ANALYSIS AND FOOD SAFETY————-CHROMATOGRAPHY

This is a separation technique which is carried out according to size, solubility, boiling point and volatility.

Basic Terms

Analyte=substance/compound to be separated

Chromatogram=print out of the  showing different separated analytes

Chromatograph=the equipment that does the separation

Eluate=solution of solvent and dissolved matter collected from elution

Eluent=solvent that carries analytes

Stationary phase=a selected compound at a fixed place fro the procedure e g silica gel

The matrix (support) can be polar or non polar. It can preparative(to purify for further analysis) or analytical(to measure relative proportion of analytes in a mixture)

Types

1.Thin Layer Chromatography TLC

Applicable for the analysis of pesticides, food, fatty acids, food , phytochemicals and water. Adsorbent like silica gel can be spread as a thick slurry on the commercially available plates to a thickness of 0.1 -0.5mm(for analysis) and 0.5-2.0mm(for purity). Components of the sample move at different rates with respect to how they can bind onto the stationary phase. The movement is measured as R_f value , a figure that is specific to each analyte. Filter paper(cellulose) and silica gel are examples of stationary phase

A modification include HPTLC,  High Performance Thin Layer Chromatography

2.High Performance Liquid Chromatography HPLC

This is a separation based on the analytes relative solubility between 2 phases. Sample ca  eb loaded in 5-20 microliter volume. The components of the chromatogram are pump, injector, column, detector and computer. Its effective in separating pharmaceuticals, mycotoxins, salts, proteins, polystyrenes, heavy hydrocarbons, phytochemicals, and enzymes

3.Gas  Chromatography

Sometimes called Gas Liquid Chromatography

It is a requirement that samples must be vaporised without decay or decomposition. Mobile phase or carrier gas is Helium or Nitrogen. The stationary phase called a column, a metal tubing. The vaporised compound will elute at different times called RETENTION TIME, RT which is specific for each analyte and so used to identify them. As the chemicals go out of the column, they are identified electronically

Detectors are used in further elucidation of the analytes. These include UV, Fluorescence FID etc. Columns are also selected based on effectiveness. However, C-18 column is regarded as universal , capable of compatibility with a wide range of compounds.

dele Fapohunda

10 December, 2022