Dosage direct de submicrotraces de bore dans la soude de purete analytique par la methode fluorimetrique a l'hydroxy-2-methoxy-4-chloro-4'-benzophenone

A method based on the highly sensitive fluorescent reaction of boric acid with 2-hydroxy-4-methoxy-4'-chlorobenzophenone (H.M.C.B.), is described for the direct determination of traces of boron in “analytical grade” sodium hydroxide. In the nanogram range, the reliability of the H.M.C.B. method is satisfactory; the fluorescent reaction is not affected by up to 8% (v/v) of water. The sample is dissolved directly in concentrated sulfuric acid and no preliminary separation is needed. Interferences from other impurities of sodium hydroxide are negligible. Results for five different “analytical grade” reagents were: (0.9±0.2)·10^-6,(3.2±0.3)·l0^-6,(3.2±0.3)·^-6, (4.0±0.4)·10^-6and(2.0±0.16)·10^-6% B.