Optical carbon dioxide sensors

Details Optical carbon dioxide sensors Optical carbon dioxide sensors

2000-02-18

2002-01-15

Warden, Jill (Department: 1743)

Chemical apparatus and process disinfecting, deodorizing, preser

Analyzer, structured indicator, or manipulative laboratory...

Means for analyzing liquid or solid sample

C422S051000, C422S051000, C422S082050, C422S082080, C436S169000, C436S800000, C436S111000, C436S103000, C436S164000, C436S172000, C252S501100

Reexamination Certificate

active

06338822

ABSTRACT:

The present invention relates to sensors for the optical determination by fluorescence of carbon dioxide in liquid and gaseous media, which consist essentially of a carrier and a light-sensitive layer applied thereto, to light-sensitive compositions, to an process for the qualitative and quantitative optical determination by fluorescence of carbon dioxide in gaseous and liquid media, and to the use of sensors for the qualitative and quantitative determination of carbon dioxide in gaseous and liquid media.
The optical determination by fluorescence of carbon dioxide in gaseous and liquid media, such as air, flue gas, respiratory air, water, aqueous solutions and blood, is a valuable aid in the qualitative and quantitative determination of carbon dioxide in the said media, having in particular great diagnostic significance especially in the analysis of respiratory air and blood. The method is notable for its high sensitivity and specificity and is therefore used broadly in analysis and in particular in diagnostics.
It is known that many fluorescent dyes show no fluorescence or substantially diminished fluorescence in media of low polarity, such as non-polar solvents or polymers. Firstly, this behaviour prevents the use of these fluorescent dyes in light-sensitive layers, which consist essentially of a polymer and the fluorescent dye dispersed therein. On the other hand, it is just these light-sensitive layers and the sensors containing these light-sensitive layers that are especially desirable because of the simplicity of their production and their stability towards aqueous probes.
In U.S. Pat. No. 5,387,523, it is proposed that this problem is overcome by using the fluorescent dye together with quaternary onium compounds, the quaternary onium compounds being understood to be, as well as the quaternary ammonium compounds specifically described, also quaternary phosphonium compounds, such as tetrabutyl phosphonium bromide. On the other hand, it is emphasised that not all onium compounds act in the same way on the fluorescent dyes present in media of low polarity. The onium compounds with little or no activating action are for example n-hexadecyltributyl phosphonium bromide, tetrabutylammonium trifluormethyl sulphonate, tetrabutylammonium tetraphenyl borate, tetrabutylammonium hydrogen sulphate, tetrabutylphosphonium bromide and tetrabutylammonium bromide. At the same time, reference is made to the significance of the ion of opposite charge as a critical factor. Specifically mentioned active compounds are only tetrabutylammonium hydroxide, hexadecyl-trimethylammonium hydroxide, tetraethyl-ammonium hydroxide, tetramethylammonium hydroxide, benzyltrimethylammonium hydroxide and benzyltrimethylammonium methylate.
These quaternary hydroxides are indeed capable of activating the fluorescent of dyes in media of low polarity, but they have the disadvantage that, owing to the high basicity of the ion of opposite charge, they break down by Hofmann elimination into tertiary amine, 1-alkene and water, or by nucleophilic substitution they break down into tertiary amine and hydroxy compound. For this reason, sensors containing such a quaternary hydroxide together with a fluorescent dye in a polymer of low polarity have low stability. As a result of this, such sensor mixtures cannot be stored for a long period of time, and apparatus containing the sensors has to be constantly recalibrated, in order to compensate the change in sensitivity caused by the decomposition.
It has been found that sensors with good stability are obtained, the sensitivity of which remains constant over a considerable length of time, the sensors being storable for a long period of time, and apparatus containing the sensors does not have to be constantly calibrated, if a light-sensitive layer is applied to a carrier, the layer containing in addition to a polymer and a polyanionic fluorescent dye also a quaternary onium phenolate as activator.
A first object of the present invention is sensors for the optical determination by fluorescence of carbon dioxide in gaseous and liquid media, consisting essentially of a carrier and a light-sensitive layer applied thereto, which are characterised in that, in addition to a polymer and an anionic fluorescent dye, the light-sensitive layer contains a quaternary onium phenolate.
A quaternary phenolate preferably corresponds to formula I
in which X is nitrogen, phosphorus or arsenic, the radicals R
1
, R
2
, R
3
and R
4
, independently of one another, each signify straight-chain or branched, saturated or unsaturated, unsubstituted or substituted alkyl, unsubstituted or substituted aralkyl, and the radicals R
5
, R
6
, R
7
, R
8
and R
9
, independently of one another, each signify hydrogen, straight-chain or branched, saturated or unsaturated, unsubstituted or substituted alkyl, unsubstituted or substituted mono- or diarylalkyl or unsubstituted or substituted aryl, whereby only two of radicals R
1
, R
2
, R
3
and R
4
may respectively signify aryl, and 2 or 3 of radicals R
1
, R
2
, R
3
and R
4
may be linked together forming a heterocyclic ring system with 5-7 ring members in the individual rings, and whereby two adjacent radicals out of radicals R
5
, R
8
, R
7
, R
8
and R
9
may be respectively linked together forming a saturated, unsaturated or aromatic ring with 5-7 ring members which is anellated at the phenyl radical.
In formula I, X preferably signifies nitrogen.
Halogen in the context of the invention signifies fluorine, chlorine, bromine or iodine. Halogen is preferably fluorine, chlorine or bromine, and most preferably chlorine.
The expression saturated or unsaturated alkyl includes alkyl radicals with 1 to 30 carbon atoms and the corresponding alkenyl and alkinyl radicals. For the radicals R
1
, R
2
, R
3
and R
4
, alkyl signifies especially alkyl radicals with 1 to 8 carbon atoms and most preferably alkyl radicals with 1 to 6 carbon atoms, as well as the corresponding alkenyl and alkinyl radicals. For the radicals R
5
, R
6
, R
7
, R
8
and R
9
, alkyl signifies especially alkyl radicals with 1 to 10 carbon atoms and most preferably alkyl radicals with 1 to 4 carbon atoms, as well as the corresponding alkenyl and alkinyl radicals. These alkyl radicals may be mentioned by way of example: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec.-butyl, tert.-butyl, n-pentyl, 2-methylbutyl, 3-methylbutyl, 2,2-dimethylpropyl, n-hexyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 5-methylpentyl, 2-ethylbutyl, 3-ethylbutyl, n-heptyl, n-octyl, iso-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-hexadecyl, and n-octadecyl. These alkenyl radicals may be mentioned by way of example: vinyl, allyl, methallyl, 1-butenyl, 2-butenyl, 3-butenyl, 2-pentenyl, 3-pentenyl, 4-pentenyl, 2-hexenyl, 3-hexenyl, 4-hexenyl, 2-, 3-, 4-, 5- and 6-heptenyl, 2-, 3-, 4-, 5-, 6- and 7-octenyl. These alkinyl radicals may be mentioned by way of example: propargyl, 2-butinyl, 3-butinyl and 3-phenylpropargyl.
For the radicals R
1
, R
2
, R
3
and R
4
, substituted alkyl may be especially alkyl radicals which are substituted once to three times by hydroxy, halogen, cyano, C
1
-C
4
-alkoxy or C
1
-C
4
-alkoxy-carbonyl, whereby in the case of multiple substitution, the substituents may be the same or different. For the radicals R
5
, R
6
, R
7
, R
8
and R
9
, substituted alkyl may be especially alkyl radicals which are substituted once to three times by hydroxy, halogen, cyano or C
1
-C
4
-alkoxy, whereby in the case of multiple substitution, the substituents may be the same or different.
Aryl preferably signifies phenyl or naphthyl and preferably phenyl.
For the radicals R
1
, R
2
, R
3
and R
4
, substituted aryl may be especially aryl radicals which are substituted once to three times by C
1
-C
4
-alkyl, C
1
-C
4
-alkoxy, C
1
-C
4
-alkyl-C
1
-C
4
-alkoxy, phenyl-C
1
-C
4
-alkyl, halogen, halogen-C
1
-C
4
-alkyl, hydroxy, cyano or C
1
-C
4
-alkoxycarbonyl, whereby aryl preferably signifies phenyl. C
1
-C
4
-alkyl radicals are methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec.-butyl and tert

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