Optical-chemical sensor

Details Optical-chemical sensor Optical-chemical sensor

2003-01-02

2004-12-28

Gakh, Yelens (Department: 1743)

Chemical apparatus and process disinfecting, deodorizing, preser

Analyzer, structured indicator, or manipulative laboratory...

Means for analyzing liquid or solid sample

C422S052000, C422S051000, C422S068100, C422S082050, C422S082060, C422S082080, C422S082110

Reexamination Certificate

active

06835351

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to an optical-chemical sensor which is suitable for the continuous and discontinuous determination by luminescence optics of the concentration of chloride in an aqueous sample and which comprises a luminescence indicator and a polymer carrying the luminescence indicator, as well as to a process for the production of such an optical-chemical sensor.
BACKGROUND OF THE INVENTION
Chloride is the mainly anionic substance of extracellular liquids in the body and plays an important role in maintaining the distribution equilibrium of water, the osmotic pressure and the equilibrium of anionic and cationic constituents. The normal values of chloride in the human blood serum are approximately 97-108 mmol/l; the total concentration of anionic substances is approximately 154 mmol/l. Pathological chloride values—of up to 170 mmol/l—are found in the case of osmotic diuresis plus insufficient water supply, when the mechanism of the thirst regulation is disturbed, in the case of nephrogenic diabetes insipidus and in the case of enteral bicarbonate losses. Minimum values—of down to 30 mmol/l—are found in the case of gastro-intestinal chloride losses and are associated with the chronic pyelonephritis (Addison's disease) and renal failure. Therefore, chloride is the halide which in clinical diagnostics has to be determined most frequently.
Besides titrimetric and photometric determination methods, which are very accurate but also involve much work, potentiometric methods with ion-selective electrodes have become generally accepted in practice. The disadvantages are the minor specificity of chloride-selective electrodes, their sensitivity to proteins and the need for a reference electrode.
Recently, a series of optical sensors having indicator systems partly working in different manners have been proposed for the chloride determination. The so-called coextraction optode (EP 0 358 991) is based on a lipophile pH indicator dye with a lipophile counterion, is very sensitive to lipophile anionic constituents of the sample and only provides useful results when the pH value is very exactly known.
It is known that both the luminescence intensity and the luminescence decay time of certain luminescence indicators are diminished by dynamic luminescence quenching of halide ions. This is expressed by the Stern-Vollmer equation:
F
0
F
=
1
+
k
q
·
τ
0
·
[
Q
]
=
1
+
K
SV
·
[
Q
]
In this equation, F
0
and F stand for the relative luminescence intensities in the absence and presence of a quencher, [Q] for the concentration of the quencher, k
q
for the bimolecular rate constant for the quenching, &tgr;
0
for the lifetime of the excited state in the absence of a quencher and K
SV
for the Stern-Vollmer quenching constant. Thus, it is possible to deduce the chloride concentration of the sample from the relative luminescence intensity and/or the luminescence decay time of the luminescence indicator.
A chloride-sensitive optode on the basis of a quinoline or acridine dye which is covalently linked to a glass surface and the luminescence of which is quenched as a function of the halide concentration was proposed in AT-B 384 891.
Chloride-sensitive luminescence indicators having quaternized heteroaromatic N atoms have a low pH cross-sensitivity and a low cross-sensitivity to physiological concentrations of disturbing ions. However, when it comes to commercial applications involving very large numbers, the disadvantages are the absorption wavelengths of <450 nm which are in the ultraviolet spectral range (not accessible with blue LEDs that are commercially available at a moderate cost) and the chemical immobilization on the surfaces of suitable transparent carrier materials, which is cumbersome in particular when dealing with large numbers.
For the investigation of the chloride transport and of regulation mechanisms in isolated membrane vesicles, reconstituted liposomes and living cells and tissues by luminescence measuring, a series of quinoline and acridine derivatives and lucigenine (a bisacridine) are commercially available (Richard P. Haughland, “Handbook of Fluorescent Probes and Research Chemicals”, 6
th
edition, pp. 577-579).
A chloride-sensitive optical-chemical sensor on the basis of a 3,6-bis(dimethylamino)-acridine being present in a polyacrylamide layer and having a lipophile aliphatic hydrocarbon chain with up to 30 C atoms is described in U.S. Pat. No. 5,691,205. This indicator can be excited by a blue light source (LED) at 488 nm.
The production of this known sensor comprises the production-at the end of a light-conducting fiber-of a thin membrane or layer consisting of polyacrylamide by photopolymerization of a monomer solution consisting of acrylamide-N,N′-methylenebis(acrylamide), riboflavin and ammonium peroxodisulfate. Subsequently, the membrane or layer is immersed into an indicator solution, the lipophile indicator diffusing into the membrane or layer. U.S. Pat. No. 5,691,205 does not give information on stability properties of that sensor, particularly the leaching property of the indicator in the case of a quite long contact with measuring liquids, such as blood.
In the case of the sensor known from U.S. Pat. No. 5,691,205, the disadvantages are, particularly with a view to the production of large numbers of constant quality, the manufacturing step of the membrane or layer by photopolymerization of a monomer solution and the covering of the membrane or layer with an indicator. With regard to a constant quality of the sensors, this step is very cumbersome.
SUMMARY OF THE INVENTION
The present invention has as its object to provide an optical-chemical sensor which is suitable for the determination by luminescence optics of the concentration of chloride in an aqueous sample and which does not have the above-indicated disadvantages. In particular, it should be possible to excite the sensor by commercially available LEDs (excitation wavelength >460 nm), to manufacture very large numbers thereof at a moderate cost and in a reproducible way and, preferably, to use it for the determination of physiological chloride concentrations.
In an optical-chemical sensor which is suitable for the continuous and discontinuous determination by luminescence optics of the concentration of chloride in an aqueous sample and which comprises a luminescence indicator and a polymer carrying the luminescence indicator, the object of the invention is achieved in that the luminescence indicator is a non-lipophile acridine or bisacridine compound and the polymer is a linear-chain hydrophile polymer soluble in an organic solvent. The term of “linear-chain” should express that the polymer is not cross-linked.
It is obvious that the polymer should not be soluble substantially in the sample, e.g. blood, sea water, salt-containing aqueous liquids.
The advantages of such a sensor for measuring chloride are
a wide dynamic measuring range, in particular in the physiologically relevant concentration range of chloride;
the high sensitivity;
the high stability and reproducibility;
the high selectivity for chloride; and
a low pH cross-sensitivity in the physiologically relevant pH-value range.
Preferably, the acridine or bisacridine compound is selected from a group comprising methylacridinium methosulfate (MAC), 4-nitrophenylbutylacridinium methosulfate (NPBA), N,N′-di-(3-sulfopropyl)-9,9-bisacridinium (SPBA), N,N′-diacetic acid ethyl ester-9,9-bisacridinium (AEBA) and lucigenine.
As polymer, ion-permeable multiple block copolymers containing acid amide and nitrile and/or acid imide and/or carboxylate groups are preferred.
For example, such a linear-chain hydrophile polymer is commercially available multiple block copolymer HYPAN, available from HYMEDIX Int. Inc., Dayton, N.J., which will be mentioned in more detail below. It is decisive that this polymer can be dissolved in an organic solvent such as DMSO, wherein it is likewise easy to evaporate the solvent after the solution has been applied to a transparent carrier

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