The purpose of this study was to find a suitable cosolvent to CS₂ so that desorption efficiency can be improved for both polar and non-polar organic solvent mixtures collected on an activated charcoal tube. Cosolvents added to CS₂ include: DMF(N,N-dimethylformamide): CS₂ (v/v 1:99), DMF: CS₂(vlv 3:97), BC (butyl carbitol, 2-(2-butoxy ethoxy) ethanol): CS₂(v/v 1:99), and BC: CS₂(vlv 3:97)).
The results obtained were as follows :
1. Comparing the desotption efficiency of CS₂ with those of CS₂ with 1, 3, 5 % DMF and 1, 3 % BC cosolvents for two different groups of charcoal tubes each containing 8 different polar and non-polar organic solvents with 3 different concentration levels, the desorption efficiencies of the cosolvent-added CS₂ increased significantly for all polar organic solvents regardless of concentration levels tested. For non-polar organic solvents, no noticeable improvement was detected except xylene and trichloroethylene. The desorption efficiency of xylene increased significantly while that of trichloroethylene increased significantly at the lowest concentration level tested.
2. Either 5 % DMF or 3 % BC was the most suitable cosolvent because the desorption efficiency for non-polar organic solvent mixtures was similar or slightly improved compared with that of CS₂, while those of for polar organic solvent mixtures were above 75 % except for cyclohexanone.
3. The smallest variations in desorption efficiency represented by the ratio calculated from the maximum to minimum desorption efficiency for all concentration levels tested were found when 3 % BC was used as a cosolvent.
The above results indicate that the desorption efficiency of CS₂ particularly for polar organic solvent mixtures collected on a charcoal tube can be significantly improved by the use of cosolvents such as 5 % DMF or 3 % BC. A caution, however, is in order for selecting a cosolvent whenever the cosolvent itself is being used in the workplace or the impurities contained in the cosolvent may interfere with the analytical results. In addition, to improve desorption efficiencies for such organic solvents as cyclohexanone or ketones, it is recommended to use suitable collection and desorption media other than the traditional method of charcoal tube collection/CS₂ desorption.
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