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I don't know what methods could be used for preserving it for scientific research, but cuttlefish ink has been preserved to use as a writing ink since ancient times. Usually it has been dried and powdered.
I've looked into this in the past ( I ahd a crazy idea of making my own drawing inks!!!) any way the key ingredients to make ink and thus preserve it are
Gum arabic: Exuded by acacia (acacia senegal) and other African trees, it is a very common thickener and colloidal stabilizer. Some candies are made from up to 45% gum arabic. Also called acacia. CAS 9000-01-5: Gum acacia; gum arabic; acacia gum; Indian gum.
Ferrous sulfate: Also known as kankatum, green vitriol or copperas.
(FeSO4, 7 H2O) iron sulphate in hydrated crystal form (278.01 g/mol).
Tannin: Tannic (or gallotannic) acid, extracted by water-saturated ether from crushed gallnuts ( galls, nutgalls, or gall apples ). It is an anhydrid of gallic acid (see next): COOH.C6H2(OH)2O.COC6H2(OH)3
Gallic acid: Produced (with glucose) by the hydrolysis of tannin in acid. Used in calotype photography. C6(COOH)H(OH)3H (170.12 g/mol)
and of course the pigment, in this case the ceph ink. The only problem I can see with this is that it will change the chemical composition of the ink rendering it useless for research!!!!!! So I'd freeze or dry it.