Closed microwave-assisted digestion

G. C. L. Araujo, M. H. Gonzalez, A. G. Ferreira, A. R. A. Noggueira, J. A. Nobrega, Effect of acid concentration on closed-vessel microwave-assisted digestion of plant materials, Spectrochim. Acta, 57B (2002), 2121-2132. 

The determination of metal purity and the elemental composition of alloys is of utmost importance to the metallurgical industry. Microwave-assisted digestion is often well-suited to metals and metallurgical samples that pose no difficulty and dissolve readily and safely with the aid of microwaves [148,186-196]. For example, hydrofluoric acid can be used in closed vessels to digest silicate matrices and stop the hydrolysis of refractory elements without loss of volatile fluorides or passivation. After cooling, boric acid can be added to complex unreacted hydrofluoric acid [14]. The solid sample itself may absorb microwave radiation, thus creating a heated surface on which the acid or acids can react. Microwave muffle furnaces are commercially available [197] based on oven linings made... 

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. 

Heavy metals, boron (B(V)), arsenic and total phosphorus were determined in the fraction < 20 pm to improve the comparability of the results. This fraction was separated from the freeze-dried and non-milled samples by ultrasonic sieving (Ackermann 1980). Metals were analysed after microwave-assisted digestion with aqua regia at 180 °C in closed vessels by inductively coupled plasma optical emission spectroscopy, atomic fluorescence spectroscopy (mercury) and hydride atomic absorption spectroscopy (arsenic). 

Supp. Cond. Oxidation of N and P using 22% (v/v) hydrogen per oxide and closed-vessel microwave assisted digestion in two stages % recoveries above 94.7% for phosphate 29 m 3 < o 3 3 3... 

Semi on-line microwave-assisted digestion of shellfish tissue for the determination of selenium by electrothermal atomic absorption spectrometry) May and Stoeppler (1984, Pretreatment studies with biological and environmental materials. IV. Complete wet digestion in partly and completely closed quartz vessels for subsequent trace and ultratrace mercury determination) ... 

Microwave-assisted digestion in a closed vessel This method is based on degradation of plastic with... 

Zischka M., Kettisch P., Schalk A. and Knapp G. (1998) Closed microwave-assisted wet digestion with simultaneous control of pressure and temperature in all vessels, Fresenius J. Anal. Chem. 361 90-95. 

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. 

Very recently, a novel microwave-assisted high-temperature UV digestion system for accelerated decomposition of dissolved organic compounds or slurries was developed [95, 96]. The technique is based on a closed, pressurized, microwave decomposition device wherein UV irradiation is generated by immersed electrodeless Cd discharge lamps (228 nm) operated by the microwave field in the oven cavity. The immersion system enables maximum reaction temperatures of up to 250-280 °C, resulting in a tremendous increase in mineralization efficiency. 

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