Microwave digestion system

Based on their microwave digestion system, Milestone offers the MicroSYNTH labstation (also known as ETHOS series) multimode instrument (Fig. 3.4 and Table 3.1), which is available with various accessories. Two magnetrons deliver 1000 W microwave output power and a patented pyramid-shaped microwave diffuser ensures homogeneous microwave distribution within the cavity [12]. 

Table 25.1 Digestion conditions for mushroom samples in the microwave digestion system...

For digestion, CEM Mars 5 microwave closed system was used in this study. 0.5 g of samples was digested with 5 luL of HNOj (65%) and 2 mL of (30%) in a microwave digestion system for 17 min and final diluted to 25 ruL with deionized water. A blank digest was carried out in the same way. Digestion conditions are given in Table 25.1. 

Decomposition in closed Teflon vessels at medium pressure (up to 8 bar) with microwave heating [43-44]. Microwave Digestion System MDS-81D (CEM Corporation, North Carofina, USA Floyd Inc., South Carolina, USA). 

Fig. 4.13 The Prolabo A-301 microwave digestion system. Reproduced with permission of Prolabo.

Particle size distribution was measured by a Particle Size Analyser (Malvern 2600C). For bulk chemical compositions samples were digested in diluted HNO3 solution using a CEM microwave digestion system. Dissolved samples were analysed by ICP-AES technique (Labtest PSX7521). Phase conditions were determined by X-ray diffraction analysis (XRD, Philips PW 1710). Scanning electron microscopic... 

Modern microwave digestion systems monitor both pressure and temperature in the containers. As the temperature or pressure reaches the set point, power to the oven is cut. The oven power as well as the maximum pressure and temperatures can be set. Both digestion time and oven power can be programmed so that each sample is treated in a reproducible manner. The initial digestion is done slowly at low temperature, and the temperature is increased after the majority of the readily digested matrix is dissolved. 

In addition, the practice of adding acid to water with constant stirring should be observed. When acid mixtures are prepared, only the quantity to be used should be prepared, as these may not be safe to store. Finally, pressure relief valves should be provided to any sealed container in which a digestion is to take place. One should be aware, however, that some analyte can be lost as droplets when these valves vent. This is one of the advantages of the pressure-monitored microwave digestion system. In this, the pressure is controlled by modulating the input power, so venting is avoided. 

The results confirmed that the ancillary materials used in an analytical procedures might contribute to blank values more than reagents themselves do, especially glassware and microwave digestion systems. Although the latter have been extensively employed to shorten the time required for sample dissolution, some problems have been ascribed to this procedure, as reported by Lima et al. [8],... 

Levine, K.E., Batchelor, J.D., Rhoades, C.B., Jones, B.T. Evaluation of a high-pressure, hlgh-temperature microwave digestion system. J. Anal. At. Spectrom. 14, 49-59 (1999)... 

Heltai, G., Percsich, K. Moderated pressure microwave digestion system for preparation of biological samples. Talanta 41, 1067-1072 (1994)... 

Legere, G., Salin, E.D. Capsule-based microwave digestion system. Appl. Spectrosc. 49, 14A-20A (1995)... 

Krushevska, A., Barnes, R.M., Amarasiriwaradena, C.J. Decomposition of biological samples for inductively coupled plasma atomic emission spectrometry using an open focused microwave digestion system. Analyst 118, 1175-1181 (1993)... 

Modern microwave digestion systems monitor both pressure and temperature in the containers with automatic shut-down safety valves. The oven temperature and pressure can be set and when this is achieved, the power is switched off. This continues for several stages of the set programs until completion of mn and it will turn off automatically. The microwave vessels are available commercially and toughened to handle most samples. 

Microwave digestion systems have become very popular for decomposing samples. The photo shown is a closed-vessel microwave digestion system for high-pressure digestions. A microwave oven with a built-in fume exhaust system is shown along with sample trays that contain up to 1 2 samples. Teflon sample vessels can be operated at temperatures up to 2300 C and 625 psi. 

Direct your Web browser to http //chemistry.brookscole.com/skoogfac/. From the Chapter Resources menu, choose Web Works. Locate the Chapter 36 section, and find the links for microwave digestion systems. Look up information on open-vessel microwave digestion systems versus closed-vessel systems. Summarize the advantages and disadvantages of these two approaches. 

Figure 5.6 Schematic of an atmospheric, open-focused microwave digestion system.

Figure 5.7 Schematic of a pressurized microwave digestion system.

Reliable analytical information can be obtained by using microwave digestion sampling for trace element determination in brain and liver. Krachler et al.52 reported two microwave digestion systems (open-focused and closed-pressurized). They created a mineralization of human brain and bovine liver as dissolution steps prior to the determination of 16 trace elements (bismuth, cadmium, cobalt, cesium, copper, iron, mercury, manganese, molybdenum, lead, rubidium, antimony, tin, strontium, thallium, and zinc) by ICP-MS. 

Hydrothermal procedure was performed by heating at 90 °C for 72 h (samples denoted (Sn)MCM-41/HT) and synthesis with applying of microwave irradiation was carried out at 90 °C for 3 h (samples denoted (Sn)MCM-41/MW). The sample was transferred into a microwave digestion system (CEM Corporation, MAR-5). All solid products were filtered off, washed with deionized water, dried at 100 °C and calcined in a stream of air at 550 °C for 6 hours. The prepared samples are listed in Table 1. 

A90. Rhoades, C.B. and R.T. White Mainstream smoke col- 20A108. lection by electrostatic precipitation for acid dissolution in a microwave digestion system prior to trace metal determination J. AOAC Int. 80 (1997) 1320-1331. 20A109. 

A Perkin-Elmer SCIEX ELAN 9000 ICP-MS was employed for element determination after microwave digestion of fuel samples, performed using an Anton Paar Multiwave 3000 microwave digestion system. 

Figure 1.6 A commercial anal3ftical microwave digestion system for sealed vessel digestion of multiple samples. Courtesy of CEM Corporation, Matthews, NC (www.cem.com).

A closed vessel microwave digestion system (MLS-1200 mega, Mileston s.r.l, Italy) was used for the extraction of the standard-spiked PUF and filter samples... 

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