Introduction to Paper Chromatography

Introduction to Paper Chromatography

Paper chromatography is a widely used analytical technique which separates mixtures of compounds based on their different affinities towards various solvents. It's often referred to as 'wet chemistry', due to its reliance on wetting agents like water. This method was first invented by Meyer and Othmer in the mid-twentieth century and has since grown into one of the most popular techniques within forensic science and biochemistry laboratories worldwide.

The process involves soaking paper with solvent systems that contain both polar and nonpolar components. These paper strips have been treated with a stationary phase, such as cellulose fibers, to retain the mixture during separation. When a sample containing multiple compounds is applied close to the bottom of the strip, each component moves upwards through the sheet under capillary action caused by evaporation. As the compounds move along, they stop, or come back down, depending on how well they interact with the mobile phase—the combination of the stationary phase and solvent system.

This interaction determines the distribution coefficient of each compound between the stationary and mobile phases. Compounds with higher affinity for the stationary phase will travel more slowly; those less attracted will advance further along the paper before saturation sets in. Once the separation is complete, you can identify individual compounds visually using a UV lamp or other detection methods.

Although it has seen competition from newer technologies, like gas chromatography, liquid chromatography, and high performance liquid chromatography, paper chromatography remains relevant due to its low cost, ease of operation, and ability to detect even very small amounts of certain chemicals. However, it does suffer limitations such as lower resolving power compared to packed-column gas chromatographic analysis- especially when dealing with voluminous samples. Additionally, it cannot handle large volumes efficiently, making it unsuitable for quantitative work.