Determination of Water Soluble Fluoride, Chloride, Bromide and Nitrate in Iron Ores by Supersonic Extraction-Ion Chromatography

An ion chromatography method with ultrasonic extraction has been developed to simultaneously determine the water solubility of fluoride, chloride, bromide and nitrate in iron ores. The sample solution was extracted ultrasonically and precipitation separation was carried out by centrifugation. The clarified solution was passed through IC-RP, IC-Na and a 0.22 μm filter membrane. The anions were separated and data were collected by using AS-19 type anion separation column and ASRS 300-4 mm self-electric chemistry suppressor with the 25.00 mmol/L NaOH as eluent. The organic matter in the sample solution was absorbed by IC-RP column and the heavy metal ions were replaced by IC-Na column, which is the same cation as that in eluent. Based on the study of the extraction efficiency for water solubility anions, the extraction time was 30 min. In order to eliminate the effect of a negative peak from water, a certain amount of eluent was added into the standard and sample solutions to make the conductivity in each solution match each other. Under optimal conditions, the detection limits of F^-, Cl^-, Br^- and NO₃^- were 2.1, 3.5, 2.5 and 2.0 μg/g, respectively. The linear correlation was good for the work curve, and the linearly dependent coefficient was greater than 0.999. The accuracy and precision of this method was verified by iron ore standard material GBW 07218a and the results were consistent with certified values. The RSD (n=10) was less than 5% and recovery rates with interior standard were 96%-104%. The results for the actual samples were consistent with those obtained by ion selective electrode method. The method has the benefits of applying to a wide linear range, is simple and has rapid and high efficiency, making it suitable for routine lab inspection work.