Gunpowder and rocket fuel good for storing, priority in the use of ammunition labored with this gunpowder. Gunpowder and rocket fuel are unstable, ammunition must be removed from the storage place, processed or destroyed.
First of all it is necessary to recognise the position of a substance spot. Only in very few cases the sample is a dye which can be seen with the naked eye. Much more often for unspecific visualisation substances can be viewed under UV light, since many substances show a UV absorption. If a fluorescent indicator is added to the layer, all substances absorbing in the respective region of wave length cause a quenching of the fluorescence, i.
Customary fluorescent indicators are excited at nm or less frequently at nm with a mercury lamp showed in Table 7. The identification of separated substances is possible via the R f value compared to the pure compound, which is often applied simultaneously on the same plate. For a number of compounds their native fluorescence can be used for visualisation, which is excited by UV light mostly long-wave UV e. This allows not only determination of the R f value, but often enables a further qualitative assignment.
Such compounds often occur in the extract of gunpowders. If these methods do not allow localisation or characterisation of substances, especially post-chromatographic detection methods can be applied chemical reactions on the TLC plate.
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. For compounds which are not UV active, a number of chemical stains can be used. These can be very general, or they can be specific for a particular molecule or functional group. Iodine is among the most common stains. Plates are placed in a jar containing iodine crystals, or covered in silica gel with iodine dispersed throughout, for approximately one minute.
Most organic compounds will be temporarily stained brown. Some popular general use stains are Permanganate, ceric ammonium molybdate CAM , and p-anisaldehyde. These can be kept in jars which plates are dipped into, or in spray bottles. To develop a plate with permanganate, spray or dip the plate and heat it with a heat-gun. Hold the plate face up 10 to 20 cm above the heat gun until the bulk water evaporates. Overheating will turn the entire plate brown, obscuring the spots.
If glass plates are used it is often easier to see spots through the backing because it is harder to overheat. CAM and p-anisaldehyde stained plates are developed similarly. Overheating CAM stained plates turns everything blue. There are common problems in TLC that should be avoided.
Normally, these problems can be solved or avoided if taught proper techniques. Rarely, water is used as a solvent because it produces an uneven curve front which is mainly accounted for by its surface tension. Thin layer chromatography of three analgesics and caffeine under U.
It is not a recommended technique in the laboratory. Due to the nature of the uv hazard polycarbonate safety spectacles which absorb short wavelength U. The samples were dissolved in ethanol for spotting onto the plate. The TLC plate was run in an open beaker under short wavelength u.
The movement of the dark purple spots samples during the running of the plate can be observed in the animation. The original movie can be viewed here. It is easy to see which are the two active ingredients in the unknown commercial pain relief medicine by comparison of the spots with the standard reference materials running on either side caffeine and acetominophen.
TLC is very simple to use and inexpensive. Undergraduates can be taught this technique and apply its similar principles to other chromatographic techniques. There are little materials needed for TLC chamber, watch glass, capillary, plate, solvent, pencil, and UV-light.
Therefore, once the best solvent is found, it can be applied to other techniques such as High performance liquid chromatography. More than 1 compound can be separated on a TLC plate as long as the mobile phase is preferred for each compound. The solvents for the TLC plate can be changed easily and it is possible to use several different solvents depending on your desired results. As stated earlier, TLC can be used to ensure purity of a compound.
It is very easy to check the purity using a UV-light. You can modify the chromatography conditions easily to increase the optimization for resolution of a specific component. TLC plates do not have long stationary phases. Therefore, the length of separation is limited compared to other chromatographic techniques. Also, the detection limit is a lot higher. If you would need a lower detection limit, one would have to use other chromatographic techniques. TLC operates as an open system, so factors such as humidity and temperature can be consequences to the results of your chromatogram.
Retention Factor After a separation is complete, individual compounds appear as spots separated vertically. Apparatus Plates Stationary Phase As stated earlier, TLC plates also known as chromatoplates can be prepared in the lab, but are most commonly purchased. Solvent Mobile Phase Proper solvent selection is perhaps the most important aspect of TLC, and determining the best solvent may require a degree of trial and error. How fast the compounds travel up the plate depends on two things: If the compound is soluble in the solvent, it will travel further up the TLC plate How well the compound likes the stationary phase.
If the compound likes the stationary phase, it will stick to it, which will cause it to not move very far on the chromatogram. Useful Solvent Mixtures A solvent that can be used for separating mixtures of strongly polar compounds is ethyl acetate : butanol : acetic acid : water, Pipettes Spots are applied to the plate using very thin glass pipettes. The capillary should be thin enough to apply a neat spot, but not so thin as to prevent the uptake of an adequate quantity of analyte.
Here is a popular method of producing TLC pipettes. Heat a glass capillary in the very tip of a Bunsen burner flame just until it becomes pliable and then pull the ends apart until the center of the capillary is significantly narrower.
Snap this in half and use the thin end to apply spots. Cut the plate to the correct size and using a pencil never ever use a pen , gently draw a straight line across the plate approximately 1 cm from the bottom.
Do not use excessive forces when writing on a TLC plate as this will remove the stationary phase. It is important to use a pencil rather than a pen because inks commonly travel up the plate with the solvent.
Ferric chloride. Amino acids, amines. Aldehydes, ketones. Good general stain, very well for hydroxyl or carbonyl compounds. Colors vary. Potassium permanganate. Works well for all compounds that can be oxidized. Yellow on purple. Yellow or light brown on purple. Bromocresol Green. Yellow spot on blue background. Good general stain, very well with polyhydroxylated and carbonyl compounds. Blue or green spot. Upon heating, very sensitive! Good general stain, particularly sensitive towards nucleophiles.
Varying colors on light pink plate upon heating. Does not work with alkenes, alkynes or aromatic system unless functional groups are present. Phosphomolybdic acid PMA. Very sensitive. Dark green spot on light green plate. Sensitivity can be enhanced by use of cobalt II chloride.
Indoles, amines. Pink or red-violet. Dragendorff-Munier Stain. Amines even the ones that are low in reactivity.
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