Optochemical sensor

Details Optochemical sensor Optochemical sensor

2001-03-12

2002-08-13

Snay, Jeffrey (Department: 1743)

Chemical apparatus and process disinfecting, deodorizing, preser

Analyzer, structured indicator, or manipulative laboratory...

Means for analyzing liquid or solid sample

C422S082080

Reexamination Certificate

active

06432363

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optochemical sensor comprised of a polymer matrix and a luminescent dye incorporated therein, whose emission capacity is variable upon excitation with an electromagnetic radiation, in particular light, by detectable substances such as gaseous or dissolved O
2
, SO
2
, H
2
O
2
, Cl
2
, nitrogen oxides, halogenated hydrocarbons, wherein the polymer matrix is formed of at least one polymer without addition of plasticizers, which polymer contains phenyl groups in its main chain, as well as a method for producing an optochemical sensor whose emission capacity is variable upon excitation with an electromagnetic radiation, in particular light, by detectable substances such as gaseous or dissolved O
2
, SO
2
, H
2
O
2
, wherein an at least 1 to 25 wt.-% solution of a polymer containing phenyl groups in its main chain is prepared in an organic solvent and the mixture is cured to form a homogenous membrane.
2. Description of the Prior Art
Sensors for measuring the concentration of defined substances or gases in solutions or solids, for instance in biological material, usually operate electromechanically and involve the drawback that, in quantitatively detecting the gas to be determined, they will consume a portion of the substance to be determined, thus falsifying the measuring result. In order to exclude during a measuring procedure, any change of the concentration of the substance to be measured, optochemical sensors have recently been developed, which are characterized in that they do not modify the composition of the analyte, but indicate the quantitative detection of the concentration of the substance to be detected merely by extinguishing the luminescence of the luminescent substance incorporated in the sensor with characteristic parameters such as, for instance, the luminescence intensity, the phase shift of the luminescence signal or the decay period of the luminescence being examined. The quantitative detection of the substances to be measured is feasible by comparing the luminescence signal with a calibration function, for instance, by means of an electronic data processor.
A sensor, as well as a method for producing the same, of the initially defined kind may be taken, for instance, from EP-A 0 550 424, which mentions specific polymers in which gases such as, for instance, oxygen and CO
2
are to be readily dissolvable. Other optochemical sensors of similar types are disclosed, for instance, in WO 97/11067 and EP-A 0 601 816, wherein, due to the polymers used, none of those sensors allows sterilization, in particular by applying elevated temperatures, and hence subsequent usability in biological materials.
From DE-A 33 46 810, a method and a device for determining the concentration of oxygen in a gaseous or liquid environment have become known, which are based on luminescence quenching, using the shortened service life or reduced emission intensity of certain metal complexes in the presence of oxygen for determining the content of oxygen.
Furthermore, a device for determining the concentration of oxygen in gases, liquids and tissues has become known, for instance, from DE-A 31 48 830, in which the gas concentration of the measuring sample is determined by irradiating a luminescent surface formed by a “single-grain” layer applied on a transparent substrate by means of a bonding or adhesive layer, with light of a defined wavelength, exposing said surface to the measuring sample and measuring the reduction of the light emission of said surface. However, that known device, which may be readily employed for defined measuring ranges of the oxygen content contained in the measuring probe, involves the drawback that the optochemical sensor employed cannot be purified or sterilized by chemical methods either before or after having carried out a measurement, and hence, in principle, is hardly usable in biological material and if so, to a limited extent only.
An optical sensor for monitoring the partial pressure of oxygen which operates in a manner substantially analogous to that of DE-A 31 48 830 is known also from EP-A 0 190 829, wherein, however, the optochemical sensor employed in that device is embedded in a polymer matrix containing a plasticizer such that the sensor may be used only in conjunction with substances, solutions or materials that will not dissolve out of the sensor the plasticizer incorporated in the matrix.
From WO 87/00023 are known methods for measuring the concentration of oxygen by the aid of optochemical sensors, wherein also the sensors used in those methods have the disadvantage of frequently containing plasticizers or being made of materials unable to resist thermal treatment and/or chemical treatment, so that the sensor cannot be subjected to purification and sterilization either before or after its use.
SUMMARY OF THE INVENTION
The present invention, thus, aims to provide an optochemical sensor which may be repeatedly purified and/or sterilized and, thus, may be exposed to elevated temperatures so as to be applicable for the measurement of substances to be detected, in particular in the gaseous state or in gases present in the dissolved state, in biological materials and, in particular fermenter solutions.
To solve these objects, the optochemical sensor according to the invention, departing from a sensor of the initially defined kind, is essentially characterized in that the polymer is selected from polysulfones, polyether sulfones, polyether imides and/or polyoxyphenylenes and that the polymer has a glass transition temperature of above 140° C. Since the polymer or carrier matrix is comprised of at least one pure polymer containing phenyl groups in its main chain, wherein it is provided according to the invention that the polymer is selected from polysulfones, polyether sulfones, polyether imides and/or polyoxyphenylenes, a matrix for the optochemical sensor is formed, which matrix will be sufficiently stable to be subjected to a sterilization and/or chemical purification treatment without changing its composition, mechanical, thermal and optical stabilities or any other physicochemical properties. Such a stability relative to both physicochemical purification procedures and sterilization, e.g., by means of elevated temperatures and pressures is important, in particular, in the application of the optochemical sensor according to the invention for measuring the oxygen content in biological material, and enables the sensor to be arranged, for instance, directly in a fermenter during the fermentation process, supplying continuously reproducible values during the entire period of the fermentation process without involving the risk that substances will be dissolved out of the sensor material or migrate into the fermentation broth, which cause impurities of the fermenter content and subsequently can be eliminated from the fermenter content not at all or only with great difficulties, thus constituting permanent possibly deleterious impurities, for instance, in food and semiluxuries.
The matrices proposed according to the invention, which are made of polysulfones, polyether sulfones, polyether imides and/or polyoxyphenylenes, after manufacturing and curing are sufficiently flexible to form sensor films in which luminescent dyes may be present in the dissolved state or in a homogenously distributed manner and, at the same time, are sufficiently stable to resist chemicals like those contained in solutions of biological materials or directly in biological materials and even those used for the purification and regeneration of the sensor. The polymers, furthermore, may be selectively dissolved in specific organic solvents, for instance, in order to reach a uniform distribution of the luminescence dye or luminescent colorant material within the matrix of the sensor. Moreover, a matrix formed of such a polymer is highly permeable to light, hardly exhibits any intrinsic luminescence and is sufficiently photostable, too. In addition, biocompatibility tests with sensors of the inventi

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