ION-CHROMATOGRAPHIC DETERMINATION OF SULFUR SODIUM POTASSIUM MAGNESIUM AND CALCIUM IN AROMATIC POLYAMIDE FIBER

Ion chromatography (IC) was applied to the determination of some inorganic elements in aromatic polyamide fiber (Twaron).For the determination of anions,the sample in a platinum crucible was covered with Eschka mixture containing 3 parts of anhydrous Na2CO3 and 2 parts of zinc oxide,and heated in a muffle furnace at 450 ℃ for 1 h,some more of the Eschka mixture was added and heated at 850 ℃ for 1.5 h,to decompose the organic substance completely.The cooled melt in the crucible was dissolved in deionized water,and diluted to 100 mL in a volumetric flask with a mixed solution containing 18 mmol·L-1 Na2CO3 and 17 mmol·L-1 NaHCO3.This sample solution was used for IC determination of anions.For the IC-determination of cations (e.g.alkali metal and alkaline earth metal ions),the sample in the crucible was burned directly in a muffle furnace,without adding the Eschka mixture,until complete oxidation of the organic substances was attained.The residue in the crucible was treated ultrasonically with 1 mol·L-1 HNO3 or 1 mol·L-1 HCl,and transferred to a 100 mL volumetric flask,wash the crucible and diluted to 100 mL with deionized water.Working conditions of the IC determination were described,and the results of the 5 elements were found by the standard curve method.Detection limits for SO2-4,Na+,K+,Mg2+ and Ca2+ were found as 0.02,0.25,0.25,0.70 and 0.80 mg·L-1 respectively.