Extraction-chromatographic separation of boron on a column with stationary solution of 2,3-naphthalenediol and diphenylguanidine
A new method has been developed for the separation of boron from interfering anions (F~ and NO J) for its photometric determination with quinalizarine. Boron (in the form of boric acid) is held on a column packed with teflon impregnated with a solution of 2,3-naphthale nediol and diphenylguanidin e in isoamyl alcohol. With the aqueous phase fluorides and nitrates and, in addition, phosphates and chlorides are washed out, and boron is eluted with 01 M sulfuric acid. The separation was successful even with a 50-fold excess of nitrates and a 20-fold excess of fluorides. The error for the separation of 20— 50 |ig of boron was 2 to 7%. For a photometric separation of boric acid, boron must be usually separated from interfering anions. During experimental tests of the various methods of determination of small amounts of boric acid, particularly in plant materials (photometric determination with curcumine, quercetin carminic acid, and quinalizarine, fluorimetric determination with benzoin), the quinalizarine method proved to be the most suitable. With this method of determination , however, the presence of fluoride and nitrate ions interferes 1. For an analytical separation of small amounts of inorganic components, their extraction proved to be of advantage. If, however, such a system, where the recovery is quantitative, is not known, and if none of the properties of the extract can be employed for the determination of the component separated, it is more convenient for quantitative analysis to apply extraction chromatography (reversed phase partition chromatography) than a multiple extraction and successive reextraction of the component determined from the combined extracts into the aqueous phase. In our previous works we selected solution of 2,3-naphthale nediol (ND) and diphenylguanidin e (DPG) in n-butanol as the best system for the isolation of boric acid 2, and examined the effect of the various factors on the recovery 3. We found that with the organic phase obtained by dissolving 5 . 10~ 2 mol. 1 ~1 of ND and 5 . 10 -2 mol.l -1 of DPG in n-butanol, 97% of boron can be extracted (for V0[a = Vaq).