I am a retired U.S. patent agent but with no experience in chemical patents which are a specialized sub-field in patent practice.
Some people make a serious avocation of pursuing their own patents and can be successful but it is a big time commitment and steep learning curve that, if a good idea at all, would be for a serial inventor.
Since you denominated your possible cost in Euros I assume you are not in the US. Nonetheless you can file a provisional application in the US for very little cost and low formality requirements (in contrast to a PCT application). You might then rely, for a year, on the Paris Convention to give you the ability to disclose the invention to potential investors and business partners without breaking novelty.
Such a simple invention may already be known and a good starting place is a professional search that might cost a few hundred dollars. It could turn out that the substance is not new but your intended use is new. That would dictate a different approach to drafting a specification and claim set.
If either of the two ingredients is part of a family of substances with similar properties (almost always the case) your claims need to be broad enough to encompass those or competitors have an easy work-around.
To be novel means, at least, never written about at the day you file in a publicly available document in any language at any time.
