METHOD FOR DETERMINING A POTENTIAL POISONING OF A SENSOR OF AN ELECTRONIC NOSE BY A VOLATILE COMPOUND

Abstract

A method determines a potential poisoning of a sensor of an electronic nose by a volatile compound following an exposure of the sensor to a gaseous sample including at least this volatile compound. If there is poisoning, the method determines whether the sensor is still functional such that the sensor is still capable of carrying out one or a plurality of reliable measurements, or on the contrary, whether the sensor is saturated and must no longer be used. The method may be used with any type of electronic nose.

Claims

1-10. (canceled)

11. A method for determining a potential poisoning of a sensor of an electronic nose by a volatile compound following a n.sup.th exposure of the sensor to a gaseous sample comprising at least the volatile compound, n being an integer greater than or equal to 1, which comprises at least the steps of: a) eliminating the gaseous sample from the sensor after the exposure of the sensor to the gaseous sample; b) measuring a baseline B.sub.n of the sensor after eliminating the gaseous sample; c) calculating a poisoning indicator IE via formula:
IE=(B.sub.n−B.sub.n-1)−(f×U.sub.n) wherein: B.sub.n-1 is a baseline of the sensor before the exposure of the sensor to the gaseous sample; U.sub.n is an amplitude of a signal emitted by the sensor during its exposure to the gaseous sample; f is a weighting parameter; and d) comparing the poisoning indicator IE thus calculated with a threshold value S1; whereby: if IE is less than the threshold value S1, then the sensor is not poisoned; and if IE is greater than or equal to the threshold value S1, then the sensor is poisoned.

12. The method of claim 11, wherein the threshold value S1 is equal to 0.

13. The method of claim 11, wherein f is greater than 0 and less than 1.

14. The method of claim 11, which further comprises, if IE is equal to or greater than the threshold value S1, the steps of: e) calculating a functionality indicator IF of the sensor via formula: $\mathrm{IF}=\frac{B_n-B}{p}$ wherein: B is a reference baseline; p is a parameter representative of a working range of the sensor; and f) comparing the functionality indicator IF thus calculated with a threshold value S2; whereby: if IF is less than the threshold value S2, then the sensor is still functional, and if IF is greater than or equal to the threshold value S2, then the sensor is no longer functional.

15. The method of claim 14, wherein B is an initial baseline of the sensor.

16. The method of claim 14, wherein p is an upper limit of the working range of the sensor.

17. The method of claim 14, wherein the threshold value S2 ranges from 0.4 to 0.9.

18. The method of claim 11, wherein the sensor comprises a sensitive portion that is functionalised by one or more receptors capable of interacting physicochemically with the volatile compound, and wherein the receptor or receptors are selected from biological molecules and biomimetic molecules.

19. A computer program, comprising instructions that, when the program is executed by a computer, lead the computer to implement steps c) and d) of the method of claim 11.

20. An electronic nose, comprising a data processing unit configured to implement steps c) and d) of the method of claim 11.

21. The method of claim 11, wherein f is at most equal to 0.5.

22. The method of claim 11, wherein f is equal to 0.05.

23. The method of claim 14, wherein the threshold value S2 is equal to 0.7.

24. A computer program, comprising instructions that, when the program is executed by a computer, lead the computer to implement the steps c), d, e) and f) of the method of claim 14.

25. An electronic nose, comprising a data processing unit configured to implement steps c), d), e) and f) of the method of claim 14.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0067] FIG. 1A illustrates an example of the profile that the signal emitted by a front electronic nose sensor has, during and after an exposure to a gaseous sample comprising a volatile compound with which the sensor is capable of reacting, in the absence of poisoning of the sensor by the volatile compound; in this figure, the intensity of the signal, noted I and expressed in arbitrary units (au) is indicated along the ordinate axis, whereas the time, noted t, is indicated along the abscissa axis.

[0068] FIG. 1B illustrates an example of the profile that the signal emitted by a front electronic nose sensor has, during and after an exposure to a gaseous sample comprising a volatile compound with which the sensor is capable of reacting, in case of poisoning of the sensor by the volatile compound; in this figure, the intensity of the signal, noted I and expressed in arbitrary units (au) is indicated along the ordinate axis, whereas the time, noted t, is indicated along the abscissa axis.

[0069] FIG. 2 illustrates an example of the profile that the signal emitted by an electronic nose sensor has when it is subjected to a series of exposures to gaseous samples comprising a volatile compound with which the sensor is capable of reacting, in case of repeated poisoning of the sensor by the volatile compound up to the saturation of this sensor; in this figure, the intensity of the signal, noted I and expressed in arbitrary units (au) is indicated along the ordinate axis, whereas the time, noted t, is indicated along the abscissa axis.

[0070] FIG. 3 illustrates, in the form of a decision tree, an example of implementation of the method of the invention in an electronic nose.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0071] I—Poisoning and Saturation of a Sensor by a Poisonous Volatile Compound:

[0072] Reference is made firstly to FIGS. 1A and 1B that each illustrate an example of the profile that the signal emitted by a front electronic nose sensor has, during and after a n.sup.th exposure to a gaseous sample comprising a volatile compound with which the sensor is capable of reacting, n being an integer greater than or equal to 1, in the absence of poisoning of the sensor by the volatile compound for FIG. 1A and in the case of a poisoning of the sensor by the volatile compound for FIG. 1B.

[0073] In these figures, the arrows f1 indicate the start of the exposure of the sensor to the gaseous sample, for example by injection of this sample into the chamber of the electronic nose, whereas the arrows f2 indicate the start of the elimination of the gaseous sample from the chamber of the electronic nose, for example by injection of a neutral gas (ambient air, dry air, nitrogen, argon, etc.) into this chamber.

[0074] As shown in FIGS. 1A and 1B, the sensor has, before the exposure of the gaseous sample, a baseline, noted B.sub.n-1, which corresponds to the intensity of the signal that the sensor emits in the absence of any contact of its sensitive portion with a volatile compound with which it is likely to react.

[0075] The exposure of the sensor to the gaseous sample causes an immediate increase of the intensity of the signal emitted by the sensor. This intensity reaches a plateau at which it is maintained until the start of the elimination of the gaseous sample. The amplitude of the signal, noted U.sub.n, is given by the difference between the intensity of the signal at the plateau and the baseline B.sub.n-1.

[0076] Due to the elimination of the gaseous sample, the intensity of the signal emitted by the sensor drops until reaching a new baseline, noted B.sub.n.

[0077] In the absence of poisoning of the sensor by the volatile compound, the baseline B.sub.n is identical to the baseline B.sub.n-1 or, as illustrated in FIG. 1A, only differs from the baseline B.sub.n-1 by a low delta (A).

[0078] On the other hand, as illustrated in FIG. 1B, a poisoning of the sensor by the volatile compound results in a delta (A) between the baselines B.sub.n and B.sub.n-1 that is much greater than that observed in the absence of poisoning of the sensor, this Δ being able to go up to 100% of the amplitude U.sub.n of the signal emitted by the sensor during its exposure to the gaseous sample.

[0079] Reference is now made to FIG. 2 that illustrates an example of the profile that the signal emitted by an electronic nose sensor has when it is subjected to a series of exposures to gaseous samples comprising a volatile compound with which the sensor is capable of reacting, in case of repeated poisoning of the sensor by the volatile compound up to the saturation of this sensor.

[0080] In an arbitrary and purely illustrative manner, the exposures of the sensor are five in number in FIG. 2.

[0081] In this figure, the directional arrows in solid lines indicate the start of the exposures of the sensor to gaseous samples whereas the directional arrows in dotted lines indicate the start of the elimination of the gaseous samples from the chamber of the electronic nose.

[0082] The baseline that the sensor has initially, that is to say before the first exposure of the sensor, is noted B.sub.0, whereas the baseline that the sensor has after each of the five exposures is noted respectively B.sub.1, B.sub.2, B.sub.3, B.sub.4 and B.sub.5.

[0083] In a similar manner, the amplitude of the signal emitted by the sensor during each of the five exposures is noted respectively U.sub.1, U.sub.2, U.sub.3, U.sub.4 and U.sub.5.

[0084] The dotted line noted Γ indicates, for its part, the upper limit of the working range of the sensor, this working range corresponding to the interval of values of the physical quantity that must be measured by the sensor wherein the sensor is capable of providing reliable measurements.

[0085] By allocating the value 0 to the baseline B.sub.0, the sensor is considered as functional as long as the physical quantity measured varies between 0 and Γ′ or, in other terms, the signal emitted by the sensor falls within the interval [0; Γ].

[0086] As shown in FIG. 2, successive exposures of a sensor to gaseous samples comprising a poisonous volatile compound result in a progressive increase, exposure after exposure, of the baseline of the sensor with, consequently, a reduction of the amplitude of the signal emitted by the sensor during the exposures.

[0087] Thus, for example, U.sub.2 is equal to 90% of U.sub.1; U.sub.3 is equal to 60% of U.sub.1; U.sub.4 is equal to 40% of U.sub.1 whereas U.sub.5 only represents 20% of U.sub.1.

[0088] The amplitude of the signal emitted by the sensor during the first three exposures falls within the interval [0; Γ], which means that, although the sensor is poisoned (given the Δ existing between B.sub.1 and B.sub.0), it is still functional.

[0089] On the other hand, the signal emitted by the sensor during the 4.sup.th exposure leaves the interval [0; Γ], which means that the sensor is no longer functional because saturated by the poisonous volatile compound and that the measurements provided by this sensor are no longer reliable.

[0090] It is precisely to prevent a sensor and, hence, the electronic nose that comprises this sensor from providing unreliable measurements that it is proposed according to the invention: [0091] on the one hand, to determine whether a sensor is or is not poisoned by a volatile compound following an exposure to a gaseous sample comprising this volatile compound by calculating a poisoning indicator IE and by comparing this indicator with a threshold value S1; and [0092] on the other hand, in the case where it results from the preceding calculation that the sensor is poisoned, to determine whether the sensor is still functional or not by calculating a functionality indicator IF and by comparing this indicator with a threshold value S2.

[0093] II—Poisoning Indicator IE of a Sensor:

[0094] If reference is made again to FIGS. 1A and 1B, the poisoning indicator IE corresponds to the Δ between the baselines B.sub.n and B.sub.n-1 from which is subtracted the amplitude U.sub.n of a signal emitted by the sensor while it is exposed to the gaseous sample, this amplitude being weighted by a weighing parameter f.

[0095] In other terms, IE is equal to: (B.sub.n−B.sub.n-1)−(f×U.sub.n).

[0096] Thus, if IE is less than the threshold value S1, then the sensor is not poisoned whereas, if IE is greater than or equal to the threshold value S1, then the sensor is poisoned.

[0097] The threshold value S1 is preferably equal to 0.

[0098] The weighting parameter f is then positive and less than 1, advantageously at most equal to 0.5. Even better, f is equal to 0.05.

[0099] The profile shown in FIG. 1A is typically a profile for which, for a weighting parameter f of 0.05, IE is less than 0, thus marking an absence of poisoning of the sensor by the volatile compound, whereas the profile shown in FIG. 1B is typically a profile for which, with the same weighting parameter, IE is greater than 0, marking, on the contrary, a poisoning of the sensor by the volatile compound.

[0100] If reference is made to FIG. 2, the poisoning indicator IE of the sensor may be measured from the first exposure of this sensor to a gaseous sample, in which case IE is equal to: (B.sub.1−B.sub.0)−(f×U.sub.1) and, if we take f=0.05, then IE is equal to (B.sub.1−B.sub.0)−0.05U.sub.1.

[0101] III—Functionality Indicator IF of a Poisoned Sensor:

[0102] The functionality indicator IF corresponds to the Δ between the baseline B.sub.n—of which it is reminded that this concerns the baseline to which the sensor returns following an exposure to a gaseous sample—and a reference baseline, noted B, divided by a parameter, noted p, representative of the working range of the sensor.

[0103] In other terms, IF is equal to: (B.sub.n−B)/p.

[0104] Thus, if IF is less than the threshold value S2, then the sensor, although poisoned, is still functional and may still be used for at least one measurement whereas if IF is greater than or equal to the threshold value S2, then the sensor is saturated by the volatile compound and may no longer be used, at least temporarily.

[0105] The baseline B is, preferably, the initial baseline, noted B.sub.0 of the sensor.

[0106] The parameter p is, preferably, the upper limit of the working range of the sensor.

[0107] The threshold value S2 is, for its part, between 0.4 and 0.9 and, preferably equal to 0.7.

[0108] If reference is made again to FIG. 2, it is noted that, for p=Γ and S2=0.7, the functionality indicator obtained after the first exposure of the sensor to a gaseous sample, namely IF=(B.sub.1−B.sub.0)/Γ, is less than 0.7 or, in other words, at 70% of the interval [0; Γ].

[0109] The same applies for the functionality indicator obtained after the second exposure of the sensor to a gaseous sample, namely IF=(B.sub.2−B.sub.0)/Γ. The sensor is therefore still functional after this second exposure.

[0110] On the other hand, the functionality indicator obtained after the third exposure of the sensor to a gaseous sample, namely IF=(B.sub.3−B.sub.0)/Γ, is greater than 0.7, which means that the sensor is no longer capable of carrying out a new reliable measurement.

[0111] The same applies a fortiori for the functionality indicator obtained after the fourth and fifth exposures of the sensor to a gaseous sample.

[0112] IV—Diagram of One Implementation of the Method of the Invention in an Electronic Nose:

[0113] Reference is made to FIG. 3 that illustrates, in the form of a decision tree, an example of implementation of the method of the invention in an electronic nose.

[0114] The starting point of this decision tree is a measurement that has been performed by a sensor during an exposure of this sensor to a gaseous sample comprising a volatile compound with which this sensor is likely to react.

[0115] This exposure is preferably but is not necessarily the first exposure of the sensor to a gaseous sample comprising the volatile compound.

[0116] Following the measurement carried out by the sensor, the poisoning indicator IE of the sensor is calculated and compared with the threshold value S1 by the data processing unit of the electronic nose.

[0117] If IE is less than the threshold value S1, then the electronic nose indicates that the sensor is capable of carrying out a new reliable measurement.

[0118] If IE is greater than or equal to the threshold value S1, then the data processing unit of the electronic nose calculates the functionality indicator IF of the sensor and compares this indicator with the threshold value S2.

[0119] If IF is greater than or equal to the threshold value S2, then the electronic nose indicates that the sensor is no longer able to carry out reliable measurements and the sensor is inactivated and intended to be replaced.

[0120] If IF is less than the threshold value S2, then the electronic nose indicates that the sensor is capable of carrying out a new reliable measurement.

[0121] If a new measurement is carried out, then the data processing unit of the electronic nose recalculates, at the end of this measurement, the poisoning indicator IE of the sensor and compares it again with the threshold value S1 and, depending on the case, recalculates the functionality indicator IF and compares it with the threshold value S2. This diagram is reproduced as long as the electronic nose does not indicate that the sensor is no longer able to carry out a reliable measurement.

REFERENCES CITED

[0122] S. Brenet et al., Analytical Chemistry 2018, 90, 9879-9887 [0123] French patent application 3 071 061