File Name: paper and thin layer chromatography .zip
Regret for the inconvenience: we are taking measures to prevent fraudulent form submissions by extractors and page crawlers. Correspondence: Halilovi? Received: December 26, Published: January 9, Application of thin layer chromatography for qualitative analysis of gunpowder in purpose of life prediction of ammunition.
Regret for the inconvenience: we are taking measures to prevent fraudulent form submissions by extractors and page crawlers. Correspondence: Halilovi? Received: December 26, Published: January 9, Application of thin layer chromatography for qualitative analysis of gunpowder in purpose of life prediction of ammunition. Int J Biosen Bioelectron. DOI: Download PDF.
Thin layer chromatography can be used to monitor the progress of a reaction, identify compounds present in a given mixture, and determine the purity of a substance.
A number of enhancements can be made to the original method to automate the different steps, to increase the resolution achieved with TLC and to allow more accurate quantitative analysis.
This method is referred to as "high-performance TLC". Our goal is to examine and to compare the quality of the results obtained by thin-layer chromatography, high-performance thin layer chromatography and vacuum stability test in the analysis of samples of gunpowders.
Thin layer chromatography as a qualitative method has shown good quality of results that can be used for a good life prediction of the ammunition. Keywords: thin-layer chromatography, high-performance thin layer chromatography, vacuum stability test, life prediction of the ammunition, gunpowder, diphenylamine, centralite I.
One of the major problems concerned with the manufacture and use of propellants is the measurement of their chemical stability and the prediction of their safe storage life.
A solution of nitrocellulose in methanol concentration 0. Solutions of the same nitrocellulose sensitized by adding ca. In addition they can lead to a loss of calorific value, changes in ballistic properties and cracking in large diameter charges. Small amounts of stabilizing compounds are included in propellant formulations, either singly or as mixtures, in order to react with the degradation products, thus reducing the probability of the adverse effects.
For propellants of new formulations, in particular with stabilizers and other relevant components which were not used before in propellant formulations, more elaborate methods, such as the multi-temperature ageing procedure, have to be used.
Until recently, the stabilizers considered a group of aromatic compounds with the ability to react quickly with nitric oxides that occur during the thermal decomposition of nitrocellulose, thereby preventing their autocatalytic effect on further decomposition more recently, this group of stabilizers is treated as "secondary stabilizers" because they reduce the effects of decomposition that is already occurring. Table 1 List of most common organic stabilizers used in production of ammunition.
The gunpowders for classical ammunition, whether single-phase, double or triple, as well as a large number of rocket fuels as the basic component of the composition contain nitrocellulose. Nitrocellulose has a similar aspect to cotton, is white and has a fibrous texture. It is produced from cellulose. The appearance of the nitrocellulose molecule is shown in Figure 1. The undesirable characteristic of nitrocellulose is chemical degradation with the release of gaseous products.
One of simplified mechanisms of nitrocellulose degradation is shown bellow. Long-term storage of nitrate ester compounds, they react with moisture inside or moisture around the packaging, resulting in nitric acid HNO 3 and nitrogen oxides such as NO 2 and NO 3.
These reactions of nitric oxide and nitric acid are exothermic reactions that increase the ambient temperature during decomposition: 9. Effective stabilizer is a defined term which is used to assess the stability in the single temperature test. Daughter stabilizers are substances with stabilizing capabilities that were not included in the propellant formulation but were produced from the initial stabilizers during propellant manufacture or ageing.
Most stabilizer depletion products fall into this class. Certain stabilizers can appear both as initial stabilizer incorporated in basic formulation and as daughter stabilizer produced from initial stabilizer , this even in the same propellant.
The content of "effective stabilizer" is calculated from the contents of all initial stabilizers diphenylamine, 2-nitro-diphenylamine, ethyl centralite, methyl centralite, akardite-II, p-nitro-N-methylaniline, resorcinol-except if they are used as surface moderants and the content of N-nitrosodiphenylamineas follows.
For propellants without diphenylamine as well as for propellants with diphenylamine and other stabilizers. Percentage effective stabilizer is the amount of effective stabilizer found, expressed as a percentage by weight of the propellant sample. Initial level is the percentage of effective stabilizer found in the propellant sample prior to ageing.
Thin layer chromatography TLC and high performance thin layer chromatography HPTLC — now also called planar chromatography — are, like all chromatographic techniques, based on a multistage distribution process. This process involves: a suitable adsorbent the stationary phase , solvents or solvent mixtures the mobile phase or eluent , and the sample molecules.
For thin layer chromatography the adsorbent is coated as a thin layer onto a suitable support e. On this layer the substance mixture is separated by elution with a suitable solvent. The principle of TLC is known for more than years now. Specific examples of these applications include: analyzing ceramides and fatty acids, detection of pesticides or insecticides in food and water, analyzing the dye composition of fibers in forensics, assaying the radiochemical purity of radiopharmaceuticals, or identification of medicinal plants and their constituents.
This layer of adsorbent is known as the stationary phase. After the sample has been applied on the plate, a solvent or solvent mixture known as the mobile phase is drawn up the plate via capillary action.
Because different analytes ascend the TLC plate at different rates, separation is achieved. For example, with silica gel, a very polar substance, non-polar mobile phases such as heptane are used. The mobile phase may be a mixture, allowing chemists to fine-tune the bulk properties of the mobile phase.
After the experiment, the spots are visualized. Often this can be done simply by projecting ultraviolet light onto the sheet; the sheets are treated with a phosphor, and dark spots appear on the sheet where compounds absorb the light impinging on a certain area. The plate is shown in Figure Chemical processes can also be used to visualize spots; anisaldehyde, for example, forms colored adducts with many compounds, and sulfuric acid will char most organic compounds, leaving a dark spot on the sheet.
To quantify the results, the distance traveled by the substance being considered is divided by the total distance traveled by the mobile phase. The mobile phase must not be allowed to reach the end of the stationary phase. This ratio is called the retardation factor Rf. If the solvent front is 6 cm then the R f value for the pigment at 3cm would simply be 0. Figure 3 Application of a sample on a micro precoated sheet with the aid of a capillary and a TLC spotting guide.
In the thin layer chromatography analysis, a glass plate is coated by adsorbent materials such as silica. Silica is the most commonly used adsorbent material for TLC analysis. Structurally silica gel consists of a matrix of Si-OH groups which can interact with molecules via hydrogen bonding and adsorption. A few micro liters of a dilute solution is put onto the silica surface of the plate using a micro capillary.
The plate is then placed in a jar containing a solvent generally mixtures of ethylacetate and hexanes. As time goes, the solvent gradually rises up the plate due to capillary action carrying the components of the sample with it. Different molecules are carried up the plate to different distances due to variable interactions with the adsorbent material.
For example, when silica is used, polar molecules with groups such as hydroxy OH or amine NH 2 will tend to form hydrogen bonds with the silica matrix Si-OH groups and will therefore not move as fast up the plate.
While relatively non-polar molecules will have fewer interactions with the matrix and will tend to be more soluble in the solvent phase and therefore rise faster up with the solvent front. Once the solvent has risen a particular distance sufficient to separate components of the spot, the plate is either visualized directly using ultraviolet light, or it is developed using a stain to check for specific types of molecules.
In general, a substance whose structure resembles the stationary phase will have low R f , while one that has a similar structure to the mobile phase will have high retardation factor. Retardation factors are characteristic, but will change depending on the exact condition of the mobile and stationary phase.
For this reason, chemists usually apply a sample of a known compound to the sheet before running the experiment. The success of thin layer chromatography as a highly efficient micro analytical separation method is based on a large number of advantageous properties: high sample throughput in a short time suitable for screening tests pilot procedure for HPLC after separation the analytical information can be stored for a longer period of time the TLC ready-to-use layer acts as storage medium for data separated substances can be subjected to subsequent analytical procedures e.
IR, MS at a later date rapid and cost-efficient optimisation of the separation due to easy change of mobile and stationary phase. For a chromatographic separation the sample must meet several requirements to obtain good results. It is not possible do go into detail here. However, eventually several steps for sample pretreatment may be necessary. These include sampling, mechanical crushing of a sample, extraction steps, filtration and sometimes enrichment of interesting components or clean-up, i.
In our experiment, we prepared the samples of gunpowders into pieces of diameter up to 2mm and extracted into dichloroethane. The aim of a chromatographic separation determines how the sample should be applied to the TLC plate or sheet.
The most frequent technique still is application with a glass capillary as spot or short streak. Application as streak will yield better results especially for instrumental quantification. For both types of application some manual skill is required to obtain reproducible results. Substance zones which are too large from the beginning will cause poor separations since during chromatography they will become even larger and more diffuse. The mixture to be separated and the reference solution are applied to the micro pre coated sheets as spots by means of glass or plastic capillaries.
Only use each capillary once to avoid contamination of the following samples. The capillaries fill themselves quickly when dipped into organic sample solutions, with aqueous solutions filling will be much slower. Before emptying the capillary roll the submerged end horizontally on filter paper. Place the capillary on the layer vertically and carefully, vertically so that the capillary empties itself and carefully to avoid damage to the layer. Damaged layers result in unevenly formed spots.
To keep spots as small and compact as possible, it is advisable to apply a solution in several portions with intermediate drying blow with cold or hot air. This is especially important for aqueous sample solutions. The following figures demonstrate the clean and easy application of samples with the above-mentioned spotting guide.
It is recommended to apply 0. The sample zone on the starting line should be mm in diameter, cm apart from the edge of the plate. After application allow the solvent of the samples to evaporate completely about 10minutes or blow with cold or hot air. Development of a chromatogram should never start before the solvent of the applied samples is evaporated completely.
The most frequently used separation technique is ascending TLC in the customary trough chamber standard method, linear development. Usually it is applied as single development. However, multiple development, with or without change of eluent step technique can improve separation results. For 2-dimensional development only 1 spot of the sample is applied in one edge of a plate. Thus complicated mixtures give 2-dimensional chromatograms taking advantage of the different separating properties of two eluents.
Thin layer chromatography T LC is a chromatographic technique used to se parate the components of a mixture using a thin stationary phase supported by an inert backing. It may be performed on the analytical scale as a means of monitoring the progress of a reaction, or on the preparative scale to purify small amounts of a compound. TLC is an analytical tool widely used because of its simplicity, relative low cost, high sensitivity, and speed of separation. TLC functions on the same principle as all chromatography: a compound will have different affinities for the mobile and stationary phases, and this affects the speed at which it migrates. The goal of TLC is to obtain well defined, well separated spots. After a separation is complete, individual compounds appear as spots separated vertically. Each spot has a retention factor Rf which is equal to the distance migrated over the total distance covered by the solvent.
Paper Chromatography of Gel Ink Pens It would be tempting to try to explain paper chromatography in terms of the way that different compounds are adsorbed to different extents on to the paper surface. Students witness first-hand how components of a solution can be. The Science Practices SP assessed were 4. Answer : Paper chromatography has some limitations such as: Semi-quantitative in nature. Paper chromatography is A. Write your answers in the spaces.
Chromatography is a useful technique to precisely separate, analyze, and purify a wide range of samples, including food, pharmaceuticals, pesticides, air and water samples, and tissue extracts. You would have seen the separation of different coloured compounds using the simple paper chromatographic separation technique in your school laboratory. The technique was simple to understand and did not require any expensive equipment. It provided you a visual understanding of the concepts of separation science. In your college time you would also have come across thin layer chromatography separations of compounds which even after separation may or may not be identifiable by the eye without treatment of the separation plate. Read on to learn more about chromatography, advantages of chromatography, its types, and differences between TLC and paper chromatography.
Ascending. Descending. -In this method, the solvent is kept in a trough at the top of the chamber and is allowed to flow down the paper. -The liquid moves down.
Thin-layer chromatography TLC is a chromatography technique used to separate non-volatile mixtures. This layer of adsorbent is known as the stationary phase. After the sample has been applied on the plate, a solvent or solvent mixture known as the mobile phase is drawn up the plate via capillary action. Because different analytes ascend the TLC plate at different rates, separation is achieved. For example, with silica gel, a very polar substance, non-polar mobile phases such as heptane are used.
Thin layer chromatography is a kind of chromatography used to separate and isolate mixtures that are non-volatile in nature. Just like other chromatography processes, this one consists of a mobile phase and a stationary phase. The latter one here is a thin layer of absorbent material, such as aluminium oxide, silica gel, or cellulose. This layer is applied to plastic, glass, or aluminium foil sheets called an inert substrate. The mobile phase in the TLC procedure is a solvent or a mixture of it. If you want to learn more about the thin layer chromatography procedure, you have landed at the right place. Here we will be discussing its principle, process, and applications in different industries.
Not all plates will be used inthis experiment; some will be needed in lab the following week.
This book discusses the practical approach in the application of paper and thin layer chromatography techniques in the biological sciences.