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

to detect vapors covering a range of approximately C4 to C24 n-alkanes. Particles, liquids, and high mo-lecular weight compounds with high boiling points if ingested can contaminate and in some cases damage the instrument. To prevent this from occurring care should be taken to insure that

Replicate direct sample measurements (offset in x and y-directions) are shown in Figure 15 for a 100-ppm water standard at 65oC. The high degree of reproducibility at this level is shown in the inset showing a standard deviation of approximately 6% for 15 replicate measurements. Ethanol headspace measurements

Replicate direct sample measurements (offset in x and y-directions) are shown in Figure 15 for a 100-ppm water standard at 65oC. The high degree of reproducibility at this level is shown in the inset showing a standard deviation of approximately 6% for 15 replicate measurements. Ethanol headspace measurements

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

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