Tuesday, 2 July 2013

What is Chromatography?

Chromatography in broad terms is the separation of components in a mixture by distribution of the components between two phases – one that is static i.e. the stationary phase and one that moves i.e. the mobile phase. As the mobile phase moves, the components of the mixture move at different rates on the stationary phase as shown in Figure 1.1. Chromatography can be carried out on an apparatus that is planar or a column.

Figure 1:1 Theory of column chromatography separations

When chromatography is performed on a flat surface such as a sheet e.g. paper or plate which could be glass, plastic or metal, it is called Planar Chromatography. The separated components are characterised by distance travelled on the plate relative to the distance travelled by the mobile phase (eluent) i.e. the retention factor, Rf.  There are two types of planar chromatography:
  • Paper Chromatography is when the stationary phase is a special grade cellulose paper simply referred to as chromatography paper, which could be unmodified or modified with other chemicals.
  • Thin-Layer Chromatography (TLC) is when the stationary phase material usually silica or alumina has been coated on to a plastic, glass or metal plate.
When chromatography is performed in a column as previously shown in figure 1.1, which again could be glass, metal or plastic, it is called Column Chromatography (also referred to as Elution Chromatography) because separated components actually get eluted from the column. The separated components are characterised by the time it takes to travel through the column i.e. the retention time, tR. Each separated component will have its own unique tR for a given set of experimental conditions.
Column chromatography techniques vary with different types of stationary phases coupled to different types of mobile phases. Classification purely on the basis of the physical nature of the mobile phase gives techniques such as:
  • Gas Chromatography (GC), in which the mobile phase is a gas, typically hydrogen or helium.
  • Supercritical Fluid Chromatography (SFC) implies that the mobile phase is in a supercritical state i.e. neither gas nor liquid.
  • Liquid Chromatography (LC) obviously means that the mobile phase is a liquid. Note that we have liquid-planar chromatography e.g. TLC as well as liquid-column chromatography techniques. 
An excerpt from book - HPLC Fundamentals by Bunmi Adeyoju

Tuesday, 8 February 2011

TLC Reader for Yamazen Flash Chromatography System

In normal phase chromatography, chemists would typically run a TLC on their samples prior to column chromatography. This involves the time-wasting process of calculating the TLC Rf values for the target compound. Yamazen has introduced a TLC plate reader to work in an automated mode with its Flash Chromatography Systems. So that now, a chemist would run a TLC and simply place the TLC plate on the reader, then the TLC image reader would read and calculate the Rf vlaues. These values and the solvent mixture is fed to Yamazen's patented automated method setting software which develops a gradient method that elutes the compound of interest at 4-column volumes. This minimizes solvent use and waste disposal while achieving good sample separation. Hence, Eco-friendly and substantial savings on lab expenses.
Yamazen Science is at booth #409, ACS Exposition, Anaheim California, March 28-30, 2011

Tuesday, 14 December 2010

Prep Chroma announces training dates for March 2011

Introduction to Preparative LC (1 day)
Date: 29th March 2011
Location: Manchester
Email: info@prepchroma.com for further details

Introduction to LCMS (1 day)
Date: 31st March 2011
Location: Manchester
Email: info@prepchroma.com for further details

Monday, 8 November 2010

Cellufine (Cellulose-based) Chromatography Media

Cellufine (Cellulose-based) Chromatography Media are now available to order through Prep Chroma.

Cellufine is the preferred chromatography media for the purification of proteins, enzymes and other bio-active substances. It is made from spherical cellulose with its typical characteristics of high mechanical strength, chemical stability and bio-compatibility. And particularly suited to pharmaceutical and Food applications.

Cellufine product range covers all liquid chromatography modes - Gel Filtration, Ion-Exchange, Affinity and Hydrophobic Interaction Chromatography. These products are available as bulk as well as in mini-column formats for use on HPLC instruments.

For more information please contact info@prepchroma.com

Tuesday, 29 June 2010

SiliaChrom HPLC Columns (SiliCycle, Canada)

SiliaChrom HPLC columns (Silicycle, Canada), can now be ordered from Prep Chroma.
SiliaChrom HPLC columns cover a wide range of applications such as normal phase, reverse phase, ion-exchange - silica and polymer-based, chiral, sugar and protein analysis. And cover analytical, semi-preparative and preparative analysis. Guard columns are also available. For technical and ordering information contact info@prepchroma.com

Monday, 19 April 2010

LC-MS Training Course in Manchester July 2010

Registration is now open for our LC-MS training course (4 days) running in Manchester in July. E-mail info@prepchroma.com for registration details.

Tuesday, 9 March 2010

Cecil Instruments launch Semi-Prep HPLC Pump

Using over 40 years experience of HPLC instrumentation, Cecil Instruments have added an enhanced semi-prep HPLC pump to their existing Adept range. The pump has a flow rate range of 0.01 to 50ml/min and can be used in isocratic as well as high pressure gradient modes. It offers the advantage of smooth, easy and reproducible transitions in scaling up from analytical to semi-preparative work.
Being a modular HPLC component, this pump can be used with AutoQuest autosampler, Column heater/chillers, WaveQuest UV/VIS ultra-fast scanning detectors, and fraction collectors for complete automation in the long-term, fast and reliable collection of fractions. It may also be used with third party systems.
It is easy and fast to install, virtually plug and play. Please mail info@prepchroma.com for more information.