Method for measuring oxygen concentration

A method of measuring oxygen concentration in a fluid, comprising the steps of:

• (a) contacting a test fluid with a sensor composition comprising a phosphorescent substance, whose phosphorescent emission is sensitive to quenching by oxygen, admixed in an oxygen-permeable matrix, the sensor composition exhibiting a nonexponential phosphorescent emission when irradiated with light containing wavelengths strongly absorbed by the luminescent substance,
• (b) irradiating the sensor composition with light containing wavelengths strongly absorbed by the phosphorescent substance,
• (c) terminating the irradiation of step (b),
• (d) measuring the intensity of phosphorescent light emitted by the sensor composition at a plurality of times subsequent to step (c),
• (e) fitting the measured intensity values as follows:
• I(t)=A.sub.1 e.sup.-k.sbsp.1.sup.t +A.sub.2 e.sup.-k.sbsp.2.sup.t
• wherein I(t) is the measured intensity at time t, e is the exponential function, and A.sub.1, k.sub.1, A.sub.2, and k.sub.2 are fitting parameters,
• (f) determining the average decay rate of phosphorescent emission by the sensor composition, k, from the fitting parameters in step (e) as follows:
• k=(A.sub.1 k.sub.1 +A.sub.2 k.sub.2)/(A.sub.1 +A.sub.2),
• (g) determining the oxygen concentration in the test fluid by comparing the average decay rate determined in step (f) with a similarly obtained k value for at least one reference fluid of known oxygen concentration.

A method of measuring oxygen concentration in a fluid, comprising the steps of:

• (a) contacting a test fluid with a sensor composition comprising a phosphorescent substance, whose phosphorescent emission is sensitive to quenching by oxygen, admixed in an oxygen-permeable matrix, the sensor composition exhibiting a nonexponential phosphorescent emission when irradiated with light containing wavelengths strongly absorbed by the phosphorescent substance,
• (b) irradiating the sensor composition with light containing wavelengths strongly absorbed by the phosphorescent substance,
• (c) terminating the irradiation of step (b),
• (d) measuring the intensity of phosphorescent light emitted by the sensor composition at a plurality of times subsequent to step (c),
• (e) fitting the measured intensity values as follows:
• I(t)=A.sub.1 e.sup.-k.sbsp.1.sup.t +A.sub.2 e.sup.-k.sbsp.2.sup.t
• wherein I(t) is the measured intensity at time t, e is the exponential function, and A.sub.1, k.sub.1, A.sub.2, and k.sub.2 are fitting parameters,
• (f) determining the average decay time of phosphorescent emission by the sensor composition, .tau., from the fitting parameters in step (e) as follows:
• .tau.=(A.sub.1 k.sub.1.sup.-1 +A.sub.2 k.sub.2.sup.-1)/(A.sub.1 +A.sub.2),
• (g) determining the oxygen concentration in the test fluid by comparing the average decay time determined in step (f) with a similarly obtained .tau. value for at least one reference fluid of known oxygen concentration.

A method of measuring oxygen concentration in a fluid, comprising the steps of:

• (a) contacting a test fluid with a sensor composition comprising a luminescent substance, whose luminescent emission is sensitive to quenching by oxygen, admixed in an oxygen-permeable matrix, the sensor composition exhibiting a nonexponential luminescent emission when irradiated with light containing wavelengths strongly absorbed by the luminescent substance,
• (b) irradiating the sensor composition with light containing wavelengths strongly absorbed by the luminescent substance,
• (c) terminating the irradiation of step (b),
• (d) measuring the intensity of luminescent light emitted by the sensor composition at a plurality of times subsequent to step (c),
• (e) from the measured intensities in step (d), determining the slope of emission decay during the period of linear decay of luminescent emission by the sensor composition,
• (f) determining the oxygen concentration in the test fluid by comparing the slope value obtained in step (e) with a similarly obtained slope value for at least one reference fluid of known oxygen concentration.

A method of measuring oxygen concentration in a fluid, comprising the steps of:

• (a) contacting a plurality of reference fluids of known oxygen concentration with a sensor composition comprising a luminescent substance, whose luminescent emission is sensitive to quenching by oxygen, admixed in an oxygen-permeable matrix, the sensor composition exhibiting a nonexponential luminescent emission when irradiated with light containing wavelengths strongly absorbed by the luminescent substance,
• (b) irradiating the sensor composition with light containing wavelengths strongly absorbed by the luminescent substance,
• (c) terminating the irradiation of step (b),
• (d) measuring the intensity of luminescent light emitted by the sensor composition during a plurality of times subsequent to step c),
• (e) from the measured intensities in step (d), determining the intensity versus time profile of emission decay for each reference fluid during the period of linear decay of luminescent emission by the sensor composition,
• (f) contacting a test fluid of unknown oxygen concentration with the sensor composition and repeating steps (b) and (c) with the test fluid,
• (g) measuring the time it takes for the intensity of luminescent light emitted by the sensor composition subsequent to step (f) to fall to a predetermined intensity value which can be referenced against the intensity versus time profiles determined in step (e), and
• (h) determining the oxygen concentration in the test fluid by comparing the time value measured in step (g) with the intensity versus time profiles determined in step (e) for the reference fluids of known oxygen concentrations.

A method of measuring oxygen concentration in a fluid, comprising the steps of:

• (a) contacting a plurality of reference fluids of known oxygen concentration with a sensor composition comprising a luminescent substance, whose luminescent emission is sensitive to quenching by oxygen, admixed in an oxygen-permeable matrix, the sensor composition exhibiting a nonexponential luminescent emission when irradiated with light containing wavelengths strongly absorbed by the luminescent substance,
• (b) irradiating the sensor composition with light containing wavelengths strongly absorbed by the luminescent substance,
• (c) terminating the irradiation of step (b),
• (d) measuring the intensity of luminescent light emitted by the sensor composition during a plurality of times subsequent to step (c),
• (e) from the measured intensities in step (d), determining the intensity versus time profile of emission decay of each reference fluid during the period of linear decay of luminescent emission by the sensor composition,
• (f) contacting a test fluid of unknown oxygen concentration with the sensor composition and repeating steps (b) and (c) with the test fluid,
• (g) measuring the intensity of luminescent light emitted by the sensor composition at a given time interval subsequent to step (f), which time interval falls within the period of linear decay for the sensor composition, and
• (h) determining the oxygen concentration in the test fluid by comparing the intensity value measured in step (g) with the intensity versus time profiles determined in step (e) for the reference fluids of known oxygen concentrations.