Apparatus and method for determining the concentration in a sample
First Claim
1. A method of determining the concentration of a constituent of a sample within a fluid carrier passing along a medium, the effective index of refraction of said medium being changed due to passage of said carrier therethrough, comprising the steps of:
- (a) obtaining an optical measurement of light that is passed through said medium containing said sample; and
(b) compensating said optical measurement by substantially nullifying effects due to a change in said effective index of refraction of said medium due to passage of said fluid carrier therethrough which results from said fluid.
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Abstract
Apparatus and method for determining the concentration of a constituent in a sample using chromatographic and optical measuring techniques. A sample containing a constituent to be analyzed is fractionated by a chromatographic column. A light beam is passed through the constituent fraction in the column, and the light absorbance (or transmittance) is measured. The fluid carrier (or solvent) eluting through the column will generally increase the transmissivity of the light passing through the column due to a difference between the indices of refraction of the carrier fluid and the chromatographic packing material. Such increased transmissivity will generally offset any decrease in the transmittance due to trace amounts of the constituent in the sample. The optical measurement is compensated to nullify such increased transmissivity, so as to allow measurement of such trace amounts of constituents.
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Citations
29 Claims
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1. A method of determining the concentration of a constituent of a sample within a fluid carrier passing along a medium, the effective index of refraction of said medium being changed due to passage of said carrier therethrough, comprising the steps of:
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(a) obtaining an optical measurement of light that is passed through said medium containing said sample; and (b) compensating said optical measurement by substantially nullifying effects due to a change in said effective index of refraction of said medium due to passage of said fluid carrier therethrough which results from said fluid. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of determining the concentration of a constituent in a fluid medium, comprising the steps of:
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(a) passing a fluid medium containing a constituent whose concentration is to be determined along a chromatographic column having an effective refractive index, said fluid medium changing said effective refractive index of said chromatographic column as it passes through said chromatographic column; (b) directing a beam of light along an optical axis and through said fluid medium passing along said chromatographic column; (c) detecting said beam of light so as to generate an output signal; and (d) compensating said output signal to compensate for any changes in said effective refractive index of said column, whereby the compensated output signal is indicative of the concentration of said constituent within said fluid medium. - View Dependent Claims (11, 12, 13, 14, 15)
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16. Apparatus for determining the concentration of a constituent within a sample, comprising:
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a chromatographic column for fractionating said sample to obtain a fraction comprising said constituent, said column having an effective refractive index; optical measuring means for obtaining a measurement of the concentration of said constituent as a function of light passing through said fraction; compensating means for compensating said measurement to substantially nullify any effect in said measurement due to a change in the effective refractive index of said column during measurement of said concentration of said constitutent. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24)
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25. Apparatus for determining the concentration of a constituent in a fluid medium, comprising:
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(a) a chromatographic column having an effective index of refraction; (b) means for passing a fluid medium containing a constituent whose concentration is to be determined through said chromatographic column, said fluid medium changing said effective index of refraction of said column; (c) means for passing a beam of light through said chromatographic column and said fluid medium; (d) means for detecting said beam of light to generate an output signal; and (e) means for compensating said output signal in respect of any change in said effective index of refraction of said chromatographic column due to passage of said fluid medium, such that said output signal is substantially a function of the concentration of said constituent within said fluid medium. - View Dependent Claims (26, 27, 28, 29)
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Specification