Determination of Fluoride and Chloride in Gypsum and Its Products by Ion Chromatograpy with Continuous Self-regenerated Chemical Suppressor

Traditional determination of fluoride and chloride in gypsum and its products has the disadvantages of complicated pretreatment, long detection time, poor accuracy and low sensitivity. To remedy this, an ion chromatography method which can simultaneously determine the fluoride and chloride in gypsum and its products has been successfully developed. The sample was extracted firstly by ultrasonic processing and eluted by Na₂CO₃-NaHCO₃. The solution was then separated by anion column and suppressed by self-electric chemistry suppressor. Finally, the solution was detected using a conductivity detector. By optimizing the pretreatment and separate conditions, the concentrations of the fluoride and chloride have good linear relationships with the peak area in the measured range with correlation coefficients of 0.9999 and 0.9998 for F^- and Cl^-, respectively. The proposed method yielded the detection limits of 0.15 ng/mL and 0.28 ng/mL for F^- and Cl^-, respectively, the recovery of 95.0%-99.7% and the RSD of less than 5% (n=8). The proposed method utilizes ultrasonic extraction and avoids purification. The pretreatment can be completed in less than 0.5 h and the loss of target analyte can be avoided. Compared with the ion selective electrode method, the detection limit of this method improves from μg/mL to ng/mL.