Practical investigations
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I have been reading the Investigating Wines tutorial. I have managed to follow and understand how to do every experiment except for the “Identifying Acids” experiment. I have came to the conclusion that I will put a sample of tartaric, citric, succinic and ethanoic acids on to the chromatography paper, as well as a sample of wine. Does the sample of wine have to be put through a filter of activated charcoal? What solvent should I use in the chromatography tank? I also came up with the idea of once the experiment has taken place, and the paper has dried, to apply an indicator to the paper through a spray. Would this work and would I use bromophenol blue?
To take your questions one by one:
Yes, the (red) wine does need to be decolourised first, otherwise there will be an interference with the eventual colours on the chromatography paper.
You need to use a solvent which hydrogen bonds with the acid components, so that they can be “drawn” up through the paper. Water works well, but you might want to try ethanol or even a water-ethanol mixture. Why not experiment with all of these?
Using a “spray” to develop the spots is an excellent idea. A house-plant polythene water bottle - fitted with a spray - is a good choice of apparatus.
I have experimented with bromophenol blue and bromocresol green, but cannot remember which works better.
The main thing about this particular experiment is that you need to carry it out several times under different sets of conditions to get the best set of results. For example, you need to practise your technique with the polythene bottle, varying the distance between bottle and paper, the amount of liquid to use, etc., so as to drench the entire paper. Use too much liquid, however, and your spots will “run”. The secret is to practise your technique, preferably on blank sheets of paper before carrying it out on the real thing. Also you will need to perfect the use of a capillary tube to administer just the correct amount of wine or reference acid on to your chromatography paper (don’t forget to use different capillary tubes for each liquid).
Once you are ready, it is probably advisable to have several experiments running concurrently, otherwise you will waste a great deal of time. With patience and practice, excellent and most rewarding results can be obtained.
Risk assessment
Before attempting any practical work based on the advice and suggestions on this website, you must do the following. Identify any hazards, assess the risks from these hazards, and then decide appropriate control measures to reduce the risks. You must have these approved by those in authority in your school or college laboratory. Do not rely on what is said on this website.
For further guidance see our tutorial on Risk Assessment.
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updated: 26 February 2004
