Very sorry to hear that Mark. I guess you could try a salt bath or dirt quarantine and some other treatments...
BUT, I've had great success in recent months using "Nifurstyreneate Monosodiumsalt" (C13H8NO5�ENa Mw 281.20), which is contained in a treatment sold here in the form of a yellow powder for use in treating ailments of Japanese "koi" carp and goldfish (I was originally introduced to this for treatment of an ill Oscar I kept). Instead of diluting the powder in water, as per the instructions on the package, it is applied by moist Q-tip directly to the wound, be it a tail or a limb. It really works wonders. See if this ingredient isn't in medicine sold at your pet/pond shops there.
Better yet, inquire with a vet, though he or she might not be familiar with chemical or this treatment in particular.
Also, depending on the wound, 3% solution hydrogen peroxide can be used, if used very, very carefully, using a slightly moistened Q-tip an applying it only to the area of the wound and then only for 10 seconds or so before giving it a good rinsing with water. This should deal with any fungus growth on the wound and help sterilize the area. It should also hasten the dropping off of the tail if it's hanging on only ever so slightly. Remember though, this stuff is VERY caustic when used with amphibians.
I've snipped off "dead" tail before in extreme cases with a very sharp pair of sterilized scissors...but mentioning that course of action in this forum before generated howls of protest and lectures from sensitive souls here who otherwise hardly post at all.
My Triturus, in particular, are notorious tail biters. I recently successfully mended the tail of a Cynops injured by a Triturus and also a Paramesotriton chinensis whose limb was savaged by another. In both cases, the injured body part fell off, without my having to resort to amputation (never, by the way, consider amputating any area of the half of the tail nearest the body!). In both cases I relied mainly on the powder, used hydrogen peroxide only sparingly in the initial stage, and treated the newts on live moss, not in the water.
Hope others here with more experience than me can provide information on treatment strategies that have worked for them.
Good luck