JOURNAL O F CHEMICAL EDUCATION
0
A CHROMATOGRAPHIC DEMONSTRATION DAVID A. PORSS Commonwealth Scientific Melbourne, Australia
SCALE WATER
TOP OF C E U L O S E PACKING
RED (ERMHFQSI
SOLUTION B
N B)
YELLOW (TARTAR YELLOW) PURPLE (BROMCRESOL
WRPLC)
SOLUTION A YELW(TARTAR
YELLOW)
GREEN (BROMCRESOL WEEN)
b"
C O T T W W O L PLUG
Industrial Reseach Organization,
WHEN a "Better Food Exhibition" was held in Melbourne recently, we were asked to demonstrate visually the chromatographic procedure used in the isolation of flavoring compounds. Because of the fire risk and their penetrating odor, organic solvents couldnot be used and were replaced by water. A number of indicators and dyes were tested on sheets of filter paper with water at various pH's and those which appeared promising were tested on alumina, silica gel, and cellulose columns. Cellulose columns were the most satisfactory, and two mixtures containing 10 mg. each of three compounds dissolved in 250 ml. saturated aqueous sodium borate were used. Solution A contained erythrosine B (tetraiodofluorescein), tartar yellow (tartrazine), and bromcresol green; solution B had bromcresol purple in place of bromcresol green. The column was 60 X 2 cm. and contained 45 cm. of packing. A slurry of Whatman Ashless Powder for Chromatography; Standard Grade was poured into the column in amounts that when compacted with a polyethylene plunger gave 5 cm. of packing. Five ml. of solution A was added to the column containing no water above the cellulose, and when the mixture had been adsorbed 5 ml. of water was added, and when this had been taken up by the cellulose, a further 30 ml. water was added. By the time the 30 ml. water had passed onto the cellulose the mixture had separated into an upper red band and a yellow-green band about a quarter of the way down the column. Solution B was then added, followed by solution A , etc. The diagram shows the column after two lots of solution A and one lot of solution B had been added. The eluate was collected in 2- X a/s-in. test tubes in a fraction collector operating on five-minute intervals. It is thought that this demonstration might be of use to instructors who wish to illustrate a, chromatographic separation with simple apparatus and without organic solvents.
