Method for characterizing an analyte present in a gas sample containing at least one parasitic chemical species

A method for characterising an analyte A present in a gas sample located in contact with a measuring surface of an electronic nose, the measuring surface including M sensitive sites distinct from one another, of rank m ranging from 1 to M, having receptors configured to interact by adsorption/desorption with the analyte A and with at least one parasitic chemical species P present in the gas sample, the method including the following steps:

• fluid injection, for contacting with the measuring surface:
• during a first phase Ph1, a carrier gas which may contain the parasitic species P with a concentration cP(n)i;
• then
• during a second phase Ph2, the gas sample containing the analyte A in a concentration cA(n) and the parasitic species P in a concentration cP(n)f, the value cP(n)f having a non-zero deviation ΔcP(n) from the value cP(n)i;
• determining a measurement signal S(n,m)(t) during the fluid injection step representative of interactions of the analyte A and of the parasitic species P with receptors, for each of the sensitive sites M;
• determining first signatures Su(n,m)f from the measurement signal S(n,m)(tϵPh2) associated with the gas sample, which has been corrected by a reference value S(n,m)i from the measurement signal S(n,m)(tϵPh1) associated with the carrier gas;
• determining a difference ΔcP(n) in concentration of the parasitic species P between the first phase Ph1 and the second phase Ph2;
• reiterating the preceding steps, by incrementing the rank n until N first signatures representative of interactions of the analyte A and the parasitic species P with the receptors are obtained, with N>1, the gas samples being such that the differences ΔcP(n) are different in pairs;
• forming a matrix of first signatures SuA,P, of dimensions N×M, formed from N first signatures Su(n,m)f determined for the M sensitive sites;
• and of a relative concentration vector ΔcP, of dimension N×1, from determined N differences ΔcP(n);
• determining an estimated solution {{circumflex over (k)}P|A;
• ĉA;
• {circumflex over (k)}A};
• the product of which ĉA{circumflex over (k)}AT forms a matrix of corrected signatures SucA characterising the analyte A present in the N gas samples, the estimated solution:
• minimising the cost function f=SuA,P−ΔcPkP|A−cAkAT, and
• maximising the cost function g=SuA,P−ΔcPkP|AT:
• where
• cA, kA and kP|A are variables defined as follows:
• cA is a concentration vector of analyte A, of dimension N, formed from N concentration values cA(n) of the gas samples,
• kA is an affinity vector of the analyte A, of dimension M, formed from the M values of an interaction affinity of the analyte A with the receptors of the sensitive sites,
• KP|A is is an affinity vector of the parasitic chemical species P, of dimension M, formed from the M values of an interaction affinity of the parasitic chemical species P with the receptors of the sensitive sites in the presence of the analyte A.