super heated steam when passes through the column and strikes the surface of the SAW detector. Often this destroys the electrodes on the surface of the crystal and the detector must be replaced. To prevent high concentrations of water vapor and particles from entering the instrument an inert

heating of water samples above this can produce very high concentrations of condensable water vapor leading to the formation of droplets in the relatively cool sampling needle and loop trap. For example, water at 60oC produces a vapor concentration of 130 micrograms/milliliter and preconcentration of even 1

sensitivity to very volatile organic compounds (VVOC), a valve temperature of 70oC and an inlet temperature of 50oC works well. Although the column can be operated isothermally, better chromatography is achieved with at least a 1oC/second temperature ramping of the column. Sample times longer than 5 seconds are

ineffective due to ethanol breakthrough in the tenax filled loop trap. Detector sensitivity is an exponential function of temperature and a minimum detector temperature setting of 0oC results in maximum sensitivity. A linear response is achieved from 0 to over 3000 ppmv of ethanol. Ambient

compared and indexed. As an example, a response midway between C10 and C11 would have a retention time index of 1050. Properties of Ethanol Physical properties of ethanol are shown in Figure 5. Although it is relatively volatile it also is very soluble in water which accounts for the low

using the zNose? electronic nose or portable gas chromatograph. Even though ethanol is at the lower limit of detectable compounds, concentrations well into the low part-per-million range can be quantified with good precision and accuracy. Because ethanol is very soluble in water, headspace measurements are best

performed with water samples elevated to at least 40oC. Use of a PTFE inlet filter is recommended to prevent water droplets from forming, entering the instrument, and possibly damaging the sensitive vapor detector. A summary chart of ethanol MDL amounts is shown in Table I. For good

dependent, allow the instrument to display air concentrations as ppmv values. As an example, the ethanol response using a 415 ppmv vapor standard is compared to that of n-alkane vapors (C6-C10) using a 1ps3a1b method in Figure 10. The system software correctly displays the Kovats index of ethanol as