In addition, the solid trap/thermal desorption gas condensation method has other advantages [11-13]: larger amounts of analytes can be concentrated on a solid sorbent out of a gas matrix through active or passive sampling; the sorbent packing and attendant equipment are small in size and light weight; the trap tube is in the relative front area of the gas path, which may reduce the manual disturbance; there are many choices of sorbents for different pathology marker gas, thus a good combination of different sorbents may allow for the determination of a wide range of VOCs; the humidity interference can be decreased by hydrophobic sorbents, dry gas purge, and splitting of the sample during analysis.

With the advantages mentioned, the solid trap condensation method remains one of the most widely spread techniques for VOC analysis in practice.

Despite its advantages, however, there are some bottlenecks that need to be addressed. First, variations in the split ratio affect the mass of analytics entering the detector relative AV-951 to that loaded on the sorbent material. Second, the field samples taken either in environmental matrices, or in food, flavor, and fragrances typically contain up to hundreds of VOCs. Thus, the analyst has the difficulty of having a calibration mixture that contains all of the observed analytes.Figure 1 shows the system architecture of the pre-condensation system for the e-nose.

At first, appropriate sorbents are selected for the object gas, and then the exhaled breath is transferred through the sorbents-filled trap tube. The VOCs of exhaled breath are then kept in the Carfilzomib trap tube.

The gas flow path of the trap stage is shown by the bold line in Figure 1(a). After sampling, the trap tube is heated to desorb VOCs. The object component then flows along with inert gas into the sensor chamber. We can utilize the different Site URL List 1|]# response patterns of exhaled breath to differentiate between patients and healthy people. The gas flow graph of the thermal desorption stage is shown by the bold line in Figure 1(b).Figure 1.System layout of the pre-condensation for the e-nose. (a) Adsorption stage; (b) Desorption stage.The solid trap/thermal desorption process can be treated as a dynamic quality balance process. The sample gas passes through the solid sorbents with constant speed, and the object component is trapped by the solid sorbents. The trapping process is usually composed of three stages: mass transfer, intragranular diffusion, and physical adsorption.