PORTABLE ANALYTICAL SYSTEM FOR DETECTING ORGANIC CHEMICALS IN WATER

• US 20080289397A1
• Filed: 04/21/2008
• Published: 11/27/2008
• Est. Priority Date: 04/20/2007
• Status: Active Grant

• Current Assignee: Parker Intangibles LLC (Parker-Hannifin Corporation)
• Original Assignee: Parker-Hannifin Corporation
• Inventors: Robinson, Alex, Cost, William M., Siegal, Michael P., Howell, Stephen W., Whiting, Joshua J., Hassan, Kazi Zulfiqur Ali, Mowry, Curtis D.
• Granted Patent: US 8,302,458 B2
• Time in Patent Office: Days
• US Class Current: 73/23.4
• CPC Class Codes: G01G 23/3728 with wireless means
• CPC Class Codes: G01G 3/16 measuring variations of frequency of oscillations of the body
• CPC Class Codes: G01N 2030/0095 Separation specially adapted for use outside laboratory, e.g. field sampling, portable equipments
• CPC Class Codes: G01N 2291/014 Resonance or resonant frequency
• CPC Class Codes: G01N 2291/0256 Adsorption, desorption, surface mass change, e.g. on biosensors
• CPC Class Codes: G01N 2291/0423 Surface waves, e.g. Rayleigh waves, Love waves
• CPC Class Codes: G01N 29/022 Fluid sensors based on microsensors, e.g. quartz crystal-microbalance [QCM], surface acoustic wave [SAW] devices, tuning forks, cantilevers, flexural plate wave [FPW] devices microdevices per se B81B
• CPC Class Codes: G01N 29/2462 Probes with waveguides, e.g. SAW devices
• CPC Class Codes: G01N 30/76 Acoustical detectors measurement of mechanical vibrations or ultrasonic, sonic or infrasonic waves G01H

Abstract

A portable analytical system for detecting organic chemicals in water comprising a miniature preconcentrator and a SAW detector, the latter being characterized by a nanoporous carbon coating that provides improved response compared to prior art polymer coatings, particularly when detecting low concentrations of trihalomethane chemicals, such as chloroform and bromoform.

Claims

1. A system for detecting organic compounds in water comprising:

a preconcentrator for collecting the compounds;

a gas chromatograph column for separating the compounds as desorbed from the preconcentrator; and

a surface acoustic wave detector for determining the mass of the compounds separated by the gas chromatograph.

2. A system as set forth in claim 1, wherein the surface acoustic wave detector changes its frequency depending on the mass of compound adsorbed and desorbed on a sensing surface.

3. A system as set forth in claim 2, wherein the sensing surface has a porous carbon coating.

4. A system as set forth in claim 3, wherein the porous carbon coating is a nanoporous carbon coating.

5. A system as set forth in claim 4, wherein the nanoporous carbon coating was applied by pulsed laser deposition.

6. A system as set forth in claim 5, wherein the carbon coating has a carbon density of about 0.8 to about 1.3 g/cm³ and a coating thickness of about 1 to about 3 μ

m.

7. A system as set forth in claim 4, wherein the operating frequency of the surface acoustic wave detector is greater than 10 MHz and less than 200 MHz.

8. A system as set forth in claim 4, wherein the operating frequency of the surface acoustic wave detector is greater than 50 MHz and less than 150 MHz.

9. A system as set forth in claim 4, wherein the operating frequency of the surface acoustic wave detector is about 100 MHz.

10. A system as set forth in claim 4, comprising a data acquisition device for receiving and processing a frequency output of the surface acoustic wave detector.

11. A system as set forth in claim 1, wherein the preconcentrator includes a porous polymer resin material as an adsorber.

12. A system as set forth in claim 1, wherein the preconcentrator includes one or more metal collection tubes having a diameter less than 0.20 inch OD and containing therein a dual bed including a porous polymer resin material followed by a carbon-based adsorbent resin, and a heating wire wrapped around the tube.

13. A system as set forth in claim 12, comprising flow control devices for directing flow through the collection tube in one direction during adsorption and in the reverse direction during desorption.

14. A system as set forth in claim 13, wherein the surface acoustic wave detector changes its frequency depending on the mass of compound adsorbed and desorbed on a sensing surface, and the sensing surface has a nanoporous carbon coating.

15. A system as set forth in claim 14, comprising a sample purger for purging chemicals from a sample for adsorption in the preconcentrator.

16. A system as set forth in claim 14, comprising a sample purger for purging chemicals from a sample for adsorption in the preconcentrator.

17. A portable field instrument for detecting purgeable trihalomethane compounds in water, comprising

a sample vessel wherein chemicals are purged and entrained in a carrier gas;

a preconcentrator connected to the sample purger for adsorbing the chemicals from the carrier gas;

a heater for heating the preconcentrator for desorbing the trihalomethane compounds;

a gas chromatograph column to which the desorbed compounds are passed from the preconcentrator;

a heater for heating the gas chromatograph column for causing the compounds to desorb after different retention times in the gas chromatograph column; and

a surface acoustic wave detector to which the compounds are sequentially passed from the gas chromatograph column, the frequency of the surface acoustic wave detector changing as a function of the mass of compound adsorbed and desorbed from a sensing surface of the surface acoustic wave detector, whereby the mass quantity of the compounds is measured by the change of frequency of the surface acoustic wave device.

18. A method for detecting organic compounds in water comprising:

using a preconcentrator to collect the compounds;

using a gas chromatograph column to separate the compounds as desorbed from the preconcentrator; and

using a surface acoustic wave detector to determine the mass of the compounds separated by the gas chromatograph.