DOSIMETER MATERIAL FOR AMMONIA AND / OR AMINES, ITS PRODUCTION AND USE

Description

[0001] The invention relates to a dosimeter material for ammonia and / or amines, the indicator used, and methods for their production and use, in particular for quality control in foodstuffs.

[0002] In the food industry, there is a great need for routine, non-invasive determination of food shelf life and freshness. During the degradation of biological tissue, such as spoilage of animal products, protein degradation products such as amines are released into the environment in a gaseous phase. Detecting these amines can be used to determine the freshness of food and, accordingly, to indicate any changes in shelf life (spoilage, ripeness). Currently, amines can only be detected using complex laboratory analysis.

[0003] The analysis of amines in food chemistry / quality control / food monitoring generally involves complex procedures requiring extensive equipment, e.g., gas chromatography combined with mass spectroscopy. Such techniques also require complex and time-consuming sample preparation. Furthermore, trained personnel are required to operate the complex equipment. This overall costly determination of food quality means that monitoring food production can only be carried out on a random basis. Similar problems arise in both environmental and medical analysis. The food processing industry, in particular, is urgently seeking time- and cost-effective methods that allow for meaningful monitoring of the shelf life of packaged products for each individual package.

[0004] The general idea of ​​quality control in the gas phase of packaged food products is known from the prior art. For example, EP 0449798 A2 proposes a method for quality control of packaged organic substances. In this method, the organic substance is enclosed together with an optical sensor element and thus brought into contact with the gas phase between the organic substance and the packaging. Such a change in the composition of the gas phase due to decomposition of the organic substance leads to a change in the color of the sensor element, which can be visually detected. This method is also proposed for the detection of ammonia or amines, among other things. A more specific variant is the use of porphyrins, in combination with a film, as an optical sensor for amines. This is also known from the prior art.For example, the utility model DE 212010000225 U1 describes a packaging material for determining the freshness of food, which consists of a sensor material and a film, whereby the detection of ammonia and amines released during the decomposition of fish or meat can be carried out by means of porphyrins.

[0005] Various tailor-made zinc(II) and chromium(III) metalloporphyrins were used as chromophores for the colorimetric detection of amines (Heier, PC (2014) Novel metallo-porphyrin based colourimetric amine sensors and their processing via plasma enhanced chemical vapor deposition at atmospheric pressure synthesis, characterisation and mechanistic studies. Dissertation, University of Mainz). For the zinc(II) metalloporphyrin, a shift of the Soret band from 420 nm to 433 nm was observed, and for the chromium(III) metalloporphyrin, a shift of the Soret band from 435 nm to 452 nm was observed. The small absorption changes of the porphyrins used are unfavorable for use as amine sensors. Furthermore, chromium porphyrins are considered to be a health hazard, and their use in connection with food is therefore critical.

[0006] Phosphorus porphyrins with the formula porphyrin-P(V)Cl 3 are known in the prior art, which were activated by substituting the two phosphorus-bound chlorine ligands with alkoxy groups (Segawa et al., 1992. Journal of the Chemical Society, Chemical Communications 15, pp. 1066-1067). Matsumoto et al., 2015. International Journal of Photoenergy, pp. 1-12, disclose various phosphorus porphyrins with different axial phosphorus ligands for photodynamic therapy and photodynamic inactivation.

[0007] The object of the invention is to provide a dosimeter material that can be adjusted to predetermined concentrations of ammonia and / or amines without cross-sensitivities to other substances, in particular to water, that is harmless to health, and that can be evaluated visually, photometrically and / or fluorimetrically.

[0008] The object is achieved by the subject matter of the claims, in particular by a dosimeter material having the features of claim 4.

[0009] The invention also relates to the indicator according to claim 1 as an intermediate product in the production of the dosimeter material according to the invention. The subclaims specify advantageous embodiments.

[0010] The dosimeter material for ammonia and / or amines according to the invention comprises an indicator which undergoes an irreversible color change in the presence of ammonia and / or amines, and an immobilization matrix for the indicator which is permeable to ammonia and / or amines, wherein the immobilization matrix is ​​impermeable to water.

[0011] The indicator according to the invention comprises a phosphoporphyrin activated by covalent bonding to a silanol group (also referred to as silinol group) with the formula porphyrin-P(V)X 3 , where X is Cl or Br, wherein activation of the porphyrin-P(V)X 3 by a covalent bond occurs through the reaction of only one of the halogen ligands of the porphyrin-P(V)X 3 with the silanol group, preferably of silica gel. The silanol group is part of a substance which has a large number of silanol groups and has a high surface area. For example, the indicator comprises a phosphoporphyrin activated by covalent bonding to a silanol group of a substance comprising silica gel with the formula porphyrin-P(V)X 3 , where X is Cl or Br. Preferably, the indicator comprises a phosphoporphyrin activated by covalent bonding to a silanol group of silica gel having the formula Porphyrin-P(V)X 3 , where X is Cl or Br.

[0012] In phosphorus porphyrins of the type porphyrin-P(V)X 3 , where X comprises in particular the halogens Cl or Br, two halogen ligands are axially bound to the phosphorus, and a halide counterion is responsible for the charge balance of the complex.

[0013] The indicator according to the invention can in particular comprise dibromo-phosphorus-(V)-tetraphenylporphyrin bromide (TPP-P(V)Br 3 ), dichloro-phosphorus-(V)-tetratolylporphyrin chloride (TTP-P(V)Cl 3 ), dichloro-phosphorus-(V)-2,3,7,8,12,13,17,18-octaethylporphyrin chloride (OEP-P(V)Cl 3 ) or preferably dichloro-phosphorus-(V)-tetraphenylporphyrin chloride (TPP-P(V)Cl 3 ).

[0014] A dosimeter material comprising an indicator according to the invention is particularly suitable for reacting with ammonia and / or amines in the gas phase.

[0015] The dosimeter material according to the invention is further characterized in that activation of the porphyrin P(V)X 3 takes place by covalent bonding of one of the halogen ligands to a silanol group of surface-rich substances, in particular in silica gel.

[0016] According to the invention, a dosimeter material for ammonia and / or amines is preferred in which the indicator comprises dichlorophosphorus(V)tetraphenylporphyrin chloride (TPP-P(V)Cl 3 ) activated by covalent bonding to silica gel.

[0017] The inventors have shown that TPP-P(V)Cl 3 activated by covalent bonding to silica gel reacts surprisingly irreversibly with ammonia and / or amines. This reaction leads to an irreversible color change of the TPP-P(V)Cl 3 indicator. This behavior is generally observed in the reaction of phosphoporphyrin indicators with the formula porphyrin-P(V)X 3 with silanol groups. The reaction of the indicator with water also causes a color change of the indicator. Since the indicator is very sensitive to traces of moisture in the gas phase, it is necessary to avoid a possible reaction of the indicator with water for the selective detection of ammonia and / or amines. According to the invention, the indicator is incorporated into a water-impermeable immobilization matrix.

[0018] The phosphoporphyrin indicators according to the invention, including the TPP-P(V)Cl 3 indicator, react with ammonia and / or amines in a molar ratio of 1:1. Since this reaction is irreversible, the irreversible color change can be interpreted as the existing dose of ammonia and / or amines over time in the analyzed sample, especially in a gas mixture. The inventive combination of phosphoporphyrin indicator and water-impermeable immobilization matrix can thus be used as a water-insensitive dosimeter for ammonia and / or amines.

[0019] According to the invention, a color change is preferably understood to mean a change from green to red that can be qualitatively evaluated with the naked eye and, in addition, a significant wavelength shift within the absorption and fluorescence spectra - possibly with a change in the spectral shape - of the indicator material, which can be quantitatively recorded and evaluated by measurement (possibly automatically).

[0020] In order to ensure that the samples to be examined containing ammonia and / or amines can react optimally with the phosphoporphyrin indicator, in particular with the TPP-P(V)Cl 3 indicator, in the dosimeter material, the dosimeter material is available, for example, as granules and / or foil, preferably as foil.

[0021] The dosimeter material is further preferably characterized in that the immobilization matrix comprises polymers that are impermeable to water and permeable to ammonia and / or amines, in particular polystyrene and / or preferably low-density polyethylene.

[0022] The process for producing the phosphoporphyrin indicator involves activating the porphyrin P(V)X 3 by covalent bonding through a reaction of only one of the halogen ligands of the porphyrin P(V)X 3 with a silanol group of the surface-rich material, preferably silica gel. This reaction takes place at elevated temperature, preferably between 80 and 140 °C, preferably at 120 °C, and preferably for 8 to 30 hours.

[0023] A preferred method for preparing the TPP-P(V)Cl 3 indicator comprises activation of the TPP-P(V)Cl 3 by covalent bonding to silica gel through the reaction of one of the chlorine ligands of the TPP-P(V)Cl 3 with a silanol group of the silica gel.

[0024] The process for producing the dosimeter material preferably comprises mixing the indicator with the immobilization matrix, wherein the process is preferably carried out under exclusion of water, and the mixture of indicator and immobilization matrix can preferably be in the form of granules and / or foil.

[0025] The dosimeter material according to the invention can be used to detect ammonia and / or amines, whereby the color change of the indicator can preferably be detected visually. Areas of application include, for example, food quality control, medical applications such as breath gas analysis or wound healing dressings, or environmental analysis.

[0026] Further advantages, features, and possible applications of the present invention will become apparent from the following description in conjunction with the figures. They show: Fig. 1 UV / VIS spectrum of dichlorophosphorus(V)tetraphenylporphyrin chloride (TPP-P(V)Cl 3 ) in DCM. Fig. 2 Synthesis of tetraphenylporphyrin (TPP). Fig. 3 Phosphorylation of TPP. Fig. 4 Binding of TPP-P(V)Cl 3 to a silanol group on the surface of silica gel. Fig. 5 Reaction of an amine with the activated chlorine ligand of TPP-P(V)Cl 3 . Fig. 6 Color change of the indicator powder: green in the absence of amines (left) and red after reaction with amines (right). Fig. 7 Color change of the dosimeter material granules: green in the absence of amines (left) and red after reaction with amines (right). Fig. 8 Absorption (A) and fluorescence (B) spectra of the indicator before (green) and after (red) reaction with amines. Fig. 9 Change in the fluorescence lifetime of the indicator: (A) green, (B) red.

[0027] The starting material for producing the inventive indicator for ammonia and / or amines is a phosphorus porphyrin with the general formula porphyrin-P(V)X 3 , for example dichlorophosphorus-(V)-tetraphenylporphyrin chloride (TPP-P(V)Cl 3 ). This is a porphyrin substituted with phenyl residues in the meso position. Pentavalent phosphorus, which contains two axial chlorine ligands, is coordinately bonded to the aromatic ring system. Charge balancing occurs via a chloride counterion.

[0028] Phosphorus porphyrins, like other porphyrin complexes with elements of the fifth main group (arsenic, antimony, and bismuth), have the special feature that they can occur in two different oxidation states: the rather unstable +III state, which is also called hypervalent, and the stable +V oxidation state. These differ, among other things, in their absorption spectrum. Phosphorus (V) porphyrins exhibit a UV / VIS spectrum typical for porphyrins, with one Soret band and two Q bands ( Fig. 1 ).

[0029] In addition to the coordinate bond to the nitrogen atoms of the porphyrin ring and to the two axial ligands (halide, e.g. chloride), phosphorus(V) porphyrins carry a positive charge that is compensated by a halide anion, e.g. a chloride anion. The axial halide ligands can be substituted by suitable nucleophiles. Exchange by halogen, hydroxy, alkoxy, or aryloxy groups is known, for example. However, it is known from the literature that only both ligands are substituted in solution. In contrast, according to the invention, only one of the halide ligands of the porphyrin-P(V)X 3 , in particular only one of the chlorine ligands of the TPP-P(V)Cl 3 , is activated.

[0030] The preferred process according to the invention for producing the TPP-P(V)Cl 3 indicator comprises the following steps: a) Formation of tetraphenylporphyrin by reaction of pyrrole with benzaldehyde in boiling propionic acid: TPP-P(V)Cl 3 is first prepared in a two-step synthesis. Pyrrole reacts with benzaldehyde in boiling propionic acid in a two-hour reaction (according to Adler et al. (1967) A Simplified Synthesis for meso-Tetraphenylporphine. J. Org. Chem. 32 (2): 476) to form meso-tetraphenylporphyrin (TPP; Fig. 2 ). The TPP crystallizes with a yield of approximately 20% upon cooling. After filtration, washing with methanol, and drying at approximately 120 °C, the clean crude product can be phosphorylated. b) Formation of TPP-P(V)Cl 3 from tetraphenylporphyrin by phosphorylation of the tetraphenylporphyrin by reaction with phosphorus trichloride and phosphoryl chloride in boiling pyridine: For this purpose, TPP reacts with an excess of a 1:1 mixture of phosphorus trichloride and phosphoryl chloride in boiling pyridine ( Fig. 3). c) Removal of the pyridine: The pyridine is preferably distilled off. d) Purification of the TPP-P(V)Cl 3 : This is preferably carried out by column chromatography on aluminum oxide. e) Activation of the TPP-P(V)Cl 3 by covalent bonding to silica gel through the reaction of one of the chlorine ligands of the TPP-P(V)Cl 3 with a silanol group of the silica gel: To prepare the active indicator, the green-colored TPP-P(V)Cl 3 dissolved in dichloromethane (DCM) is mixed with silica gel under exclusion of moisture, and the solvent is slowly evaporated in a rotary evaporator. Subsequently, a chlorine ligand of the phosphoporphyrin reacts with a silanol group of the surface-rich silica gel or with a silanol group on the surface of nanoparticles, preferably at a temperature between 80 and 140 °C, preferably at 120 °C, in a drying cabinet for 8 to 30 hours ( Fig. 4 ).

[0031] Through this special reaction, the second chlorine ligand of TPP-P(V)Cl 3 is activated ( Fig. 5 ), so it can react very sensitively with traces of ammonia and / or amines. Upon activation, a reaction can occur not only with ammonia and / or amines but also with water, which is associated with a visually perceptible color change from green to red ( Fig. 6 ).

[0032] During the activation of the phosphoporphyrin, it is very likely that, due to steric hindrance, only one chlorine ligand initially reacts with a silanol group of the silica gel in a solid-phase reaction. This strongly activates the second chlorine ligand, and a surprisingly irreversible reaction with water, ammonia, and / or amines can occur.

[0033] In US7772215 "Water detection composition and water detection indicator," a phosphoporphyrin with two axial chlorine ligands is also first prepared. In most examples, the chlorine ligands are exchanged for hydroxy ligands in a further synthesis before the new phosphorus complex is adsorbed onto silica gel in the presence of calcium chloride. In one example, the phosphoporphyrin with axial chlorine ligands is directly adsorbed onto silica gel in this way. The silica gel is then dried at 100°C and can detect moisture (anhydrous silica gel is green; moist silica gel is red to reddish-brown or pink). This process can be reversed here by drying the silica gel through heating, making it reversible. The absorption of the phosphoporphyrin complex involves electrostatic interactions with the silanol groups of the silica gel. No covalent bonding with the silanol groups occurs in this case.

[0034] In contrast to US7772215, in the present invention the silanol groups of the silica gel react with the central phosphorus atom to form a covalent bond, since here the phosphorus complex with the chlorine ligands is brought into chemical reaction with the silanol groups of the silica gel at elevated temperature, preferably between 80 and 140 °C, and preferably for 8 to 30 hours. Although the silica gel-porphyrin complex of the present invention also shows a color change from green to red with water, there is no color change back from red to green upon drying (e.g., by heating). The crucial difference to US7772215 is that the water-induced color change of the indicator according to the invention is irreversible. The reason for this is that in the present invention the phosphorus porphyrin is covalently bonded to a silanol group of the silica gel, and only the second remaining chlorine ligand reacts with water.

[0035] For reliable detection of ammonia and / or amines with the dosimeter material according to the invention, the side reaction of the indicator with water, which also causes a color change from green to red and is extremely sensitive to traces of moisture in the gas phase, must be prevented. After production of the indicator, e.g. the TPP-P(V)Cl 3 indicator, it must therefore be protected from traces of moisture. At the same time, the diffusion of ammonia and / or amines and contact with the active indicator must not be prevented. By embedding the active indicator in a semipermeable matrix, i.e. an immobilization matrix permeable to ammonia and / or amines and impermeable to water, cross-sensitivity to water is excluded. The decisive factor in the present invention is therefore the embedding of the moisture-sensitive indicator in an immobilization matrix, preferably in a polymer matrix.The amine-permeable polymer not only acts as a carrier / immobilization matrix for the indicator, but also prevents a moisture-induced color change of the indicator and is thus an essential component in the function of the dosimeter material according to the invention.

[0036] Suitable immobilization matrices are polymers that are not permeable to water (including water vapor) but are permeable to ammonia and / or amines. Low-density polyethylene (LDPE; density between 0.910 and 0.940 g / cm³) is particularly suitable. Polymers such as polystyrene (PS) are also suitable as immobilization matrices. Furthermore, a polymer blend is conceivable, as long as such a multi-component system exhibits the physical properties required for an immobilization matrix according to the invention with regard to gas diffusion and water absorption.

[0037] To produce the PS-based dosimeter material, the indicator is stirred into a highly viscous solution of polystyrene in toluene and then poured into thin layers approximately 1-2 mm thick. After the toluene evaporates, a highly active film is formed. A disadvantage of this manufacturing process, however, is the potential residual solvent in the film, which could contaminate the food packaged within it. This potential toxicity can be avoided by using a film produced by thermal extrusion.

[0038] A preferred alternative to this manufacturing process is therefore thermal mixing of the indicator with the highly hydrophobic polymer LDPE, which has good permeability to ammonia and amines. LDPE is also known from the state of the art for its extremely low water absorption, while at the same time possessing high permeability to nitrogen, oxygen, carbon dioxide, as well as many odors and aromas. The green indicator powder is thermally dispersed in the polymer via extrusion. LDPE has the advantage of a low processing temperature of 160 - 220 °C. This process produces green granules. The presence of amines leads to a color change of the granules from green to red ( Fig. 7 The green granules can then be processed into a film, which also changes color from green to red in the presence of amines.

[0039] The indicator can be added to the immobilization matrix in any desired amount. Preferably, the indicator is added to the immobilization matrix in an amount just sufficient to impart sufficient color to the immobilization matrix to be visible to the naked eye. According to a particularly preferred embodiment, the indicator is added to the immobilization matrix in an amount of 0.1 to 5.0% (w / w), based on the total amount of the immobilization matrix.

[0040] By adding light-scattering additives in varying ratios to the phosphoporphyrin, sensitivity can be increased by increasing the optical contrast. Titanium oxide, in particular, which is known as a white pigment in the paint industry, improves the visibility of the visually and colorimetrically detectable color change from green to red in the indicator.

[0041] The problem of water cross-sensitivity of the indicator is solved by embedding it in the immobilization matrix: Even after several weeks of immersion in water, no moisture-induced color change is observed in LDPE dosimeter films.

[0042] The dosimeter material according to the invention exhibits selectivity for ammonia and / or amines. It exhibits particularly good response behavior with amines with a molar mass below 150 g / mol. Examples of amines within the meaning of the present invention are diethylamine, trimethylamine, triethylamine, ethanolamine, hexylamine, cadaverine, and putrescine. In cross-sensitivity tests, no color change of the dosimeter material with thiols, amino acids, alcohols, aldehydes, or ketones was observed (see Example 6).

[0043] The dosimeter material according to the invention exhibits high sensitivity to ammonia and / or amines. A colorimetrically detectable color change occurs with a sensor area of ​​one square centimeter and a film thickness of 100 µm in the range of at least 20 nmol. Through metrological evaluation, in particular of fluorescence properties, this sensitivity can be improved by at least a factor of 100. The significant change in the absorption and fluorescence spectra of the dosimeter material after reaction with ammonia and / or amines is Fig. 8 shown.

[0044] The qualitative and / or quantitative detection of ammonia and / or amines, particularly in a gas mixture, can be carried out by a method comprising the following steps: a) providing a dosimeter material according to the invention; b) interacting the ammonia and / or the amines with the dosimeter material; c) measuring a fluorescence property and / or absorption property of at least a portion of the dosimeter material.

[0045] Quantification via the absorption properties of the indicator can be carried out over the range between 490 and 530 nm or over the range 400 to 450 nm ( Fig. 8 A) .

[0046] Fluorescence, unlike absorption, is background-free, and changes in the fluorescence spectrum are much more sensitive to measurement. In the fluorescence spectrum, excitation in the wavelength range between 400 and 450 nm or multiphoton excitation in the range 700 to 800 nm results in a significant change in the maxima at 600 nm, 650 nm, and 720 nm ( Fig. 8 B) For precise quantification, the ratio of two of these maxima can be determined.

[0047] The reaction of the dosimeter material with amines also leads to a significant change in the fluorescence lifetime. Fig. 9 On the left, images with color coding for the fluorescence lifetime of the dosimeter material (A: green; B: red) are shown. The fluorescence lifetime measurements were performed using a multiphoton microscope with time-correlated single-photon detection. The black background consists of the immobilization matrix, and the embedded indicator appears as particles with a size of 20 to 90 nm. The quantitative evaluation of the color coding is shown on the right. Parallel to the color change from green to red, the fluorescence lifetime increases significantly from 1100–1300 ps to 1600–1800 ps after the indicator reacts with amines.

[0048] Biogenic amines are decarboxylation products of amino acids. Biogenic amines are ubiquitous in foodstuffs in low concentrations. Above certain concentrations, biogenic amines can adversely affect human health, causing pharmacological, physiological, and toxic effects. Their levels often increase as a result of the use of poor-quality raw materials, during controlled or spontaneous microbial fermentation, or during food spoilage. Particularly affected are foods such as fish, meat and sausage, cheese, wine, beer, sauerkraut, soy sauce, and yeast extract. For this reason, biogenic amines are particularly well-suited as chemical indicators for the hygienic quality and freshness of selected foods that are associated to some degree with fermentation or degradation.

[0049] The dosimeter material according to the invention offers the major advantage over the prior art of direct detection of potentially harmful amines. The dosimeter material can directly indicate released ammonia and / or amines through changes in color, absorption, and fluorescence properties. These changes correlate with a quantifiable change (increase) in the ammonia and / or amine concentration, allowing the condition of the samples under investigation, especially biological test materials, to be continuously and prospectively monitored.

[0050] In principle, the dosimeter material according to the invention can be used to monitor all issues involving the release of ammonia and / or amines due to spoilage, aging, or maturation. In the field of food, this applies to all products of animal origin, since after slaughter or product processing, sustained degradation processes begin that, at a certain point, affect the consumption of the food. In other cases, increased amine formation also indicates a maturation process, which can be viewed positively (e.g., in cheese maturation or herring production). In the latter cases, the dosimeter material can also be used as a maturation indicator.

[0051] Food packaging is generally impermeable to odors and aromas. The dosimeter material can be applied to the inside of the packaging, ensuring that the color change is caused only by the amines in the packaging material and not by any amines in the atmosphere. For this purpose, the packaging film should be impermeable to amines, and the indicator can be separated from the packaged product with an amine-permeable film. Sandwich films could also be used.

[0052] The color change from green to red, detectable even at traces of ammonia and / or amines, is particularly well-suited for use in smart food packaging. In smart food packaging, the dosimeter material allows for direct readings of food shelf life (green = fresh; red = no longer fresh, first signs of spoilage) from transport through retailer to the final consumer. This approach offers simple, mobile detection of ammonia and / or amines without the need for complex laboratory analysis.

[0053] Furthermore, a fast, sensitive, automated assessment of food shelf life is possible. The dosimeter material can be used in a wide variety of ways thanks to the detection of fluorescence or absorption.

[0054] The dosimeter material can therefore detect ammonia and / or amines in a way that is both simple and understandable for end users and quantifiable for industrial users. There is currently no comparable product on the intelligent packaging market with such diverse application possibilities: 1. Dosimeter for the end user

[0055] As the carrier of food labeling, packaging is an essential source of information for consumers. It therefore has a significant influence on purchasing decisions. Consumers generally have difficulty assessing the freshness of a food product wrapped in plastic film in the supermarket, as sensory analysis based on smell, touch, and appearance is only possible to a limited extent. For end consumers who need a quick statement about the shelf life of a food product while shopping, most of the assessment methods currently on the market or newly developed ones are unsuitable because they are too complicated and expensive, or contain harmful dyes. A shelf life indicator must be very cost-effective to produce and must also provide an easily recognizable signal (ideally like a traffic light: green => good condition; red => the food has changed).When purchasing pre-packaged fish or meat, the end consumer is directly informed about the freshness of the product by the color change of the dosimeter material in the packaging. 2. Dosimeters for food processing plants and food retailers

[0056] The dosimeter material is also of interest to food processing companies for checking the shelf life of packaged food. In this case, the dosimeter material does not necessarily have to be visible to the end consumer. The dosimeter material could ensure continuous monitoring throughout the entire production and transport process, as the color change can be automatically analyzed and quantified. Automated online monitoring could replace the previously common random sampling with a quick inspection of each individual package. Furthermore, food producers could use such a freshness indicator to promote the safety of their products, as the dosimeter material cannot be tampered with even through the industry-standard repackaging of the goods.

[0057] In food retail, freshness could also be quantitatively assessed, for example, by measuring fluorescence intensity with a suitable measuring device. This could also help reduce the amount of food thrown away before its critical shelf life has been reached. 3. Other applications

[0058] The dosimeter material can also be used in medical analysis. If a porphyrin-based dosimeter can be adjusted to the desired sensitivity and its temporal response modified, it can also be used in the medical sector, for example, in clinical diagnostics. In the breath gas analysis of kidney failure, the amines dimethylamine and trimethylamine, for example, play an important role. For this purpose, highly sensitive detection in the ppm range is necessary. The dosimeter material can be used as a test strip or integrated into a breath bag to improve the ability of exhaled amines to react with the film. Other medical indications associated with the formation of amines, such as in dentistry, are also conceivable. Due to the increased sensitivity and the possibility of quantitative evaluation, application in wound healing bandages ("smart bandages") is also conceivable.

[0059] Such a sensor can also be used in the field of environmental analysis, e.g. for water and soil protection.

[0060] The dosimeter material according to the invention and the corresponding method for detecting ammonia and / or amines offer numerous advantages: 1. The substances produced during spoilage (or ripening), namely ammonia and / or amines, are detected directly, without a detour, for example, via pH determination. 2. Detection takes place primarily in the gas phase, meaning the dosimeter material does not necessarily have to come into contact with the food, which enables use with a wide variety of packaging types. 3. The detection of ammonia and / or amines is very sensitive and selective; even traces of semi-volatile biogenic amines such as cadaverine and putrescine can be detected. 4. The changes in absorption and fluorescence of the indicator are far more pronounced than with other known amine indicators. Fluorescence, in particular, results in the formation of very characteristic fluorescence maxima. However, the color change from green to red, which is visible to the naked eye, is also clearly visible and interpretable. 5.The indicator reacts irreversibly with ammonia and / or amines, making it impossible to "recolor." This makes any manipulation, such as repackaging, more difficult on the way to the end user. 6. Compared to other known indicators for ammonia and / or amines, the dosimeter material is harmless to health; neither toxic nor carcinogenic effects are known. The individual components, porphyrin (e.g., TPP and TPP-P(V)Cl 3 ), silica gel, and polymers, are considered harmless to health. 7. The dosimeter material can be produced cost-effectively and would thus enable a disposable dosimeter, particularly interesting as a shelf life indicator for food packaging.

[0061] The invention is described in more detail using the following examples. Example 1: Synthesis of meso-tetraphenylporphyrin (TPP)

[0062] 100 g of benzaldehyde in 1.5 l of propionic acid are placed in a solution and brought to a boil. After cautiously adding 63 g of pyrrole dropwise, the mixture is heated under reflux for a further 2 h. After cooling and crystallization of the porphyrin, the suspension is filtered. The violet filter cake is washed first with propionic acid and then with methanol. It is then dried at approximately 120 °C until constant weight is reached. Yield: 28.3 g (19.6% of theory) Example 2: Synthesis of dichloro-phosphorus (V)-tetraphenylporphyrin chloride

[0063] 8 g of TPP are placed in 200 ml of pyridine dried over a molecular sieve under argon as a protective gas. 40 ml of a 1:1 mixture of phosphorus trichloride and phosphoryl chloride is carefully added dropwise, and the dark-red solution is heated to boiling under reflux for 4 h. After the reaction is complete, the now dark-green solution is evaporated to dryness in a rotary evaporator. The residue is taken up in a small amount of dry DCM and initially purified by chromatography with hexane / DCM 1:2 over aluminum oxide. After removing the impurities, the product can be eluted from the column with DCM mixed with approximately 1% ethanol. After evaporating the solvent in a rotary evaporator, the pure phosphorus porphyrin is obtained. Yield: 7.9 g (64.7% of theory). Example 3: Preparation of the TPP-P(V)Cl 3 indicator

[0064] 20 g of silica gel 60 (0.040 - 0.063 mm, for column chromatography) are pulverized as thoroughly as possible in an agate mortar. After drying for 24 hours at 120 °C, the silica gel is stirred into a solution of 200 mg of TPP-P(V)Cl 3 in 60 ml of dried DCM. After distilling off the solvent in a rotary evaporator, the green indicator powder is activated for 24 hours at 120 °C in a drying cabinet. The indicator is cooled and stored in a desiccator with the exclusion of moisture. Example 4: Production of the dosimeter material

[0065] In a Prism laboratory extruder, a granulate is produced from a mixture of 910 g of LDPE and 90 g of indicator powder. The extrusion temperature range is between 140 and 160 °C. The twin-screw speed is set to 250 rpm, resulting in a residence time of approximately 30 seconds. The hot plastic strand emerging from the extruder is cooled in a water bath and shredded into granules. In the next step, the green granules are further processed into film in a Collin 75D flat film extruder. The processing temperature is between 160 and 185 °C, with a residence time of approximately 3 minutes. The film emerging from the die is cooled by rollers and extruded to a thickness of 100 - 250 µm. A screw speed of 60–100 rpm generates a pressure of 150–200 bar in the extruder. If the indicator concentration is too high for the film, it can be diluted by adding pure LDPE in the second step of film production. Example 5: Reaction of the dosimeter material with ammonia, amines and water

[0066] To investigate the response of the dosimeter material, ammonia and some amines were tested with both the indicator powder and the dosimeter foil. For this purpose, approximately 10 mg of the powder, or approximately 1 cm² of the foil, was placed in a 10 ml test tube with a septum, and 5–100 µl of the gas phase was injected into the reaction vessel above the respective amine using a Hamilton syringe. The only difference between the foil and the powder is the reaction time of the color reaction. While the powder usually changes color immediately upon gas addition, the process with the foil is hindered by diffusion and can take some time (up to several hours). The advantage of the foil, however, is that cross-sensitivity to water vapor is eliminated. The foil can be stored in water for several days without changing its color. Table 1 shows the boiling point and vapor pressure of selected amines, as well as the color reaction of these amines with the indicator: +++ Color reaction after addition of a small gas phase volume (amines with high vapor pressure: > 100 hPa at 20°C); ++ Color reaction after addition of a medium gas phase volume (amines with medium vapor pressure: 1-100 hPa at 20°C); + Color reaction after addition of a large gas phase volume (amines with low vapor pressure: < 1 hPa at 20°C); - No color reaction. Amine Boiling point at 20°C [°C] Vapor pressure at 20 °C [hPa] Color reaction Ammonia solution 25% 37,7 483 +++ Diethylamine 56 253 +++ Trimethylamine 31-23 wt% in ethanol approx. 31 +++ Triethylamine 90 69 ++ Ethanolamine 171 0,5 ++ Hexylamine 130 - 132 10,6 ++ 1,6-Diaminohexane 199 - 204 0,25 + Cadaverine (1,5-diaminopentane) 178 - 180 + Puterecin (1,4-Diaminobutane) 158 - 160 + histamine 167 (at 1.1 hPa) + Triethanolamine 360 <0,01 -

[0067] Preliminary tests with the dosimeter foil on old fish or meat also showed a positive color reaction after some time. Example 6: Cross-sensitivity to other substances that may occur during food spoilage

[0068] Various low-molecular-weight compounds were brought into contact with both the highly sensitive indicator powder and the dosimeter foil at high concentrations for several days. In these cross-sensitivity tests, no color change was observed with hydrogen sulfide, thiols, amino acids, alcohols, aldehydes, or ketones. Example 7: Simplified considerations regarding the sensitivity of the dosimeter material:

[0069] The following is an estimate of the amount of amine required to make the dosimeter material change from green to red. For the model, we assume a dosimeter foil spot with an area of ​​1 cm2. The foil thickness is 250 µm. With an LDPE density of approximately 1 g / cm3, the dosimeter foil spot has a mass of 25 mg. The indicator component contained therein, at 3%, amounts to 0.75 mg of powder. The indicator contains 1% of the active porphyrin component, so the sensor spot contains 7.5 µg of TPP-P(V)Cl3. Since the molar mass of the porphyrin is 750 g / mol, a quantity of 10 nmol can be calculated. If it is assumed that the porphyrin reacts 1:1 with amines for the color reaction, the dosimeter foil spot must absorb approximately 10 nmol of amine from the gas phase.If, for example, 1,6-diaminohexane with a vapor pressure of 0.25 hPa at 20 °C is considered as a high-boiling model compound for amines and it is assumed that the food packaging contains a gas volume of 0.25 l, it can be calculated from the ideal gas equation that approximately 2.5 µmol of this high-boiling amine are in the gas phase: . N = p * V R * T = 25 Pa * 0,25 l ¯ = 2,5 μmol 8314.5 [Pa l mol -1< K -1< ]* 293.15 K

[0070] From these considerations it follows that there is sufficient amine present in the gas phase to induce a color change of the dosimeter foil spot.

Claims

1. An indicator which in the presence of ammonia and / or amines undergoes an irreversible colour change, wherein the indicator comprises a phosphorus porphyrin activated by a covalent bond to a silanol group, wherein an activation of phosphorus porphyrin with the formula porphyrin-P(V)X3, wherein X is Cl or Br, occurs through a covalent bond from the reaction of only one halogen-ligand of the porphyrin-P(V)X3 with the silanol group, wherein the silanol group is part of a compound which comprises a plurality of silanol groups and a large surface area.

2. The indicator according to claim 1, wherein the indicator comprises a phosphorus porphyrin activated by a covalent bond to a silanol group of a compound comprising silica gel, wherein the compound preferably is silica gel.

3. The indicator according to claim 1 or 2, comprising a phosphorus porphyrin that is dichlorophosphorus tetraphenylporphine chloride (TPP-P(V)Cl3) , dibromophosphorus tetraphenylporphine bromide (TPP-P(V)Br3), dichlorophosphorus tetratolylporphyrine chloride (TTP-P(V)Cl3), or dichlorophosphorus 2,3,7,8,12,13,17,18-octaethylporphyrine chloride (OEP-P(V)Cl3), preferably dichlorophosphorus tetraphenylporphine chloride (TPP-P(V)Cl3).

4. The indicator according to any of claims 1 - 3, comprising:

5. A dosimeter material for ammonia and / or amines, particularly in gaseous form, comprising an indicator according to any of claims 1 - 4 and an immobilisation matrix for the indicator permeable to ammonia and / or amines, wherein the immobilisation matrix is impermeable to water.

6. The dosimeter material according to claims 5, wherein the dosimeter material is present as granules and / or film, preferably as film.

7. The dosimeter material according to any of claims 5 or 6, wherein the immobilisation matrix comprises polymers impermeable to water and permeable to ammonia and / or amines selected from the group comprising polystyrene, low-density polyethylene, and a combination thereof, preferably low-density polyethylene.

8. A method for producing the indicator according to any of claims 1 - 4, wherein activation of porphyrin-P(V)X3 occurs through a covalent bond from the reaction of only one halogen ligand of the porphyrin-P(V)X3 with the silanol group, preferably of silica gel.

9. A method according to claim 8, wherein the activation of dichlorophosphorus tetraphenylporphine chloride occurs through a covalent bond to silica gel from the reaction of one of the chloride ligands of the dichlorophosphorus tetraphenylporphine chloride with a silanol group of silica gel.

10. A method for producing the dosimeter material according to any of claims 5 to 7, comprising mixing the indicator, optionally produced according to any of claims 8 or 9, with the immobilisation matrix, wherein the method is performed under exclusion of water, and the mixture of indicator and immobilisation matrix is preferably produced as granules and / or film.

11. A use of the dosimeter material according to any of claims 5 to 7 for the detection of ammonia and / or amines, wherein the colour change of the indicator can preferably be determined visually or by the detection of fluorescence or absorption thereof.

12. The use of claim 11, wherein the use occurs in quality control of food or in medical applications such as breath analysis or in wound dressings, preferably in quality control of food.