WO2020225828A1

WO2020225828A1 - A process for detection and distinction of nitroaromatic explosives using amines

Info

Publication number: WO2020225828A1
Application number: PCT/IN2020/050412
Authority: WO
Inventors: Santhosh Babu SUKUMARAN; Goudappagouda .; Kiran ASOKAN
Original assignee: Council Of Scientific And Industrial Research
Priority date: 2019-05-07
Filing date: 2020-05-07
Publication date: 2020-11-12

Abstract

The present invention provides a process for the detection as well as distinction of the nitro aromatic explosive compounds by using amine compounds on the basis of visual color change method, wherein said amine compounds are primary, secondary and tertiary.

Description

A PROCESS FOR DETECTION AND DISTINCTION OF NITROAROMATIC

EXPLOSIVES USING AMINES

FIELD OF THE INVENTION

The present invention relates to a detection and distinction of nitro aromatic explosives using amine compounds. Particularly, present invention provides a process for the detection as well as distinction of the nitro aromatic explosive compounds by using amine compounds on the basis of visual color change method, wherein said amine compounds are primary, secondary and tertiary.

BACKGROUND AND PRIOR ART OF THE INVENTION

In current era, due to higher risks of terrorism everywhere, easy and efficient detection of explosives became very important task. Different explosive compounds, more particularly nitro aromatic compounds are used as explosives as they are easily available and cheap. Most of the times nitro aromatic compounds like trinitrotoluene, dinitrotoluene, nitrobenzene etc. are used as explosives. Being the primarily used nitroaromatic explosives produced during military preparation of landmines, TNT and its derivatives is also one of the key sources of dangerous water contamination. Hence, on-spot detection and distinction methods of these explosives are still an area of interest for the researchers.

Several methods have been reported in the literature for the detection of nitroaromatic compounds. Current sensing methods of nitro-based explosives are gas and liquid chromatography, mass spectrometry, ion-mobility spectroscopy, enzymatic assays, and electrochemical detection.

The article titled“Dual-emitting quantum dot nanohybrid for imaging of latent fingerprints: simultaneous identification of individuals and traffic light-type visualization of TNT” by Hong-Yuan Chen et. al and published in the journal“Chem. Sci., 2015, 6, 4445” reports a nanohybrid comprising green- and red-emitting QDs for simultaneous fingerprint imaging and TNT visualization in fingerprints.

The article titled“Nanomaterials for luminescence detection of nitroaromatic explosives” by Leyu Wang et.al and published in the journal “TrAC Trends in Analytical Chemistry, Volume 65, February 2015, Pages 13-21” reports on the current diverse methodologies, principles and techniques for detection of nitroaromatic explosives based on the luminescence of nanomaterials.

Trinitrotoluene, commonly known as TNT, is a major secondary explosive used in terror attacks. Detection of such compounds by very cost effective and simple techniques would be a great achievement and of national importance. The major drawback in the established TNT sensors is majority of them exhibit same or nearly same results for structurally similar nonexplosive also. Hence detection (at low concentration) and distinction of TNT from other nitroaromatic compounds is highly important.

Therefore, there is a need in the art to provide a simple and cost-effective method of detection and distinction for the nitroaromatic explosive compounds. Simple and label-free alternative to use optical detection in association with designed colorimetric arrays of charge-transfer acceptor/donor complexes made of simple drop-casting method or by making a thin film is useful way to solve the problems associated.

OBJECTS OF THE INVENTION

Main objective of the present invention is to provide a process for the detection as well as distinction of the nitroaromatic explosive compounds by using selective amine compounds, wherein said amine compounds are primary, secondary and tertiary.

Another objective of the present invention is to provide a kit for the detection and distinction of nitro aromatic amines, which enables the on-spot detection and distinction of nitroaromatic explosive compounds.

SUMMARY OF THE INVENTION

Accordingly, present invention provides a process for the detection and distinction of the nitroaromatic explosive compounds by using amines wherein said amines are primary, secondary or tertiary.

In an embodiment of the present invention, said process comprises:

i. drop casting the 10 to 20 mL of reagent amine samples in alcohol on glass slide and allowing to dry for 5 to 10 minutes and adding 10 to 20 mL of nitroaromatic molecules in acetone solvent and again allowing to dry for period in the range of 5-10 minutes, followed by detecting and identifying the explosive compound by color change, which is visible by bare eyes. In yet another embodiment of the present invention, the alcohol used is methanol but not restricted to it.

In yet another embodiment of the present invention, the slide is to be cleaned with acetone and isopropyl alcohol for 10 to 15 minutes each in an ultrasonic bath and to be blow dried with a hot-air gun before use.

In yet another embodiment of the present invention, said amines are further selected from the group comprising of:

In yet another embodiment of the present invention, said nitroaromatic compounds are selected from the group consisting of 2-methyl-l, 3, 5-trinitrobenzene (TNT), l-methyl-2, 4- dinitrobenzene (DNT), nitrobenzene (NB), p-nitrotoluene, o-nitrotoluene, research department explosive (RDX) or p-nitrophenol.

In yet another embodiment of the present invention, said process detects and differentiates the 2-methyl-l, 3, 5-trinitrobenzene (TNT), l-methyl-2, 4-dinitrobenzene (DNT) and nitrobenzene (NB) in 10^-06, 10^-05, 10^-04 and 10^-03 molar concentrations.

In yet another embodiment, present invention provides a kit for the detection and differentiation of nitro aromatic explosive compounds, wherein the kit comprises:

a) Droppers and spatula (1);

b) well plate (2);

c) Paper-strips (3);

d) spraying bottles (4) of amines as mentioned above and;

e) standard analyte sample of nitroaromatic compound (5). In yet another embodiment of the present invention, said dropper is utilized for spotting the samples on well-plate; wherein said spatula is utilized for taking analyte on well-plate; wherein said well-plate is utilized to take analyte sample on it for testing; wherein said spraying bottle is utilized to carry reagent amines for testing and spraying the amine solution in methanol on analyte sample.

In yet another embodiment of the present invention, said paper-strips are utilized for the detection of explosive compounds by touching the paper-strip on explosive compound and spraying reagent amine solution on paper-strip for visible color detection.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1: Photograph of the well plate showing visible color detection of TNT using various aliphatic acyclic primary amines.

Figure 2: Photograph of the well plate showing visible color detection of DNT using aliphatic acyclic primary amines.

Figure 3: Photograph of the well plate showing visible color detection of NB using aliphatic acyclic primary amines.

Figure 4: Photograph of the well plate showing three different visible color detection of TNT using amines 4, 5, 6.

Figure 5: Photograph of the well plate showing visible color detection of TNT using various aromatic primary amines.

Figure 6: Photograph of the well plate showing visible color detection of DNT using various aromatic primary amines.

Figure 7: Photograph of the well plate showing visible color detection of TNT using various aromatic primary amines.

Figure 8: Photograph of the well plate showing visible color detection of DNT using various aromatic primary amines.

Figure 9: Photograph of the well plate showing visible color detection of TNT using various benzylic amine derivatives.

Figure 10: Photograph of the well plate showing visible color detection of DNT using various benzylic amine derivatives.

Figure 11: Reflectance spectra of amines 4N and 3N with different concentration of TNT. Figure 12: Reflectance spectra of amines 3NM and 2N with different concentration of TNT. Figure 13: Reflectance spectra of amines 4N and 3N with different concentration of DNT. Figure 14: Reflectance spectra of amines 3NM and 2N with different concentration of DNT. Figure 15: Reflectance spectra of amines 4N and 3N with different concentration of NB. Figure 16: Reflectance spectra of amines 3NM and 2N with different concentration of NB. Figure 17: FT-IR spectra of amine 4N with different concentration of TNT.

Figure 18: FT-IR spectra of amine 3N with different concentration of TNT.

Figure 19: FT-IR spectra of amine 3NM with different concentration of TNT.

Figure 20: FT-IR spectra of amine 2N with different concentration of TNT.

Figure 21: FT-IR spectra of amine IN with different concentration of TNT.

Figure 22: FT-IR spectra of amine 4N with different concentration of DNT.

Figure 23: FT-IR spectra of amine 3N with different concentration of DNT.

Figure 24: FT-IR spectra of amine 3NM with different concentration of DNT.

Figure 25: FT-IR spectra of amine 2N with different concentration of DNT.

Figure 26: FT-IR spectra of amine 4N with different concentration of NB.

Figure 27: FT-IR spectra of amine 3N with different concentration of NB.

Figure 28: FT-IR spectra of amine 3NM with different concentration of NB.

Figure 29: FT-IR spectra of amine 2N with different concentration of NB.

Figure 30: FT-IR spectra nitroaromatic acceptor molecules.

Figure 31: FT-IR spectra nitroaromatic acceptor molecules.

Figure 32: Reflectance spectra of amine 4 and 5 with different concentration of TNT.

Figure 33: Reflectance spectra of amine 6 with different concentration of TNT.

Figure 34: Reflectance spectra of amine 7 with different concentration of TNT.

Figure 35: Reflectance spectra of amine 9 with different concentration of TNT.

Figure 36: FT-IR spectra of amine 4 with different concentration of TNT.

Figure 37: FT-IR spectra of amine 5 with different concentration of TNT.

Figure 38: FT-IR spectra of amine 6 with different concentration of TNT.

Figure 39: FT-IR spectra of amine 7 with different concentration of TNT.

Figure 40: FT-IR spectra of amine 9 with different concentration of TNT.

Figure 41: Explosive detection kit. DETAILED DESCRIPTION OF THE INVENTION

Present invention provides a process for the detection as well as distinction of nitro aromatic explosive compounds by using selective amine compounds, wherein said amine compounds are primary, secondary and tertiary. A simple and label-free alternative to use optical detection in association with designed colorimetric arrays of charge-transfer acceptor/donor complexes made of simple drop-casting method or by making a thin film is provided.

The present invention provides a process for the detection and distinction of nitroaromatic explosive compounds Tri nitro toluene (TNT), Dinitro toluene (DNT), Nitro benzene (NB) by using selective amine compounds; wherein said amine compounds are primary, secondary and tertiary.

The process of detection and distinction of nitroaromatic explosive compounds comprises of drop casting the 20 mL of free amine samples in an alcohol on glass slide (glass substrates to be cleaned with acetone and isopropyl alcohol (IPA) for 10 to 15 minutes each in an ultrasonic bath and to be blow dried with a hot-air gun before use) and allowing to dry for 5 to 10 minutes and adding 10 to 20 mL of nitroaromatic molecules in acetone solvent and again allowing to dry for 5-10 min. The color change is identified by bare eyes. Preferably, the alcohol is methanol but is not restricted to it.

The detection process of the present invention provides different classes of amines which show different and distinguishable colors upon contact with nitro aromatic explosive compounds, wherein said amines are selected from the classes of amines comprising of

i. aliphatic acyclic primary amines;

ii. aliphatic cyclic primary amines;

iii. aromatic primary amines;

iv. benzylic amines and;

v. aliphatic and aromatic secondary and tertiary amines (Miscellaneous amines).

Classes of amines used for the detection as well as distinction of the nitroaromatic explosive compounds further comprises of following amines:

Aliphatic acyclic primary amines:

Aliphatic cyclic primary amines:

Aromatic primary amines:

Benzylic amine derivatives:

The same detection process of the present invention enables distinction of TNT from other nitroaromatic compounds of the same category through colorimetric detection. After contacting amine with TNT, the colourless amine showed a rapid colorimetric change which can be easily identified by the naked eye. The amine is carefully optimized to achieve visible detection of TNT at mM concentration. The process gives a new simple colorimetric (visual) detection of TNT in 0.035 ppm level and even it differentiates the DNT and NB by giving different color.

A series of nitroaromatic molecules such as trinitrotoluene (TNT), dinitrotoluene (DNT) and nitrobenzene (NB) in various concentrations such as 10^-06, 10^-05, 10^-04 and 10^-03 molar in acetone can be identified and differentiated with the process. The nitro aromatic compounds that can be detected and distinguished by the process comprises of:

The detection and distinction process of different aromatic compounds by using amines on well plate comprises of keeping constant amine concentration of 1 mM and different TNT concentrations ranging from 1 mM to 1 mM in acetone. A dark red color is observed at 1 mM concentration of TNT and as the concentration of TNT decreases, the intensity of the red color also decreases and this indicates that TNT can be detected even at lower concentrations (pM). Similarly, visible color detection of DNT and NB is conducted using all the four amines.

The interaction of TNT with 4N amine is seen by placing various concentrations of 20 mL TNT solution in acetone and mixing with 20 mL of 1 mM methanol solution of 4N amine having primary amine group well plate. An immediate red color is appeared and which is intensified to dark red within 5 min as depicted in Figure 1. This is caused by the formation of a colored Meisenheimer complex with a new charge transfer band located at around 467 nm. The detection range for TNT by the naked eye is limited to 1 pM. Further, it has been extended to DNT and NB, however, no immediate color change is observed within 2-5 min. A violet and yellow coloration is appeared for DNT and NB, respectively, after 5 min. DNT gives violet color with 4N amine till 10^-4 M concentration and NB gives light yellow color till lmM concentration as shown in Figures 2 and 3. Only NB is not delivering any color with amines such as 2N amine and IN amine. Figure 1-4 show the photograph of the well plate showing visible color detection of TNT, DNT, NB using various amines.

The nitroaromatic explosive-amine complexes are analysed by reflection mode UV-Vis spectra in order to understand the colorimetric detection of TNT. As shown in Figure 1, the red areas on the film corresponding to TNT-amine complex exhibited a new broad peak in the range of 350-700 nm upon interaction with amines such as 4N amine and 3N amine as shown in Figure 11, 3NM amine and 2N amine as shown in Figure 12. All the four amines resulted in similar color change with TNT.

In the case of DNT, the violet coloration upon contact with amines is due to the weak CT band that appeared between 250-410 nm as shown in Figures 13 and 14. Similarly, NB also exhibits a weak CT band and hence results in a yellow colour as shown in Figures 15 and 16. Nitroaromatic compounds can be detected and differentiated selectively using the complex formation with amines. The extent of donor-acceptor interaction varies with the class of nitroaromatic molecules and enables to see a visible colour change upon complexation with amines.

In FT-IR spectrum of primary amines, the N-H stretching frequency is located at 3300 cm ¹ and 1411 cm ¹ and wagging frequency at 730 cm ¹. The intensity of amine peak has come down in the presence of nitroaromatic explosive molecules. In addition, a shift in each peak is also observed as shown in Figures 17-21. FT-IR changes for TNT, DNT and NB clearly shows the molecular level changes upon complexation with various amines as shown in Figures 17-21, Figures 22-25 and Figures 26-29, respectively. The shift in N-H stretching frequency confirms the formation of a Meisenheimer complex between the NH₂ group and TNT.

Figures 30 and 31 show FT-IR spectra for nitroaromatic acceptor molecules.

Figures 7 and 8 show detection with aliphatic cyclic amines which give color detection for only TNT till ImM, but not for DNT and NB. And charge transfer complex is confirmed by reflectance spectra and IR Figures 35, and 39.

Aromatic primary amine gives different color for TNT alone, amine 7 with TNT gives brown color and amine 8 with TNT gives purple, and amine 10 with TNT gives orange. All these has been detected till mM concentration as shown in Figures 5, and these complexes are confirmed by reflectance and FT-IR spectra Figures 35, and 40.

Aliphatic secondary amine and aromatic primary and secondary amines 15-25 are not sensing TNT, DNT and NB as shown in Figure 40. Present invention provides a kit for the detection and distinction of nitroaromatic explosive compounds which comprises of droppers and spatula (1), well plate (2), Paper-strips (3), spraying bottles with amine solution (4) and standard analyte sample (Standard samples of nitroaromatic compounds are provided as solid, but solution can be prepared in acetone (1 mM)) (5), as illustrated in Figure 41. Kit is utilized in the following manner:

Dropper: For spotting the sample on well-plate.

Spatula: For taking analyte on well plate.

Well-plate: Take analyte sample on it for testing, and spray reagent.

Paper-strips: One more method for detection of explosive, touch the paper-strip on explosive and spray reagent amine solution on paper-strip for visible color detection.

Spraying bottle: for carrying the reagent amines solution in methanol (ImM).

Here the reagent amines 4N, 3NM and 3N, have been introduced for colorimetric detection of explosives. It can work for bulk quantity as well as small amounts of the samples. For bulk quantity, the solutions of these reagent amines in the spraying bottle can be directly sprayed on the bulk explosive materials. And for small amount of analyte from the illegally transporting explosives or from the explosion spot can be transferred on to the well plate and detected by applying the spray reagent amine. The kit also contains paper strips, which can be used by dipping it in the analyte directly and spraying reagent amine solution from spray bottle on it for colorimetric detection. Analyte on paper strip changes various colors upon contact with the reagent.

EXAMPLES

Following examples are given by way of illustration therefore should not be construed to limit the scope of the invention.

Example 1: Visible color detection of nitroaromatic explosives using amines in well plate.

In general, amine concentration was kept constant (1 mM) in acetone and TNT concentration was varied from 1 mM to 1 mM.

Solid explosive materials or solution in acetone (1 mM) is transferred to a well plate/glass slide. The solutions of amines in methanol (1 mM) can be directly sprayed on the analyte samples on well plate or glass slide. The nitroaromatic compounds can be differentiated by the visible color change obtained after the formation of the Meisenheimer complex.

A dark red color was observed at 1 mM concentration of TNT in acetone. As the concentration of TNT decreases, the red color intensity also decreases and this indicates that TNT can be detected even at lower concentrations (mM). Similarly, visible color detection of DNT and NB is conducted using all the four amines (2N, 3N, 3NM, 4N).

Example 2: Visible colour detection of nitroaromatic explosives using amines in a well plate. The interaction of TNT with 4N amine was examined by placing various concentrations of 20 mL TNT solution in acetone and mixing with 20 mL of 1 mM methanol solution of 4N amine having primary amine group in a well plate.

Example 3: Visible colour detection of nitroaromatic explosives using amines on Whatman filter paper strips.

The paper strips can be used by dipping it in the solution of the analyte (acetone, 1 mM) or solid explosive sample directly and spraying reagent amine solution in methanol (1 mM) from spray bottle on it for colourimetric detection. Analyte on paper strip changes various colors upon contact with the reagent.

ADVANTAGES OF THE INVENTION

• A new simple colorimetric (visual) detection and differentiation of TNT, DNT and NB.

• A three different classes of amines are introduced which deliver three drastically different and distinguishable colors upon contact with TNT.

• A distinction of TNT from other nitroaromatic compounds of the same category through colorimetric detection is provided.

• Amines of the present invention in contact with TNT, show a rapid colorimetric change which can be easily identified by the naked eye.

• The amines can visibly detect and differentiate the TNT, DNT and NB at mM concentration (0.035 ppm level).

Claims

We claim

1. A process for detection and distinction of a nitroaromatic explosive compound by using amines; wherein said amines are primary, secondary or tertiary.

2. The process as claimed in claim 1, wherein said process comprises:

i. drop casting the 10 to 20 mL of reagent amine samples in an alcohol on glass slide and allowing to dry for 5 to 10 minutes and adding 10 to 20 mL of nitroaromatic molecules in acetone solvent and again allowing to dry for period in the range of 5-10 minutes, followed by detecting and identifying the explosive compound by color change, wherein the color change is visible by bare eyes.

3. The process as claimed in claim 2, wherein the alcohol used is methanol but not restricted to it.

4. The process as claimed in claim 2, wherein the glass slide is to be cleaned with acetone and isopropyl alcohol for 10 to 15 minutes each in an ultrasonic bath and to be blow dried with a hot-air gun before use.

5. The process as claimed in claim 1, wherein said amines are further selected from the group comprising of:

6. The process as claimed in claim 1, wherein said nitroaromatic compounds are selected from the group consisting of 2-methyl-l, 3, 5-trinitrobenzene (TNT), l-methyl-2, 4- dinitrobenzene (DNT), nitrobenzene (NB), p-nitrotoluene, o-nitrotoluene, research department explosive (RDX) or p-nitrophenol.

7. The process as claimed in claim 1, wherein said process detects and differentiates the 2-methyl-l, 3, 5-trinitrobenzene (TNT), l-methyl-2, 4-dinitrobenzene (DNT) and nitrobenzene (NB) in 10^-06, 10^-05, 10^-04 and 10^-03 molar concentrations.

8. A kit for the detection and differentiation of nitro aromatic explosive compounds comprises:

a) Droppers and spatula (1); b) well plate (2);

c) Paper-strips (3);

d) spraying bottles with amine solution (4) and;

e) standard analyte sample of nitroaromatic compound (5).

9. The kit as claimed in claim 8, wherein said dropper is utilized for spotting the sample on well-plate; wherein said spatula is utilized for taking analyte on well-plate; wherein said well-plate is utilized to take the analyte sample on it for testing; wherein said spraying bottle is utilized to carry reagent amines for testing and spraying the amine solution in methanol on analyte sample.

10. The kit as claimed in claim 8, wherein said paper-strips are utilized for the detection of explosive compounds by touching the paper-strip on explosive compound and spraying reagent amine solution on paper-strip for visible color detection.