Abstract
In order to determine fluorine, chlorine and bromine in organic compounds precisely (within ± 0.3% of the theoretical values), several analytical conditions were discussed. Blank values were measured from the combustion system with or without a purification tube. In a combination of the eluent and diluting solution which were made of different lots of the same manufacturer, chloride ion blank value was 6133μVs. When the manufactures were different, the blank value was 5827μVs. Moreover, in the reagents of the same manufacturer and the same lot, but prepare at different times the value was 3404μVs. These values corresponded to 0.71.34% of the total peak areas. Thus the eluent and the diluting solution should be prepared simultaneously from the same lot of reagents Because the pH of the sample solution affected the sensitivity of detection, the combustion, absorption, and dilution of standard samples and unknown samples were performed under the same condition. The pH of eluent influenced the precision of detection. In the range of pH 10.269.87, the precision decreased with the decrease in pH. The most satisfactory precisions for the three ions were obtained at pH 10.72, but the resolution of bromide and phosphate ions tended to decrease at this pH. In this method, 4 mM Na2CO3-4 mM NaHCO3 solution(pH 10.26) was used as an eluent. Calculation was based on the sensitivity factor method. The sensitivity factors obtained by standard samples were in satisfactory precision. The relative standarddeviations of fluorine, chlorine and bromine determinations were 0.0183, 0.0070 and 0.0050, respectively.
