Semi-volatile compounds

SPME can be used to extract organic compounds from a solid matrix as long as target compounds can be released from the matrix into the headspace. For volatile compounds, the release of analytes into the headspace is relatively easy because analytes tend to vaporise once they are dissociated from their matrix. For semi-volatile compounds, the... 

Evaporative lightscattering Universal non-volatile or semi-volatile compounds, compatible to gradients Low ng... 

EPA. 1988a. USEPA Contract Laboratory Program statement of work for organicanalysis. Semi-volatile compounds. D-I/SV to D-45/SV. 

Polycyclic musk fragrances (PMFs) are a major class of compounds. More than 5000 tons of polycyclic musks are synthesized worldwide annually (Kannan et al., 2005). HHCB and AHTN are two of the most frequendy used PMFs worldwide. They are semi-volatile compounds with a log of 5.4—6.3 (Ricking et al., 2003). They am poorly... 

Claxton, L. D., Assessment of Bacterial Mutagenicity Methods for Volatile and Semi-Volatile Compounds and Mixtures, Environ. Int. J., 11, 375-382 (1985). 

Yang and Her [ 193] have described a rapid method for the determination of down to 200 ppt of semi-volatile compounds such as 1-chloronaphthalene, nitrobenzene and 2-chlorotoluene in soils by coupling solid-phase microextraction with attenuated total reflectance Fourier transform infrared spectroscopy. 

Accelerated solvent extraction is a new technique for the extraction of a range of organic pollutants from soils and related material. The technique is based on the use of a solvent or combination of solvents to extract organic pollutants at elevated pressure and temperature from a solid matrix. The range of organic pollutants for which the technique is proposed includes semi volatile compounds, organochlorine pesticides, organophosphorous pesticides, chlorinated herbicides, polychlorinated biphenyls and polycyclic aromatic hydrocarbons [66-69]. 

Semi-volatiles, S02, and N0X were also measured in the pyro-gas. The majority of the semi-volatile compounds detected were phthalates. The methods used to detect the semivolatiles (gas chromatography/mass spectrometry analysis using dry sorbent resins) could have been the source of the phthalates, because these methods can give rise to phthalate contamination.1... 

Determination of the optimum time for which the SPME sorbent will be in direct contact with the sample is made by constructing an extraction-time profile of each analyte(s) of interest. The sorption and desorption times are greater for semi volatile compounds than for volatile compounds. To prepare the extraction-time profile, samples composed of a pure matrix spiked with the analyte(s) of interest are extracted for progressively longer times. Constant temperature and sample convection must be controlled. Stirring the... 

For semi volatile compounds, inlet optimization is very simple. Classical splitless inlet conditions, followed by an initial column temperature cool enough to refocus the analyte peaks following the desorption, work well. Thus, a typical condition would be a temperature of about 250° C, a head pressure sufficient to maintain optimum GC column flow and an initial column temperature at least 100°C below the normal boiling point of the analyte. For semivolatile analytes, a classical splitless inlet liner can be used, as the cool column will refocus these peaks. The desorption time in the inlet must be determined by experimentation, but typically, runs between 1 and 5 minutes. 

Based on available results, dynamic and static HS mode is complementary rather than competitive. The better choice in each case will depend on the sample-analyte interaction. Thus, the dynamic modes are better suited to semi-volatile compounds in water, while the static modes are to be preferred for solid and semi-solid samples. 

The desorption temperature usually ranges from 150 to 250°C for semi-volatile compounds. Usually, the optimum desorption temperature is roughly equal to the boiling point of the least volatile analyte [214]. In order to prevent broadening of the chromato-... 

This design affords shorter analysis times with minimal solvent consumption also, no preconcentration step is required as preconcentration is achieved simultaneously with distillation by retaining distilled analytes on the solid-phase material. This device features a broad range of uses in the analysis of semi-volatile compounds in solid samples with high moisture contents. 

COMPARISON OF USE AND ASE FOR THE EXTRACTION OF SEMI-VOLATILE COMPOUNDS FROM THE WAX FRACTION OF PINE NEEDLES (CONCENTRATIONS ARE GIVEN IN ng/g DRY MASS)... 

Long-term properties of polymers are severely affected and the service-life is reduced due to the migration of additives. There is also the possibility that some of the additives accumulate in the environment and affect our health and the environment. SPME has been applied for the extraction of several common polymer additives. Since additives often have rather low volatility, a significant advantage with SPME and HS-SPME compared to HS-GC-MS is the ability to extract even semi-volatile compounds [9,13]. 

In sorbent tube sampling (Figure 3.5), volatile and semi-volatile compounds are pumped from the air and trapped on the surface of the sorbent. By sampling a measured quantity of air (typical volumes of 10-500 m3), quantitative sampling is possible. The sorbent tube is then sealed and transported back to the laboratory for analysis. Desorption of volatile and semi-volatile compounds takes place either by the use of organic solvents (solvent extraction) or heat (thermal desorption), followed by analysis using gas chromatography (see later). 

The choice of solvents is determined by cost, spectral qualities (for HPLC use), extraction efficiency, toxicity and commercial availability. Methylene chloride (dichloromethane) has been the preferred solvent for many semi-volatile compounds due to its high extraction efficiency and relatively low cost. However, for most petroleum species a non-polar solvent such as hexane is more effective for relatively fresh or recent spills. In aged polluted sites where absorption may have taken place, the addition of a polar solvent such as acetone to hexane is common. The hexane/acetone cocktail usually meets all requirements but may not always be compatible with the extraction technique. The following are examples of extraction techniques ... 

Snyder columns are designed to allow highly volatile solvents to escape whilst retaining the semi-volatile compounds of interest. They are normally fitted onto the top of flasks containing extracts. The flasks may be heated, the design of the column allows volatile solvent to escape during the process. The analytes of interest condense from a vapour to a liquid phase and are collected in the solvent reservoir. 

Dynamic thermal desorption (DTD), which closely resembles the DHS technique, is also commonly used in combination with GC in the analysis of (semi)volatile compounds in both solid and liquid matrices (85-88). In DTD,... 

Volckens, J. and Leith, D., Effects of sampling bias on gas-particle partitioning of semi-volatile compounds, Atmos. Environ., 37, 3385-3393, 2003. 

Various procedures have been used by different research workers for the sampling and analysis of MVOCs. These procedures have different selectivities (Parliament, 1986), which have led to different conclusions on the specific compounds produced by the different micro-oiganisms even when growing under identical conditions. A particular difficulty is that the compounds of relevance in this context also have a very wide variability in boiling point from very volatile compounds to so-called semi-volatile compounds. 

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