This article will provide an overview of stationary phases, from what they are and the various types of stationary phases available, to their various applications. The various advantages and disadvantages of using each type of stationary phase will also be discussed.
Stationary phases are an important tool in analytical chemistry and chromatography. They provide a stationary surface on which the sample molecules can interact, thus enabling the separation of components of a mixture. Stationary phases can be solid or liquid and are usually held in a column in a chromatograph. The molecules of the sample interact with the stationary phase, resulting in different interactions for different molecules, which leads to their separation.
The type of stationary phase used depends on the type of sample and the application. Generally, the most common type of stationary phases are polymeric-based stationary phases, such as polyethylene glycol (PEG), polypropylene glycol (PPG) and polydimethylsiloxane (PDMS). These have the ability to interact with a wide range of molecules, making them suitable for many applications. Other types of stationary phases include bonded silica and carbon stationary phases, which are used for specific molecules and applications.
In addition, stationary phases can be modified to create tailored properties to better suit the purpose. For example, the polarity of the stationary phase can be adjusted to better separate molecules of different polarities. Furthermore, the surface of the stationary phase can be modified with ligands that bind to target molecules, making it easier to separate them.
Stationary phases, also known as “solid supports” in chromatography, refer to any solid material used to separate mixtures in liquid or gas form. Different types of stationary phases are available, and each type serves a different purpose. The most common include reversed phase (RP), normal phase (NP), hydrophilic interaction chromatography (HILIC), and size exclusion (SEC).
Reversed phase (RP) chromatography utilizes organic or "hydrophobic" stationary phases that interact with the targeted molecules in a liquid sample. These interactions then cause the molecules to slow down, allowing for separation and analysis. RP stationary phases are the most commonly used in the pharmaceutical industry and are often used to separate proteins and peptides.
Normal Phase (NP) chromatography utilizes non-polar or “hydrophilic” stationary phases for the separation of samples with polar components. This type of chromatography is particularly useful for separating substances such as carbohydrates, lipids, and alcohols.
Hydrophilic Interaction Chromatography (HILIC) utilizes mobile phases that are water and organic buffer-based and interact with the sample molecules to allow for efficient separation. HILIC is especially useful for separating polar and non-polar molecules such as sugars, amino acids, and lipids.
Size Exclusion (SEC) chromatography utilizes porous stationary phases composed of beads or gels to separate molecules based on their size. While all molecules pass through the beads, molecules of larger molecular weights or sizes are slowed down while smaller molecules are allowed to pass through more quickly. This method is commonly used to separate proteins and measure their molecular weights.
Stationary phases are used in a variety of applications, such as liquid chromatography and gas chromatography. In liquid chromatography, stationary phases can be used to separate mixtures of compounds into individual components, which can then be identified and quantified. Stationary phases are also used in gas chromatography to identify and quantify volatile organic compounds (VOCs) in environmental samples.
In addition, stationary phases are used in the analysis of pharmaceuticals, food products, and other sample matrices. For example, they can be used to measure the content of active ingredients in pharmaceuticals to ensure they meet certain standards. They are also used to quantify levels of contaminants and unwanted substances in food products.
The wide range of applications of stationary phases makes them a key component in analytical laboratories around the world. Furthermore, advances in technology have allowed for the development of new stationary phases that offer better performance and increased efficiency. These new stationary phases provide an invaluable service to analytical laboratories and researchers around the world.