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Sugar Syrup Mounting Media

Simple sugar syrups may be used as temporary aqueous mounting media, for lipid stains etc. These may be made or purchased. Apart from their availability as laboratory supplies, they may be available in many grocery stores in the form of corn syrup, high fructose corn syrup, golden syrup and similar products. Some of these are pale yellow, while others may be uncoloured (Karo brand corn syrup, which has often been recommended, is an example). Avoid distinctly brown products which may contain flavourings and colouring. Honey should be avoided as it may contain pollen grains and bacteria. Many food syrups are a mixture of glucose (dextrose) and fructose (levulose), and may have been made from invert sugar derived from sucrose. High fructose syrup is usually made from corn by chemically converting a large part of its glucose content into fructose, although a distinct amount of glucose still remains.

If making your own syrup, dextrose, fructose or sucrose are suitable. Others may be as well, but they tend to be more expensive and give no particular advantage. The least expensive is probably sucrose (ordinary table sugar) and it makes no difference whether it is sourced from sugar cane or sugar beet as they produce chemically identical compounds composed of a dimer of glucose and fructose. This likely inverts when made into a syrup in any case, with a resulting glucose-fructose mixture.

Syrups are easily made by adding a weight of whichever sugar is needed equal to or up to twice the volume of water used, i.e. if you use 200 ml water then add between 200g and 400g sugar, depending on how thick you want the syrup. Heat gently to dissolve the sugar. Avoid boiling as it may cause the sugar to caramelise and turn into toffee, which will need to be disposed of in some fashion! Allow the syrup to cool and filter through glass wool or very loosely packed cotton wool (it will tend to matt). Keep in mind that syrups of this kind are close to being supersaturated and may rapidly crystallise. Gently warming usually redissolves precipitated crystals.

When used alone as mounting media simple syrups need to be ringed to stop evaporation and consequent precipitation of the sugar. They are not a good choice for permanent preparations even when ringed.


 

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