TA/DTA

There are four basic hyphenated methods that result in the sample being destroyed. These are GC-MS, HPLC-MS, AAS/ICP-MS and TA/DTA-MS. All mass spectroscopic methods destroy the sample after separation however, both AAS and ICP destroy the sample no matter what follow-on method of analysis is used. In most cases, TA and differential thermal analysis (DTA) will also destroy the sample. The follow-on methods then analyze the components that result from this decomposition. DTA may also be used to follow transitions in the sample without destroying it. Because the sample is identified, there is typically no reason to collect the analyte of interest, and so destruction is not of concern. However, if there is a limited amount of sample, care should be taken in using one of these methods. 

Another question may be asked suppose / have observed an event at ta, what is the probability distribution w(01 ta) of the time I have to wait until the next event The joint probability for having one event between ta — dta and ta, and one in (tb, tb + dtb) with no events between them is... 

An analytical scheme for the TA-EGD-EGA coupled simultaneous technique is shown in Figure 2.32. The evolved gas from TA (DTA/DSC or TG) is introduced into the EGA system after passing through the EGD system. The evolved gas is directly introduced to a thermal conductivity detector (TCD), avoiding second reactions. Two methods are used for the TA and EGA coupled simultaneous technique (1) on-line coupled simultaneous technique in series and (2) off-line combined method. In technique (1), TA is connected serially with a Gas chromatograph (GC) [61-65], mass spectrometer (MS) [57, 64, 65], Fourier transform infrared (FTIR) spectrometer [66, 67], non-dispersive IR (NDIR) spectrometer [68, 69] or thermo-gas-titrimetric... 

Closely related mixed amido/imido/guanidinato tantalum complexes of the type Ta(NR R )[(R R2N)C(NR )2]( = NR ) (R R = Me, Et R = Cy, Pr R = Pr", BuO were synthesized by the insertion of carbodiimides into to tantalum-amide bonds in imidotantalum triamide precursors, and the effects of ligand substitution on thermal properties were studied by TGA/DTA measurements. In addition, selected compounds were pyrolyzed at 600 °C and the decomposition products were studied by GC-MS and NMR spectroscopy. ... 

When solids react, we would like to know at what temperature the solid state reaction takes place. If the solid decomposes to a different composition, or phase, we would like to have this knowledge so that we can predict and use that knowledge In preparation of desired materials. Sometimes, intermediate compounds form before the final phase. In this chapter, we will detail some of the measurements used to characterize the solid state and methods used to foUow solid state reactions. This will consist of various types of thermal analysis (TA), including differentlEd thermal analysis (DTA), thermogravimetric analysis (TGA) and measurements of optical properties. 

However at elevated temperatures (T2 > Tj, Figure 9) the increased entropy (TAS) associated with an open shell structure overcomes the ti —ti enthalpy of dimerisation associated with these distorted Ti-stacked structures and they undergo a solid-solid phase transition (Figure 9) The high temperature phase is typically associated with a Ti-stack of regularly spaced radicals which exhibit longer inter-radical S- S contacts (ca. 3.7 A). This process was first observed by Oakley60 in the DTA radical thiadiazolopyrazine-l,3,2-dithiazolyl 26, and a number of other derivatives have subsequently been identified which exhibit similar behaviour. These are compiled in Table 1. 

Fig. 1.26. Instrument DSC 2920 with DTA-measuring cell. This installation is not designed for low temperatures, but can be modified for this purpose. (Commercial standard installations for low temperatures have not been found by the author.) (Schema and photograph TA Instruments, Inc. New Castle DE 19720, USA.)...

TG-DTG-DTA-T-P, Mettler Instrument Corporation, Company Brochure 79) TA 2000 C, Thermoanalyzer for Simultaneous TG-DSC,... 

A series of derivatives of tetramic acid were synthesized and complexed to cop-per(II) (Cu-TA,Fig.21) [176,177]. At 300 MHz,the Rt value of Cu-aTA is 0.073 0.004 mM 1 s-1 and the R2 value is 0.091 0.006 mM 1 s 1 [176]. The ability of the Cu-TA derivatives to cross membranes was measured using defolliculated Xeno-pus laevis oocytes as model cells. Using MR microscopy techniques, Cu-aTA, Cu-bTA, Cu-cTA and Cu-eTA were all found to cross into the cytoplasm of the cells [177]. Additionally, atomic absorption spectroscopy revealed the presence of Cu-dTA and Cu-fTA, suggesting that while the complexes failed to cross the cell membrane that they were stored in the membrane-bilayer. Liquid chromatography experiments demonstrated that Cu-aTA crosses membranes intact [176]. 

Fig. 1.25. Scheme of a DTA measuring cell. 1, Crucible with sample 2, sample 3 thermocouple (reference crucible not enlarged) 4, gas inlet 5, ceramic support (TA Instruments, Newcastle, DE, USA)... 

As shown in Fig. 4.8.1, a TG apparatus typically consists of a (1) recording balance, (2) furnace, (3) furnace temperature controller, (4) temperature programmer, (5) temperature detector, and (6) recorder. Most commercial models, e.g., Perkin-Elmer Model TGA-7, TA Instruments 2950 TGA, Mettler TC11ATG50, Seiko Instruments SSC 5200 TG-DTA 220, and Shimadzu TGA-50, consist of these basic components. 

Most commercial DTA and DSC models are patterned after those shown in the figures. Representative commercially available models include Perkin-Elmer DSC 7 and DTA 1700, TA Instruments 2910 DSC and DTA, Mettler TC11/... 

The thermogravimetric analyser is a SDT-DTA from TA Instruments, supported by an HP PC and software for control and data handling. The system consists of a dual beam horizontal balance. Each arm holds one cup and there is one thermocouple under and in contact with each cup. One cup contains the char sample and the other cup is empty, used as a reference for temperature effects. Detailed description of the instrument can be found somewhere else. Ceramic cups were used for most of the experiments. The apparatus has been recently upgraded and it was possible to operate in a TGA-DSC mode. Therefore, not only the temperature and the weight have been registered but also the heat demand of the process. Table 2 and Table 3 show the experimental matrix for this work. 

Lanigan RS and Yamarik TA (2002) Final report on the safety assessment of EDTA, calcium disodium EDTA, diammonium EDTA, dipotassium EDTA, disodium EDTA, TEA-EDTA, tetrasodium EDTA, tripotassium EDTA, trisodium EDTA, HEDTA, and trisodium HE-DTA. International Journal of Toxicology 21 95-142. 

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