Solvent

chloroform: methanol (96:4)

Figure 12.17 Silver nitrate TLC of triacylglycerols.

S, saturated fatty acid M, monoenoic fatty acid D, dienoic fatty acid T, trienoic fatty acid

Triacylglycerols with similar total numbers of double bonds can be separated using a chlo-roform-methanol solvent. The proportions of the solvent are adjusted to achieve resolution of compounds with either a total of up to four double bonds or more than four.

Table 12.10 Destructive staining procedures

Reagent Method Comments

30-50% sulphuric acid in Spray the plate and heat at 180°C for Detects all lipids by carbonization of water (v/v) 5 min on a hot plate or 30 min organic materia] producing black in an oven charred areas. At lower temperatures

(~80°C) sterols give a purple-red

Chromic acid

6gl_1 potassium dichromate in 55% sulphuric acid

Spray the plate and heat at 180°C for 5 min on a hot plate or 30 min in an oven

All lipids give black charred spots

50% orthophosphoric acid in water

After spraying, heat on a hot plate at 300 °C for 5 min

All lipids give black charred spots from acidic phosphoglycerides (phosphatidyl serine and phosphatidyl inositol). Other modifications which may improve the quality of the separation include the addition of sodium carbonate or ammonium sulphate in the preparation of the silica gel or the preliminary removal of the simple lipids to the top of the plate by running it in acetone-hexane solvent (1: 3). When the extract is rich in acidic phosphoglycerides it is preferable to use a solvent containing ammonia.

Table 12.11 Examples of non-destructive stains

Reagent Method Comments

Table 12.11 Examples of non-destructive stains

Reagent Method Comments

Iodine vapour

Place the dried plate in a

Dark yellow-brown spots appear

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