WO2014096474A1

WO2014096474A1 - Colorimetric method for the detection of the cyanide anion

Info

Publication number: WO2014096474A1
Application number: PCT/ES2013/000276
Authority: WO
Inventors: Ana María COSTERO NIETO; Raul GOTOR CANDEL; Margarita PARRA ÁLVAREZ; Salvador GIL GRAU
Original assignee: Universitat De València
Priority date: 2012-12-17
Filing date: 2013-12-17
Publication date: 2014-06-26
Also published as: ES2482467A1; ES2482467B1

Abstract

The invention relates to the use of a chromogenic compound, called compound 1, for the detection of the cyanide anion (CN), both in a gaseous state, from the HCN compound, and in a solution, preferably in an aqueous solution. The invention also relates to the methods for the detection of said molecule in both states, by means of the use of compound 1, and to the devices used to carry out said methods, comprising the chromogenic compound 1.

Description

COLORIMETRIC METHOD OF DETECTION OF THE CYANIDE ANION

FIELD OF THE INVENTION The invention relates to the use of a chromogenic compound called compound 1 for the colorimetric detection of cyanide anion (CN) both in its gaseous form, from the hydrogen cyanide compound (HCN), and in solution.

STATE OF THE TECHNIQUE

Cyanide anion (CN) is considered an extremely dangerous compound both in physiological systems and in the environment. Its toxicity in physiological systems is due to its binding to the active center of the cytochrome oxidase enzyme, with the consequent inhibition of the electron transport chain in mitochondria [Yu-Chu Yang J. A. B., et al. Chem. Rev. 1992, 92, p.1792]. Intoxication can occur both by ingestion and through the skin. Cyanide-containing salts are common chemical compounds originated not only from industrial wastes, but also from biological sources and can appear as contaminants in water. Cyanide is also used in many chemical processes in industries such as petrochemicals, gold mining, electroplating, photographic, iron manufacturing, synthetic fibers, herbicides and jewelry, among others. Waste from these processes is partly responsible for cyanide contamination.

The gaseous form of cyanide anion, that is, hydrogen cyanide (HCN), is in turn a very dangerous molecule and is included in the category of war gases, within the group of blood agents (AC). Hydrogen cyanide was used in World War II as a weapon of mass destruction (under the name of Zyklon B), and the ease of its preparation makes it potentially dangerous as it can be used in terrorist attacks. The fact that both the cyanide anion in solution, and the hydrogen cyanide in the gaseous state, are molecules in addition to pollutants, toxic to health, necessitates the development of effective methods for their detection.

There are, in the state of the art, numerous methods for the detection of cyanide in liquid samples. These detection methods include sensors

i electrochemicals [Shan D., et al., Anal. Chem. 2004, 76, p.178; Lindsay AE, et al., Anal. Chim. Acta 2006, 558, p.158], polymers [Shiraishi Y., et al. ACS Appl. Mater. Interfaces,

2011, 3, p.4649; Vallejos S., Chem. Commun. 2010, 46, p.7951], gold nanoparticles [Kim H. J., et al., Chem. Commun. 2011, 47, p.28865], CdSe quantum dots [Jin W. J., et al., Chem. Commun. 2005, p.883; Touceda-Varela A., et al., Chem. Commun. 2008, p.1998], coordination complexes [Kim Y.-H., et al., Chem. Commun., 2002, p.512; Liu H., et al., Tetrahedron 2005, 61, p. 8095; Chow C.F., et al., Inorg. Chem. 2004, 43, p. 8387; Zelder F.H., et al., Inorg. Chem. 2008, 47, p. 1264; Zeng Q., et al., Chem. Commun. 2008, p. 10947], and the fluorogenic and chromogenic chemosensors [Xu Z., et al., Chem. Soc. Rev. 2010, 39, p. 127; Isaad J. et al., Tetrahedron, 2011, 67, p. 4939; Lin Y.D., et al., Tetrahedron,

2012, 68, p. 2523; Guliyev R., et al., Org. Lett. 2012, 14, p. 1528; Dong M. et al., Org. Lett. 2012, 14, p. 130; Sumiya S., et al., Tetrahedron, 2012, 68, p. 690]. Colorimetric sensors are especially interesting due to their speed, low cost and the possibility of detecting the naked eye avoiding the use of expensive equipment or difficult portability.

The use and design of colorimetric sensors for the detection of cyanide in liquid media has been favored by the high reactivity of said anion towards electrophilic carbon atoms [García F., et al., Chem. Commun. 2005, p. 2790; Zhang X., et al., Sens. Actuators, B, 2008, 129, p. 15211]. The electrophilia of the compounds of the triaryl-carbocation family can be regulated by modifying the functional groups of the aromatic rings and thus, a specific choice of said functional groups, can lead to the carbocationic atom presenting the electrophilia suitable for cyanide anion [Afkhami A., et al., Sens. Actuators, B, 2007, 122, p. 437; Kaur P., et al., Inorg. Chem. Commun. 2009, 12, p. 272]. In the state of the art there are chemo-dosimeters or chemo-sensors of the cyanide anion in solution that use said strategy, using for this a commercial molecule such as, for example, violet or methyl violet crystal. However, many of these chemo dosimeters do not show selectivity to the detection of the cyanide anion in the presence of other contaminating anions, such as in the presence of the bisulfide anion (HS), which is one of the most important interferents for the detection of CN ^" by said technique.

On the other hand, there are hardly any specific colorimetric methods or sensors in the state of the art that have selectivity and sensitivity for the detection of cyanide anion from HCN in the gaseous state [Feng L, et al., Anal. Chem. 2010, 82, p. 9433; Yang M., et al., Sens. Actuators, B, 2011, 155, p. 6929]. The methods and systems used in the state of the art for the detection of HCN in the gas phase carry out said detection through an indirect route, using a pH indicator that detects the HCI generated by the reaction of HCN with HgCI ₂ [Petrusevski, VM et al. The Chemical Education Journal (CEJ), Vol. 9, No. 1 (Serial No. 16), 2006]. In addition, the chromogenic compounds or chemo-sensors used for the detection of the cyanide anion in solution cannot be used for the detection of the cyanide anion from the HCN in the gaseous state, since said compounds, when deposited on a suitable support for the detection of the gas phase of said anion, would decompose and lose their coloration, thus not serving for the chromogenic detection of CN ^" from the gas phase HCN.

To solve the problems of selectivity existing in the state of the art with respect to the methods of colorimetric detection of the cyanide anion in solution in the state of the art, as well as to provide a new colorimetric method for the detection of the cyanide anion from HCN in gaseous state, the present invention describes the use of a chromogenic compound, designated throughout the present invention interchangeably, compound 1 or chromogenic compound 1, capable of detecting both cyanide anion from HCN in gaseous state with great selectivity and specificity , as the cyanide anion in solution. Compound 1 is known in the state of the art [Gotor, R. et al, Chemistry European Journal, 2011, 43, p. 1 1994], but not its use for the detection of cyanide, neither in solution, nor in its gaseous form. Therefore, the present invention discloses the use of said compound 1 in the monitoring of water samples for human and / or animal consumption, as well as industrial wastes, showing a high recognition specificity of the cyanide anion in solution and the cyanide anion in gas form, the detection limits also being reached through the use of said compound 1, well below the values considered dangerous for humans.

DESCRIPTION OF THE INVENTION

Brief Description of the Invention

An embodiment of the present invention describes the use of chromogenic compound 1 for the colorimetric detection of cyanide anion, either in its gaseous state, from the detection of gaseous HCN, or in solution. For CN detection ^" from the HCN in gas form, it is necessary that the compound 1 be deposited on a solid base, preferably of a basic nature. Basic support systems are necessary to: a) deprotonate hydrogen cyanide to the cyanide anion and b) prevent the formation of the dipole or zwitterionic form (electrically neutral form but which has positive and negative charges on different atoms) non-reactive compound 1 .

Chromogenic Compound 1

Another of the objects described in the present invention relates to a cyanide anion colorimetric detection device, either from the HCN in gaseous form, or in solution, comprising the chromogenic compound 1, said compound being deposited on a solid support, preferably of a basic nature, when the CN ^" anion from the HCN in gaseous form is specifically detected.

Another object described in the present invention refers to a method of detecting cyanide anion, either in gaseous form, or in solution by means of the device described in the present invention for said purpose.

For the purposes of the present invention, the term "device" or "colorimetric detection device" used interchangeably throughout this document refers to any electronic device, kit, reagent, buffer, test medium, test strip, support or similar capable of housing or understanding the compound described in the present invention. Description of the figures.

Figure 1. UV spectrum of free compound 1 (solid line) at a concentration of 1x10 ^"5 M dissolved in H ₂ 0: MeCN (99: 1) and at a pH: 10.6, and in the presence of 1000 equivalents of CN ^" (line dotted). The arrows indicate the Amáx at which chromogenic compound 1 absorbs, free and in the presence of CN ^" . The wavelength (λ) expressed in nm is represented on the abscissa axis. The expressed absorbance is represented on the ordinate axis. in arbitrary units (ua).

Figure 2. Graph of the kinetics of compound 1 in the presence of 1000 equivalents of KCN at different pHs. The different analyzed pH values are shown on the abscissa axis. The extinction rate of the absorbance peak at a λ = 563 nm is shown on the ordinate axis.

Figure 3. Graph of the kinetics of compound 1 in the presence of 1000 equivalents of KCN at various temperatures. The different analyzed temperature values are shown on the abscissa axis. The extinction rate of the absorbance peak at a λ = 563 nm is shown on the ordinate axis.

Figure 4. Graph of the relative transmittance ((A ₀ -A) / A ₀ ) x100, expressed as a percentage, of different samples of compound 1, only (blank) or in the presence of the different anions indicated. The temperature at which said reaction has taken place is 20 ° C. In the lower part of the figure, the color changes (gray scale in black and white figures) of different solutions of chromogenic compound 1 (2 ml volume 99: 1 water. 10 ^"5 M acetonitrile buffered at pH 10.6 are observed. with Borax / HCI), after the addition of 1000 equivalents of the indicated interfering anions. The interfering anions used, from left to right are: white (compound 1), compound 1 + F ^" , compound 1 + CI ^" , compound 1 + Bf, compound 1 + CN ^" , compound 1 + HS ^" , compound 1 + SCN, compound 1 + AcO ^" , and compound 1 + HP0 ^2" . The anions were added in 20 μcu aliquots of 1 M aqueous solutions, as salts of sodium: F ^" , CI ^" , HS ^" , HP0 ^2" and AcO ^" and as potassium salts the other anions: CN ^" , SCN and HP0 ₄ ^{2 "} .

Figure 5. Graph of the absorption kinetics at 563 nm of compound 1 in water: acetonitrile (99: 1) in the presence of 1000 equivalents of KCN (solid line) or 1000 equivalents of NaSH (dotted line). The time expressed in hours is represented on the abscissa axis. The absorbance at 563 nm expressed in arbitrary units (a.u.) is represented on the ordinate axis.

Figure 6. The color change is shown in the upper photo (grayscale in the black and white figures) of compound 3 or methyl violet (2ml 10 ^" 5M water: acetonitrile 99: 1 pH 10.6 with Borax / HCI), after the addition of 1000 equivalents of different anions. From left to right the interfering anions used they are: control (Compound 3), Compound 3 + F ^" , Compound 3 + CI ^" , Compound 3 + Br ^' , Compound 3 + CN ^" ' Compound 3 + SH ^" , Compound 3 + SCN ^" , Compound 3+ HP0 ^2" , Compound 3+ OAc ^" , Compound 3 + OH ^" . The anions were added in 20 ml aliquots of 1 M solutions. The anions F ^" , CI ^" , SH ^" , HP0 ^2" , AcO ^" and OH ^" were added as Sodium salts and the remainder as potassium salts The compound 3 is shown in the lower picture together with the different interfering anions mentioned above after exposure to _{25 nm} UV light for 2 minutes.

Figure 7. Test strips for the detection of cyanide anion, from the gaseous HCN compound. Each of the strips is composed of different concentrations of compound 1 adsorbed onto a sheet of aminated silica. The concentrations of compound 1 from top to bottom are: 5-10 ^"3 , 5-10 ^{" 4} , 5-10 ^"5 and 5 10 ^{" 6} nmol.

Figure 8. Analysis of color differences (gray scale in black and white figures) observed in different samples of compound 1 at different concentrations (25, 2.5 and 0.25 μηηοΙ / cm ² ) and in the presence of different interfering anions: HCN, H ₂ S, CO, HCI and NH ₃ .

Figure 9. Modification of the blue component of the colors (gray scale in black and white figures) of compound 1 in the presence of an excess of the interfering anions: HCN, H ₂ S, CO, HCI and NH ₃ .

DETAILED DESCRIPTION OF THE INVENTION One of the objects of the present invention refers to the use of compound 1 for the colorimetric detection of cyanide anion (CN).

Compound 1

In a preferred embodiment of the use of compound 1 as described in the present invention, it is characterized in that the cyanide anion can be detected both in its gaseous state, from the HCN compound in the form of gas, and in solution.

In another preferred embodiment of the use of compound 1 for the detection of cyanide anion from HCN in the gaseous state (HCN), said compound 1 is deposited on a solid support, preferably of a basic nature and said solid support being selected from any of the following: Hydromed / Cs ₂ C0 ₃ , polyethylene oxide / Cs ₂ C0 ₃ , Si0 ₂ treated with K ₂ C0 ₃ and aminated silica, aminated silica being preferred as solid support.

Another object described in the present invention relates, as we have said previously, to the use of compound 1 for the colorimetric detection of cyanide (CN) in solution. In a preferred embodiment of the use of compound 1 for the colorimetric detection of cyanide anion (CN) in solution, said solution is carried out in any of the solvents selected from: water, ethanol, DMSO or CH ₃ CN, being preferred as solvent the water.

In addition to the use of compound 1 for the colorimetric detection of cyanide anion in solution, the present invention describes the use of compounds 2 and 3 described herein, also for the colorimetric detection of said anion in solution. i_

Compound 3

The chromogenic compounds 1, 2 and 3, described in the present invention, have a π-electronic system called "push-pull" that absorbs visible light and generates strongly colored species. In the presence of cyanide, a nucleophilic addition to the central atom of said compounds 1, 2 and 3, which converts it into a carbon with sp ³ hybridization, which causes an interruption of conjugation. This change causes a rupture of the "push-pull" system which extinguishes its absorption in the visible with the consequent disappearance of the color, giving rise, preferably, as described in the present invention, to compounds 4, 5 and 6, which They lack coloration (Scheme 1).

Compound 1 R = NMe ₂ , X = 0 Compound 4 R = NMe ₂ , X = 0

Compound 2 R = H, X = 0 Compound 5 R = H, X = 0

Compound 3 R = NMe ₂ , X = NMe Compound 6 R = NMe ₂ , X = NMe

Scheme 1. Scheme of the reaction that occurs for the detection of cyanide anion. The chromogenic chemosensors 1, 2 or 3 suffer a nucleophilic attack by cyanide that eliminates the conjugation between the aromatic rings, which causes the initial color to die out.

Another object described in the present invention relates to a cyanide anion colorimetric detection device comprising the compound 1 described in the present invention.

In a preferred embodiment, the device described in the present invention is capable of detecting the cyanide anion both in the gaseous state, from the HCN compound, and in solution.

In another preferred embodiment, the device of the invention, when used for the colorimetric detection of cyanide anion in the gaseous state (HCN), is characterized in that said compound 1 is deposited on a solid support, preferably of a nature basic and said solid support being selected from any of the following: Hydromed / Cs ₂ CC> 3, polyethylene oxide / Cs ₂ C0 ₃ , Si0 ₂ treated with K ₂ C0 ₃ and aminated silica, the animated solid silica support being preferred . In another preferred embodiment, the device of the invention, when used for the colorimetric detection of cyanide anion in solution is characterized in that the compound 1 is dissolved in any of the solvents selected from: water, ethanol, DMSO or CH ₃ CN , water being preferred as solvent. Another object described in the present invention refers to a device for detecting cyanide anion in solution comprising compound 2 or compound 3. In a preferred embodiment, said device is characterized in that compounds 2 or 3 are dissolved in any of the solvents selected from: water, ethanol, DMSO or CH ₃ CN, water being preferred as solvent.

Another of the objects described in the present invention refers to a method of colorimetric detection of the cyanide anion by the use of the compound 1 or the device comprising it and which is used for said purpose, as described in the present invention.

In a preferred embodiment, the cyanide anion colorimetric detection method is characterized in that it detects said cyanide anion both in its gaseous form, from the gaseous HCN compound, and in solution. In a preferred embodiment, the method of colorimetric detection of the CN anion ^" in solution is characterized in that the optimum pH for colorimetric detection of CN ^" ranges from 8.5 to 10.6, the pH value of 10.6 being preferred.

In another preferred embodiment, the method of colorimetric detection of CN anion ^" in solution is characterized in that the optimum temperature for colorimetric detection of CN ^" varies between 10-60 ° C, with a temperature of 20 ° C being preferred.

In order to be able to reuse compounds 1, 2 and 3 for the detection of CN ^' repeatedly, a simple and rapid method of regenerating them was developed. This method is based on photo-ionic dissociation under ultraviolet light that The compounds experience as compound 4. The most common mechanism of said photochemical reaction involves the heterolytic rupture of the CC bond (cyanide-sensor) (Scheme 2).

Reversible reaction Scheme 2. Compound 1 and cyanide in the presence of UV light ₂₅ 4nm-

Therefore, in another preferred embodiment, the cyanide anion colorimetric detection method is characterized in that compound 1, as well as compounds 2 and 3 or the device comprising both compound 1, and compounds 2 and 3, each separately, can be regenerated by irradiating them with UV light.

The examples described below are intended to illustrate the present invention, but without limiting the scope thereof.

Example 1. Synthesis of chromogenic compounds 1 and 2.

The synthesis procedure of the chromogenic compound 1 described in the present invention was carried out by lithiation of the 4-bromophenol compound in the presence of 2 equivalents of butyllithium, followed by the addition of Michier ketone. Extraction in acidic medium causes dehydration of carbinol in situ and directly yields chromogenic compound 1 (Scheme 3).

Compound 1

Scheme 3. Synthesis of chromogenic compound 1

By means of the synthesis procedure of the compound 1 described in the present invention, other compounds capable of detecting the CN anion ^" in solution can also be synthesized. Among these compounds that can be synthesized by said process is the chromogenic compound 2 described in the present invention. The synthesis of said compound 2 was also carried out by lithiation of the compound 4-bromophenol in the presence of 2 equivalents of butyl lithium, followed by the addition of 4-dimethylaminobenzophenone In the same manner as for the synthesis of compound 1, the extraction of said compound 2 in acidic medium causes dehydration of carbinol in situ and directly yields the chromogenic compound 2 (Scheme 4).

Compound 2 Scheme 4. Synthesis of chromogenic compound 2. Example 2. Detection of cyanide anion (CN) in solution.

To detect the cyanide anion in solution, a 10 ^" 5M solution of compound 1 in acetonitrile was started. This solution shows a UV absorption band centered at A _max = 507 nm (ε = 29800 mol ^{" 1} cm ^"1 ). By adding 20 μΐ_ of a 1 M solution of potassium cyanide (KCN) in water to that solution, that main band disappears and the UV-Vis spectrum shows a maximum absorption at A _max = 272 nm (ε = 34800 mol ^"1 cm ^{" 1} ) (Figure 1) In order to clarify the reaction mechanism and demonstrate that cyanide was added to the electrophilic carbon, compound 4 was prepared alternatively by reaction of compound 1 with KCN at 80 Acetonitrile ° C. The isolated compound was unequivocally identified as compound 4 by different techniques: infrared (IR) spectroscopy, nuclear magnetic resonance (NMR) and high resolution mass spectrometry (HRMS), thus, the spectrum obtained by the spec technique Infrared troscopy showed an absorption band at 2239 cm ^"1 characteristic of the nitrile group while the ¹ H-NMR spectrum showed the expected signals for methyl groups and for aromatic groups, with coupling constants for aromatic doublets (J = 8.7 Hz) that rule out a possible attack on carbonyl carbon. In the ¹³ C-NMR spectrum, the central carbon atom undergoes a screening (Δδ "15 ppm) attributable to the adjacent nitrile. In the same way, the structure of compound 4 is compatible with the data obtained by the HRMS technique, so it is clearly demonstrated that the compound obtained from the reaction of compound 1 with KCN in acetonitrile, is compound 4. Next, proceeded to detect the CN anion ^" in different solvents by using compound 1, in order to obtain the optimal conditions for the detection of said anion. The solvents used were: H ₂ 0, EtOH, DMSO, CH ₃ CN THF, CHCI ₃ , CH ₂ CI ₂ , Et ₂ 0 and toluene: Compound 1 exhibited sensing capacity, that is, clearly detected the presence of the CN anion ^" , in H ₂ 0, EtOH, DMSO and CH ₃ CN. In contrast, in THF, CHCI ₃ , CH ₂ CI ₂ , Et ₂ 0 or toluene, hardly any color changes were observed or the detection rate was very slow.

As a result of the good results obtained using water as a solvent, the CN ^" anion detection studies were carried out in said medium. To that end, basic solutions of compound 1 in water were started. These solutions show a maximum absorption at A _max = 563 nm (ε = 36600 M ^"1 cm ^{" 1} ) that disappears when KCN is added, while a new maximum absorption appears at A _max = 227 nm (ε = 51800 M ^"1 cm ^"1 ) (Figure 1). Similarly, compounds 2 and 3 were dissolved in basic aqueous medium and the absorption maximums they show are at A _m max = 583 nm (ε = 85500 M ^"1 cm ^{" 1} ) and at A _max = 581 nm ( ε = 65910 M ^"1 cm ^{" 1} ), respectively; in both cases that band disappears in the presence of cyanide. Therefore, since compound 1 can be dissolved in water, this fact allows compound 1 to be used for the detection of CN anion ^" in water samples and thus detect whether or not they are contaminated with the presence of CN anion. ^" , allowing or not its use for human consumption. In the same way, compounds 2 and 3 described in the present invention can also be used for the detection of CN ^" anion in water samples.

To obtain the optimum pH required in the detection of CN ^" anion, different kinetic studies were carried out as a function of pH. For this, 10 ^{" 5} M solutions of compound 1 in water were prepared: acetonitrile (99: 1) buffered at pH 8.4, 9.5, 10.6 and 1 1.2 using Borax / HCI buffer solutions at a temperature of 20 ° C. 2 ml aliquots of each solution were treated with 20 μΐ of a 1 M aqueous solution of KCN. Next, the extinction rate of the absorbance peak at A of 563 nm was measured (Figure 2). All the curves obtained squared with first-order kinetics. When representing ln [(A ₀ - A) / A ₀ ] (where A _{0 is} the initial absorbance of the solution and A the absorbance at different times after the addition of the anion) versus time, the slope of the adjusted functions gave us the speed constants (k _r ). When representing these constants against pH (Figure 2), the increase in said speed constants kr was observed in the range of pH 8.5 to 10.6, where k _r is maximum (/ Τφ _Η

s ^"1 ). These data are consistent with the negative logarithm value of the basicity constant (pK _b ) for cyanide (4.69): at pH 9.5 61% of cyanide is present in the solution while at pH 10.6, almost 95% is dissociated.If the pH is increased further, the reaction rate drops due to the loss of the sensor's electrophilic character.At pH 10.6, compound 1 has a half-life at 20 ° C in the presence of cyanide.

To decrease the detection times of the cyanide anion in solution, kinetic experiments were carried out at different temperatures (Figure 3). Following a procedure similar to that followed for the analysis of the optimum pH, but under thermostated conditions, the speed constants were determined at different temperatures. In addition, the Arrehnius graphs (ln (/ c _r ) vs T ¹ ) of this data allowed us to obtain the activation energy of the process E _a = 23.029 kJmol ^" . From the results obtained and shown in Figure 3 it is shown that the optimum temperature for the detection of cyanide is 20 ° C.

Once the optimum pH and temperature conditions were obtained for the detection of the CN anion ^" in solution, preferably in water, the system was tested against potential interfering anions. To this end, 1000 equivalents of the anions F, Cl ^{" were added.} , Br ^" , CN ^" , HS ^" , SCN ^" , AcO ^" and HP0 ₄ ^2" to 2 ml aliquots of a 10 ^"5 M solution of compound 1 in water: acetonitrile (99: 1) (pH 10.6 Borax / HCI ), at a temperature of 20 ° C. In each sample the intensity of absorption at λ = 563 nm was measured, while cyanide eliminates 97% of the color, various anions (F, Cl ^" , Br ^" , AcO ^" , HP0 ^{2 "} ) showed a minimum response (below 4%) and the most common interfering anions, which are HS ^" and SCN ^" , only decreased color by 27% HS anion ^" and 6% the anion SCN ^", even after 24 h of reaction (Figure 4). to avoid the occurrence of false positives due to anion ^HS", we proceeded to make a comparison n kinetics between two samples of compound 1 to which were added: a) 1000 CN anion equivalents ^", and b) anion equivalent 1000 ^HS". The velocity constant of compound 1 in the presence of HS anion ^" (k _{HS ^~ = 5.67x10 ^{" 6} s ^" ) was sufficiently inferior to the velocity constant of compound 1 in the presence of CN anion ^" (k _{CN ^' lk _{HS ^' = 17.9) to discriminate interference due to HS ^" (Figure 5).

The present invention therefore describes the first cyanide chemodosimeter capable of producing a selective signal, even in the presence of sulfhydryl anions. In parallel to the experiments shown with compound 1, the same tests were performed, but using the chromogenic compounds of formulas 2 and 3 in the presence of 1000 equivalents of the interfering anions: F, Cl ^" , Br ^" , CN ^" , HS ^" , SCN ^" , AcO ^" and HP0 ^{2 "} . The results show that the addition of cyanide and hydrogen sulphide anions eliminate color immediately, while in the presence of the other anions there are no color changes. Low spectrometry Sample resolution confirmed that the cyanide and hydrogen sulphide anions had been added to compounds 2 and 3. The higher cyanide detection rate shown by these chromogenic compounds 2 and 3 compared to compound 1, gives them an advantage from the point of sensitivity, but compounds 2 and 3 are so reactive that The hydrogen sulfide anion itself becomes a potential interference, subtracting specificity from the detection method.

Example 3. Detection limits (LOD) of CN anion ^" by using compound 1.

To determine the limits of detection of the CN anion ^" in solution, specifically in aqueous solution, by means of the chromogenic compound 1 described in the present invention, its detection capacity was tested at a very low concentration of CN ^" , specifically at a level few parts per million (ppm). For this, various concentrations of KCN were added to 10 ^"5 M solutions in water: 99: 1 acetonitrile (pH 10.6 Borax / HCI) of compound 1 and the absorbance extinction was measured at λ = 563 nm. The detection limits were established according to the formula S> p _b | _ank -3σ [Zhu M., et al., Org. Lett., 2008, 10, p. 1481]. The results obtained show that the chemosensing compound 1 gave instead of a colorimetric signal after the addition of 0.65 ppm of KCN after 10 min. If said reaction mixture is maintained for 60 minutes, an LOD of 165 parts per billion (ppb) can be achieved. Both CN detection values ^" obtained through the use of compound 1, are below those indicated by the EPA (Environmental Protection Agency) for drinking water, which is 0.8 ppm [EPA safe drinking water http: //agua.epa .gov / drink / contaminants].

The limits of detection of CN ^" in aqueous solution through the use of compounds 2 and 3, following the same protocol as for compound 1, were found to be 300 and 400 ppb respectively, with an immediate response but with very limited detection limits. exceeding the detection limits obtained by using compound 1.

Example 4. Regeneration of compound 1. Samples of compound 1 were prepared, treated with potassium cyanide and, after complete discoloration, were placed under the irradiation of a 50 watt UV lamp at 254 nm. Under these conditions, said samples recover the color after 2 minutes of irradiation. The UV-vis spectrum of the regenerated sample shows a complete recovery of the absorbance intensity, which confirms the success of the regeneration process. As the cyanide remains in the solution, the reaction reverts to the leuco-cyanide species and the sample slowly discolors again. To avoid this problem, cyanide must be removed from the solution for example by passing the solution through a column packed with sand and iron (Fe) [Ghosh RS, et al., Water Environ. Res. 1999, 71, p. 1217].

A similar behavior is observed when compounds 2 and 3 are used for the detection of cyanide anion. In addition, said method can be used to discriminate between the detection of the cyanide anion and the detection of the hydrogen sulphide anion, since while the discoloration in the presence of cyanide is reversible by irradiating with UV light at 254 nm, the leuco-hydrogen sulphide does not recover the color when irradiated with said UV light [Tachikawa T., et al., J. Photopoly. Sci. Tec. 2003, 16, p. 187] (Figure 6).

Consequently, chromogenic compounds 2 and 3 have been shown to be suitable for rapid and selective detection of CN ^" or SH ^" in solution, while compound 1 is capable of detecting the presence of CN anions ^" in solution quantitatively and more selective than compounds 2 and 3.

Example 5. Detection of hydrogen cyanide (CN) anion from HCN in the gaseous state by using compound 1.

To study the ability of compound 1 to recognize cyanide anion from HCN in its gaseous state, various support systems have been developed. Among the systems developed, it was the polymers Hydromed / Cs ₂ C0 ₃ and polyethylene oxide / Cs ₂ C0 ₃ , Si0 ₂ treated with K ₂ C0 ₃ and aminated silica which showed the best results for the detection of HCN in the gaseous state. Of all of them, the aminated silica was the simplest and cheapest support while showing a good response quickly, selectively and appropriately. To demonstrate the efficacy of compound 1 in the detection of the gaseous cyanide anion, as part of the HCN compound, 5 μΙ of aqueous solutions 10 ^'3 , 10 ^"4 , 10 ^" ⁵ and 10 ^"6 M, of compound 1 were taken and deposited on plates of aminated silica in the form of a system of four drops with a separation of 1 cm between each of the drops (Figure 7) The amount of compound 1 in each drop is 5x10 ^'3 , 5x10 ^{' 4} , 5x10 ^"5 , 5x10 ^{" 6} nmol respectively. The surface of the silica strip that did not contain the drops of compound 1 It was masked with a layer of polyethylene film to prevent gas absorption in areas where it is not desired. These silica strips were hung inside a 500 ml flask along with a small vial containing different amounts of KCN. The strip is preferably placed in the lower part of the flask since at the working temperature (approximately 20 ° C), hydrogen cyanide is denser than air. The system is closed with a septum and sulfuric acid is added to the salt by means of a syringe with a long needle. As the HCN is formed, the colored spots on the silica plate begin to disappear. The number of red spots that remain depends on the amount of HCN generated and therefore on the amount of CN ^" gaseous anion detected.

Compound 1 is also capable of regenerating, in the presence of UV light, in this type of systems, in the same way as in the case of the detection of CN ^' in solution, whereby the colored stain of the silica strips is regenerates

As previously mentioned, the gaseous cyanide anion, forming part of the HCN compound in the form of gas, is very dangerous for humans. The average population can tolerate a concentration of approximately 50 ppm for 20 min-1 hour without subsequent effects, while a concentration of 546 ppm is fatal after a period of 10 minutes [Ballantyne B. Clin Toxicol, 1988, 26, p. 325]. The use of the compound 1 on a base formed by compounds of a basic nature, preferably, on a base of aminated silica, for the detection of the gaseous cyanide anion, forming part of the HCN compound in the form of gas, is capable of reaching a LOD of 2 ppm after 3 minutes of exposure, which means that it can detect hydrocyanic acid before it is dangerous to humans.

Example 6. Comparative analysis of different interfering gases for the detection of gaseous HCN by compound 1.

To demonstrate the ability of compound 1 for the detection of CN ^" anion from the gaseous HCN, specifically from the HCN compound in the form of gas, experiments were performed to detect said anion in gaseous form in the presence of different gases that could act as interfering in said detection In this sense, the aminated silica strips were contacted with 60 ppm of hydrogen chloride (HCI), ammonia (NH ₃ ), carbon monoxide (CO) and hydrogen sulfide (H ₂ S) in a 500 ml volume vessel. Hydrogen chloride and ammonia were injected into the system as 37% and 32% aqueous solutions respectively and carbon monoxide was obtained commercially (Sigma-Aldrich). On the other hand, hydrogen sulfide was generated in situ by the addition of sulfuric acid to sodium hydrogen sulfide. After 30 minutes of exposure, the aminated silica test strips were removed from the contaminated atmosphere, scanned on a commercial scanner (HP LaserJet M1005) and the color differences were compared (Figure 8).

As can be seen in Figure 8, the interfering gases HCI and NH ₃ do not cause any change in the color of the sensor, compound 1. Visually the color is the same as that of the target, although the ammonia partially extends the spot in the siliceous support. CO and H ₂ S do change the color of the sensor but in a different way than HCN does. In the case of carbon monoxide, the RGB color coordinates were 179, 120, 126, which translates into a brown color at 30 minutes that evolves to green after 24 hours. On the other hand, H ₂ S cannot be considered an interference because the sensor acquires a clear blue color (RGB 175, 170, 176).

If the blue color coordinate is analyzed exclusively, it can be seen that a greater difference is shown, since only HCN results in an increase in said coordinate as can be seen in Figure 9.

The chromogenic compounds 1, 2 and 3, as described in the present invention, can therefore be used as chemical sensors to detect cyanide in aqueous medium. Compound 1 shows a much more selective behavior than compounds 2 and 3 in recognizing this anion, being able to easily discriminate between the cyanide anion and hydrogen sulfide. Moreover, chromogenic compounds 2 and 3 are more reactive than compound 1 and for this reason they are less selective, giving rise to the same reaction both in the presence of cyanide and in the presence of hydrogen sulfide, although the photochemical behavior of the products of obtained reaction allows to distinguish between both. The optimum pH and temperature for the detection of the cyanide anion through the compound 1 described in the present invention are a pH value = 10.6 and a temperature of 20 ° C. The compound 1 can also be regenerated after the detection process of the cyanide anion in solution, by irradiation with UV light, so it can be used continuously. On the other hand, the present invention shows that by using compound 1, cyanide anion from HCN can be detected in the gaseous state, said anion forming part of the gaseous HCN compound. Of the supports studied, the aminated silica is the one that has resulted in better results when used as a support. Prepared test strips can be regenerated, so they can be reused continuously. The detection limits for the cyanide anion in the gaseous state reached with this system are below the values considered dangerous for humans.

Claims

1. Use of compound 1 for the colorimetric detection of cyanide anion (CN)

Compound 1

2. Use of compound 1 for the colorimetric detection of CN ^" according to claim 1, characterized in that said detection is carried out from the compound hydrogen gas cyanide (HCN).

3. Use of compound 1 for the colorimetric detection of CN ^" according to claim 2 wherein compound 1 is deposited on a solid support of a basic nature.

4. Use of compound 1 for the colorimetric detection of CN ^" according to claim 3 wherein the solid support is selected from any of the following: Hydromed / Cs ₂ C0 ₃ , polyethylene oxide / Cs ₂ C0 ₃ , Si0 ₂ treated with K ₂ C0 ₃ and aminated silica.

5. Use of compound 1 for the colorimetric detection of CN ^" according to claim 4 wherein the solid support is an aminated silica.

6. Use of compound 1 for the colorimetric detection of CN ^" according to claim 1 wherein the cyanide anion is in solution.

7. Use of compound 1 for the colorimetric detection of CN ^" according to claim 6 wherein the dissolution is carried out in any of the solvents selected from: water, ethanol, DMSO or CH ₃ CN.

8. Use of compound 1 for the colorimetric detection of CN ^" according to claim 7 wherein the solvent is water.

9. Colorimetric cyanide anion (CN) detection device comprising compound 1.

10. The CN ^' colorimetric detection device according to claim 9, characterized in that said detection is carried out from the gaseous hydrogen cyanide compound (HCN).

11. CN ^" colorimetric detection device according to claim 10 wherein the compound 1 is deposited on a solid support of a basic nature.

12. CN ^" colorimetric detection device according to claim 11 wherein the solid support is selected from any of the following: Hydromed / Cs ₂ C0 ₃ , polyethylene oxide / Cs ₂ C0 ₃ , S¡0 ₂ treated with K ₂ C0 ₃ and aminated silica.

13. CN ^" colorimetric detection device according to claim 12 wherein the solid support is an aminated silica.

14. CN ^" colorimetric detection device according to claim 9 wherein the cyanide anion is in solution.

15. CN ^" colorimetric detection device according to claim 14 wherein the dissolution is carried out in any of the solvents selected from: water, ethanol, DMSO or CH ₃ CN.

16. CN ^" colorimetric detection device according to claim 15 wherein the solvent is water.

17. Colorimetric detection method of cyanide anion (CN) by using compound 1 according to any one of claims 1 to 8 or the device comprising it according to any of claims 9 to 16.

18. The method of colorimetric detection of CN ^" according to claim 17 wherein the optimum pH for the colorimetric detection of the cyanide anion in solution ranges from 8.5 to 10.6.

19. Colorimetric CN detection method ^" according to claim 18 wherein the optimum pH is 10.6.

20. Colorimetric detection method of CN ^" according to any of claims 17 to 19 wherein the optimum temperature for the colorimetric detection of the cyanide anion in solution varies between 10-60 ° C.

21. Colorimetric detection method of CN ^" according to claim 20 wherein the optimum temperature is 20 ° C.

22. Colorimetric detection method of CN ^" according to any of claims 17-21 wherein the compound 1 or the device comprising it is regenerated by irradiation with UV light.