Pyrolysis derivatization technique

In the last decade, pyrolysis derivatization techniques have been increasingly used by many researchers in the characterization of organic matter. Derivatization has the potential to... 

Alkyd enamels occurring as original baked enamels or spraying enamels may be identified by the THM pyrolysis derivatization modification of the Py-GC technique. These alkyd polyesters are converted to methyl derivatives of their polyol,... 

As an alternative, a two-step Py-GC/MS technique can be applied allowing the identification of volatile diterpenoids in the first step and of the polymeric fraction in the second step [33]. The procedure involves an on-line derivatization at 250°C with TMAH, followed by the pyrolysis of the remaining high molecular weight fraction. 

The pyrolysate of cellulose acetate contains both volatiie and iess volatile compounds. In order to identify a wider range of compounds with different voiatilities by GC analysis, it is common to appiy two chromatographic conditions, one for the analysis of more volatile compounds and another for more polar and less volatile ones. The second technique may be associated with derivatizations. The results for the pyrolysis of a cellulose acetate sample at 590° C followed by GC/MS with the separation on a polar chromatographic column are shown in Figure 7.3.1. This particular separation was done on a 60 m Carbowax column with 0.32 mm i.d., 0.25 n film thickness. 

As seen in Section 12.3, pyrolysis coupled with more sensitive analytical techniques may detect the prosthetic groups, such as in the case of albumins analyzed by off-line Py-GC/MS with the derivatization of the pyrolysate. 

Pyrolysis involves the thermal decomposition, degradation, or cracking of a large molecule into smaller fragments. Pyrolysis GC is an excellent technique for identifying certain types of compounds which cannot be analyzed by derivatization, e.g., polymers. The pyrolysis temperamre is typically between 400°C and 1000°C. A number of analytical pyrolyzers have been introduced and are commercially available. The devices consist of platinum resistively heated and Curie point pyrolyzers. The carrier gas is directed through the system, and the platinum wire is heated to a certain temperature. The material decomposes, and the fragmentation products are analyzed. ... 

Gas chromatography finds routine use as an analytical tool in numerous industries, universities, and government and private laboratories. Gas chromatography is used to separate and identify components of gaseous, liquid, or volatile solid mixtures. For nonvolatile compounds, special techniques can be used to derivatize the sample to a form amenable to GC. Alternatively, nonvolatile samples can be pyrolyzed and their pyrolysis products are separated and analyzed. ... 

Derivatization of the sample renders many of these polar pyrolysis products sufficiently volatile for gas chromatographic separation. Thus it is possible to separate and detect many more strucmrally significant products than observed by conventional pyrolysis techniques.The most common of the derivatization processes is a methylation reaction where organic matter is mixed with tetramethylammonium hydroxide (TMAH) prior to pyrolysis. Throughout the literature, several different terms have been employed to describe derivatization reaction and in this chapter the term thermochemolysis will be used. 

A report from a forensic science laboratory in 1989 described a technique to pyrolyze synthetic polymer samples and simultaneously chemically derivatize (methylate) the pyrolysis products prior to analysis by capillary GC and GC/MS, a technique that was referred to as simultaneous pyrolysis methylation-capillary gas chromatography (SPM-GC) and SPM-GC/MS. The methylation is caused to take place in situ by the simple expedient of adding a few microliters of methanol containing tetramethyl ammonium hydroxide (TMAH) to the sample in the sample holder of the pyrolysis device. When applied to sediment samples for characterization of the organic matter, this technique is referred to as TMAH-Py-GC/MS. The methylation procedure quite likely allows measurement of many compounds that otherwise would pass undetected. Table 7.8 shows a list of compounds that were identified in programs of river and lake sediments subjected to analysis by TMAH-Py-GC/MS. ... 

IR and NMR spectroscopy are relatively easy-to-apply for a qnaUtative and comparative evaln-ation of the chemical structure and the DA determination. These techniques are nondestructive methods and do not need initial treatment such as hydrolysis, pyrolysis, and derivatization. This chapter describes the structural characterization of chitin and chitosan (as oligomers and polymers) by IR, near-IR, and various types of NMR spectroscopy techniques. This study provides information on (1) composition, sequence, and type of residues and (2) any structural changes occurring in the molecules as a result of different processes (degradation, deacetylation, and acetylation). The influences of acids, alkali, moisture, and impurities on the NMR and IR spectra of the original molecules will be also discussed. 

The GC instrument is a rather simple, yet very powerful. It is one of the most common analytical tools used in plastics analysis. When used properly, it can provide both qualitative (identification) and quantitative (amount) information about the individual components in sample mixtures. For a mixture to be suitable for gas chromatographic analysis it should be relatively volatile at temperatures below 350°C (450°C for high-temperature GC). In other words, the components of interest must become a gaseous form by rapid heating without any degradation or destruction of their chemical structure. This does not mean that other components are not amenable to GC analysis. In theory, most components can be analyzed by GC if a proper sample pretreatment or proper sample introduction technique is used (e.g., pyrolysis GC, sample derivatization) [1-5]. 

If the sample to be analyzed is nonvolatile, the techniques of derivatization or pyrolysis GC can be utilized. This latter technique is a modification wherein a nonvolatile sample is pyrolyzed before it enters the column. Decomposition products are separated in the gas chromatographic column, after which they are qualitatively and quantitatively determined. Analytical results are obtained... 

While liquid-liquid, headspace, and sorbent-based extractions are perhaps the most commonly nsed and pnbhshed sample preparation techniqnes for GC, there are numerous additional techniques to consider. While we do not attempt to fully describe every technique that has ever been nsed, the techniques described below are certainly of importance in the arsenal of sample preparation techniques for GC. These include supercritical-fluid extraction, accelerated solvent extraction, microwave-assisted extraction, pyrolysis, thermal desorption, and membrane-based extractions, pins comments on antomation and derivatization. 

In the 1990s the search for characteristic pyrolysis products of complex biomolecules with the use of GC-MS and MS-MS instruments has firmly established the usefulness of analytical pyrolysis techniques when used in a biochemical marker detection, rather than in a fingerprinting mode. Either direct pyrolysis followed by analysis of thermal fragmentation products or, alternatively, chemical derivatization followed by analysis of the derivatized products... 

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