Patent Grant
7071000
This application is a divisional of co-pending U.S. patent application Ser. No. 09/652,489 filed Aug. 31, 2000, which issued on Mar. 8, 2005, as U.S. Pat. No. 6,864,091, the entire text of which is incorporated herein by reference.
The present invention relates generally to probes for reaction product analyzers such as scanning mass spectrometers and photothermal deflection spectrometers, and more particularly to a sampling probe for delivering reactants to substances such as catalysts and for sampling resulting reaction products.
Various conventional reaction product analyzers are used for analyzing characteristics of reaction products formed by reacting reactants. One such analyzer is a mass spectrometer. One type of spectrometer known as a scanning mass spectrometer may be used to identify the particles present in each reaction product in an array of reaction products. This type of spectrometer has a probe which delivers reactants to each substance (e.g., a catalyst) in an array of substances. The reactants are allowed to react to form reaction products and the probe draws a portion of each reaction product into an ionization chamber of the scanning mass spectrometer for analysis. Using scanning mass spectrometers, hundreds of reaction products can be analyzed over a relatively short period of time. Such scanning mass spectrometers and methods for their use are further described in U.S. Pat. No. 5,959,297, issued Sep. 29, 1999, entitled, “Mass Spectrometers and Methods for Rapid Screening of Libraries of Different Materials”, which is hereby incorporated by reference.
A photothermal deflection spectrometer is another type of reaction product analyzer used to analyze characteristics of reaction products. In photothermal spectrometers, a sample (e.g., a reaction product) is excited with optical radiation from a source such as an infrared laser. The sample absorbs some of the radiation resulting in a change in the sample temperature and density which affect other properties of the sample. Photothermal spectrometers measure the changes in the refractive index of the sample resulting from exciting it with radiation. One such photothermal spectrometer is described in U.S. Pat. No. 6,087,181, issued Jul. 11, 2000, entitled, “Sampling and Detection of Trace Gas Species by Optical Spectrography”, which is hereby incorporated by reference.
Conventional sampling probes used with product analyzers have a recessed tip which is positioned over each substance in an array of substances deposited on a substrate for delivering the reactant and drawing the reaction product. Although the tip does not touch the substrate which holds the substances, it is positioned near the substrate (e.g., within about 100 micrometers) to hold the reactants and reaction products in the recess and to physically prevent them from contaminating adjacent substances in the array. The longer the period of time the reactants are held in the recess, the longer they can react. When a gap is left between the tip and the substrate, the reaction time is generally determined by the diffusion time of the reactants from the center of the recess to its edge. A conventional scanning mass spectrometer probe has a relatively short reaction time, typically on the order of 1 millisecond to about 10 milliseconds.
Due to the inherent limitations of conventional sampling probes, reaction products from low activity reactants are difficult to detect, particularly where relatively long reaction times are required. Further, the conventional sampling probes do not entirely eliminate the potential for contamination of adjacent substances on the substrate.
Among the several objects and features of the present invention may be noted the provision of a sampling probe which significantly increases the contact time or residence time between the reactants and the substances; the provision of a sampling probe which significantly reduces the potential of contaminating adjacent substances on a substrate; and the provision of a probe which is capable of detecting reaction products from low activity reactants.
Briefly, apparatus of this invention is a sampling probe for delivering a reactant to a substance deposited on a substrate to form a reaction product and for transporting the reaction product to a product analyzer for analysis. The probe includes a tip positionable over the substance on the substrate. The probe has a recess in the tip sized and shaped for receiving at least a portion of the reaction product. The probe has a product sampling passage extending from the recess adapted for connection to the product analyzer for transporting at least the portion of the reaction product to the product analyzer. Further, the probe has a reactant delivery passage extending to an outlet positioned outside the recess for delivering reactant to the substance on the substrate to form the reaction product.
In another aspect of the invention, the probe includes a barrier surrounding the area outside the recess for reducing emission of reaction products beyond the barrier.
In yet another aspect of the present invention, the probe comprises an inner body and an outer body having an inner cavity sized and shaped for receiving the inner body. The inner body includes a tip for engaging the substrate and has a recess sized and shaped for receiving at least a portion of the reaction product. The probe also includes a reactant delivery passage and a product sampling passage.
In still another aspect of the present invention, the probe comprises a tip, a mixing chamber positioned inside the probe for mixing reactants therein, and a plurality of reactant source passages extending through the probe from a plurality of reactant sources to the mixing chamber. A reactant delivery passage extends from the mixing chamber to an outlet positioned at the tip for delivering reactants to the substance on the substrate.
In another aspect of the present invention, the probe comprises a body, a tip, a resiliently compliant element positioned between the tip and the body for permitting the tip to move relative to the body, a recess in the tip, a product sampling passage, a vent passage and a reactant delivery passage.
The present invention also includes a method for sampling reaction products. The method includes delivering a reactant through a sampling probe to contact a substance deposited on a substrate and reacting the reactant to form a reaction product. At least a portion of the reaction product is withdrawn through the sampling probe and analyzed. The sampling probe is contacted with the substrate during at least a portion of the delivering, reacting and withdrawing steps.
In another aspect of the invention, a method of present invention includes delivering a reactant through a sampling probe to contact a substance deposited on a substrate and reacting the reactant to form a reaction product. The reactant has a contact time of greater than 1 second. The method also includes the steps of withdrawing at least a portion of the reaction product through the sampling probe and analyzing the withdrawn portion of the reaction product.
Other objects and features of the present invention will be in part apparent and in part pointed out hereinafter.
Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.
Referring now to the drawings and in particular to
As further illustrated in
As illustrated in
Each of the horizontally-oriented and vertically-oriented actuator assemblies 14, 16, respectively, is substantially identical. Thus, for brevity only the vertically-oriented actuator assembly 16 shown in
As illustrated in
The probe 20 includes a product sampling passage 130 extending upward from an inlet 132 in the recess 118 through the threaded fitting 110 and outer body 104 to a tube 134 (
To prevent reactant from contaminating adjacent substances M deposited on the substrate S, a vent passage 148 is provided in the probe 20. The vent passage 148 extends from an annular cavity 150 surrounding the cavity 106 of the outer body 104 to tubes 152 (
Conventional instrumentation is also provided on the probe 20. For instance, a heater 156 (
As will be appreciated by those skilled in the art, the probe may have other embodiments without departing from the scope of the present invention. As illustrated in
The probe 170 also includes reactant source passages 192 extending through the outer body 176 from the tubes 138 (
A vent passage 200 is also provided in the probe 170. The vent passage 200 extends from an annular cavity 202 formed in the lower face of the outer body 176 to the tubes 152 (
As illustrated in
The upper piece 218 of the outer body 214 includes a product sampling passage 240 extending upward from the recess 238 to the tube 134 (
An overflow vent passage 254 extends through the outer body 214 from a cavity 256 in the body positioned above the spacer 230. Holes 258 extending through the spacer 230 between the cavity 256 and the mixing chamber 244 permit the reactants to pass through the inner body 212 and enter the overflow vent passage 254. It is envisioned that conventional instrumentation may also be provided in the outer body 214. For example, a hole 260 may be provided in the outer body 214 for receiving a thermocouple for measuring the temperature of the probe 210.
To use the reaction chamber 10 described above, solid and/or liquid substances M are deposited on a substrate S and the substrate is loaded onto the stage 18 in the enclosure 12. The horizontally-oriented actuator assemblies 14 are activated to sequentially align each of the substances M on the substrate S with the probe 20 (or 170 or 210). When one of the substances M is aligned with the probe, the vertically-oriented actuator assembly 16 is activated to lower the probe over the substance. Reactants are injected through the reactant source passages 136 (or 192 or 242) and downward through the corresponding reactant delivery passages 142 (or 196 or 246) in the probe toward the substance to contact the substance. The overflow vent passage 254 allows for higher reactant flow rates with excess reactants being vented through the vent passage 254. Significantly, this approach prevents back diffusion of product gases into the source passage, and allows the contact time (i.e., residence time) to be controlled substantially by the flow rate through the product sampling passage 240 and the recess volume. The reactants are allowed to react in the presence of the substance M on the substrate S to form a reaction product, and at least a portion of the reaction product is withdrawn through the product sampling passage 130 (or 240) to a product analyzer for analysis. In the first and second embodiments, any reactants and/or reaction products which escape from the recess 118 (or 184) are drawn through the holes 154 (or 204) in the cover 120 (or 180) and the vent passage 148 (or 200) to the facility exhaust so they do not contaminate adjacent substances M on the substrate S. Alternatively, the reactants and reaction products can be vented from the recess 238 through the interior of the inner body 212 to the vent passage 254.
Preferably, the probe 20 is used with a plurality of substances deposited in an array on the substrate S, and the steps of delivering, reacting, withdrawing, and analyzing are performed sequentially for each of the substances deposited on the substrate.
Because the inner bodies 102, 212 of the probes 20, 210 of the first and third embodiments include the compressible resilient bellows element 114, 234, the tip 116, 236 can actually contact the substrate S to improve the reaction product sampling. Although the probes 20, 210 may contact the substrate S for other lengths of time without departing from the scope of the present invention, in some preferred embodiments the probes contact the substrate for between about 10 seconds and about 2 minutes. Even though the tip 116 of the first embodiment contacts the substrate S, a perfect seal is not formed between the tip and the substrate on a molecular level. Thus, in embodiments where reactants are delivered to the tip 116 through outlets which are external to the recess 118, at least a portion of the reactants can diffuse under the tip into the recess to react in the presence of the substance M, and reaction products can be withdrawn by the probe 20. The sampling probe 20, 210 contacts the substrate S during at least a portion of the delivering, reacting and withdrawing steps. Preferably, the probe 20, 210 contacts the substrate S during the entire time the reactants are delivered to the recess 118, 238, reacted in the recess and the reaction products are withdrawn from the recess. Although the probe 170 of the second embodiment does not necessarily include a compressible tip, it can be brought very near (e.g., to within about 100 micrometers) the substrate S to improve sampling capability.
Using the touch-down probes 20, 210 of the first and third embodiments, contact times greater than about 1 second (e.g., between about 2 seconds and about 10 seconds) can be achieved. Contact time (i.e., residence time) is a function of reaction cavity volume and reactant flow rate through the cavity and as such, is likewise dependent upon probe design parameters (such as reaction cavity inlet port and outlet port geometries) and process conditions (such as fluid pressures). The residence time is equal to the reaction cavity volume divided by the reactant flow rate through the cavity. Using the probes 20, 210 of the first and third embodiments, improved contact times can be achieved, and extremely small quantities of reaction products from low activity reactants can be detected. Although the recess 118 may have other volumes without departing from the scope of the present invention, the recess of one preferred embodiment has a volume of about 10 microliters. Although the product sampling passages 130 may have other flow rates without departing from the scope of the present invention, the flow rate of the product sampling passage of one preferred embodiment is between about 1 and about 10 microliters per second. Thus, the probe 20 of one preferred embodiment has a contact time of between about 1 second and about 10 seconds.
Although the probes 20, 210 of the first and third embodiment are described as contacting the substrate S, a perfect seal is not created on a molecular level. It is envisioned that the tip 116, 236 of the probes 20, 210 can be treated with a compressibly resilient material (e.g., a synthetic rubber, quartz fiber or graphite diffusion gasket) to improve sealing capability. Alternatively, it is envisioned that the tip 116, 236 may include grooves 262 (
Although the probes of the present invention are described as being used in combination with a scanning mass spectrometer, those skilled in the art will appreciate that the probe may be used with other reaction product analyzers. For example, it is envisioned that the probes of the present invention may be used in combination with a photothermal deflection spectrometer as described in U.S. Pat. No. 6,087,181.
In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.
When introducing elements of the present invention or the preferred embodiment(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.
As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
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| Number | Date | Country | |
|---|---|---|---|
| 20030100120 A1 | May 2003 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 09652489 | Aug 2000 | US |
| Child | 10334099 | US |
