Capillary electrophoresis CE is a powerful analytical technique used to separate and analyze complex mixtures of charged molecules, such as amino acids, based on their electrophoretic mobility in a narrow capillary filled with an electrolyte solution. The separation of molecules with similar charge-to-mass ratios can be achieved by optimizing the separation conditions, such as the buffer pH, the type and concentration of the electrolyte, the capillary temperature, and the applied voltage.The theoretical basis of capillary electrophoresis lies in the electrophoretic mobility of the charged molecules. Electrophoretic mobility is defined as the velocity of a charged molecule v under the influence of an electric field E and is given by the equation: = v / EThe electrophoretic mobility of a molecule depends on its charge q , size, and shape, as well as the viscosity of the medium in which it is moving. The relationship between these factors can be described by the following equation: = q / 6r where r is the hydrodynamic radius of the molecule.In the case of amino acids, which are zwitterionic molecules, the net charge depends on the pH of the buffer solution. At a pH below their isoelectric point pI , amino acids will carry a net positive charge, while at a pH above their pI, they will carry a net negative charge. By adjusting the pH of the buffer solution, you can control the net charge of the amino acids and thus their electrophoretic mobility.To separate amino acids with similar charge-to-mass ratios, you can use a technique called capillary zone electrophoresis CZE . In CZE, the capillary is filled with a buffer solution, and the sample is introduced at one end. An electric field is applied across the capillary, causing the positively charged amino acids to migrate towards the negatively charged cathode. The separation is based on the differences in their electrophoretic mobility, which is influenced by their charge, size, and shape.To improve the separation of amino acids with similar charge-to-mass ratios, you can also use capillary electrophoresis with a micellar electrokinetic chromatography MEKC approach. In MEKC, a surfactant is added to the buffer solution, forming micelles. The amino acids can interact with the micelles, resulting in partitioning between the micellar and aqueous phases. This partitioning introduces an additional separation mechanism based on the hydrophobicity of the amino acids, which can help to resolve molecules with similar charge-to-mass ratios.In summary, capillary electrophoresis can be used to analyze the composition of a sample containing multiple positively charged molecules with similar charge-to-mass ratios, such as amino acids, by optimizing the separation conditions and employing techniques like CZE and MEKC. The theoretical basis of this separation technique is the electrophoretic mobility of the charged molecules, which depends on their charge, size, shape, and the viscosity of the medium.