Digestion flow systems, microwave

Pichler, U., Haase, A., Knapp, G., Michaelis, M. Microwave-enhanced flow system for high-temperature digestion of resistant organic materials. Anal. Chem. 71, 4050-4055 (1999)... 

Performance in microwave-assisted processes depends on a number of variables including the microwave power output, exposure time, solvent and sample size used. However, specific treatments such as digestion are additionally dependent upon factors such as the digesting acid, pressure and its relationship to temperature in closed-vessel systems, the residence time in flow systems, the number of cycles used in an FMAS extractor, etc., all of which should be optimized for each specific situation. 

Perez-Jordan MY, Salvador A, de la Guardia M. 1998. Determination of Sr, K, Mg and Na in human teeth by atomic spectrometry using a microwave-assisted digestion in a closed flow system. Anal Lett 31(5) 867-877. 

Phosphorus (total) Waste waters Microwave-assisted digestion with an acidic peroxydisulfate solution UV-Vis 0.9 mg L 1 Multi-syringe flow system exploiting multi-commutation orthophosphate detected as phosphomolybdenum blue [441]... 

Pereira ER, Rohweddee JJR and Aeeuda MAZ (1998) On-line microwave slurry sample digestion using flow systems for the spectrophotometric determination of iron in seafood. Analyst (London) 123 1023-1028. 

Microwave assisted wet digestion has attracted considerable attention and has been successfully applied to plant material. Both open and closed vessels have been used, but the most popular approach is the sealed bomb method (Kingston and Jassie, 1988 Sulcek and Povondra, 1989 Matusiewicz, 1991). Karanassios et al. (1991) describe microwave stopped flow digestion systems that can give rapid (ie, less than 5 min) reproducible extractions of elements of environmental concern from plant samples. 

Many different designs for microwave-assisted flow digestion systems have been published [25, 32, 101], which open up new possibilities, primarily in fully automated sample preparation for elemental analysis. 

According to the location of the digestion unit in the system, there are two types of manifolds described in the literature to date before and after the injection unit. In the former arrangement, the sample is introduced into the microwave oven in a continuous flow [104] or stopped flow mode [105] after decomposition, the injected sample flows to the microwave oven unit together with the reagent(s) to be decomposed, and is then cooled and degassed prior to its delivery to the detector... 

A microwave-heated, flow-through digestion container (coiled Teflon tubing) was design for a commercial (Prolabo A300) focused microwave system (instead of microwave oven) and applied to the on-line preparation of biological samples, including milk, blood, and urine [108]. 

Fig. 5.5. (A) Scheme of a flow digestion system and the principle of pressure equilibration A pressure reactor, B heating zone, C cooling zone, D digestion coil, E cooling device, F connection for gas supply, G restrictor tube, H collector vial, I temperature sensor, J high-pressure pump, K injection valve, L sample loop, M sample, N and O peristaltic pumps. (Reproduced with permission of the American Chemical Society.) (B) Manifold for dynamic microwave-assisted extraction I solvent, 2 pump, 3 microwave oven, 4 extraction chamber, 5 temperature set-point controller, 6 thermocouple, 7 fluorescence detector, 8 recording device, 9 restrictor, 10 extractor. (Reproduced with permission of Elsevier.)...

M.I.G.S. Almeida, M.A. Segundo, J.L.F.C. Lima, A.O.S.S. Rangel, Multi-syringe flow injection system with in-line microwave digestion for the determination of phosphorus, Talanta 64 (2004) 1283. 

A digestion step carried out in a closed-flow microwave heating system ... 

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