High Performance Liquid Chromatography (HPLC) is an analytical technique used for the separation of compounds soluble in a particular solvent. Liquid chromatography was initially discovered as an analytical technique in the early twentieth century and was first used as a method of separating colored compounds. This is where the name chromatography chroma means color, graphy means writing, was derived. All chromatographic separations, including HPLC operate under the same basic principle; every compound interacts with other chemical species in a characteristic manner.
Modern high performance liquid chromatography or HPLC has its roots in this separation, the first form of liquid chromatography. The chromatographic process has been significantly improved over the last hundred years, yielding greater separation efficiency, versatility and speed.
Chromatography can be described as a mass transfer process involving adsorption. HPLC relies on pumps to pass a pressurized liquid and a sample mixture through a column filled with a sorbent, leading to the separation of the sample components. The active component of the column, the sorbent, is typically a granular material made of solid particles (e.g. silica, polymers, etc.), 2-50 micrometres in size. The components of the sample mixture are separated from each other due to their different degrees of interaction with the sorbent particles. The pressurized liquid is typically a mixture of solvents (e.g. water, acetonitrile and/or methanol) and is referred to as a "mobile phase". Its composition and temperature play a major role in the separation process by influencing the interactions taking place between sample components and sorbent. These interactions are physical in nature, such as hydrophobic (dispersive), dipole-dipole and ionic, most often a combination.
HPLC is distinguished from traditional ("low pressure") liquid chromatography because operational pressures are significantly higher (50-350 bar), while ordinary liquid chromatography typically relies on the force of gravity to pass the mobile phase through the column. Due to the small sample amount separated in analytical HPLC, typical column dimensions are 2.1-4.6 mm diameter, and 30-250 mm length. Also HPLC columns are made with smaller sorbent particles (2-50 micrometre in average particle size). This gives HPLC superior resolving power when separating mixtures, which makes it a popular chromatographic technique.
Increasingly, food analysis methods are built around high-performance liquid chromatography (HPLC), which has proven to be an optimal technology for detecting and/or quantifying the vast majority of food analytes. These methods employ a stepwise approach that first removes the sample matrix, then isolates the analytes of interest and individually resolves them on a chromatographic column. The efficiency of the separation depends on, among other things, the differential interaction of analytes of interest with both mobile and column stationary phases. Of course, classifying food analytes according to their relative volatility and polarity are factors that must be considered when selecting an appropriate analytical method for their determination. Keeping track of the increasing diversity of food products with their ever-expanding profusion of additives is a daunting analytical challenge; one that must be continually met if we are to ensure the quality and safety of our food supply. HPLC is powerfully current because it's fundamental principle-selection through differential molecular interaction-is based on fundamental variations in classes of properties across all chemical species. This selection principle continues to be a rich source of methodological innovation for analytical separation, detection and quantification.
Modern high performance liquid chromatography or HPLC has its roots in this separation, the first form of liquid chromatography. The chromatographic process has been significantly improved over the last hundred years, yielding greater separation efficiency, versatility and speed.
Chromatography can be described as a mass transfer process involving adsorption. HPLC relies on pumps to pass a pressurized liquid and a sample mixture through a column filled with a sorbent, leading to the separation of the sample components. The active component of the column, the sorbent, is typically a granular material made of solid particles (e.g. silica, polymers, etc.), 2-50 micrometres in size. The components of the sample mixture are separated from each other due to their different degrees of interaction with the sorbent particles. The pressurized liquid is typically a mixture of solvents (e.g. water, acetonitrile and/or methanol) and is referred to as a "mobile phase". Its composition and temperature play a major role in the separation process by influencing the interactions taking place between sample components and sorbent. These interactions are physical in nature, such as hydrophobic (dispersive), dipole-dipole and ionic, most often a combination.
HPLC is distinguished from traditional ("low pressure") liquid chromatography because operational pressures are significantly higher (50-350 bar), while ordinary liquid chromatography typically relies on the force of gravity to pass the mobile phase through the column. Due to the small sample amount separated in analytical HPLC, typical column dimensions are 2.1-4.6 mm diameter, and 30-250 mm length. Also HPLC columns are made with smaller sorbent particles (2-50 micrometre in average particle size). This gives HPLC superior resolving power when separating mixtures, which makes it a popular chromatographic technique.
Increasingly, food analysis methods are built around high-performance liquid chromatography (HPLC), which has proven to be an optimal technology for detecting and/or quantifying the vast majority of food analytes. These methods employ a stepwise approach that first removes the sample matrix, then isolates the analytes of interest and individually resolves them on a chromatographic column. The efficiency of the separation depends on, among other things, the differential interaction of analytes of interest with both mobile and column stationary phases. Of course, classifying food analytes according to their relative volatility and polarity are factors that must be considered when selecting an appropriate analytical method for their determination. Keeping track of the increasing diversity of food products with their ever-expanding profusion of additives is a daunting analytical challenge; one that must be continually met if we are to ensure the quality and safety of our food supply. HPLC is powerfully current because it's fundamental principle-selection through differential molecular interaction-is based on fundamental variations in classes of properties across all chemical species. This selection principle continues to be a rich source of methodological innovation for analytical separation, detection and quantification.
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