Gas sampling devices

As mentioned above in Sect. 2.4.1.2.2, frequently gases are evolved during electrochemical reactions, especially at the counter electrode. Information about volume and composition of one or both of these gases can be necessary to clarify the electrochemical process. Probably small gas amounts have to be sampled. The gas sampling device in Fig. 5, made of glass. 

Fig. 5 Gas sampling device Filling with fluid VI and V2 are closed, V4, V5, and V6 are opened, V3 is opened until the device is filled completely and the fluid runs over at Ov ...

Timmer, B.H., Bomer, J.G., van Delft, K.M., Otjes, R.P., Olthuis, W., Bergveld, P., van den Berg, A., Fluorocarbon coated micromachined gas sampling device. Micro Total Analysis Systems, Proceedings 5th ytTAS Symposium, Monterey, CA, Oct. 21-25, 2001, 381-382. 

Figure 19.8 Rotary kiln reactor. 1 thermometer 2 bearing 3geartransmission 4electric furnace 5 rotary kiln 6 temperature controller 7 seal 8 tube condenser 9 filter 10 total flow meter 11 computer 12 gas sampling device 13 tar reservoir 14feed and discharge opening 15 electric motor [16]. (Reproduced with permission from Elsevier)...

Attention is once again drawn to the fact that a gas-tight syringe may also be used for dosage of the gas-chromatographic system from the septum of the gas-sampling device. 1 ml of gas is generally used as the sample volume. 

Sampling from pneumatic conveyors parallels gas sampling. The exception is that soflds loadings can be as high as 50 kg of soHds per kg of gas. Commercially available samplers extract particles directly from a transport line. Fixed position samplers are mounted directly on the pneumatic conveyor pipe. Devices are available which extract samples from the product stream by the projection of a sample tube iato the flow. Particles impact on the tube and fill the open cavity. The tube is then withdrawn, and an internal screw discharges the collected material (20). In another model, the RX Sampler (manufactured by Gustafson) (29), samples are withdrawn usiag compressed air. 

Isokinetic sampling The sampling of a gas such that the motion of the gas entering the sampling device is identical to that of the gas being sampled. 

Particle counters A manual or automatic device used to determine the particulate concentration of a given gas sample. 

Soiling index The degree of soiling of a filter paper fitted in a sampling device tluough which a contaminated gas has been passed. 

The pressure of a gas sample can be measured in a device similar to a barometer, called a manometer. Figures 4-2B and 4-2C show two types. Figure 4-2 B shows a closed-end manometer. Here the downward pressure exerted by the column of mercury is balanced by the pressure of the gas sample placed in the flask. The gas pressure is, in the example shown, 105 mm. As in the barometer, only mercury vapor is present in the right-hand tube. 

There are several types of sample introduction systems available for GC analysis. These include gas sampling valves, split and splitless injectors, on-column injection systems, programmed-temperature injectors, and concentrating devices. The sample introduction device used depends on the application. 

The simplest way to prove this hypothesis would be to find ETO in the vapor. If Tom can sample another drum with a gas-tight sampling device and get it to you, you can do IR or GC on the sample. GC on the... 

Kumar and Kuloor s device (K15) This device avoids the necessity of continuous control, and it can collect gas samples without disturbing the flow conditions in the main equipment as shown in Fig. 1. The device consists of a graduated burette (1) for collecting the bubbles and a levelling reservoir (2). The stopcock (3) at the top of (1) permits the levelling liquid to fill the burette, and thus prepare it for bubble collection. The reservoir (2) is divided into two chambers by an overflow tube (4). The outer chamber is connected to this tube by the stopcock (5). The burette and the reservoir are connected through a rubber tube. The capacity of the reservoir is about one and a half times that of the burette. 

Zero-headspace procedures involve the collection of a soil sample with immediate transfer to a container into which the sample fits exactly. The only space for gases is that within the soil pores. The volume of sample collected depends on the concentration of volatiles in the soil. It is imperative that the container employed can be interfaced directly with the gas chromatograph. Several commercial versions of zero-headspace sampling devices are available. The sample is transported to the laboratory at 4°C, where it is analyzed directly by purge-and-trap gas chromatography (EPA 5035) or other appropriate techniques, such as vacuum distillation (EPA 5032) or headspace (EPA 5021). 

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