Thermobalance Mettler

The preparation of Ba02 was carried out by decomposition of BaC03 in high vacuum 10-6 mm on the thermobalance (METTLER Thermoanalyzer) at 800 °C to BaO and subsequent oxidation with dry oxygen (Fig. 55). The complete oxidation could be achieved only after cycling in the temperature region 500 to 600 °C. 

Thermogravimetric analysis (TGA) of the gel was earried out using a thermobalance (Mettler Toledo) in the temperature range between 30 °C and 800 °C with a heating rate of 20 K/min. 

Both polymorphic forms of natamycin (Section 3.1.3) were examined by means of differential scanning calorimetry (DSC) and by thermogravime-tric analysis (TGA) [13]. Figures 2 and 3 show the DSC curves of the two polymorphs, recorded on the DSC 30 of the Mettler TA 4000 System. The obtained data are shown in Table 1. Also shown are the weight losses at the specified temperatures, obtained from a TGA curve, run on a Mettler TG 50 thermobalance. 

Figure 12-7 Schematic of thermobalance A beam B sample cup and holder C counterweight D lamp and photodiodes E coil F magnet G control amplifier H tare calculator 1 amplifier and J recorder. (Courtesy of Mettler Toledo, Inc., Columbus, OH.)...

The loading of moisture- or oxygen-sensitive samples into the Mettler thermobalance sample holder is conveniently carried out by use of the controlled atmosphere enclosure shown in Figure 3.9 (3). The sample is introduced, via an enclosed sample holder, into the enclosure and loaded into the furnace chamber after the controlled atmosphere has been introduced. After loading, the furnace chamber is closed and the enclosure is removed. 

Two other important milestones in the development of the modern thermobalance occurred in 1958 and 1964. A multifunctional instrument, called the Derivatograph. was described by Paulik 35) et al. in 1958. The instrument could record not only the TG curve, but also its first derivative (DTG) and the differential thermal analysis jDTA) curve. In 1964. Weide-mann (3) described the Mettler system, which was perhaps the most sophisticated thermobalance ever commercially available. This system is described in detail by Wiedemann and Bayer (8). 

The Mettler TA1 thermoanalyzer, as developed by Wiedemann (3, 60), was perhaps the most elaborate and versatile of any thermobalance ever constructed. It is no longer available commercially, having been superseded by the Mettler TA 2000 and TA 3000 systems. However, because of its uniqueness, the Mettler TAl is described here. 

The coupling of the Mettler thermobalance to a gas chromatograph or mass spectrometer is discussed in Chapter 8. 

The first combination of thermogravimetry (TG) and a mass spectrometer was by Zitomer (36) in 1968 who coupled a Du Pont thermobalance with a time-of-flight mass spectrometer. He applied the technique to the thermal decomposition of various polymers. Lastly, Wiedemann (37) described an elaborate TG-DTA-EGD-MS system in 1969. The system consisted of a Mettler thermoanalyzer couple to a Balzer quadrupole mass spectrometer that permitted the sample to be studied at low (10 6 Torr) or normal (I atm) pressures. 

Perhaps the most widely used TG-MS system, which includes DTG. DTA, and gas pressure measurements, is the Mettler thermoanalyzer. The system, which consists of a precision thermobalance, a high-vacuum system, a mass spectrometer, and a DTA measuring system, has been described in detail by numerous investigators (68-73). 

Figure 8.14. Mettler thermobalance-quadrupole mass spectrometer system (37,69).

FIGURE 31-1 Thermobalance components. The balance beam is shown as A. The sample cup and holder are 0 C is a counterweight. /) is a lamp and photodiodes, E is a magnetic coil, and F is a permanent magnet. The computer data-acquisition, data-processing, and control systems are components G, //. and /. Component J is the printer and display unit. (Courtesy of Mettler-Toledo.)... 

Mettler-Toledo TC50 Thermobalance Model for Many Modern Instruments... 

Figure 3.2. Three examples of commercial thermobalances, including typical thermocouple placement (a) a top-loading model (courtesy of Netzsch Instruments) (b) a side loading model (courtesy of Mettler-Toledo) (c) a bottom-loading model (courtesy of TA Instruments).

Thermogravimetric measurements were made with Mettler Toledo thermobalance (TGA/SDTA831 , LF/1100°C) using platinum crucibles. The samples (about 10 mg) were heated in flowing air (60 ml min ) from 25 to 700 C at 5 K min . 

Later developments by the Mettler Company include a desktop thermogravimetry apparatus, the TA 4000. This system consists of a computer processor (TCIO A) and the thermobalance, shown in schematic cross section in Fig. 7.4. The readability of the balance is 1 ng. The electrical range of mass compensation is from 0 to 150 mg, and the overall capacity of the balance is 3,050 mg. The temperature range is room temperature to 1,250 K with heating rates of 0 -100 K/min. The TA 4000 system also includes tabletop modules for DSC and TMA, all coupled to the same data processor. 

Wiedemann Hans G. (1928-) Ger. born, Swiss thermoanal., inventor of progressive thermobalances designed for Mettler (book Chemische thermodynamik und thermoananlytik 1979)... 

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