We were tasked with testing a multicomponent aqueous solution for injection used in veterinary medicine. The composition of the solution included the following components: folic acid, tryptophan, nicotinic acid, thiamine hydrochloride, ascorbic acid, sodium acetate, and benzyl alcohol. The composition indicates that the drug is intended to stimulate the vital activity of the body. It was required to determine the activity and stability of four components: folic acid, tryptophan, nicotinic acid, and thiamine hydrochloride. The complexity of the simultaneous determination of these components was that they differ greatly in their acid-base properties and solubility in water. We managed to solve the problem using an Agilent HPLC/DAD/MS instrument and selected the parameters to determine all four components together reliably and accurately or each separately by one method.