Chemistry: analytical and immunological testing – Including sample preparation – Liberation or purification of sample or separation of...
Reexamination Certificate
1998-12-31
2003-04-01
Drodge, Joseph W. (Department: 1723)
Chemistry: analytical and immunological testing
Including sample preparation
Liberation or purification of sample or separation of...
C436S161000, C436S164000, C436S180000, C422S063000, C422S070000, C422S082050, C422S105000, C422S105000, C422S105000, C073S023350, C073S061550, C073S061590, C073S863240, C096S105000, C095S089000, C210S096200, C210S198200, C210S500230, C210S650000, C210S656000
Reexamination Certificate
active
06541272
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an apparatus for separation of at least one component from a fluid sample, and then analysis of the at least one component. More particularly, the present invention relates to an apparatus and method for separating and analyzing the quantities of organics, such as volatile organic compounds (VOCs) in a fluid sample such as ground water, drinking water or waste water.
BACKGROUND OF THE INVENTION
In recent years, there has been an increased awareness of the potential contamination of water with organics, which include, but are not limited to nonvolatile organic compounds, alcohols and polymers, and volatile organic compounds (VOCs) such as benzene, toluene, xylene, perchloroethylene, and trichloroethylene. Many of these contaminants in groundwater supplies have originated from the excessive and widespread use of chlorinated hydrocarbons as degreasers, leaks from underground storage tanks, leachate from municipal and industrial landfill sites, or releases in industrial effluent streams.
Methods to separate these contaminants have been developed. One such method, the purge and trap method, is a dynamic head space procedure carried out by purging the VOCs from the fluid sample with the help of an inert fluid, such as N
2
. The purged VOCs are then trapped in a material to which the VOCs reversibly adsorb. After a predetermined period of time, the VOCs are released from the trap in a concentrated form, and injected into a detector, such as a gas chromatograph or a gas chromatograph coupled to a mass spectrometer. However, this method possesses inherent limitations. In particular, cryogenic trapping of the organic contaminant is required prior to analytical analysis of the contaminate. Cryogenic trapping can result in freezing of moisture in the trap, and a decrease of the efficiency of the apparatus. Furthermore, cold spots in the plumbing of the apparatus also results in carryover problems and memory effects. Consequently, blanks must be run between fluid samples.
Another method used is liquid-liquid extraction. In this method, an organic solvent in which the organic is very soluble, is mixed with the fluid having the VOC contaminant. During this mixing, the organic becomes solubilized in the organic solvent, and thus is removed from the fluid. However, this method also contains inherent limitations. Initially, it involves the use organic solvent. Such solvents are themselves hazardous waste, which are very expensive to dispose of after use. Another potential problem with this method involves replacement costs for replacing solvent containing solubilized organics, which is discarded.
Membrane extraction has also been used to remove and measure a contaminant from a fluid sample. In this method, a fluid sample containing an organic is continuously contacted with a membrane having chemical and physical properties that permits the organic to diffuse into and across the membrane, but prevents the fluid sample from diffusing across and into the membrane. As a result, the organic is separated from the fluid. Hence, this method does not require any solvents or solid phases. However, this method as generally used heretofore, possesses inherent limitations. Initially, such methods are generally used in continuous monitoring, and require large amounts of fluid sample. Hence, it is very difficult with presently known membrane extraction systems to remove the organic from a small amount of fluid sample. Furthermore, in order to obtain accurate measurements of the organics in the fluid, an equilibrium must be established in the membrane such that the amount of organic leaving the membrane and the amount entering the membrane are in a steady state. Until this steady state is achieved, measurements of the amount of organic in the fluid will be inaccurate. Moreover, in order to reach this steady state, the fluid sample must flow continuously through the feed chamber, which requires large amounts of fluid sample.
Still another drawback to this method is the lag time involved in obtaining accurate measurements. This lag time is the result of the need to equilibrate the membrane to the concentration of organics in the solution, as explained above, and the necessity of the organics to diffuse through a boundary layer of fluid formed on the surface of the membrane prior to diffusing through the membrane itself.
Accordingly, what is needed is an apparatus and method that permit separation and analysis of organics in a discreet sample of fluid, such as water, having a small volume, e.g., about 1 &mgr;l to about 1 ml, or a moderate volume, e.g. about 1 ml to about 10 ml.
What is also needed is an apparatus or method of separating and analyzing organics in a discreet fluid sample that is not dependent upon equilibration of a membrane, i.e., the reaching of a steady state of component traversing the membrane. As a result, samples of fluid with vastly different concentrations of organics can be analyzed quickly and accurately.
The citation of any reference herein should not be construed as an admission that such reference is available as “Prior Art” to the instant application.
SUMMARY OF THE INVENTION
There are provided, in accordance with the invention, a new and useful apparatus and method for separating and analyzing at least one component of a fluid sample that do not possess the shortcomings of apparatuses and methods described above. Hence, the present invention is not dependent upon equilibration of the permeation of the component through a membrane, and can analyze a fluid sample having a discreet volume, even if the volume is small (about 1 &mgr;l to about 1 ml) or medium (about 1 ml to about 10 ml) in size. As a result, the present invention offers the advantages of permitting analysis of discreet volumes of fluid samples accurately and quickly.
Broadly, the present invention extends to an apparatus for separating and analyzing at least one component of a fluid sample, the apparatus comprising a feed chamber having an entrance and an exit, a first flow means for flowing a first carrier fluid through the feed chamber, a means for injecting a pulse of fluid sample into the flow of the first carrier fluid such that the pulse of fluid sample enters the feed chamber, an exit chamber downstream from the feed chamber, at least one membrane through which the at least one component can selectively permeate, wherein the at least one membrane is located between the feed chamber and the exit chamber, and is fluid registry with the feed chamber and the exit second chamber, a detector in fluid communication with the exit chamber, wherein the detector analyzes the at least component that passes through the membrane and enters the exit chamber, and a second flow means for flowing the at least one component which passes through the at least one membrane and enters the exit chamber, to the detector.
Furthermore, the present invention extends to an apparatus for separating and analyzing at least one component of a fluid sample as described above, wherein the fluid sample comprises an aqueous solution, the at least one component comprises an organic, and the first carrier comprises a water, water with salt or other additives, organic solvents, nitrogen, carbon dioxide, argon, neon, or a combination thereof.
Numerous means are presently available to the skilled artisan to form the first flow means of the invention. A particular means having applications herein comprises a first reservoir which holds the first carrier fluid upstream from the feed chamber, and a pump connected to the first reservoir and in fluid communication therewith. The pump pumps the first carrier fluid from the first reservoir, through the entrance, and then through the exit of the feed chamber. Thus, a flow of the first carrier fluid through the feed chamber is created. Other means of forming such a flow include placing the first carrier fluid in the first reservoir under pressure, and locating a valve downstream from the first reservoir and upstream of the entrance of the feed chamber, where
Drodge Joseph W.
Klauber & Jackson
New Jersey Institute of Technology
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