Assisted distillation

Figure 8.4 Apparatus for sample preparation using physical separation. A - fractionation tube and trap for assisted distillation (A septum injector, B carrier gas inlet, C Florisil trap for collecting volatile pesticides) B, Shapiro-type freeze concentrator and C, apparatus for solvent sublation.

O. Armakou and P. Mizsey. Rigorous investigation of heat pump assisted distillation. Heat Recovery Syst. CHP, 15(3) 241-247, 1995. 

Powder milk samples have also been introduced directly as slurries for analysis by ET-AAS [67, 70, 71]. MW-assisted distillation of I for indirect determination of the element in commercial and formula milks has also been described [75]. 

P. Bermejo Barrera, M. Aboal Somoza, A. Bermejo Barrera, M. L. Cervera, M. de la Guardia, Microwave assisted distillation of iodine for the indirect atomic absorption spectrometric determination of iodide in milk samples, J. Anal. Atom. Spectrom., 16 (2001), 382-389. 

Munoz, D. Velez, M. L. Cervera, R. Montoro, Rapid and quantitative release, separation and determination of inorganic arsenic (As(III) + As(V)) in seafood products by microwave-assisted distillation and hydride generation atomic absorption spectrometry, J. Anal. Atom. Spectrom., 14 (1999), 1607-1613. 

Dehydration Anhydrous ethanol is required for blending gasoline. It can be obtained by additional dehydration, for example, with molecular sieves or carrier-assisted distillation. 

As noted earlier, not all open-vessel systems (viz. those that operate at atmospheric pressure) are of the focused type. A number of reported applications use a domestic multi-mode oven to process samples for analytical purposes, usually with a view to coupling the microwave treatment to some other step of the analytical process (generally the determination step). Below are described the most common on-line systems used so far, including domestic ovens (multi-mode systems) and open-vessel focused systems, which operate at atmospheric pressure and are thus much more flexible for coupling to subsequent steps of the analytical process. On the other hand, the increased flexibility of open-vessel systems has promoted the design of new microwave-assisted sample treatment units based on focused or multi-mode (domestic) ovens adapted to the particular purpose. Examples of these new units include the microwave-ultrasound combined extractor, the focused microwave-assisted Soxhlet extractor, the microwave-assisted drying system and the microwave-assisted distillation extractor, which are also dealt with in this section. Finally, the usefulness of the microwave-assisted sample treatment modules incorporated in robot stations is also commented on, albeit briefly as such devices are discussed in greater detail in Chapter 10. 

Microwave-assisted distiller Microwave energy has also been used to facilitate the distillation of various compounds from solid samples [11,63-65]. Figure 5.12A depicts a typical microwave-assisted distillation apparatus. It consists of a laboratory-made poly-tetrafluoroethylene (PTFE) vessel of 120 ml inner volume and 10 mm wall thickness, and a 60 ml collector flask. The screw cap of the vessel includes a drilled PTFE disc located on its upper part that avoids sample ejection during distillation. A hole made in the vessel cap provides a means for evacuating volatile compounds via a PTFE tube that is passed through the vent holes of the microwave cavity and is then adapted to a glass line finished by a bubbler which is inserted in the collector flask. A domestic microwave oven equipped with a 2450 MHz magnetron is normally used for this purpose, altered only as required to connect the sample vessel with the collector flask. 

Fig. 5.12. (A) Microwave-assisted distillation set-up - C collector TL tansfer line V vessel WR water reservoir. (Reproduced with permission of Elsevier.) (B) Microwave-assisted distillation/ solid-phase extraction apparatus. The parts designated by capital letters are described in the text. (Reproduced with permission of the American Chemical Society.)...

Conte, E. D., Shen, C. Y., Perschbacher, P. W., and Miller, D. W. 1996. Determination of geosmin and methylisoborneol in catfish tissue (Ictalurus punctatus) by microwave-assisted distillation—solid phase adsorbent trapping, J. Agricul. Food Chem., 44 829-835. 

Fuge, R., Johnson, C. C. (1986).The geochemistry of iodine - a review. Environmental Geochemistry and EIealth,Yo. 8, No. 2, pp 31-54, ISSN 0269-4042 Gamallo-Lorenzo,D., Barciela-Alonso, M. C., Moreda-Pineiro, A., Bermejo-Barrera, A. Bermejo-Barrera, P. (2005). Microwave-assisted alkaline digestion combined with microwave-assisted distillation for the determination of iodide and total iodine in edible seaweed by catalytic spectrophotometry. Analitka Chimica Acta, Vol. 542, pp 287-295, ISSN 0003-2670... 

Fonyo, Z., Benko, N. (1998). Comparison of Various Heat Pumps Assisted Distillation Configurations. Trans. IChemE.,16, Part A, 348-360. 

High pressure distillation Membrane assisted distillation... 

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