is shown to be a useful tool for quantifying the concentration of ethanol in air and water samples. How the zNose™ Quantifies the Chemistry of Aromas A simplified diagram of the zNose™ system shown in Figure 2 consists of two sections. One section uses helium

detector may experience overloading at the lowest temperature settings. Ethanol Minimum Detection Limit A measurement detection limit is defined by replicate measurements at the lowest quantifiable level. Statistically this is defined for 7 replicate measurements as 3.14 x standard deviation. Using a 1ps2a1b method, 70oC valve, 50oC inlet,

direct injections of liquid standards do not contain high molecular weight compounds and are less than 1 microliter. Similarly when sampling air in dusty environments a pre-filter should be used to prevent particles from entering the inlet of the instrument. Sampling headspace vapors above liquid samples should be

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

gas, a capillary tube (GC column) and a solid-state de¬tector. The other section consists of a heated inlet and pump, which samples ambient air. Linking the two sections is a “loop” trap, which acts as a preconcentrator when placed in the air section (sample position) and as an

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