Helium sparging

Helium sparging is a simple technique a helium tank is connected to the solvent reservoirs of the chromatograph, and helium is bubbled into 

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Figure 5.2 A, valve, column and flow cell asseidily of a ainiaturized liquid chromatograph for use with small bore columns (Reproduced with permission from ref. 14) and B, mobile phase reservoir designed for solvent degassing by heat and helium sparging (Reproduced with permission from ref. 34. Copyright Elsevier Scientific Publishing Co.)...

For oxidative detection removal of dissolved air from the mobile phase is necessary to prevent air bubble formation at the column outlet, which disturbs the electrolysis process. Vacuum filtration usually is sufficient to remove enough air for bubble-free operation. However, air readily redissolves in the mobile phase. Continuous helium sparging is therefore the only effective degassing method for longer periods. 

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. 

Allison Trentman of the City of Lincoln, Nebraska, Water Treatment Plant Laboratory loads vials of water samples into the auto-sampler in preparation for analysis for trihalomethanes. The helium sparging tube is the vertical tube on the front of the unit on the left. 

The HPLC pump draws the mobile phase from the reservoir via vacuum action. In the process, air dissolved in the mobile phase may withdraw from the liquid and form bubbles in the flow stream unless such air is removed from the liquid in advance. Air in the flow stream is undesirable because it can cause a wide variety of problems, such as poor pump performance or poor detector response. Removing air from the mobile phase, called degassing, in advance of the chromatography is a routine matter, however, and can be done in one of several ways 1) helium sparging, 2) ultrasonic agitation, 3) drawing a vacuum over the surface of the liquid, or 4) a combination of numbers 2 and 3. 

Helium sparging refers to the vigorous bubbling of helium gas through the mobile phase. This can be done while it is contained in the reservoir by using a metal bubbler with tubing attached to a cylinder... 

A purge-and-trap procedure is one in which a volatile analyte is purged from solvent by helium sparging and trapped on a sorbent held in a cartridge through which the helium then passes. 

Helium sparging is a method for degassing a solvent consisting of a vigorous bubbling of helium gas through the solvent. 

The prednisone tablets use deaerated water as the medium. There are numerous methods for deaeration of medium (14,22). As mentioned above, there are also automated methods available. The method described in <711> uses heat, filtration, and vacuum. Helium sparging is also a typical method... 

Heat capacity change, 269 Height equivalent to a theoretical plate. 8 Helium sparge, 188 Hemodialysis, 283 Heptane, 72,76. 173 Heptanoic acid, 260 1-Heptanol, 182, 183 Herbicides, analysis by RPC, 292 Herbicides, chromatography on polar sorbents, 103 Hesperidin, 293... 

There are three common ways to deaerate a dissolution medium (1) vacuum filtration, (2) helium sparging, and (3) heating. Vacuum is commonly applied after filtration of the dissolution medium, with continued exposure of the filtrate to the low vacuum created by the aspirator (with or without heating). Potentially, the water pressure (i.e., degree of vacuum) of the water aspirator can affect this method of deaeration. Care should be taken to ensure that adequate suction has been applied. The time of exposure should be noted. 

Helium sparging is commonly used to displace the dissolved air in HPLC mobile phase. The same principle can be used for deaeration of media. The time... 

All solvents should be fully degassed by vacuum, helium sparging, or sonication prior to use. 

Helium Sparging—A solvent degassing technique in which helium gas is bubbled through solvents to displace dissolved gases before solvent mixing, compression, and pumping. 

Commonly used reversed-phase LC solvents, including water, acetonitrile, and methanol, are ideal for LC/MS. All reversed-phase solvents need to be degassed prior to LC/MS analysis to maintain the stability of ion signals. This can be achieved by sonihcation, helium sparging, or vacuum membrane degassing. When solvents of high aqueous content are to be used, the source and probe temperatures should be raised to assist desolvation in the ion source. Normal-phase solvents such as dichloromethane, hexane, toluene, and other hydrocarbons are not suitable for ESI-MS because a polar mobile phase for ionization is needed in ESI. These normal-phase solvents and their typical solutes are sufficiently volatile to be analyzed by APCI and work well with APCI-MS. 

Three methods are commonly used to degas HPLC solvents applying a vacuum, helium sparging, or using an in-line membrane degassing device. 

Mobile-phase degassing is an important step in the LC/MS experiment and can be accomplished via on-line membrane or vacuum devices, sonication, helium sparging or as part of the mobile-phase filtration step. Degassing will eliminate pump cavitation, ensure reproducible retention times and minimize possible sputtering from the ion source. 

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