PTFE pre-filter, shown in Figure 8, is recommended. The filter shown comes in a plastic housing with luer fittings and is easily attached to the inlet of the instrument with a simple luer adaptor. Because the filter housing is plastic inlet temperatures should always be less than
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
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
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
Temperature System sensitivity is controlled by sample preconcentration time and detector temperature. Detector sensitivity is an exponential function of detector temperature as shown in Figure 12 and maximum sensitivity is achieved with a minimum detector temperature of 0oC. At very high water vapor concentrations in the sampled air the
optimize the trapping efficiency of the loop trap system temperatures are necessarily low. Maximum SAW sensitivity is achieved by using a crystal temperature of 10oC or 0oC. A valve temperature of 70oC and an inlet temperature of 50oC are recommended. Because the loop trap contains only 1
552 and concentration as 415 ppm The zNoseŽ system response is linear over a wide range of vapor concentrations. This is clearly shown by the N-point responses obtained from a series of 1-liter tedlar bags injected with increasing amounts of ethanol as shown in Figure 11. Detector Sensitivity vs
and 10oC detector temperatures, 7-replicate measurements at 100 and 13-ppm ethanol concentrations yield MDLs of 14.1 and 5.2 ppm respectively as shown in Figure 13. . Detection of Ethanol in Water Headspace vapors from water standards (20 mL water in a 40 mL vial) were sampled directly