WO2011072349A1

WO2011072349A1 - Biodegradable sensor containing h2s indicators and method for producing same

Info

Publication number: WO2011072349A1
Application number: PCT/BR2010/000394
Authority: WO
Inventors: Telma Teixeira Franco; Cristiana Maria Pedroso Yoshida; Edison Tutomu Kato Junior
Original assignee: Universidade Estadual De Campinas - Unicamp
Priority date: 2009-12-18
Filing date: 2010-11-24
Publication date: 2011-06-23

Abstract

The present invention relates to a method for producing a sensor for detecting sulfhydric acid, and to a biodegradable sensor for detecting sulfhydric acid (H₂S) characterised in that it comprises paper, chitosan, calcium carbonate and an iron ion indicator. The aim of the present invention is to detect and/or indicate quickly by colorimetry the presence of sulfhydric acid (H₂S). In the foodstuff industry, products such as canned vegetables (hearts of palm, mushrooms), minimally processed foods and foods consumed in the natural state (such as honey and vacuum-canned meat) may become microbiologically contaminated before, during or after processing. In anaerobic conditions, sulphite-reducing microorganisms such as Clostridium produce H₂S as a metabolite.

Description

Patent Descriptive Report for "BIODEGRADABLE SENSOR CONTAINING H ₂ INDICATORS AND PREPARATION PROCESS"

FIELD OF INVENTION

The present invention relates to a method of obtaining a hydrogen sulfide detection sensor and a further object of the present invention is the hydrogen sulfide detection sensor (H2S). The present invention aims to detect and / or indicate rapidly and colorimetrically the presence of hydrogen sulfide gas (H2S).

H ₂ S is a flammable, colorless gas with a sweet taste and a characteristic rotten egg odor. At high concentrations, it is highly toxic to humans and may lead to death. Normally H ₂ S is olfactory perceived when it is present in low air concentrations, ranging from 0.0005 to 0.3 parts per million (ppm). However, humans lose olfactory perception at high H2S concentrations, which makes contact with this gas very dangerous (ATSDR, 2006). H2S can be generated from various sources, for example: in natural gas plants, petrochemicals, charcoal, papermaking industries, viscose manufacturing industries, sulfur producing plants, iron foundries, food and tanning industries (SVENDSEN 2001). .

In the food industry, products such as canned vegetables (palm hearts, mushrooms), minimally processed foods, fresh foods such as honey and vacuum-packed meat can be contaminated microbiologically before, during or after processing. Under anaerobic conditions microorganisms such as Clostridium sulfite reducing produce H ₂ S as metabolite.

BACKGROUND OF THE INVENTION Currently in the area of food many freshness sensors have been developed, but based mostly on pH change, packaging integrity (oxygen sensors) by incorporating oxidation sensitive pigments that have their color changed when in contact with oxygen, carbon dioxide indicators that have the same principle as pH indicators, that is, their coloration is altered by the change in acidity, patent document CA2499145 teaches a device for detecting microorganisms in foods where a pH indicator detects variation acidity caused by the presence of a metabolite; Patent document CA2559708 teaches a microorganism detection device which also uses a pH indicator (bromothymol blue and methyl orange) that undergoes color change resulting from the presence of carbon dioxide from bacterial growth; CA2590091 teaches a sensor for the detection of microorganisms in food with a pH indicator (bromothymol blue and methyl red) packed in a gas-permeable container which when in contact with carbon dioxide undergoes a color change indicating microorganism growth; DE102004019427 teaches the same principle as the above-described devices, but requires direct contact with food to detect possible contamination. US7 56597 also relates to an indicator of microbiological contamination which is based on antigen-antibody type reactions resulting in colorimetric variation of the medium indicating the presence of microorganisms.

BRIEF DESCRIPTION OF THE INVENTION

The present invention relates to a method of obtaining a hydrogen sulfide detection sensor and a further object of the present invention is the hydrogen sulfide (H ₂ S) detection sensor with quick indication and easy readability. Colorimetric indicators, ferrous sulfate (FeS0 ₄ ) and myoglobin were separately incorporated into a chitosan filmogenic matrix and applied to the surfaces of cardboard, 250g / m ² , previously impregnated with sodium carbonate (Na ₂ C0 ₃ ).

An advantageous aspect of the present invention is the short detection time and ease of visualization with the commonly applied methods for detection of H ₂ S, and in the presently used methodology a skilled technician and a considerable period to obtain the results the proposed sensor can be used. even be understood by a child and gives results in times between 30 and 60 seconds, preferably within 30 seconds.

The sensor can be applied in industries that use or generate hydrogen sulfide gas, where fugitive emissions may occur, which, depending on the concentration, pose different risks to worker health. Another application would be to ensure safety and quality of food products.

The number of reported incidents has led to growing concerns about worker safety and food quality, for example: accidents with workers in oil plants resulting from gas leaks, accidents with workers in grain storage silos, palm hearts and pickled mushrooms contaminated with Clostridium sp. and more recently cases of food poisoning in children who consumed honey contaminated by Clostrium sp.

In view of this it is necessary a reliable means of detecting the presence of H ₂ S thus informing the employee if the place is safe, and also to the consumer if the food product is quality and safety for acquisition and subsequent ingestion. The proposed biodegradable sensor seeks to detect a wide concentration range of H ₂ S (> 0.1 ppm) and is easy to read. It thus promotes the worker and / or consumer who does not have access to sophisticated equipment and testing or specialized knowledge can understand if the work environment and / or product is safe.

BRIEF DESCRIPTION OF THE FIGURE

Figure 1. Colorimetric response of the paper indicator system (FeSO) to different exposure times to gas H ₂ S (a) 0; (b) 30; (c) 60; (d) 90; (e) 120; (f) 180s.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a process for obtaining a hydrogen sulfide detection sensor. A further object of the present invention is the rapid detection and easily readable hydrogen sulfide (H ₂ S) detection sensor.

Said biodegradable sensor preparation process comprises the following steps:

(a) coating a paperboard with a calcium carbonate solution;

(b) drying said paper resulting from step (a);

(c) coating said paper resulting from step (b) with an indicator chitosan suspension; and

(d) drying the paper resulting from step (c).

More specifically the process of preparing said biodegradable sensor comprises the following steps:

(a) coating a preferably cardboard of grammage 250 g / ^m2 with a calcium carbonate solution;

(b) drying said paper resulting from step (a) to a preferred temperature of 150 ° C; (c) coating said card stock resulting from step (b) with an indicator chitosan suspension; and

(d) drying the paper resulting from step (c) to a temperature preferably 150 ° C.

Said calcium carbonate solution preferably has a concentration of 4g / 100g.

Said chitosan suspension has a preferred concentration of 3.33% by weight of chitosan powder with an acetylation degree of about 18%.

Said indicator chitosan suspension may be prepared from the following steps:

(a) adding acetic acid to chitosan;

(b) homogenizing the solution obtained in step (a);

(c) preferably slowly adding an indicator solution; and

(d) homogenizing the solution resulting from step (c).

Said indicator chitosan suspension may preferably be prepared from the following steps:

(a) adding acetic acid to chitosan preferably in powder form;

(b) homogenizing the solution obtained in step (a) preferably at room temperature;

(c) preferably slowly adding an indicator solution to be selected from ferrous sulfate (FeSO ₄ ) and myoglobin preferably at a concentration of 10% by weight of the indicator; and

(d) homogenizing the solution resulting from step (c) preferably for a period of 10 minutes.

A further object of the present invention is a biodegradable sensor comprising a paper, chitosan, calcium carbonate and an iron ion indicator selected from myoglobin or ferrous sulfate for application to as a hydrogen sulfide detector (H ₂ S). Said sensor is prepared from the above procedure to be applied in the detection of hydrogen sulphide (H ₂ S).

Colorimetric indicators, ferrous sulfate (FeS0 ₄ ) and myoglobin were separately incorporated in a chitosan filmogenic matrix and applied to the surfaces of cardboard, 250 g / m ² , previously impregnated with sodium carbonate (Na ₂ C0 ₃ ). The advantage of this work is the short detection time and easy visualization of the methods usually applied for detection of H ₂ S, being still in the methodology currently used a specialized technician and a considerable period to obtain the results the proposed sensor can be understood. even by a child and presents results in times between 30 and 60 seconds, preferably within 30 seconds.

Sensor Preparation

The present embodiment example contemplates the process of obtaining a biodegradable sensor for detection of hydrogen sulfide (H ₂ S)., Without, however, restricting the scope of protection and scaling of the invention.

Initially, the paperboard was coated with a 4g / 100g solution of calcium carbonate (Na ₂ CO ₃ ) where 3 ml of the solution was applied to the paper surface, then the paper was dried at 150 ° C in the present example. per greenhouse for a period of 90 seconds. A chitosan and acetic acid suspension in stoichiometric proportions was preferably obtained from a 3.33 mass% solution of chitosan preferably provided with about 18% acetylation grade, calculated based on the sample mass and chitosan degree of acetylation value to achieve protonation of all NH ₂ groups. The chitosan solution was homogenized under agitation in the present example without however, restrict at room temperature for a period of 50 minutes. A solution of the desired indicator selected from FeS0 ₄ and myoglobin with a preferential concentration of 10 wt.% Was slowly added and after complete dissolution of chitosan a final final solution of 3 wt.% Chitosan and 1 wt.% Was obtained. indicator being preferably maintained, in the present example, without restricting, while stirring for a further 10 minutes. To said paperboard, for example, with a weight of 250g / m ² , said chitosan-indicator solution in a suspension ratio and paper area (volume / area) is preferably 44: 1 (mL / m ² ). After this step a final dry coverage of 1.76g / m ^{2 was obtained} . Then the product obtained in the previous step was dried preferably 150 ° C for 60 seconds.

Qualitative evaluation of system sensitivity

The detection response of the H ₂ S indicator was measured by subjecting the indicator paper - film system to different exposure times to the H ₂ S gas. Fifteen aliquots of 0.1 g FeS were weighed and added to 20 ml of hydrochloric acid. 1 M. Moderate heating was applied to accelerate the reaction. After 4 minutes each sensor (9.0 cm ² ) was exposed to H ₂ S generated for periods of 30, 60, 90, 120 and 180 seconds. Figure 1 illustrates the color variation in different shades of black as a function of different exposure times.

Immediately after exposure (approximately 5 seconds) readings of the color parameters L ^* , a ^* and b ^* with colorimeter (CR-400, KONIKA MINOLTA) were taken, the results were analyzed using STATISTICA 5.0 software and can be seen in Table 01. (Analyzes were performed in triplicate)

Within the first 30 seconds of exposure, the color difference showed a statistically significant difference in the color parameter L ^* , in the In this case, this sensor is most important because it measures the variation from light to dark (white to black).

Table 01. Evaluation of the color parameters (L ^* , a ^* and b ^* ) of smart sensors by different exposure times to H ₂ S.

Exposure time

L ^* a ^* b ^*

(s)

0 87.06 ± 1,1.1 ^to 0.54 ± 0.16 ^acd 13.73 ± 1.19 ^to

77.23 ± 6.42 ^b 0.88 ± 0.26 ^to 12.17 ± 1.18 ^a

60 66.82 ± 5.38 ^b 0.48 ± 0.44 ^ac 10.1 1 ± 1.44 ^a

90 50.72 ± 5.75 ^c -0.36 ± 0.47 ^cef 6.16 ± 2.36 ^b

120 48.03 ± 1.96 ^c -0.63 ± 0.28 ^bf 4.22 ± 0.26 ^b

180 44.33 ± 3.17 ^c -0.40 ± 0.40 ^cdef 4.24 ± 0.80 ^b af - Different letters in the same column indicate significant difference (p> 0.05) from the means obtained by Tukey test.

Claims

1. Process for preparing a biodegradable sensor comprising the following steps:

(a) coating a paperboard with a calcium carbonate solution;

(b) drying said paper resulting from step (a);

(d) drying the paper resulting from step (c).

Process according to Claim 1, characterized in that it comprises the following steps:

(a) coating a paperboard preferably weighing 250 g / m ² with a calcium carbonate solution;

(b) drying said paper resulting from step (a) to a preferred temperature of 150 ° C;

(c) coating said carton paper resulting from step (b) with an indicator chitosan suspension; and

Process according to any one of the preceding claims, characterized in that it comprises a coating step (b) with a calcium carbonate solution in a concentration preferably of 4% by mass;

Process according to Claim 1 or 2, characterized in that the coating step with the application of a chitosan-indicator suspension is prepared from steps including:

(a) adding acetic acid to chitosan;

(b) homogenizing the solution obtained in step (a); (c) preferably slowly adding an indicator solution; and

(d) homogenizing the solution resulting from step (c).

Process according to Claim 4, characterized in that the preparation of said indicator chitosan suspension preferably comprises the steps:

(a) adding acetic acid to chitosan preferably in powder form;

(c) preferably slowly adding an indicator solution selected from ferrous sulfate (FeSO ₄ ) and myoglobin preferably at a concentration of 10% by weight of the indicator; and

Process according to claim 1 or 2, characterized in that it comprises a chitosan-indicator suspension coating step (c) prepared according to claims 4, in a preferred concentration of 3.33% by weight of chitosan with a of about 18% acetylation.

Process according to claim 1 or 2, characterized in that it comprises a chitosan-indicator suspension coating step (c) prepared according to claims 5, in a preferential concentration of 3.33 wt. of about 18% acetylation.

Process according to claim 7, characterized in that the chitosan-indicator solution coating step is in a suspension ratio and paper area (volume / area) preferably of 44: 1.

Process according to Claims 1 and 2, characterized in that the drying step is in a preferred time range from 60 to 90 ° C. seconds when performed in a greenhouse selected from forced air circulation or not.

(a) coating a paperboard with a calcium carbonate solution at a concentration preferably of 4% by mass;

(b) drying said paper resulting from step (a) to a preferred temperature of 150 ° C over a preferred time range of 60 to 90 seconds when performed in a greenhouse selected from forced air circulation or not, preferably 90 seconds;

(c) coating said carton paper resulting from step (b) with a chitosan-indicator suspension obtained according to claim 5, at a preferred concentration of 3.33 mass% of chitosan with an acetylation degree of about 18%. and a paper area / suspension (volume / area) ratio preferably of 44: 1; and

(d) drying the paper resulting from step (c) to a temperature preferably 150 ° C over a preferred time range of 60 to 90 seconds when performed in a greenhouse selected from forced air circulation or not, preferably 60 seconds;

1 1. Biodegradable sensor, characterized in that it comprises a paper, chitosan, calcium carbonate and an iron ion indicator selected from myoglobin or ferrous sulfate for application as a hydrogen sulfide (H ₂ S) detector.

Biodegradable sensor, characterized in that it is prepared from the process as defined in one of claims 1 to 10;

Sensor according to Claim 12, characterized in that it is for the detection of hydrogen sulfide (H ₂ S).