Volatile organic compounds matrix effect

The solubility of organic compounds in selected solvents may be estimated from the like dissolves like rule of thumb. Whilst this approach is adequate, it is at best only qualitative and does not take into account the matrix and other effects present. Cocktails of solvents of different polarity can be prepared to give the same polarity as solvents which have or may be withdrawn from use for health and safety reasons. However, the presence of water in the sample can affect the polarity of the solvent and ultimately the extract. Soils can be oven dried up to 35°C with the significant risk of loss of volatiles or chemically dried (for instance, using magnesium sulfate monohydrate) to avoid volatile loss (see Chapter 8). 

Yes there is and it is Method 5021 from the recently updated SW-846 series of methods published by the Office of Solid Waste at EPA. The method uses the static HS technique to determine VOCs from soil or other solid matrix. This section will focus on some of the details of this method because it includes many of the quality control (QC) features that were absent in the method just discussed. This method also introduces some experimental considerations with respect to trace VOC analyses of soil samples (34). The method is applicable to a wide range of organic compounds that have sufficiently high volatility to be effectively removed from soil samples using static HS techniques. The method is used in combination with a determinative technique that is described in the 8000 series. The method cautions the user to the fact that solid samples whose organic matter content exceeds 1% or for compounds with high octanol/water partition coefficients may yield a lower result for the determination of VOCs by static HS in comparison to dynamic headspace (P T). It is... 

Flame Decomposition. Utilization of a petroleum sample as a fuel for combustion in a specially devised burner system, such as that described by Wickbold (6), can be an effective way to destroy large amounts of an organic matrix. The method is applicable to those elements which are either volatile or form volatile compounds and which can be trapped quantitatively in a suitable scrubber. This technique was used to prepare samples for cold vapor atomic absorption determination of mercury. Details are included in Chapter 12. 

All headspace techniques share certain advantages and considerations. Chief among these is that the analytes are removed from the sample matrix without the use of an organic solvent, so the resulting chromatogram has no solvent peak. This may be especially important when the compounds of interest are early eluters or are, in fact, solvents, and the presence of a solvent peak would both dilute and mask the analyte peaks. In addition, the effects of sample temperature, matrix solubility, and the volatility of the analyte are important considerations in optimizing a headspace assay, whether static or dynamic. 

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