Adsorption volatile organic compound analysis

Rosel I, A., Gomez-Behnehon, J.L, and Grimalt, J.O., Gas Chromatographic-Mass Spectrometric Analysis of Urban-Related Aquatic and Airborne Volatile Organic Compounds Study of the Extracts Obtained by Water Closed-Loop Stripping and Ah Adsorption with Charcoal and Polyurethane Foam, Journal of Chromatography. Biomedical Applications, Vol. 562, p 493-506. 1991. 

Knowing the problems associated with the analysis of volatile organic compounds, you inquire about the handling of the samples. Here we go The samples (100 mL) were put into 1 L flasks, which were then sealed and stored at 5°C for several days. Then, in the cooling room, an aliquot of the water was withdrawn and analyzed for benzene. What was the original concentration of benzene in the water sample Assume that equilibrium is established between the gas phase and the water and neglect adsorption of benzene to the glass walls of the bottle. The data required to answer this question can be found in Table 3.4. 

K. Dettmer and W. Engewald. Absorbent Materials Commonly Used in Air Analysis for Adsorptive Enrichment and Thermal Desorption of Volatile Organic Compounds, Anal. BioanaL Chem. 2002,373, 490. 

Dettmer, K., Engewald, W. Adsorbent materials commonly used in air analysis for adsorptive enrichment and thermal desorption of volatile organic compounds. Anal. Bioanal. Chem. 373, 490-500 (2002)... 

Solid-phase microextraction (SPME) is a technique that was first reported by Louch et al. in 1991 (35). This is a sample preparation technique that has been applied to trace analysis methods such as the analysis of flavor components, residual solvents, pesticides, leaching packaging components, or any other volatile organic compounds. It is limited to gas chromatography methods because the sample must be desorbed by thermal means. A fused silica fiber that was previously coated with a liquid polymer film is exposed to an aqueous sample. After adsorption of the analyte onto the coated fiber is allowed to come to equilibrium, the fiber is withdrawn from the sample and placed directly into the heated injection port of a gas chromatograph. The heat causes desorption of the analyte and other components from the fiber and the mixture is quantitatively or qualitatively analyzed by GC. This preparation technique allows for selective and solventless GC injections. Selectivity and time to equilibration can be altered by changing the characteristics of the film coat. 

Determination of Adsorption Characteristics of Volatile Organic Compounds Using Gas Phase FTIR Spectroscopy Flow Analysis... 

This chapter is devoted to the description of an easy and efficient method based on the application of gas phase Flow FTIR spectroscopy analysis for determination of adsorption characteristics of volatile organic compounds. As adsorbent beds are usually operated under dynamic conditions, the adopted analytical approach is based on gas phase composition monitoring at reactor outlet during adsorption/ desorption experiments carried out under dynamic regime. This method permits further simultaneous detection of new IR bands that may originate from adsorbate dissociation during adsorption or desorption. 

Concentration Methods. The GCMS analysis of an environmental sample starts with the isolation of the organic compounds from the matrix (air, water, food, etc.) into a form suitable for introduction into the GCMS instrument, typically a solution in a volatile solvent. This concentration step includes essentially three major methods vapor stripping, solvent extraction, and lipophilic adsorption. We have recently reviewed the detailed operation of these methods (Ij, (See also Bellar, Budde and Eichel-berger, this volume) but their general features will be outlined here. 

Determination of the intact CW agents in urine or blood may proceed by the methods commonly applied to water samples. Extraction with an organic solvent and subsequent cleanup with a Florisil column is a well-established procedure. Rather volatile, scheduled compounds can often be successfully recovered and purified from biological materials by means of dynamic headspace stripping and subsequent adsorption on Tenax tubes these tubes are then subjected to GC/MS analysis. 

It is essential to preserve the integrity of the sample between the time of collection and the time of analysis. There are, however, several processes that can cause changes in the chemical composition. Examples of these include biodegradation (e.g., of nitrogen- and phosphorus-containing compounds), oxidation (e.g., of Fe(II) and organic compounds), absorption (e.g., of CO2 which affects pFl and alkalinity), precipitation (e.g., removal of CaC03, Al(OH)3), volatilization (e.g., loss of NH3, HCN), and adsorption (e.g., of dissolved metals on the walls of the container). 

The procedure in an analytical scheme for the analysis of a wide range of organic compounds may be a combination of a gas-stripping technique for the volatiles and a number of adsorption or extraction steps. Alternatively, the sample can be passed through an adsorbent resin. The organics that pass the resin can be isolated from the effluent by means... 

Table 1 lists volatiles identified in white and black truffle aromas by head-space SPME (lOO-pm PDMS) GC/MS, and Table 2 lists results by purge-and-trap (Tenax) GC/MS. Results obtained by HS-SPME-GC/MS agreed well with those obtained by headspace Tenax adsorption GC/MS for the volatile organic sulfur compounds, and the expected discrimination of the polar or very volatile compounds by HS-SPME was confirmed. Pelusio et al. concluded that HS-SPME-GC/MS is a powerful technique for analysis of volatile organic sulfur compounds in truffle aromas, but because HS-SPME (with PDMS fibers) strongly discriminates more polar and very volatile compounds, it is less suited for quantitative analysis. 

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