#paperchromatography

Paper chromatography is a type of chromatographic technique that employs a porous paper strip or sheet as the stationary phase and a liquid solvent as the mobile phase. This technique takes advantage of the differential solubility and adsorption properties of the components in a mixture, enabling their separation and identification. 

Paper Chromatography Principle

The principle of paper chromatography lies in the concept of partitioning. When a mixture is applied near one end of the paper strip, the mobile phase (solvent) moves through capillary action, carrying the mixture along with it. As the solvent travels up the paper, it interacts with the compounds in the mixture. Depending on their solubility and affinity for the paper, the components are selectively carried at different rates. This differential movement allows the separation of the mixture into its individual components. 

How Paper Chromatography Principle Works?

Well, it relies on a simple principle: different substances in a mixture will move at different speeds through a piece of special paper when they’re dissolved in a liquid. This paper is called chromatography paper, and it’s designed to absorb the liquid and let it travel. 

Sample Application: First, you take a small drop of your mixture and place it near the bottom of the chromatography paper. This is where the magic begins. 

Developing Solvent: Next, you dip the bottom of the paper into a liquid, called the developing solvent. This liquid moves up the paper by a process called capillary action, and it carries the different components of your mixture along with it. 

Separation Time: As the solvent travels up the paper, it carries the mixture’s components with it. But here’s the cool part – because each substance in the mixture interacts with the paper and solvent differently, they move at different speeds. This causes them to spread out along the paper, creating colorful bands. 

Identification: Once the solvent reaches the top of the paper, you’ve got a beautiful chromatogram. Now, you can see the different components of your mixture separated out. It’s like having a secret code that tells you what’s in your mixture! 

Types of Paper Chromatography

There are several types of paper chromatography, each with its own specific applications and techniques. Here are some commonly used variations: 

Ascending Paper Chromatography: In this method, the solvent is allowed to rise up the paper strip by capillary action, separating the mixture components as it progresses. It is particularly useful for separating small molecules and organic compounds. 

Ascending Thin-Layer Chromatography (TLC): Similar to ascending paper chromatography, but the stationary phase is a thin layer of silica gel or alumina on a glass or plastic plate. TLC offers faster separation and is commonly used in qualitative analysis. 

Descending Paper Chromatography: Unlike ascending paper chromatography, the solvent is applied at the top and allowed to flow downwards, carrying the mixture components. This technique is advantageous when analyzing non-volatile substances or those that are more soluble in the solvent. 

Two-Dimensional Paper Chromatography: This method involves the sequential application of solvents in two directions, allowing better separation and analysis of complex mixtures. 

Preparative Paper Chromatography: In this technique, larger quantities of separated components are obtained for further analysis or use. It is commonly used for isolating pure compounds. 

Applications of Paper Chromatography

Paper chromatography finds extensive applications in various fields due to its simplicity, versatility, and cost-effectiveness. Some notable applications include: 

Food and Beverage Analysis: Paper chromatography is used to analyze food additives, dyes, and contaminants. It enables the identification and quantification of components in complex food matrices. 

Pharmaceutical Industry: This technique plays a crucial role in the quality control and analysis of pharmaceutical substances. It aids in drug formulation development, stability testing, and detection of impurities. 

Forensic Science: Paper chromatography is employed to analyze ink compositions and differentiate between counterfeit and genuine documents. It helps forensic experts determine the origin of ink samples and provide valuable evidence in investigations. 

Environmental Analysis: By separating and analyzing environmental pollutants, such as pesticides and heavy metals, paper chromatography contributes to environmental monitoring and assessment. 

Biochemical Analysis: Paper chromatography is used for the separation and identification of amino acids, sugars, vitamins, and other biological compounds. It plays a vital role in protein characterization and the detection of metabolic disorders. 

Paper chromatography is an indispensable technique in the field of analytical chemistry. Its ability to separate and identify components in mixtures has proven invaluable across various scientific disciplines. By understanding the principles, types, experiment procedures, and applications of paper chromatography, scientists and researchers can harness its power to unlock valuable insights from complex mixtures. 

Chromatography technique that uses paper sheets or strips as the adsorbent being the stationary phase through which a solution is made to pass is called paper chromatography. It is an inexpensive method of separating dissolved chemical substances by their different migration rates across the sheets of paper.

Although paper chromatography technique is simple and rapid, uses minimum amount of material, comparatively less expensive than other chromatographic technique it has many disadvantages. Paper chromatography is useful only for qualitative evaluation. It has limitation to separate complex mixtures.

The main differences between TLC and paper chromatography are: The principle behind thin-layer chromatography is based on adsorption. On the other hand, the principle of paper chromatography is based on partition.

TLC analysis provides better separation for the components in the mixture and more useful chromatograms than paper chromatography. However, basic TLC has many limitations in many of the important steps like application, development, derivatization and are manual, therefore we get lot of variation in the results and quantitative evaluation is ineffective. As many of the steps are manual, errors are caused by analyst as well as environmental factors like humidity.

To overcome these limitations, HPTLC technique is used, which is a modern version of TLC wherein the principals are same but the practice is fully automated and GLP/USP/EP compliant.

Unique features of HPTLC are that it is the fastest, simplest, most economical and flexible, “visible” technique which can analyse in parallel more than 100 samples. It is risk free and multiple detections can be made without repeating chromatogram. HPTLC is used for the analysis of non-volatile organic compounds such as pharmaceuticals, APIs, botanicals, forensics, foods etc. for establishing purity, impurities, fingerprint, identification, quantification and reverse engineering.

After doing single analysis, analyst gets many data points. Data is obtained at 254nm, 366nm, and in white light also after derivatization in white light or at 366nm. Spectral evaluation is also possible, as it has wide scanning range starting from 190-900nm. Nowadays, it is also possible to couple HPTLC with other spectroscopic technique like MS, IR and NMR.

HPTLC technique can also be used for detection of biologically active compounds as it can be coupled with biological assays like antioxidant activity, antimicrobial, antidiabetic activity etc.

Thus, as this technique offers many advantages for analysis of diverse type of samples and many data points after single analysis are obtained, HPTLC which is modern version of TLC is the best choice for analysis of various samples.