We dissolved 200 mg of Anthrone in 98% pure concentrated sulphuric acid. For preparation of standard curve, glucose solutions of 0.2, 0.4, 0.6, 0.8 and 1.0% were prepared. 5 ml of anthrone reagent was added to 2 ml of each solution and the same was kept in water bath at 100 degree C for 10 minutes. But, we did not get the clear solution, we found white colour precipitation in the test tubes. We centrifuged the contents, but the precipitation was not settled at the bottom of the centrifuge tube. In fact, it was floating over the solution.
Please suggest how to overcome this problem, how to get a clear solution without precipitation?