ANALYTICAL PROCESS FOR DETECTING PEROXIDE-, HALOGEN OXOANION-, NITRATE-, NITRAMINE-, AND NITROTOLUENE-BASED EXPLOSIVES

Abstract

The invention provides an analytical process, which preferably is a one-step process, for detecting in a sample peroxide-based explosives, nitrate-based explosives and/or nitramine-based explosives, the process comprising contacting a sample suspected of containing a peroxide-based compound, especially a peroxide-based explosive, a nitramine, nitrate ester or a nitrate salt, especially a nitrate-based explosive and/or a nitramine-based explosive, with a composition comprising a Ni-porphyrin, an acid and preferably an acid-stable solvent.

Claims

1. Analytical process for detecting compounds, comprising contacting a sample suspected of containing a peroxide-based compound, a nitrate-based compound, or a nitrotoluene-based compound, or a nitramine-based compound with a composition comprising or consisting of a Ni-porphyrin, and an acid.

2. Analytical process according to claim 1, wherein the compound to be detected is an explosive.

3. Analytical process according to claim 1, wherein the peroxide-based compound is one more than one of the following triacetone triperoxide (TATP), diacetone diperoxide (DADP), methyl ethyl ketone peroxide (MEKP) and/or hexamethylene triperoxide diamine (HMTD), wherein the nitrate-based explosive is potassium nitrate (KNO.sub.3), ammonium nitrate (NH.sub.4NO.sub.3), urea nitrate (NH.sub.2COHNH.sub.2.sup.+.NO.sub.3.sup.−), nitroglycerine (NG), ethylene glycole dinitrate (EGDN), and/or pentaerythritol tetranitrate (PETN), and the nitramine-based explosive is 1,3,5-trinitro-1,3,5-triazinane (hexogen, RDX), 1,3,5,7-tetranitro-1,3,5,7-tetrazoctane (octogen, HMX), 2,4,6-trinitrophenylmethylnitramine (tetryl), 2,4-dinitrotoluene (DNT) or 2,4,6-trinitrotoluene (TNT), and/or nitrourea (NH.sub.2CONHNO.sub.2).

4. Analytical process according to claim 1, comprising treating the sample with a superbase before contacting the sample with the Ni-porphyrin and acid.

5. Analytical process according to claim 4, wherein the superbase is an organic superbase.

6. Analytical process according to claim 1, wherein nitramines after treatment with an organic superbase are indicated by the Ni-porphyrin finally generating a brown color and nitrotoluenes generating a deep violet color immediately upon treatment with superbase.

7. Analytical process according to claim 1, wherein the composition contains an acid-stable solvent.

8. Analytical process according to claim 1, wherein the acid is a free acid.

9. Analytical process according to claim 1, wherein the acid is formed by at least one substituent to the Ni-porphyrin.

10. Analytical process according to claim 1, wherein the sample is a gaseous sample taken from a container or from an environment suspected of containing a peroxide-based explosive.

11. Analytical process according claim 1, characterized in that the composition comprising or consisting of a Ni-porphyrin, an acid and optionally an acid-stable solvent, is held by a carrier, which is a porous acid-stable material and/or swelling liquid adsorbing acid-stable material that forms a gel, the carrier forming a supporting material for a liquid composition containing the Ni-porphyrin and the acid.

12. Analytical process according to claim 1, wherein the composition comprises or consists of a Ni-porphyrin, an acid and acid-stable solvent, the composition is liquid and is contacted with the sample in the form of droplets.

13. Analytical process according to claim 1, wherein a portion of the sample is contacted with the composition comprising the Ni-porphyrin and a strong acid in order to detect all peroxides, and a portion of the sample is contacted with the composition comprising the Ni-porphyrin and a weaker acid in order to detect only hydrogen peroxide.

14. Analytical process according to claim 1, wherein peroxide-based compounds are indicated by the Ni-porphyrin finally generating green color, and that nitrate-based compounds and nitramine-based compounds are indicated by the Ni-porphyrin generating green color and finally generating brown color.

15. Composition for use in an analytical process for use in detecting a peroxide-based compound, a nitrate-based compound, a nitrotoluene-based compound, or a nitramine-based compound, characterized by the composition comprising or consisting of Ni-porphyrin, an acid having a pK.sub.a of −1.2 to 0.23, with or without an acid-stable solvent.

16. Composition according to claim 15, wherein the acid is a free acid.

17. Composition according claim 15, wherein the acid is a substituent to the Ni-porphyrin and linked to a pyrrole ring of the Ni-porphyrin by an intermediate linker which has a chain length of at least 1 atom and/or the acid substituent is linked to an aryl group substituting the Ni-porphyrin in meso position directly or by an intermediate linker, which linker has a chain length of at least 1 atom.

18. Composition according to claim 15, wherein the composition is held on a carrier that is porous and/or swelling.

19. Composition according to claim 15, wherein the composition is a solution in an acid-stable solvent.

20. Composition according to claim 15, characterized in that the porphyrin is Ni-porphyrin, which is substituted in at least one of its meso positions with at least one aryl group, which is substituted with at least one electron-donating group.

21. Composition according to claim 15, wherein the Ni-porphyrin is substituted with an acid group linked to the at least one aryl group by an intermediate linker, which linker has a chain length of at least 1 atom and/or in that the porphyrin is substituted with an acid group linked to a pyrrole group by an intermediate linker which has a chain length of at least 1 atom, and/or in that the Ni-porphyrin is substituted with at least one acid group which is directly bound to at least one aryl group substituting the Ni-porphyrin in meso position.

22. Composition according to claim 15, wherein the Ni-porphyrin is present on a porous carrier that is attached to a plastic strip, in combination with a container containing the acid as a liquid, optionally the acid being in mixture with an acid-stable organic solvent, optionally in combination with a container containing a liquid superbase, in a kit-of-parts.

23. Composition according to claim 15, wherein the Ni-porphyrin has a bound acid group having a pKa of −1.2 to 0.23, which Ni-porphyrin is present on a porous carrier that is attached to a plastic strip, in combination with a container containing an acid-stable organic solvent, optionally in combination with a container containing a liquid superbase, in a kit-of-parts.

24. Composition according to claim 15, wherein the Ni-porphyrin is in a mixture with a free acid having a pKa of −1.2 to 0.23, which Ni-porphyrin and free acid are present in an acid-stable organic solvent in a container, optionally in combination with a container containing a liquid superbase, in a kit-of-parts.

25. Composition according to claim 15, wherein the Ni-porphyrin has a bound acid group having a pKa of −1.2 to 0.23, which Ni-porphyrin is present in an acid-stable organic solvent in a container, optionally in combination with a container containing a liquid superbase, in a kit-of-parts.

26. Process for producing an analytical device suitable for detecting compounds in a sample, comprising or consisting of providing a carrier that is porous and/or swelling, optionally attached to an inert base material, adding a composition comprising or consisting of a Ni-porphyrin and an acid having a pKa of −1.2 to 0.23 onto the carrier.

27. Process according to claim 26, wherein the acid is a free acid or is an acid group linked to a pyrrole ring of the Ni-porphyrin by an intermediate linker which has a chain length of at least 1 atom and/or the acid substituent is linked to an aryl group substituting the Ni-porphyrin in meso position directly or by an intermediate linker, which linker has a chain length of at least 1 atom.

28. Process according to claim 26, wherein the composition is added onto the carrier as solution in an organic solvent, followed by evaporation of the solvent from the carrier.

29. Analytical device suitable for detecting compounds in a sample, comprising or consisting of a carrier that is porous and/or swelling, optionally attached to an inert base material, the carrier being provided with a composition comprising or consisting of a Ni-porphyrin and an acid.

30. Analytical device according to claim 29, wherein the acid is a free acid or is linked to a pyrrole ring of the Ni-porphyrin by an intermediate linker which has a chain length of at least 1 atom and/or the acid substituent is linked to an aryl group substituting the Ni-porphyrin in meso position directly or by an intermediate linker, which linker has a chain length of at least 1 atom.

Description

[0055] The invention is described in greater detail by way of examples with reference to

[0056] FIG. 1 that shows a reaction mechanism according to the invention,

[0057] FIG. 2 that shows UV spectra of the reaction product obtained by the analytical process. The UV spectra shown in FIG. 2 are superimposed of a composition according to the invention of Ni-tetrakis(trimethoxyphenyl)porphyrin and trifluoroacetic acid (TFA), of the reaction product of this composition according to the invention with TATP after 2.3 min as indicated, and of the reaction product of this composition according to the invention with TATP after 12.5 min. The UV spectra prove that the Soret and Q band, which are characteristic for the Ni-porphyrin, decrease in the presence of TATP and a broad band between 550 and 700 nm is built up, which band is typical for the porphyrin radical cation, and

[0058] FIG. 3 which shows test stripes as an embodiment of the invention.

EXAMPLE 1: DETECTING SOLID TATP FROM THE HEAD SPACE

[0059] A plastic stripe (90×5 mm) equipped with a cellulose pad (5×5 mm) at one end, impregnated with Ni-tetrakis(3,4,5-trimethoxyphenyl)porphyrin by dropping 5 μL of a 1 mM solution of the porphyrin in toluene onto the cellulose pad and then the solvent is removed by evaporation. The stripe prepared in this way is moistened with a drop of 5-10 μL of perfluoropentanoic acid. The addition of the acid to the Ni-porphyrin compound of the invention herein is also referred to as activating the Ni-porphyrin or the stick. The activated stick is brought into close proximity, ca.˜3 mm to crystals of TATP present on an uncovered surface or into the headspace of TATP present in a small glass vial. After 15 s the red color of the pad turns into green. Assuming a saturation vapour pressure in the head space of the solid explosive and a volume of 3 mL of gas, 8 nmol of TATP can be detected.

EXAMPLE 2: DETECTING ORGANIC NITRATES (E.G. PETN, EGDN, NG), AND NITRATE SALTS (E.G. NH.SUB.4.NO.SUB.3., KNO.SUB.3., NaNO.SUB.3.) FROM THE HEAD SPACE

[0060] Traces of these compounds, PETN, EGDN, NG, and nitrate salts (e.g. NH.sub.4NO.sub.3, KNO.sub.3, NaNO.sub.3) each separately present on an uncovered surface, or in a small glass vial are treated with a drop (5-10 μl) of perfluoropentanoic acid. After several seconds, the activated plastic stripe prepared as in Example 1 is brought into close proximity (˜3 mm) to one of the compounds present on the surface or into the head space of the glass vial. The color of the pad turns from red to brown. The detection of nitrate salts by the invention is obtained also when the nitrate salts are present in solution or in a dry mixture, e.g. with sulfur and charcoal as in black powder.

EXAMPLE 3. DETECTING NITRAMINES (E.G. HEXOGEN, OCTOGEN, NITROUREA) FROM THE HEAD SPACE

[0061] Separately, traces of solid nitramines on a surface or in a small glass vial are moistened with a drop (5-10 μl) of a solution of an organic superbase (e.g. 20 vol. % P.sub.1-t-Bu in dissolved in acetonitrile). Then a drop (5-10 μl) of perfluoropentanoic acid is applied to the same spot. The activated stripe prepared as in Example 1 is brought into close proximity (˜3 mm) of the suspension of one of the nitramine compounds in the organic superbase on the surface or into the headspace of the glass vial. The color of the pad immediately turns from red to brown.

EXAMPLE 4: DETECTING PEROXIDES (E.G. HMTD, TATP), CHLORATES (E.G. KClO.SUB.3., NaClO.SUB.3.), AND BROMATES (E.G. KBrO.SUB.3., NaBrO.SUB.3.) IN THE SOLID STATE

[0062] The activated stripe (prepared as in Example 1) is separately brought into contact with traces of solid HMDT, TATP, or chlorate by swiping a contaminated surface. The color of the stripe immediately changes from red to green at the spots, where the pad comes into contact with traces of the solid explosive. These green spots spread out and within about 30 seconds the pad turns green. 10 μl of a 12.65 μM solution of TATP dissolved in dichloromethane were dropped as a round spot onto the previously prepared test stripe. After one minute the test stripe turned light green. Using this method, it is possible to detect 0.125 nmol (28 ng) TATP.

[0063] FIG. 3 shows a plastic stripe with a terminally attached cellulose pad impregnated with Ni-porphyrin according to the invention, prior to contact with a compound to be detected (fresh (red)), and a plastic stripe containing the same Ni-porphyrin, activated by adding acid and after contact with peroxide (peroxide (green)), and a plastic stripe containing the same Ni-porphyrin activated by adding acid and after contact with nitrate (nitrate (brown)).

EXAMPLE 5: DETECTING ORGANIC NITRATES (E.G. PETN, EGDN, NG), AND NITRATE SALTS (E.G. NH.SUB.4.NO.SUB.3., KNO.SUB.3., NaNO.SUB.3.) IN THE CRYSTALLINE STATE OR AS NEAT LIQUIDS

[0064] The activated stripe prepared as in Example 1 is brought into contact with separate traces of solid nitrate salts or organic nitrates (PETN is a solid, EDGN and NG are liquids) by swiping a contaminated surface. The color of the stick immediately changes from red to green at the spots, where the pad comes into contact with traces of the explosive. These green spots turn brown and spread out over the pad.

EXAMPLE 6: DETECTING NITRAMINES (E.G. HEXOGEN, OCTOGEN, NITROUREA) IN THE SOLID STATE

[0065] Separately, traces of solid nitramines are moistened with a drop (5-10 μl) of a solution of an organic superbase (e.g. P.sub.1-t-Bu) in acetonitrile (20 vol. % P.sub.1-t-Bu). The activated stripe (prepared as in Example 1) is brought into contact with the suspension. The color of the pad immediately turns from red to brown.

COMPARATIVE EXAMPLE 1: DETECTING NITROTOLUENES (E.G. 2,4-DINITROTOLUENE, 2,4,6-TRINITROTOLUENE)

[0066] Separate traces of these explosives, e.g. of 2,4-dinitrotoluene or of 2,4,6-trinitrotoluene, are brought into contact with an organic superbase (e.g. a solution of 20 vol. % of P.sub.1-t-Bu in acetonitrile). The solution turns immediately from colorless to deep violet (TNT) or deep blue (DNT). In this case the activated stripe is not needed.

EXAMPLE 7: DETECTING HMTD AND TATP FROM SOLUTION

[0067] For detection of HMTD and/or TATP in solution, 300 μL of Ni-tetrakis(3,4,5-trimethoxyphenyl) porphyrin (50 μM in CH.sub.2Cl.sub.2) and 50 μL trifluoroacetic acid (13 M) were transferred into a sample tube. After adding 10 μL of a 25.3 μM solution (HMTD or TATP separately in CH.sub.2Cl.sub.2), the solution turned green within several minutes due to the formation of the porphyrin π-radical cation. It was calculated that the process can detect 0.18 nmol (40 ng) TATP or (50 ng) HMTD as a color change from red to green.

[0068] Analogously, the detection limit of potassium perchlorate (KClO.sub.3) was determined as 270 ng, and the detection limit of ammonium nitrate (NH.sub.4NO.sub.3) is 85 ng,

EXAMPLE 8: SYNTHESIS OF STRUCTURE 2, CHAIN: CH.SUB.2.(CF.SUB.2.).SUB.6., ACID GROUP: CO.SUB.2.H

[0069] The 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluorooctane-1,8-diol was prepared according to a formulation by V. Montanari, K. Kumar, Eur. J. Org. Chem. 2006, 4, 874-877 with tosyl chloride and triethylamine to give the singly tosylated species 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoro-8-hydroxyoctyl 4-methylbenzenesulfonate. The 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoro-8-iodooctan-1-ol was obtained by reaction with potassium iodide (synthesized according to V. Montanari, K. Kumar, Eur. J. Org. Chem. 2006, 4, 874-877). The reaction with (2,2,6,6-Tetramethylpiperidin-1-yl)oxyl (TEMPO), potassium bromide and sodium hypochlorite gave 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoro-8-iodooctanoic acid (adapted from J. Ignatowska, O. Shyshkov, T. Zipplies, K. Hintzer, G.-V. Roschenthaler, J. Fluor. Chem. 2012, 141, 35-40). This was reacted in an acid-catalyzed esterification with methanol to give the methyl 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoro-8-iodooctanoate. The subsequent reaction with a Ni-porphyrin, sodium dithionite and sodium bicarbonate provides the porphyrin substituted with a perfluorinated acid in β-position (adapted from L. M., Jin, Z. Zeng, C.-C. Guo, Q.-Y. Chen, J. Org. Chem. 2003, 68, 3912-3917).

[0070] Another way to bind the acid to the porphyrin is a Suzuki-Miyaura coupling with a porphyrin that has pinacol esters or boronic acids in the beta position (based on Y. Zhao, J. Hu, Angew. Chem. Int. Ed. 2012, 51, 1033-1036). This porphyrin was obtained by bromination with N-bromosuccinimide (NBS) (according to T. Hu, T. Liu, C. Hu, J. Lang, J. Porphyr. Phtalocyanines 2018, 22, 751-757) and subsequent reaction with bis(pinacolato)diborone, potassium acetate and [1,1′-bis(diphenylphosphino)ferrocene]palladium(II) dichloride (in modified form according to G. Bringmann, D. C. G. Gotz, T. A. M. Gulder, T. H. Gehrke, T. Bruhn, T. Kupfer, K. Radacki, H. Braunschweig, A. Heckmann, C. Lambert, J. Org. Chem. 2008, 130, 17812-17825). In the final step, the acid is obtained by base-catalyzed ester saponification. The reaction is schematically depicted below:

##STR00002##

EXAMPLE 9: SYNTHESIS OF STRUCTURE 3, CHAIN: CH.SUB.2.(CF.SUB.2.).SUB.2., ACID: CO.SUB.2.H

[0071] Starting from 2,2,3,3-tetrafluorobutane-1,4-diol, the singly tosylated species 2,2,3,3-tetrafluoro-4-hydroxybutyl 4-methylbenzenesulfonate was obtained by the reaction with tosyl chloride and triethylamine (synthesized according to V. Montanari, K. Kumar, Eur. J. Org. Chem. 2006, 4, 874-877). This compound was converted into the 2,2,3,3-tetrafluoro-4-iodobutan-1-ol by reaction with potassium iodide (adapted from V. Montanari, K. Kumar, Eur. J. Org. Chem. 2006, 4, 874-877). The 2,2,3,3-tetrafluoro-4-iodobutanoic acid was generated by reaction with (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO), potassium bromide and sodium hypochlorite (according to J. Ignatowska, O. Shyshkov, T. Zipplies, K. Hintzer, G.-V. Roschenthaler, J. Fluor. Chem. 2012, 141, 35-40). Through an acid-catalyzed reaction in methanol, the acid is converted to the methyl ester.

[0072] Starting from the 3,4,5-trimethoxybenzaldehyde, the 2-bromo-3,4,5-trimethoxybenzaldehyde was obtained by bromination with N-bromosuccinimide (NB S) (synthesized according to R. Labruère, P. Helissey, S. Debène-Finck, S. Giorgi-Renault, Lett. Org. Chem. 2012, 9, 568-571). Subsequently, the aldehyde is protected with ethane-1,2-diol and p-toluenesulfonic acid as acetal. This offers the possibility to perform a lithium-halogen exchange with tert-butyllithium. Then trimethylborate is added and the compound is deprotected by addition of hydrochloric acid to give (6-formyl-2,3,4-trimethoxyphenyl)boronic acid (according to G. Besong, D. Billen, I. Dager, P. Kocienski, E. Sliwinski, L. R. Tai, F. T. Boyle, Tetrahedron 2008, 64, 4700-4710). This compound was converted in a Suzuki-Miyaura coupling with methyl 2,2,3,3-tetrafluoro-4-iodobutanoate to give methyl 2,2,3,3-tetrafluoro-4-(6-formyl-2,3,4-trimethoxyphenyl)butanoate (based on Y. Zhao, J. Hu, Angew. Chem. Int. Ed. 2012, 51, 1033-1036).

[0073] Subsequently, the porphyrin is obtained in an acid-catalyzed condensation reaction followed by oxidation by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) (according to J. S. Lindsey, K. A. MacCrum, J. S. Tyhonas, Y. Y. Chuang, J. Org. Chem 1994, 59, 579-587). The metallation with nickel acetylacetonate was carried out according to a prescription by M. Dommaschk, F. Gutzeit, S. Boretius, R. Haag, R. Herges, Chem. Commun. 2014, 50, 12476-12478 and the acid was subsequently released by basic ester saponification.

[0074] The reaction is schematically depicted below:

##STR00003##

EXAMPLE 10: SWAB TEST FOR THE DETECTION OF TATP

[0075] A solvent and acid resistant wiping cloth (e.g. hydrophilized polypropylene) is used to swab a surface contaminated with TATP. A solution of 0.5 mg of the Ni-porphyrin with a (CF.sub.2).sub.8 linker and a CO.sub.2H group as acid (Structure 2, preparation see Example 8) dissolved in 10 ml of chloroform is sprayed onto the wiping cloth. A color change from red to green indicates a contamination with TATP or another peroxide or a nitramine or nitrate based explosive.

EXAMPLE 10: PRACTICAL IMPLEMENTATION OF THE TEST

[0076] A plastic stripe (90×5 mm) is equipped with a cellulose pad (5×5 mm) at one end. The pad is moistened with a solution of the Ni-porphyrin in an organic solvent. The solvent is evaporated leaving the dry pad uniformly impregnated with the red colored porphyrin. This stick is storable for extended periods of time (>2 years at room temperature in a dry environment). Prior to application, the stripe is activated with a drop (5-10 μL) of perfluoropentanoic acid applied onto the pad. The stripe now remains active and ready to use for about 15 min. The acid can be applied from a dropper bottle, or released from a reservoir above the pad by mechanical force. In these examples, the following detection limits could be determined: for TATP: ˜40 ng, for KClO.sub.3: ˜270 ng, for NH.sub.4NO.sub.3: ˜85 ng, for urea nitrate: ˜350 ng, for HMTD: ˜50 ng.

COMPARATIVE EXAMPLE 1

[0077] For comparative purposes, electron rich Ni-porphyrins (Ni-tetra(4-hydroxyphenyl)porphyrins) have been prepared according to M. K. Chahal, M. Sankar, Dalton Trans. 2016, 45, 16404-16412 and used as sensors for cyanide (CN.sup.−), fluoride (F.sup.−) and picric acid according to M. K. Chahal, M. Sankar, Dalton Trans. 2017, 46, 11669-11678. To the Ni-porphyrins used in these publications, trifluoroacidic acid (TFA) and TATP and HMDT was added. After one minute at room temperature an unspecific reaction took place. Hence, these porphyrins described by Chahal et al. are not suitable for the detection of peroxide-based explosives.

COMPARATIVE EXAMPLE 2

[0078] Ni-tetra(carboxyphenyl)porphyrins with CO.sub.2H groups directly attached to the meso phenyl rings in 2, 3 or 4 position (B. Du, A. Langlois, D. Fortin, C. Stern, P. D. Harvey, J. Clust. Sci. 2012, 23, 737-751) are not suitable, and it is assumed that this is because the carboxylic group is not sufficiently acidic (pK.sub.a 4.2) to cleave peroxide or nitrate based explosives. Ni-tetrakis(4-carboxyphenyl)porphyrin (CAS #136300-60-2) was synthesized (B. J. Johnson et al. Sensors 2010, 10, 2315-2331) and dissolved in methylene chloride. TATP and HMDT was added. No color change was observed.