The only official agreement vis-a-vis Chinese partition that I know of was a Russo-Japanese agreement formalized in 1910. The earlier mentions of Chinese territorial integrity that both states had maintained in their discourse since the Treaty of Portsmouth were explicitly dropped, as was any mention of the Open Door (which both Russia and Japan had agreed to in principle in a convention of July 1907). Instead, both states provided for "common action to safeguard and defend their respective spheres of influence". In Japan's case, this meant Korea; in Russia's, it meant Outer Mongolia. The Japanese annexed Korea a month and a half after this treaty was signed (the connection ought to be obvious), while Russia established a de facto protectorate in Outer Mongolia in November 1912.
That's all I can get from Rich, Great Power Diplomacy 1814-1914, at any rate.
I don't think there were any general European agreements, but if there were to be any, I imagine that they would entail formal annexation of some of the spheres of influence; Germany to gain the remainder of Shandong, Japan to get Fujian (and possibly Liaodong), the French to get Yunnan and Guangxi, the British to gain Guangdong (and possibly Tibet), and the Russians to gain the Mongolias and Xinjiang.