Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
  • G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
  • G01N33/483—Physical analysis of biological material
  • G01N33/497—Physical analysis of biological material of gaseous biological material, e.g. breath
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N1/00—Sampling; Preparing specimens for investigation
  • G01N1/02—Devices for withdrawing samples
  • G01N1/22—Devices for withdrawing samples in the gaseous state
  • G01N1/2202—Devices for withdrawing samples in the gaseous state involving separation of sample components during sampling
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
  • G01N30/02—Column chromatography
  • G01N30/04—Preparation or injection of sample to be analysed
  • G01N30/06—Preparation
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N1/00—Sampling; Preparing specimens for investigation
  • G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
  • G01N1/40—Concentrating samples
  • G01N1/405—Concentrating samples by adsorption or absorption
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
  • G01N30/02—Column chromatography
  • G01N30/88—Integrated analysis systems specially adapted therefor, not covered by a single one of the groups G01N30/04 - G01N30/86
  • G01N2030/8809—Integrated analysis systems specially adapted therefor, not covered by a single one of the groups G01N30/04 - G01N30/86 analysis specially adapted for the sample
  • G01N2030/8813—Integrated analysis systems specially adapted therefor, not covered by a single one of the groups G01N30/04 - G01N30/86 analysis specially adapted for the sample biological materials

Definitions

• the present invention relates to an apparatus and a method for analyzing a gas mixture for breath gas qualification, and more specifically for halitosis detection.
• Alveolar and intraoral breath is a distinctive gas whose chemical composition differs markedly from inspired air.
• Some gaseous compounds are either subtracted from inspired air (by degradation and/or adsorption in the body) or added to exhaled air (breath) as products of metabolism.
• Some features of this transformation have been well understood for many years: e.g. oxygen is subtracted and carbon dioxide is added by the oxidative metabolism of glucose (Phillips M., Breath tests in medicine, Scientific American 1992:267(1 ):74-79).
• Pauling et al in 1971 , employed cold trapping to concentrate volatile organic compounds (VOCs) in breath and found that normal human breath contained several hundred different VOCs in low concentrations (Pauling L.
• Breath gas analysis is a method for gaining non-invasive information on the clinical state of an individual by monitoring volatile organic compounds present in the exhaled breath.
• breath gas composition can be related to the concentration of certain compounds in blood via mathematical modeling as for example in blood alcohol testing.
• Other applications include asthma detection by exhaled nitric oxide, lung cancer detection, diabetes detection, fructose mal- absorption with hydrogen breath test, helicobacter pylori with urea breath test, or diagnosis of organ rejection.
• the most common application is the detection of halitosis related to sulphur compounds in the breath mainly due to bacterial infection in the oral cavities.
• Breath analysis can be done with various measurement methods such as gas chromatography using mass spectrometry as detection unit, but there are also simpler methods for specific purposes, such as the Halimeter (InterScan) and the breathalyzer (for example: Drager Alcotest 3000 from Drager).
• Halimeter InterScan
• Drager Alcotest 3000 from Drager for example: Drager Alcotest 3000 from Drager.
• the traditional organoleptic method for diagnosis of oral halitosis is based on smelling the exhaled air of mouth and nose separately and comparing the two. This method is widely used but not accurate.
• a halimeter detects volatile sulphide compounds with a simple appropriate sensing device without specifically separating the gaseous breath compounds. It is used in the assessment of bad breath as a complement to the traditional organoleptic measurement.
• systems based on gas chromatography have been developed (e.g. OralChroma), which separate and measure molecular levels of the three major volatile sulphur compounds in a sample of exhaled air (hydrogen sulphide, methyl mercaptan and dimethyl sulphide).
• Gas chromatography is a well-established analytical technique that is commonly used for the separation and detection of the various chemical components present in gases and low boiling point liquids. The technique is widely used in organic chemistry research, pharmaceutical development, and forensic specimen analysis.
• a gas chromatography system typically has five major components: a carrier gas; a sample injector; a gas chromatography column; a detector; and a data processing system.
• the carrier gas also referred to as the mobile phase, is a highly-pure and relatively inert gas, such as helium.
• the carrier gas flows through the column throughout the separation process.
• the sample injector introduces a precise and, typically, very small volume of the sample, in gaseous form, into the carrier gas flowing through the column.
• the gaseous sample typically includes a number of different chemical components that are intended to be separated by the gas chromatograph.
• the inside of the column is coated with a stationary phase that adsorbs the different chemical components in the sample to differing degrees. These differences in adsorption cause differing propagation delays for the chemical components as they travel down the column, thereby effecting a physical separation of the sample into its chemical components.
• the detector is located after the column and serves to detect the various chemical components in the sample as they emerge from the column at different times.
• the data processing system reads the detector and is typically able to store, process, and record the results.
• the aim of the present invention is to propose an apparatus for analyzing exhaled breath for fast halitosis diagnosis. Therefore the invention is devoted to the detection and identification of volatile sulphur compounds with a controlled short measurement time and clear separation.
• an apparatus for separating specific chemical compounds such as volatile sulphur compounds (VSC) in a gas mixture comprises a line for delivering pressure controlled carrier gas, an exchangeable chamber for breath sample collection, an automatic system for the breath sample injection and a separation capillary column allowing the gaseous compounds to be selectively detected at the capillary outlet using a semiconductor gas sensor.
• the invention aims at providing a portable gas analysis system based on the principle of gas chromatography but comprising of modules tailored towards the rapid and specific detection of compounds characteristic for halitosis.
• the gas sample is collected in an exchangeable sample chamber of a specific volume that can be inserted into and removed from a bypass of the line for delivering a carrier gas at a controlled constant pressure set typically between 0.15 and 0.5 bar.
• the exchangeable sample chamber may optionally function as a pre-concentrator element where the specific compounds of the gas sample can be trapped at room temperature and released by heating the pre-concentrator walls.
• the working principle consists of injecting the equally pressurized gas sample to be analyzed from the sample chamber into the continuous stream of the carrier gas such as pressurized ambient air, by way of electronically controlled valves.
• the sample is transported by the carrier gas through a temperature controlled micro-fabricated separation column that separates the gas compounds of interest over time.
• the pressure of the carrier gas, the length of the capillary column, its temperature and inner wall coating are chosen with respect to achieving a sufficient separation of the compounds of interest in the shortest possible time for the sample analysis.
• the gaseous compounds are detected at the capillary column outlet using a non- selective but highly sensitive micro-gas sensor with a fast response and recovery time.
• the compounds are then identified by automatic peak detection, the concentration being evaluated according to a specific calibration using reference gases.
• Fig 1 is a diagram of an apparatus according to the invention.
• the illustrated diagram ( Figure 1) of an apparatus according to the present invention comprises a carrier gas line (1); an exchangeable sample chamber (2); a sample injection line (3); a micro fabricated separation column with polymer coating of the inner walls (4); a gas detector (5); and a data processing system (6).
• the carrier gas line (1) supplies synthetic or ambient air at constant pressure into the system.
• the pressure in line (1) as well as the connected sample chamber (2) is typically between 0.15 to 0.5 bar, and is chosen thus, that the detection time of the specific compound to be measured falls well into the limits of the measured time.
• the pressure can be generated by a pump or the carrier gas container.
• the gas mixture to be analyzed (notably samples of exhaled breath containing sulphur compounds) is filled into a fixed volume chamber (2) which can be exchanged between two measurements after closing the 2way valve (7).
• the chamber (2) is in the simplest case a tube with a cap at each end.
• a test subject breathes directly into the tube (2), closes the tube for transport by fitting the caps.
• the tube (2) can be installed in the apparatus, as shown in figure 1.
• the inlet valve (7) is opened to pressurize the sample volume.
• the injection of the sample by line (3) into the carrier gas line (1) stream and subsequently into the capillary column (4) is electronically controlled by the 3way valve (8) which lets the sample (3) pass for a preset injection time.
• the injection time is chosen between 0.5s and 3s.
• the start of the injection time sets the beginning of the measurement time.
• the capillary column (4) is a micro-fabricated channel of a high length to cross-section ratio.
• the capillary column (4) is internally coated with a polymer such as PDMS (Polydimethylsiloxane).
• PDMS Polydimethylsiloxane
• the capillary column's (4) length, width and height are designed with respect to the specific gaseous compounds to be separated and detected within the chosen measuring time. Typically, the length is chosen between 1 to 5 m, the width between 30 to 150 m (micron) and the height between 50 to 250 ⁇ (micron).
• the gaseous compounds are detected at the capillary (4) outlet using a nonselective but highly sensitive micro-gas sensor (5) with a fast response and recovery time. The non-selectivity and high sensitivity of the gas sensor is discussed as follows:
• the semiconductor gas sensor used in the apparatus is non-selective, meaning that it is sensitive to all oxidizing or reducing gases.
• the gas sensor will detect most of VOC (Volatile Organic Compounds) of interest (i.e: VSC).
• VOC Volatile Organic Compounds
• the sensor itself is not able to distinguish compounds in a mix of VOC, which is why a pre-treatment (filter, separation via micro-column) is required. If the selectivity is obtained via the column which separates the different gas molecules, the gas semiconductor gas sensor will detect the different gaseous compounds through time separation.
• the semiconductor gas sensor is highly sensitive to the VOC of interest meaning it can detect the isolated/separated gaseous compounds in the ppb-ppm range.
• the gas sensor (5) may be a semiconductor gas sensor micro- fabricated in silicon.
• the sensor (5) is, as shown, positioned directly at the output of the capillary column (4).
• the sensor signal is recorded by the data control system (6), allowing to identify and quantify the compounds by automatic peak detection, the concentration being evaluated according to a specific calibration using reference gases combined with peak area comparative calculation;
• the overall measurement is controlled by the data processing system (6) which comprises a micro-controller for automatic control of the measurement sequence such as the sample injection, the injection and measurement time.
• the preferred embodiment of the inventive apparatus is dedicated to breath gas analysis, for halitosis diagnostics.
• the elements of the apparatus are tailored to detect specific compounds in breath such as H2S (hydrogen sulphide), CH2SH (methyl mercaptan), (CH3)2S (dimethyl sulphide), known to be markers for halitosis.

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• 2013
  • 2013-04-11 CH CH00752/13A patent/CH707875B1/fr not_active IP Right Cessation
• 2014
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  • 2014-04-04 EP EP14720693.2A patent/EP2984484B1/en active Active
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  • 2014-04-09 TW TW103112987A patent/TWI642936B/zh not_active IP Right Cessation

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