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WO1995008765A1 - Procede d'identification d'analytes - Google Patents

Procede d'identification d'analytes Download PDF

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Publication number
WO1995008765A1
WO1995008765A1 PCT/GB1993/001985 GB9301985W WO9508765A1 WO 1995008765 A1 WO1995008765 A1 WO 1995008765A1 GB 9301985 W GB9301985 W GB 9301985W WO 9508765 A1 WO9508765 A1 WO 9508765A1
Authority
WO
WIPO (PCT)
Prior art keywords
analyte
characteristic
frequency
parameters
step change
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/GB1993/001985
Other languages
English (en)
Inventor
Donald James Weir
Neville John Freeman
Iain Peter May
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BAE Systems Electronics Ltd
Original Assignee
GEC Marconi Ltd
Marconi Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to GB9219261A priority Critical patent/GB2270564B/en
Application filed by GEC Marconi Ltd, Marconi Co Ltd filed Critical GEC Marconi Ltd
Priority to EP93920982A priority patent/EP0738387B1/fr
Priority to DE69319752T priority patent/DE69319752T2/de
Priority to JP50961495A priority patent/JP3390928B2/ja
Priority to US08/617,769 priority patent/US5885844A/en
Priority to PCT/GB1993/001985 priority patent/WO1995008765A1/fr
Publication of WO1995008765A1 publication Critical patent/WO1995008765A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/02—Analysing fluids
    • G01N29/036—Analysing fluids by measuring frequency or resonance of acoustic waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/02—Analysing fluids
    • G01N29/022—Fluid sensors based on microsensors, e.g. quartz crystal-microbalance [QCM], surface acoustic wave [SAW] devices, tuning forks, cantilevers, flexural plate wave [FPW] devices
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/01—Indexing codes associated with the measuring variable
    • G01N2291/014—Resonance or resonant frequency
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/02—Indexing codes associated with the analysed material
    • G01N2291/021—Gases
    • G01N2291/0212—Binary gases
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/02—Indexing codes associated with the analysed material
    • G01N2291/022—Liquids
    • G01N2291/0222—Binary liquids
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/02—Indexing codes associated with the analysed material
    • G01N2291/025—Change of phase or condition
    • G01N2291/0256—Adsorption, desorption, surface mass change, e.g. on biosensors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/04—Wave modes and trajectories
    • G01N2291/042—Wave modes
    • G01N2291/0423—Surface waves, e.g. Rayleigh waves, Love waves

Definitions

  • This invention relates to a method of identifying fluid materials, ie analytes, and is particularly but not exclusively concerned with gaseous analytes.
  • the change in the properties of the coated device resulting from interaction with the gaseous analyte causes gain and phase changes in the response of the piezo-electric device to applied voltage. This change may be monitored by incorporating the device in an oscillator circuit and monitoring the frequency.
  • the interaction effect depends upon the nature of the sensor material, ie the coating, and the gaseous ⁇ analyte. Each sensor material will have a different response to different analytes according to the degree to which the sensor material absorbs, adsorbs, or otherwise interacts with, the analyte. An important factor in this method of identifying gaseous analytes is the degree to which the interaction effect is reversible. It is important in many applications that when the sensor is withdrawn from a test material which has caused a measurement response the measurement should revert to its original value. Instead of withdrawing the sensor the analyte concentration may be reduced by a purging process, replacing the analyte carrying gas by a carrier gas (eg nitrogen).
  • a carrier gas eg nitrogen
  • thermodynamic factor is to the effect that a low heat of reaction would generally indicate a weak interaction and a high heat of reaction great interaction 'strength'.
  • kinetic factor may be unfavourable to reversibility despite a readily reversible thermodynamic reaction.
  • Each sensor in the array may employ a sensor material such as to provide a weak chemical interaction with analytes of interest and therefore a reversible response, and to have a selectivity that is different, if only mildly different, from that of other members of the array.
  • the pattern of responses across the array reflects the nature of the analyte in a specific manner.
  • Piezo-electric chemical sensors are particularly appropriate for this approach as they are low cost, easy to fabricate with different chemical selectivities and have the potential for integrating a number of sensors on a single substrate. There is nevertheless the disadvantage of having to employ a relatively complex array rather than a single sensor.
  • An object of the present invention is therefore to provide an increased degree of selectivity, without loss of reversibility, for, both, single sensors and arrays.
  • the senor in a method of identifying an analyte using a chemical sensor which is arranged to produce an oscillatory output signal and which responds selectively to different analytes by a characteristic change in the frequency of the output signal, the sensor is exposed to a step change in the concentration of the test analyte, the sensor output frequency is measured over a period following the step change to provide a frequency-ti e characteristic, and an expression for the characteristic is derived comprising a combination of exponential functions, the parameters of the functions being together indicative of the identity of the analyte.
  • step change in the analyte concentration
  • the sensor material preferably has a weak interaction with analytes of interest, the interaction being correspondingly reversible.
  • a significant advantage of the reversibility of this method of analyte detection is that the reverse process, ie purging of the analyte gas from its carrier gas, itself produces a different set of parameters providing the basis for analysis.
  • the parameters may be determined by an iterative method which may employ the Levenburg-Marquadht algorithm.
  • Initial estimates of the parameters may be obtained by assuming that a first exponential function is exclusive to the early part of the characteristic when the response, ie the frequency response, changes rapidly and a second exponential function is exclusive to the later part of the characteristic when the response changes more slowly, and determining estimates of the first and second exponential functions from point measurements within the respective parts.
  • Further selectivity may be obtained by employing a plurality of sensors exhibiting different response characteristics for the same analyte, the parameters derived from the plurality of sensors being together indicati e of the identity of the analyte.
  • the step change in concentration of the test analyte may be an increase or a decrease. Reinforcement of the analyte identification may be achieved by using both processes, the increase in concentration being followed, after a period to obtain a stable response, by a decrease in the analyte concentration by purging for example.
  • the accompanying drawing shows the frequency response of a piezo-electric or SAW based chemical sensor, subjected to a 'step' change in the ambient concentration of a particular analyte.
  • the characteristic is considered in two parts, the early part Cf and the later part C s as will be explained.
  • the frequency is at a value f ⁇ .
  • a step change in the concentration of a test analyte is imposed. The frequency then falls asymptotically towards a lower value f 2 .
  • variable component of this frequency-time characteristic can be defined by the sum of two exponential functions. Each of these can be made to yield two parameters, so that four parameters can be obtained from a single sensor even with weak sensor /analyte interaction.
  • F(t) A - A 2 (l-exp A 3 _t) - A 4 (l-exp A 5 t) F(t) thus being a non-linear function of time, t.
  • This expression comprises a parameter Aj associated with the sensor itself and which will be constant for different coating/analyte combinations, and two exponential functions. The first of these,
  • the two exponential components F and S are characteristic of the coating/analyte combination.
  • the parameters A 2 A 3 A 4 and A 5 are therefore also characteristic of the combination and because of the extra information available from four parameters, the selectivity, ie the ability to identify the test analyte from other, similar analytes, is greatly improved as compared with the basic method of comparing the overall characteristic steady state change ⁇ - 2 «
  • the determination of the parameters A 2 - Ag is effected by an iterative approach in which the slope of F() as a function of each of the parameters is computed to determine how to alter the parameters to get a better fit on the next iteration.
  • One example of an algorithm which may be employed for this purpose is the Levenburg-Marquadht algorithm.
  • the overall fall in frequency f j to f is known from the frequency-time measurement and the transition frequency f t can be chosen within this range from trial and error and experience.
  • the transition from fast exponential dominance to slow exponential dominance, occurs desirably at about nine-tenths of the frequency fall.
  • a number of frequency readings are then taken prior to the chosen transition (ie at frequencies above f t ).
  • the frequency may be measured in various ways but it is convenient to count the cycles for fixed periods of, say, 1 second.
  • the two slopes provide the bases of their respective complete exponentials, and in particular, estimates of the parameters A 2 A 3 A 3 and A 4 , and on application of the iterative process the refined versions are produced.
  • the parameters A 2 and A are given by the resulting fast exponential and the parameters A 4 and A 5 by the slow exponential .
  • an array of sensors two or preferably more may be employed. These sensors are given different sensor material coatings which all have some affinity for the analyte in question. A set of 95/08765 four parameters is obtained from each sensor in the transition to increased analyte concentration and thus identification can be established with a high degree of confidence.
  • analyte identification process can be conducted on the basis of the purging of the analyte from the test gas in cases of weak interaction, the frequency then increasing asymptotically from f 2 to fj.
  • This further analysis gives a different four parameters Ag to Ag and thus an independent analyte detection. While such analysis on the basis of the purging of the analyte can be used to reinforce the original (increased analyte) analysis, it may also be used alone.
  • the example described employed a gaseous analyte in a gaseous test mixture. It will also be possible to employ a liquid analyte in a test liquid when the sensor is responsive, by chemical or physical interaction, to the presence of the analyte.

Landscapes

  • Physics & Mathematics (AREA)
  • Biochemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Acoustics & Sound (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analyzing Materials By The Use Of Fluid Adsorption Or Reactions (AREA)
  • Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)

Abstract

L'invention concerne un procédé d'identification d'un analyte, utilisant un capteur chimique (par exemple, un oscillateur à cristal piézo-électrique) produisant une fréquence de sortie sensible aux différentes substances à analyser se traduisant par un changement caractéristique dans la fréquence. Le capteur est exposé à une variation brusque (to) selon la concentration de l'analyte et on mesure la caractéristique de la fréquence résultante. De cette caractéristique, on dérive une expression consistant en deux fonctions exponentielles (F, S), l'une (F) dérivée de la première partie de la caractéristique de fréquence, l'autre (S) dérivée de la dernière partie. Les quatre paramètres (A2, A3, A4, A5) résultant des fonctions ainsi obtenues sont caractéristiques de l'analyte en question.
PCT/GB1993/001985 1992-09-11 1993-09-21 Procede d'identification d'analytes Ceased WO1995008765A1 (fr)

Priority Applications (6)

Application Number Priority Date Filing Date Title
GB9219261A GB2270564B (en) 1992-09-11 1992-09-11 A method of identifying analytes
EP93920982A EP0738387B1 (fr) 1993-09-21 1993-09-21 Procede d'identification d'analytes
DE69319752T DE69319752T2 (de) 1993-09-21 1993-09-21 Verfahren zur identifizierung von analyten
JP50961495A JP3390928B2 (ja) 1993-09-21 1993-09-21 分析物を識別する方法
US08/617,769 US5885844A (en) 1993-09-21 1993-09-21 Method of identifying analytes
PCT/GB1993/001985 WO1995008765A1 (fr) 1992-09-11 1993-09-21 Procede d'identification d'analytes

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9219261A GB2270564B (en) 1992-09-11 1992-09-11 A method of identifying analytes
PCT/GB1993/001985 WO1995008765A1 (fr) 1992-09-11 1993-09-21 Procede d'identification d'analytes

Publications (1)

Publication Number Publication Date
WO1995008765A1 true WO1995008765A1 (fr) 1995-03-30

Family

ID=26301601

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1993/001985 Ceased WO1995008765A1 (fr) 1992-09-11 1993-09-21 Procede d'identification d'analytes

Country Status (2)

Country Link
GB (1) GB2270564B (fr)
WO (1) WO1995008765A1 (fr)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2371362B (en) * 2001-01-18 2004-08-04 Univ Nottingham Trent Method and apparatus for monitoring atmospheric particulate matter
WO2004005907A1 (fr) * 2002-07-04 2004-01-15 Victoria Link Limited Amelioration d'un procede de detection chimique

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1983001511A1 (fr) * 1981-10-13 1983-04-28 Univ Maine Detecteur de gaz a oscillateur a onde acoustique de surface
US4895017A (en) * 1989-01-23 1990-01-23 The Boeing Company Apparatus and method for early detection and identification of dilute chemical vapors

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE434438B (sv) * 1980-02-21 1984-07-23 Gambro Engstrom Ab Anordning for detektering av forekomsten av en given gaskomponent i en gasblandning
CA1180914A (fr) * 1981-08-17 1985-01-15 James M. O'connor Capteur chimique micromecanique
GB8927567D0 (en) * 1989-12-06 1990-02-07 Gen Electric Co Plc Detection of chemicals

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1983001511A1 (fr) * 1981-10-13 1983-04-28 Univ Maine Detecteur de gaz a oscillateur a onde acoustique de surface
US4895017A (en) * 1989-01-23 1990-01-23 The Boeing Company Apparatus and method for early detection and identification of dilute chemical vapors

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
NEDERLOF ET AL.: "An automated system for testing surface acoustic wave gas sensors", REVIEW OF SCIENTIFIC INSTRUMENTS, vol. 64, no. 2, February 1993 (1993-02-01), NEW YORK, USA, pages 501 - 506, XP000349079 *
WANG ET AL.: "An ultrasonic flexural plate-wave sensor for measurement of diffusion in gels", ANALYTICAL CHEMISTRY, vol. 65, no. 11, 1 June 1993 (1993-06-01), WASHINGTON, DC, USA, pages 1639 - 1642, XP000361719 *

Also Published As

Publication number Publication date
GB2270564A (en) 1994-03-16
GB2270564B (en) 1996-09-11
GB9219261D0 (en) 1992-10-28

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