and the analyzer. At times there is a benefit to sample the stream either directly or as close as possible to the stream, and in such cases there is the need for transfer optics between the sample cell and the spectrometer/analyzer. 

With only weakly absorbing solvents, low concentrations of the species to be detected or weak effects (i.e. small extinction coefficient), a long optical pathlength might be desirable. In a design described by Zak et al. [43], a cell body holding both the counter and the reference electrode is manufactured from PTFE. The working electrode is attached to the cell body with a spacer of about 0.1-mm thickness. The... 

Figure 1 Examples of gas cells for mid-infrared transmission measurements (A) photograph of a multiple-pass gas cell ( Long Path Miniceir), with a high path-to-volume (530 ml) ratio. Allows paths from 1.2 m (eight passes) to 7.2 m (48 passes) (B) schematic of a multipass cell with transfer optics for use in a center-focus sample compartment (C) and (D) photographs of Pyrex and stainless steel bodied 10-cm pathlength cells, respectively. ((A and B) Reproduced by kind permission of Infrared Analysis, Inc., Anaheim CA, USA. (C and D) Reproduced by kind permission of Specac Ltd., Orpington, Kent, UK.)...

Near-Parallel Configuration Long Optical Pathlength Thin-Layer Cell and Spatially Resolved Spectroelectrochem istry... 

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