Chemistry
Paper Chromatography
Paper chromatography is a technique used to separate and identify different components of a mixture. It involves the use of a stationary phase (paper) and a mobile phase (solvent) to carry the mixture along the paper. As the mixture travels, the components separate based on their affinity for the stationary and mobile phases, allowing for analysis and identification.
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10 Key excerpts on "Paper Chromatography"
- Srivastava, M K(Authors)
- 2020(Publication Date)
- Daya Publishing House(Publisher)
Paper Chromatography is a useful technique because it is relatively quick and requires small quantities of material. It is a planar chromatography systems where in a cellulose filter paper acts as a stationary phase on which separation of compounds occurs. Chromatography Techniques | 249 Principle [1,2] In Paper Chromatography, like thin layer chromatography, substances are distributed between a stationary phase and a mobile phase. The stationary phase is usually a piece of high quality filter paper. The mobile phase is a developing solution that travels up the stationary phase, carrying the samples with it. Components of the sample will separate readily according to how strongly they adsorb onto the stationary phase versus how readily they dissolve in the mobile phase. The principle involved is partition chromatography where in the substances are distributed or partitioned between to liquid phases. One phase is the water which is held in pores of filter paper used and other phase is that of mobile phase which moves over the paper. The compounds in the mixture get separated due to differences in their affinity towards water (in stationary phase) and mobile phase solvents during the movement of mobile phase under the capillary action of pores in the paper. The principle can also be adsorption chromatography between solid and liquid phases, where in the stationary phase is the solid surface of paper and the liquid phase is of mobile phase. But most of the applications of Paper Chromatography work on the principle of partition chromatography i.e. partitioned between to liquid phases. When a colored chemical sample is placed on a filter paper, the colors separate from the sample by placing one end of the paper in a solvent. The solvent diffuses up the paper, dissolving the various molecules in the sample according to the polarities of the molecules and the solvent. If the sample contains more than one colour, that means it must have more than one kind of molecule.
eBook - PDF- Barbara H. Stuart(Author)
- 2012(Publication Date)
- Wiley(Publisher)
For instance, biological specimens or explosive debris can require the separation of an analyte from a mixture prior to analysis. Chromatographic techniques have been widely used to deal with the separation of such samples. The general principle of chromatog-raphy is that one phase is held in place, while the other phase moves past (the mobile phase). The stationary phase can be solid particles or a liquid bonded to the inside of a capillary tube or onto the surface of solid particles packed in a column. Paper, thin layer, gas, liquid and ion chromatographies have all been used to deal with forensic samples. Separations may also be carried out under the influence of an electric field in capillaries using capillary electrophoresis techniques. 7.2 Paper Chromatography Paper Chromatography (PC) is the simplest chromatographic technique and, as the name implies, uses paper as the separation medium [1]. The paper, which is composed of cellulose, to which polar water molecules can be absorbed, acts as the stationary phase. The mobile phase consists of a less polar solvent, usually composed of an organic solvent and water. The paper is placed in a suitable solvent, and the solvent moves by capillary action through the paper and the sample. 7.2.1 Methods A strip of filter paper is employed, and a sample in solution is placed as a spot near one edge of the paper. The sample components migrate at different characteristic rates that can be used to identify components. If the compounds are colourless, then reagents may be applied to reveal circular or elliptical spots. The method is simple, but there are several limitations. The sample cannot be volatile, the length of the migration path is limited and only qualitative analysis is possible. PC can also take some time and an experiment is often left for several hours to complete.
- Chavan, U D(Authors)
- 2021(Publication Date)
- Daya Publishing House(Publisher)
The specific Retention factor (R f ) of each chemical can be used to aid in the identification of an unknown substance. Paper Chromatography Paper Chromatography is a technique that involves placing a small dot or line of sample solution onto a strip of chromatography paper. The paper is placed in a container with a shallow layer of solvent and sealed. As the solvent rises through the paper, it meets the sample mixture, which starts to travel up the paper with the solvent. This paper is made ofcellulose, a polar substance, and the compounds within the mixture travel farther if they are non-polar. More polar substances bond with the cellulose paper more quickly, and therefore do not travel as far. THIN LAYER CHROMATOGRAPHY Thin layer chromatography (TLC) is a widely employed laboratory technique and is similar to Paper Chromatography. However, instead of using a stationary phase of paper, it involves a stationary phase of a thin layer of adsorbent like silica This ebook is exclusively for this university only. Cannot be resold/distributed. Chromatography 257 gel, alumina, or cellulose on a flat, inert substrate. Compared to paper, it has the advantage of faster runs, better separations, and the choice between different adsorbents. For even better resolution and to allow for quantification, high-performance TLC can be used. An older popular use had been to differentiate chromosomes by observing distance in gel. Thin-Layer Chromatography • Thin layer chromatography (TLC), the subject of this experiment is a solid-liquid technique based on both absorptivity and solubility.
eBook - PDF- Joseph Sherma, Gunter Zweig(Authors)
- 2013(Publication Date)
- Academic Press(Publisher)
An overview of methods useful for the identification of substances by paper (and thin-layer) chromatography has been presented by Macek as an introduction to volume 48 of the Journal of Chromatography (April, 1970), in which papers presented at the International Symposium on this topic held in Italy in September, 1969 are published. Included are identification methods based on mobility, detection, derivative formation before or during chromatography, decomposition and degradation products, and the combination of Paper Chromatography with gas chromatography, thin-layer chromatography or other physicochemical methods such as spectroscopy and mass spectrometry. X. Preparative Paper Chromatography The recommended procedure for isolating milligram quantities of pure substances from a mixture is scaled-up descending chromatography using high-capacity paper sheets. As much as 0.5 ml of a solution containing the sample is streaked or applied as adjacent spots on Whatman No. 3 M M paper sheets (18 X 22 inch using repeated applica-tions from a 100 /xl pipette). A commercial sample applicator designed for preparative chromatography simplifies the spotting procedure. The streaking pipette (Fig. 26) has a horizontal reservoir of about 0.3 ml and empties only when it touches the paper surface. The sample applicator is a device which holds the streaking pipette in a vertical position where it may be drawn across the paper along a track in a straight line. The paper sheet is held in place by spring clamps, and the solution is dried simultaneously by a stream of warm air. Adjustable stops at each end lift the pipette off the paper to prevent accidental leakage. After the sample has been applied to several sheets of paper, development in a large-size cabinet proceeds according to directions given in Section VI,A. At the end of the run, after the papers have been dried, guide strips or peel strips (197) are developed with suitable color reagents.
eBook - PDF- J.R.J. Paré, J.M.R. Bélanger(Authors)
- 1997(Publication Date)
- Elsevier Science(Publisher)
Nevertheless, it will be covered here, not only for historical reasons, but also because Paper Chromatography can still be very useful in certain circumstances. 1.7.1.1 Theory Paper Chromatography is actually a liquid-liquid partitioning technique. Although paper consists of cellulose, the stationary phase consists of water saturated cellulose from the water in the atmosphere. Cellulose is formed of units of anhydride glucose linked in chain by oxygen atoms. It has been suggested that the stationary l~hase be considered as a solution of concentrated polysaccharide. To maintain the water saturation, most solvents used in Paper Chromatography contain some water. Therefore, the components that are highly water-soluble or have the greatest hydrogen- bonding capacity move slower. The degree of retention of a component is called the retardation factor (Rf) and corresponds to the distance migrated by an analyte over the distance migrated by the solvent (also called solvent front). The expression of the movement of a substance in comparison to another is the retention ratio R r and corresponds to the distance migrated by analyte A over the distance migrated by analyte B. The Rf-value is the most commonly used term and a reasonable value for good resolution is about 0.4 to 0.8. 1.7.1.2 Technique Paper Chromatography is performed on a sheet or strips of paper (most often Whatman No. 1 or Whatman No. 3 filter paper for analytical work, and Whatman No. 3 or Whatman 3MM for preparative work). Low-porosity paper will produce a slow rate of movement of the developing solvent and thick papers have increased sample capacity. The sample is dissolved in a volatile solvent and spotted with a capillary glass tube or micro-pipet on the paper. An optimum spot diameter of 2 mm is preferable and, to achieve good separation, the maximum quantity of sample should not exceed 500 ~g. The mobile phase depends on the nature of the substances to be separated.
- Prakash Singh Bisen, Anjana Sharma(Authors)
- 2012(Publication Date)
- CRC Press(Publisher)
61 4 Chromatography 4.1 INTRODUCTION What may be called chromatographic effects today were already in use some 2000 years ago. Dyers were accustomed to judge the quality of their dyes and, in particular, to detect the presence of adul-terants by letting a drop of solution spread out on a piece of cloth or paper (papyrus). The fringe of colors formed at the boundary of the spot was a useful diagnostic. This could be the root of Paper Chromatography (PC). Around the same time, column chromatography was born in the oil industry, where crude oils were purified by allowing them to percolate through beds of carbon. However, as with many great discoveries the exact origin of the process could not be pointed out, although a few can be appreciated for giving due importance to the process by using it for the separation, purification, and identification of compounds. The first to give convincing evidence of the power and versatility of the process was M. S. Tswett, a botanist, who in 1906 isolated the principal plant pigments by passing them in a solution of petroleum ether through a column of powdered chalk. Chromatography based on the differential partition between two immiscible solvents was first described, in 1941, by A. J. P. Martin and R. L. M. Synge. In this process, water was fixed within silica gel, the mobile phase used was chloroform, and the amino acids of a protein were ana-lyzed. Subsequently, other classes of compounds, for example, antibiotics, were analyzed. Today, the technique has developed in all dimensions as perhaps the single most powerful analytical and preparative method available in the laboratory. 4.2 GENERAL PRINCIPLES The basis of all forms of chromatography is the differential partition of a compound between two immiscible phases, one of which is stationary and the other, mobile.
eBook - ePubBioprocess Engineering
Downstream Processing
- Pau Loke Show, Chien Wei Ooi, Tau Chuan Ling, Pau Loke Show, Chien Wei Ooi, Tau Chuan Ling(Authors)
- 2019(Publication Date)
- CRC Press(Publisher)
6 Chromatography Kirupa Sankar Muthuvelu andSenthil Kumar Arumugasamy 6.1 INTRODUCTIONMolecules are produced through a series of reactions that take place in a biological system or in synthetic chemistry. These molecules are recovered in addition to minute quantities of unwanted compounds referred as impurities. The target molecules must be isolated from the impurities for further applications (Pavia, 2005). This can be done on the basis of distinct physical properties such as molecular weight, boiling point, freezing point, crystallization, solubility, density, and chemical properties such as functional group and reactivity.Chromatography consists a group of analytical protocols used for separating mixtures into their individual components (Walls et al., 2011). Before the identification of an unknown compound, it must be resolved to its constituents using a separation method. Since its invention, chromatography has been an important tool for qualitative and quantitative estimation of components present in a mixture.6.1.1 HISTORY OF CHROMATOGRAPHYThe development of chromatography started in the mid-1800s with the work of a German dye chemist, F. F. Runge. Filter paper and water were used to separate the dye components (Ettre and Sakodynskii, 1993). Two reasons are responsible for the separation: the binding capacity of dye components toward the filter paper and also variations in the molecular weight among the dyes. In the 1860s, C. F. Schonbein and his student studied the rate of migration of various substances through filter paper (Ettre, 2000). Schonbein predicted that the separation was due to capillary action and named the technique capillary analysis. In 1906, a Russian botanist, Mikhail Tswett segregated six pigments present in plants, for example, chlorophyll (green) and carotenoids (yellow and orange), through a column loaded with calcium carbonate (CaCO3 ) using petroleum ether as a solvent (Telepchak et al., 2004). Initially, chromatography was to be used only to separate the color components, which is the reason behind its name. The term chromatography was coined from the Greek words Khroma
eBook - ePub- John Kenkel(Author)
- 2013(Publication Date)
- CRC Press(Publisher)
12 . In this chapter, we introduce the general concepts of chromatography and give a perspective on its scope. Since there are many different classifications, this will include an organizational scheme covering the different types and configurations that exist.Chromatography is the separation of the components of a mixture based on the different degrees to which they interact with two separate material phases. The nature of the two phases and the kind of interaction can be varied, and this gives rise to the different “types” of chromatography, which will be described in the next section. One of the two phases is a moving phase (the “mobile” phase), whereas the other does not move (the “stationary” phase) (see Figure 10.1 ). The mixture to be separated is usually introduced into the mobile phase, which then is made to move or percolate through the stationary phase either by gravity or some other force. The components of the mixture are attracted to and slowed by the stationary phase to varying degrees, and as a result, they move along with the mobile phase at varying rates, and are thus separated. Figure 10.2 illustrates this concept.The mobile phase can be either a gas or a liquid, whereas the stationary phase can be either a liquid or solid. One classification scheme is based on the nature of the two phases. All techniques that utilize a gas for the mobile phase come under the heading of “gas chromatography” (GC). All techniques that utilize a liquid mobile phase come under the heading of “liquid chromatography” (LC). Additionally, we have gas–liquid chromatography (GLC), gas–solid chromatography (GSC), liquid–liquid chromatography (LLC), and liquid–solid chromatography (LSC) if we wish to stipulate the nature of the stationary phase as well as the mobile phase. It is more useful, however, to classify the techniques according to the nature of the interaction of the mixture components with the two phases. These classifications we refer to in this text as “types” of chromatography.
eBook - PDF- Haleem J. Issaq(Author)
- 2001(Publication Date)
- CRC Press(Publisher)
4 Thin Layer Chromatography Joseph Sherma Lafayette College, Easton, Pennsylvania The term thin layer chromatography will be used throughout this chapter rather than planar chromatography, a general classification that has been used recently to denote chromatography modes having a flat stationary phase. Paper Chromatography is a type of planar chromatography, but the term has been used incorrectly to include electrochromatography or electrophoresis be-cause this method does not involve the elements necessary for designation as a chromatographic method as defined by Strain in 1942 [1], i.e., substances in a narrow initial zone are caused to undergo differential migration on a porous, sorptive stationary phase having a selective resistive action by the nonselective driving force of a liquid or gaseous mobile phase. I. EARLY HISTORY OF THIN LAYER CHROMATOGRAPHY (1889 TO EARLY 1960s) The history of thin layer chromatography (TLC) has been traced back to experiments performed by the Dutch biologist Beyerinck in 1889 [2]. These predate the early work on column chroma-tography reported by Tswett in 1906 [3] but are predated by the Paper Chromatography work of Runge, Schoenbein, and Goppelsroeder [4] during the period 1834-1888. Beyerinck allowed a drop of a mixture of hydrochloric and sulfuric acids to diffuse through a thin layer of gelatin on a glass plate. The hydrochloric acid traveled faster than the sulfuric acid and formed a ring around the latter. The hydrochloric acid zone was made visible by reaction with silver nitrate and the sulfuric acid with barium chloride. Tswett did not study TLC but discussed adsorption of compounds on strips of paper during capillary analysis [5]. Consden, Martin, and Gordon reintroduced Paper Chromatography in 1944 [6], and it grew into a universally used microanalyti-cal method during the next 10 years.
- Richard J. Block, Emmett L. Durrum, Gunter Zweig(Authors)
- 2013(Publication Date)
- Academic Press(Publisher)
A simple method by Moore (1953) has been found to be satisfactory: The paper containing the spot to be eluted is cut into a strip with a pointed end. The strip is placed between two glass slides, with the point just touching a new paper strip. By downward chromatography the spot is transferred to the new paper strip at such a rate that the size of the spot remains fairly small. This is facilitated by directing a stream of air from a hair dryer against the underside of the new paper. A combination of descending chromatography and elution has been found useful in the quantitative estimation of Pt and Cu (see Chapter XIII) (Anderson, 1951). A solvent is chosen so that only one substance moves, and all other interfering ions remain near the origin. The eluate is then analyzed by microtechniques. GENERAL METHODS 49 9. PRESERVATION OF CHROMATOGRAMS (see also Chapter V) Since many color reactions tend to fade with time (e.g., ninhydrin color of amino acids), it is necessary to keep a permanent record of the chro-matogram. Contact prints of fresh chromatograms with the Contoura (F. G. Ludwig Associates) are recommended. For best results the chro-matogram is placed on top of the photographic paper, with the exposure varying from 5-15 seconds, depending on the color intensity of the spots. Addendum APPLICATION OF SAMPLE The principal factor in obtaining reproducible results in paper chroma-tography from day to day and by different operators is believed to be the application of the spot by placing the micropipette at right angles to the paper (Livingston, 1953). A parallelogram arm pipette holder was de-signed to eliminate the personal error in Paper Chromatography.* Another problem, that of concentrating an unknown dilute solution to be analyzed right on the filter paper, was solved as follows (Urbach, 1949) : Paper strips are stretched horizontally above a hot plate; both ends of the paper are weighted down by window display hooks.
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