Sensitivity Enhancement by Matrix Modification

The partition coefficient can be altered by modifying the sample matrix. A common technique is the use of the salting-out effect. For aqueous samples with a high partition coefficient (e.g. ethanol in water), the addition of salt may enhance the sensitivity by up to a factor of 10. Again, the result depends on the value of the partition coefficient. In the case of a highly volatile compound (K p 0), where nearly all of the analyte is already present in the gas phase, the sensitivity will not improve.

A similar effect is achieved with a sample containing a nonpolar volatile compound dissolved in a water-miscible organic solvent, such as dimethyl-acetamide, dimethylformamide, etc. If water is added to this solution, the solubility of the nonpolar compound will decrease and its volatility will increase.

Table 1 Partition coefficients (K) in water-air equilibrium system

Compound

Temperature 40 3 C

60 3C

803C

Tetrachloroethylene

1.5

1.3

0.9

Ethyl acetate

62.4

29.3

17.5

Ethanol

1355

511

216

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

Get My Free Ebook


Post a comment