Sealed Liquid Cells

FIGURE 4.22 A schematic diagram of a sealed liquid cell. The gasket/spacer seals the liquid between the infrared transparent windows and holds the windows a fixed distance apart, giving a known pathlength. 

FIGURE 4.23 A picture of a sealed liquid cell. Note the window with the holes drilled in it, the Teflon gasket, and the syringe with a Luer lock fitting. (Photo courtesy of PIKE 

FIGURE 4.24 A sealed liquid cell holder equipped with Luer lock fittings and Teflon stoppers. (Photo courtesy of PIKE Technologies.) 

FIGURE 4.25 The infrared spectrum of methyl ethyl ketone (MEK) obtained using a sealed liquid cell. 

FIGURE 4.26 A variable pathlength sealed liquid cell. (Photo courtesy International 

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Use of a proton transfer reaction (PTR), time-of-flight mass spectrometer and high sensitivity PTR quadruple mass spectrometer Use of sealed liquid cell for polymer analysis Analysis of ethanol derivative (spec A = 245 nm)... 

Sealed liquid cells have a gasket that seals the liquid in the cell, thus preventing evaporation and counteracting the evaporation problem snffered by the capillary thin film method. It also means that volatile, smelly, and toxic liqnids can be analyzed because they will not escape and cause harm. A schematic diagram of how a sealed liquid cell works is shown in Figure 4.22. 

A sealed liquid cell consists of two infrared transparent windows, which are typically made from KBr or one of the other infrared transparent materials listed in Table 4.1. Two small holes are drilled in one of the windows, as can be seen in Figure 4.23. 

Something to be careful about when stndying liquids is that some crystals, such as ZnSe, will react with or dissolve in strong acids or bases. The usable pH ranges for a number of ATR crystals are listed in Table 4.12. Another issue with ATR is that volatile liquids, such as acetone, may evaporate before their spectrum is measured. Many ATR accessories are equipped with volatiles covers that are placed over the liquid in an attempt to prevent evaporation. The author has had mixed results with these, and in his experience, highly volatile liquids may be best sampled using the sealed liquid cell method discussed earlier. 

Liquids Capillary thin films, sealed liquid cells, ATR... 

Sealed Liquid Cells A transmission sampling technique used to obtain the spectra of liquids. The cell consists of two infrared transparent windows held a fixed distance apart by a gasket. The cell is filled with liquid then placed in the infrared beam. 

The electrode shall contain a reproducible, permanently sealed liquid cell for making electrical connection with the inner si ace of the hemisphere. 

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