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Purge and trap unit

The arrangement of the individual components of the purge and trap unit is depicted in Rg.24-2. [Pg.525]

The purge vessel is made of Duran (Pyrex) glass [20 mm outer diameter (o.d.), 20 cm length] and accommodates a glass frit at the bottom (Schott, pore size Gl) the top S cm are widened to 40 mm o.d. to prevent bubbles entering the helium outlet. The above dimensions (ca. 50 mL internal volume) are chosen to minimize purge gas flushing time and are suitable [Pg.525]


Figure D.1 Tekmar-Dohrmann s AQUATek 70 automated purge and trap unit. (Courtesy of Tekmar-Dohrmann, Cincinnati, OH.)... Figure D.1 Tekmar-Dohrmann s AQUATek 70 automated purge and trap unit. (Courtesy of Tekmar-Dohrmann, Cincinnati, OH.)...
Fig. 24-2. Diagram of the purge and trap unit. The dashed lines indicate the Teflon-coated aluminium jacket surrounding the column. Fig. 24-2. Diagram of the purge and trap unit. The dashed lines indicate the Teflon-coated aluminium jacket surrounding the column.
Test for blanks by sampling the purge gas stream for 20 min with and without the purge and trap unit in line. The blank should be in the order of the detection limit or less (< 1 pmol), if a properly conditioned sulphur scrubber is installed, and the glassware has been cleaned and silanised as described. [Pg.528]

For calibration, microlitre amounts of a gravimetrically prepared standard solution of DMS in ethanediol are injected via the T-fitting into the helium line (see Fig. 24-1), as a sample of degassed (DMS-free) seawater is loaded into the purge vessel. This procedure provides a matrix-matched calibration and minimizes systematic errors by automatically correcting for degassing efficiency and potential DMS losses within the purge and trap unit. To avoid subsequent DMS release from particulates, the DMS-free seawater should be prepared from a filtered sample, ideally from deep water of low DMS concentration. [Pg.529]

United States Environmental Protection Agency (1986) Volatile Organic Compound in Water by Purge and Trap Capillary Column Gas Chromatography-Mass Spectrometry, Method 524.2. [Pg.309]

In the purge-and-trap procedure, vials filled to the brim with the water samples are loaded into an auto-sampler, and then when the unit is operating, samples are drawn, one by one, into a tube where helium sparging occurs. Because the THMs are volatile, the helium sparging draws them out of the samples. The helium-THM gaseous mixture then flows through a trap in which the THMs are adsorbed and concentrated. This is followed by a desorption step in which the desorbed THMs are guided to the GC column. A Hall detector is used. [Pg.342]

Purge and trap Gas flow, trap, porous polymer, thermal desorption unit, and cryofocus or solvent Liquid No Yes Good... [Pg.1075]

The Stringfellow Superfund site in California poses analytical problems similar to those encountered with most waste sites across the United States and that may be best addressed via LC/MS based methods. Most of the organic compounds in aqueous leachates from this site cannot be characterized by GC/MS based methods. Analysis of Stringfellow bedrock groundwater shows that only 0.78% of the total dissolved organic materials are identifiable via purge and trap analysis (IQ). These are compounds such as acetone, trichloroethylene etc, whose physical properties are ideally suited for GC/MS separation and confirmation. Another 33% of the dissolved organic matter is characterized as "unknown", i.e., not extractable from the aqueous samples under any pH conditions and thus not analyzed via GC. Another 66% is 4-chlorobenzene sulfonic acid (PCBSA), an extremely polar and water soluble compound that is also not suitable for GC analysis. This compound, a waste product from DDT manufacture, is known to occur at this site because of the history of disposal of "sulfuric acid waste from industrial DDT synthesis. [Pg.199]

Figure 33-6. A CDS Analytical Inc., model 6000 single unit purge and trap apparatus. Figure 33-6. A CDS Analytical Inc., model 6000 single unit purge and trap apparatus.
Analysis was performed by desorbing the organics from the traps with a Curie-point pyrolyzer unit in series with a quadrupole mass spectrometer. The data produced were similar to Py-MS data, although, quite likely, thermal desorption was taking place rather than pyrolysis. The typical mass spectrum obtained from the contaminated areas was dominated by the major ions of PCE. Table 7.5 shows the various compounds that were identified in spectra obtained from the 25 samples spaced around the contaminated area. Table 7.6 shows the compounds identified by static trapping from a particular location and by purge-and-trap GC/MS analysis of water from an adjacent well. [Pg.154]

In the dynamic headspace method, the sample is put in a thermal desorption unit in order to desorb the RS a continuous flow of a carrier gas pushes the RS into a trapping system which is refrigerated and where they are accumulated prior to analysis. Then the RS are rapidly desorbed by rapid heating and carried onto the column via the carrier gas. There are different ways to apply this technique. The arrangement when purge gas passes through the sample is often called the purge and trap technique (some other equipment uses the acronym DCI (desorption, concentration, injection)). This method is particularly useful for very low concentrations of RS as the total amount of a substance is extracted and can be applied directly to powders without need to dissolve them. The main drawback is that the dynamic headspace methods are not readily automated. ... [Pg.1136]

Purge-and-trap screening followed by off-line TD-GC-MS analysis of the collected adsorbent tubes was used to determine emissions from flame retarded polymers (in TV sets) [1011]. Volatile transformation products from additives in y-irradiated HDPE packaging were analysed by means of TD-GC-MS [1012]. Off-gassed C5-C30 polymer fractions can readily be GC analysed using a Carbo-trap 370 thermal desorption tube and a TD unit. [Pg.296]

GC chromatograph. This schematic representation shows all required components needed for operation of the system. Very specialized components can be added before the iqjector such as purge and trap or headspace analysis units. These are used to meet special sample needs. [Pg.35]


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