METHOD AND APPARATUS FOR MEASURING OF THE CONCENTRATION OF A SUBSTANCE IN A FLUID MEDIUM
First Claim
1. A method for determining the concentration of a substance in a sample in the presence of an interfering material, comprising at least the steps of directing light from a light source through said sample, measuring the absorbance of said light at a first wavelength or range of wavelengths, at which light is absorbed by said substance and interfering material, and at a second wavelength or range of wavelengths, at which light is absorbed by said interfering material but substantially not by said substance, and deriving from said measurements the required determination of the concentration of said substance corrected for the presence of said interfering material, wherein to compensate for variations in the intensity of light emitted from said light source, measurements are made at each said wavelength(s) of the intensity of light from said light source which has not passed through said sample simultaneously with said measurements of absorbance, and the said determination of the concentration of said substance is corrected for errors resulting from said variations in emitted light intensity on the basis of said measurements of light intensity.
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Accused Products
Abstract
The invention relates to a method for determining the concentration of a substance in a sample in the presence of an interfering material by means of light absorption, and an apparatus therefore. By measuring the light absorbance at two different wavelengths the disturbing influences of interfering materials such as dust particles, dirt and bubbles may be compensated for. By also measuring the intensity of the light emitted from the light source but which has not yet passed through the measurement sample, simultaneously with the measurements of the absorbance of the light transmitted through the sample, at each wavelength measured, the true concentration may be determined by improved accuracy. The invention further relates to a method for packaging of a food product into packages, at least comprising the steps of sterilising a packaging material or packages by a sterilising medium containing a sterilising substance, filling of the sterilised packages with a food product and sealing of the packages, further comprising determining the concentration of the sterilising substance in the sterilising medium. It also relates to a machine arrangement for such packaging and filling of food products.
68 Citations
22 Claims
- 1. A method for determining the concentration of a substance in a sample in the presence of an interfering material, comprising at least the steps of directing light from a light source through said sample, measuring the absorbance of said light at a first wavelength or range of wavelengths, at which light is absorbed by said substance and interfering material, and at a second wavelength or range of wavelengths, at which light is absorbed by said interfering material but substantially not by said substance, and deriving from said measurements the required determination of the concentration of said substance corrected for the presence of said interfering material, wherein to compensate for variations in the intensity of light emitted from said light source, measurements are made at each said wavelength(s) of the intensity of light from said light source which has not passed through said sample simultaneously with said measurements of absorbance, and the said determination of the concentration of said substance is corrected for errors resulting from said variations in emitted light intensity on the basis of said measurements of light intensity.
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13. Apparatus (10) for determining the concentration of a substance in a sample (40) in the presence of an interfering material, comprising at least a light source (11) and means for directing light from the light source through said sample,
means (14) for measuring the absorbance of said light transmitted through the sample at a first wavelength or range of wavelengths, at which light is absorbed by said substance and interfering material, and (19) at a second wavelength or range of wavelengths, at which light is absorbed by said interfering material but substantially not by said substance, and means (36) for determining the concentration of said substance, on the basis of said measurements of light absorbance, which apparatus, in order to compensate for variations in the intensity of light emitted from said light source, further comprises means (26, 33) for measuring the intensity of light from said light source which has not passed through said sample at each said wavelength simultaneously with said measurements of absorbance, and means (36′ - ) for correcting said determined concentration for errors resulting from said variations in intensity of light emitted from the light source, on the basis of said measurements of light intensity.
- View Dependent Claims (14, 20)
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16. Apparatus (10) for determining the concentration of a substance absorbing UV-light at one or more first wavelength(s) of between about 220 and about 320 nm, in a fluid medium (40) containing the substance to be measured, in the presence of an interfering material, comprising at least
a) a light source (11) emitting light including said first wavelength(s) and at least one second wavelength or range of wavelength(s) of about 385 nm or longer, b) a monitoring path having the length (L) traversing the medium (40), c) means for directing the light through said medium (40) over said monitoring path, d) at least one first detector (14) being adapted to measure the intensity of the UV-light transmitted over the monitoring path at the first wavelength(s), the first detector(s) providing a first, first detector output signal (15) representing the intensity of the light, at said first wavelength(s), transmitted through a sample of the liquid or gas-phase medium (40) containing the substance to be measured as well as interfering material, and a second, first detector output signal (15′ - ) representing the intensity of the light at said first wavelength(s), transmitted through a reference sample of the liquid or gas-phase medium (40′
), containing none, or substantially less, of the substance to be measured,e) at least one second detector (19) being adapted to measure the intensity of the light transmitted over the monitoring path at the second wavelength(s), the second detector(s) providing a first, second detector output signal (22) representing the intensity of the light at said second wavelength(s), transmitted through a sample of the fluid medium (40) containing the substance to be measured as well as interfering material, and a second, second detector output signal (22′
) representing the intensity of the light at said second wavelength(s), transmitted through a reference sample of the liquid or gas-phase medium (40′
), containing none, or substantially less, of the substance to be measured, andf) computing means (36) for deriving the determined concentration of the UV-absorbing substance from the relative values of the output signals by applying the Beer-Lambert equation, which apparatus, in order to compensate for variations in the intensity of light emitted from said light source, further comprises g) at least one third detector (26) being designed to measure the intensity of the UV-light before being transmitted through the sample, at the first wavelength(s), simultaneously with the measurements by the first detector(s), h) at least one fourth detector (33) being designed to measure the intensity of the light before being transmitted through the sample, at the second wavelength(s), simultaneously with the measurements by the second detector(s), and i) computing means (36′
) for correcting said determined concentration for errors resulting from said variations in intensity of light emitted from the light source. - View Dependent Claims (17, 18, 19)
- ) representing the intensity of the light at said first wavelength(s), transmitted through a reference sample of the liquid or gas-phase medium (40′
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21. Method for packaging of a food product into packages, at least comprising the steps of sterilising a packaging material or packages by a sterilising medium containing a sterilising substance, filling of the sterilised packages with a food product and sealing of the packages, further comprising the method for determining the concentration of the sterilising substance in a sample of the sterilising medium, comprising at least the steps of
directing light from a light source through said sample, measuring the absorbance of said light at a first wavelength or range of wavelengths, at which light is absorbed by said sterilising substance, and at a second wavelength or range of wavelengths, at which light is absorbed by said interfering material but substantially not by said sterilising substance, and deriving from said measurements the required determination of the concentration of said sterilising substance corrected for the presence of said interfering material in the sterilising medium, wherein to compensate for variations in the intensity of light emitted from said light source, measurements are made at each said wavelength(s) of the intensity of light from said light source which has not passed through said sample of sterilising medium, simultaneously with said measurements of absorbance, and the said determination of the concentration of said substance is corrected for errors resulting from said variations in emitted light intensity on the basis of said measurements of light intensity.
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22. Arrangement (50;
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70;
80) for packaging of a food product into packages, at least comprising means for sterilisation of a packaging material or a formed package by a sterilising substance in a sterilising medium (60), means for filling the packages with a food product (62) and means for sealing the packages (63a;
63b), further comprising an apparatus (10) for determining the concentration of the sterilising substance in the presence of an interfering material in the sterilising medium (40;
61), which apparatus comprises at leasta light source (11) and means for directing light from the light source through a sample of said sterilising medium (40), means (14) for measuring the absorbance of said light at a first wavelength or range of wavelengths, at which light is absorbed by said sterilising substance, and (19) at a second wavelength or range of wavelengths, at which light is absorbed by said interfering material but substantially not by said sterilising substance and means (36) for determining the concentration of said substance on the basis of said measurements of light absorbance, which apparatus, in order to compensate for variations in the intensity of light emitted from said light source, further comprises means (26, 33) for measuring the intensity of light from said light source which has not passed through said sample, at each said wavelength simultaneously with said measurements of absorbance, and means (36′
) for correcting said determined concentration for errors resulting from said variations in intensity of light emitted from the light source, on the basis of said measurements of light intensity.
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70;
Specification