Quite unspecific reactions are iodine adsorption and the charring technique spraying with sulphuric acid and heat treatment. More reliable results are possible with specific reagents for spraying or dipping, which form colored or fluorescent compounds with the substances to be detected. Because of the potential dangers of spontaneous combustion of NC propellants in Warehouse ordnance, which could be with disastrous consequences, a series of procedures was developed in order to control their chemical stability.
The kinetic behaviours at thermal accelerated ageing temperature is one of the most important aspects of propellants. For aging, glass vials different sizes are used.
Two samples of the same barrel are used in the experiment. This decision is based on the Table 8. When assessing the type of stabilizer, take into account the precise identification of the stabilizer, whether it is centralit ethyl centralit, EC or C1 or diphenylamine DFA or DPA. The purple color indicates the presence of centralite and diphenylamine DPA is considered or estimated as a more active stabilizer showed in Table 9. The experiment is performed on a small quantity of gunpowder or it extract in dichloroethane.
Two drops of the appropriate reagent are added to the gunpowder sample, whereupon the color appears according to the table above.
To determine the content of the stabilizer by the thin layer chromatography method, the sample is a gunpowder extract. In the experiment we extracted gunpowder samples in dichloroethane. The gunpowder can be mono-basic, double-basic or multi-basic. If as a result we get is intense purple dyeing, then it's a double-basic gunpowder. Nitroglycerin or some other nitrate ester, as the second energy base in the powder - mild violet color is not a proof of nitroglycerin.
Double-base rocket propellants are nitrocellulose NC -based energetic materials with a tendency towards slow, but constant thermal decomposition during aging. The development of samples on the TLC panel is shown in the Sample application paragraph. First, add the appropriate solution in a glass chamber to cover the bottom in a thickness of 2mm of liquid. The solution we pour into a glass bottle is selected as follows:.
After drying, in a darkened room, and under UV light, mark the visible points or points with their own color like in Figure 5. Estimation of gunpowders with stabilizer diphenylamine is based on the information shown in the Table 4. It is essential to compare the TLC plate of the sample with the standard in the Figure 5 Figure 6 according to.
Centralit is clearly recognizable, nitroso-ethylaniline and 4-nitro-centralite are clearly recognizable. Nitrozo ethylaniline and 4-nitro-centralite are clearly recognizable, dintro-centralite is eventually recognizable, centralit is still recognizable. Dintro-centralite recognizable, nitrozo-ethylaniline and 4-nitro-centralite recognizable, the centrality virtually disappeared.
Each country has its own categorization, and the indicative categorization is given in NATO standards. Smaller caliber ammunition contains 0. The results of the described experiment, in the titles above, are shown in the following Table The same gunpowder samples were examined on TLC and two additional methods and we will make a comparison of the results.
We analyzed 11 different samples of gunpowders of 6 types of cartridges 20mm, 40mm, 76mm, mm, mm, mm. The results were processed and passed the appropriate categories and in the table above we can compare the categories obtained by the TLC method with the categories adopted on the basis of the other two methods: HPTLC and VST.
The main stabilizer according to TLC is determined chemically where the result of the reaction is dyeing, as explained in the title Determine the type of stabilizer. Eight samples showed a category matching, these are samples no. The classical method depends on the eye of the observer, and this can be the cause of the different results.
Sample number 4 showed a stabilizer ratio of 1. We conclude that this is a transition group, as shown in Table 5 Table 12 by mixed green-yellow color. Sample number 5 is similar, however, the content of DPA is very high and the cause of disagreement in this case is probably human eye or inexperience.
With this sample of gunpowder we can not say with certainty that it is the first category for HPTLC because we do not know how much the initial concentration of DPA was in the gunpowder. In this case, we were guided by a theoretical mean concentration of DPA quoted in gunpowders, about 1.
Samples 4, 5, and 7 belong to the transition group according to the TLC qualitative method, and because the method is qualitative, the attitude of our laboratory is to take a tougher decision, and this is one reason for disagreement with the mathematical decision of the other two methods.
Obviously, this is a good matching result, and also, for this sample the initial concentration of the DPA stabilizer is not known. Samples 8, 9, 10 and 11 clearly showed the third category, which was confirmed by the other two methods. Clarity in determining the third category is the most important in this experiment.
In this case, it is confusing which grade to select from Table 4 Table Analyzing Figure 6, we can conclude that this is the sample in life range between E and F. In practice, there is a high likelihood of errors in these cases. In such confusions, we advise group work, or to make a quantitative experiment on one of the appropriate methods.
The method of interpreting the results leads to apparent disagreement of the categories for the three samples under the numbers 4,5 and 7 in Table For these three samples, this means that they are closer to the 2nd than the 1st category.
Obviously, the results of the TLC method are very useful and usable for the purpose of life prediction of ammunition. Thin layer chromatography for the purpose of qualitative analysis of gunpowder samples is a reliable method and largely depends on the expertise of individuals and from the interpretations of the results.
Results of qualitative thin layer chromatography analysis provides very good guidance in purpose of life prediction of gunpowders. Thin layer chromatography method can be economically employed for routine use because the consumption of mobile phase is low and, hence, there are scarcely any disposal problems.
Thin layer chromatography method does not require the use of machines or special devices, it is fully portable and easy to handle and considerably cheaper than most commercial methods. This is an open access article distributed under the terms of the, which permits unrestricted use, distribution, and build upon your work non-commercially. Withdrawal Guidlines. Publication Ethics. Withdrawal Policies Publication Ethics. Home IJBSBE Application of thin layer chromatography for qualitative analysis of gunpowder in purpose of life prediction of ammunition.
International Journal of. Research Article Volume 5 Issue 1. Figure 2 TLC plate with developed samples. Figure 4 Developing chambers and saturation. A Diphenylamine spot is much stronger than nitrodiphenylamine; barely recognizable 4-nitro-diphenylamine and 2-nitro-diphenylamine. B Diphenylamine spot and nitrodiphenylamine are clearly dispersed, 4-nitr-diphenylamine and 2-nitro-diphenylamine clearly recognizable.
C Diphenylamine spot is less intense than nitrodiphenylamine, 4-nitro-diphenylamine and 2-nitro-diphenylamine clearly recognizable. D Diphenylamine spot has virtually disappeared; Nitrodiphenylamine clearly recognizable, 4-nitro-diphenylamine and 2 nitro-diphenylamine are clearly recognizable, no dinitroproducts are not recognizable.
E Nitrodifenylamine recognizable, dinitroproducts are recognizable. F Nitrodifenylamines are not recognizable, dinitroproducts are recognizable. Table 4 Definitions of DPA stabilizer image. Less than 0. Composition Absorption maximum [nm] Colour of fluorescence Manganese-activated zinc silicate green Inorganic fluorescent pigment blue Table 7 Fluorescent indicators. Used equipment Block for sample heating. Thermometer to C.
TLC plates. Plan in the form of a plate of plastic. UV lamp mm. Pipes with threaded plugs ml 3pcs. Set a blade. Eppendorf cap 2ml pcs. Standard bottle with thread 4 ml pieces. Plastic bottles with a dropper. Safety glasses. Laboratory gloves. Aging in metal block thermostats The kinetic behaviours at thermal accelerated ageing temperature is one of the most important aspects of propellants. Two days for category 2 classification. This method is often used in research, and one such journal article reporting its usage is shown in Figure 2.
To use TLC in this manner, three lanes are spotted on a TLC plate: one for the limiting reactant, one for the co-spot, and one for the reaction mixture. The goal is to note the disappearance of the limiting reactant in the reaction mixture lane and the appearance of a new product spot.
When the limiting reactant has completely disappeared, the chemist deduces that the reaction is complete, and can then be "worked up". To demonstrate how TLC can be used to monitor a reaction, the transesterification reaction in Figure 2. In the first lane of each TLC plate marked "BA" was spotted a dilute sample of the reactant benzyl acetate, while in the third lane of each was spotted the reaction mixture marked "Pr" at different times. In the central lane marked "Co" for the co-spot , both benzyl acetate and the reaction mixture were delivered over top of one another.
Figure 2. A new spot appears below it, representing the benzyl alcohol product. Over time Figure 2. It is apparent from the TLC plates that the reaction was nearing completion at 10 minutes, and was complete at 20 minutes. The TLC demonstrates that the reaction mixture could be worked up after 20 minutes of mixing. To monitor a reaction's progress by TLC, an " aliquot " or tiny sample of the reaction mixture is necessary.
If the reaction is run at room temperature or with only mild heating, and the concentration of reactants is conducive to TLC, a capillary spotter can be directly inserted into the flask where the reaction is taking place Figure 2. A long spotter is ideal if one is available. The aliquot can then be directly spotted on the TLC plate. If the sample spot is not visible before elution it will not be visible afterwards, as compounds diffuse during elution. Otherwise, your spots will spread unpredictably over your TLC plate and your results will be unreliable.
When you spot a TLC plate you only want to use a little bit of a sample- one touch from a capillary tube is usually plenty. Otherwise your spots will be too big. Sometime your reaction mixture will be too concentrated to do TLC. In this case, remove one drop from your reaction and dilute it by adding some TLC solvent, and then spot your TLC plate. This makes it harder to read the TLC plate. To fix this, we do some double spotting. Instead of just spotting the reaction mixture, we spot both the reaction mixture and the starting material, and the reaction mixture and the product.
This is short lab. When I used to TA this lab I noticed that students tend to allow their TLC solvent to travel much higher than necessary- this takes more time. A cm solvent front is plenty tall for a TLC plate! It will be useful for confirming the identities of your unknown. For example, if you think your unknown contains ibuprofen and acetaminophen, then you should add your unknown, pure ibuprofen, and pure acetaminophen to the same TLC spot.
If it gives more than two spots it means another chemical must be present. Ink is a collection of different chemicals- you would see lots of spots after running your TLC! A: No.
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