Volatility range, automated analysis

Analytical pyrolysis has a number of characteristics that can make it a very powerful tool in the study of polymers and composite materials. The technique usually requires little sample and can be set with very low limits of detection for a number of analytes. For Py-GC/MS the identification capability of volatile pyrolysate components is exceptionally good. A range of information can be obtained using this technique, including results for polymer identification, polymer structure, thermal properties of polymers, identification of polymer additives, and for the generation of potentially harmful small molecules from polymer decomposition. In most cases of analysis of a polymer or composite material, the technique does not require any sample preparation, not even solubilization of the sample, which may be a difficult task for the type of materials analyzed. The analysis can be easily automated and does not require expensive instrumentation (beyond the cost of the instrument used for pyrolysate analysis). 

A method for analysis of polar pesticides in wine by the use of automated in-tube SPME coupled with LC/ESI-MS was proposed (Wu et al., 2002). In-tube SPME is a microextraction and preconcentration technique that can be coupled on-line with high-performance liquid chromatography (HPLC), suitable for the analysis of less volatile and/ or thermally labile compounds. This technique uses a coated open tubular capillary as an SPME device and automated extraction. Using a polypyrrole coating, six phenylurea pesticides (diuron, fluometuron, linuron, monuron, neburon, siduron) and six carbamates (barban, car-baryl, chlorpropham, methiocarb, promecarb, propham) were analyzed in wine. Structures of compounds are reported in Fig. 9.4. Due to the high extraction efficiency of the fiber toward polar compounds, benzene compounds, and anionic species, LODs ranging between 0.01 and 1.2pg/L were achieved, even if the sample ethanol content affects the recoveries of analytes. 

The detection of low level concentrations of volatile petroleum hydrocarbons in either soil or water can be performed by static headspace analysis. In this technique, the gas phase in thermodynamic equilibrium with the matrix is analysed. The soil is placed in a headspace vial to which water and soluble salts such as sodium chloride are added to aid the transfer of hydrocarbons into the headspace. Internal standards and surrogate spikes can also be introduced. The vial is heated and an aliquot of the static headspace vapour is directly injected onto the column of the gas chromatograph. The advantages of this technique for volatiles such as gasoline range organics are less sample handling which minimises losses, no introduction of solvents which can interfere with the compounds of interest (MTBE), and the technique can be easily automated. 

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