Abstract
The chromatomembrane-method is a new extraction technique. An aqueous phase flows through the macropores of a biporous material (PTFE). As a consequence of capillary phenomenons the liquid is not able to penetrate into the micropores, so that a nonpolar phase (a gas or a liquid organic phase) can flow through these micropores. At the interface boundary surface an analyt transfer can occur.
The combination of this chromatomembrane-method with the gaschromatography is described. Organic compounds in aqueous solutions was determinated after a liquid-gas-extraction or a liquid-liquid-extraction by using a chromatomembrane-cell.
The liquid-gas-extraction was preferred for the determination of volatile organic compounds (VOC´s). The VOC´s were extracted into a nitrogen stream and injected via a six-port-valve into the gaschromatographic system. By using a trap for accumulation the detection limits of the VOC´s were in the µg/l range. The influences of flow rates, temperature and salt concentration were investigated. A mathematical calculation for these effects in the chromatomembrane-method was developed.
For semivolatile or non-volatile organic compounds an extraction into a gas phase is not possible in an easy way. But these compounds can also be determinated with the CM-method, if a liquid-liquid-extraction will be taken. For this extraction it must be prevented that to large volumes of the organic solvent will be injected into the gaschromatographic system. This is the reason that another step must be carry out in the experimental system: After the organic compounds are accumulated in a trap, the solvent must be blow out of this trap with a nitrogen stream. Then the organic compounds were desorbed on a thermal way and injected into the GC. On this way semivolatile organic compounds could be detected in the µg/l range too.
The advantages of the CM-method are the easy possibility of automatisation, low detection limits, a better distribution of compounds in liquid-gas-systems and the possibility of working with very low volumes of solvents in a liquid-liquid-systems. | 
