70oC. Detecting Ethanol in Ambient Air To calibrate the instrument for detecting ethanol in air, standard vapors are first created by injecting known amounts of ethanol into a known volume of air in a tedlar bag. For example injecting 1 ?L of pure ethanol into 1000 mL of air will produce

lower limit of detectable compounds which can be analyzed by the zNose. Sensitivity is determined by the loop trap’s ability to concentrate ethanol from air samples and the ability of the SAW sensor to condense and detect it as it elutes from the GC column. To

mg of Tenax®, the breakthrough volume is relatively low and sampling times greater than 5 seconds are ineffective. The effects of system temperatures and sample time are shown in Figure 5. Use of Pre-filter with the zNose® The zNose® is a very sensitive gas chromatograph designed

of column flux, commonly referred to as a chromatogram. The chromatogram response (Figure 4) of n-alkane vapors (C6 to C14) pro¬vides a set of reference reten¬tion times. Graphi¬cally defined re¬gions, shown as red bands, pro¬vide a method dependent reference time base against which subsequent chemical responses can be

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

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