高频感应炉燃烧–红外吸收法测定银杏及银杏叶中的硫含量

采用高频感应炉燃烧–红外吸收法测定银杏叶、银杏果肉、银杏壳和银杏仁中的硫含量。样品以艾士卡试剂为熔融剂,在800℃马弗炉内熔融1 h,冷却后测定硫含量。硫的质量分数在0.40%~4.00%范围内与吸收峰面积呈良好的线性关系,线性相关系数为0.990 4,检出限为0.000 9%。测定结果的相对标准偏差为4.04%(n=11),平均加标回收率为101.03%。将红外吸收法与电感耦合等离子体原子发射光谱法及硫酸钡重量法进行比对试验,3种方法测定结果相一致。利用该方法测定了不同区域银杏叶中硫的含量,结果表明,风景区和居民区银杏叶干燥基全硫的含量较低,重工业区硫含量较高。对同一地区的银杏果肉、银杏壳、银杏仁中干燥基全硫的含量进行比较,结果表明银杏果肉硫含量最高,银杏壳次之,银杏仁最低。该方法灵敏度高,重现性好,可用于银杏及银杏叶中硫含量的准确测定。

Determination of Sulfur Content in Ginkgo Biloba and Ginkgo Leaves by Infrared Absorption Method after Combustion in an Induction Furnace

The method for determining sulfur content in ginkgo biloba and ginkgo leaves by infrared absorption method after combustion in an induction furnace was established. Eschka reagent was used as molten solvent, doped at 800℃ in muffle furnace for 1 h, then sulfur content was determined after sample being cooled. The mass concentration of sulfur was linear with its absorption peak area in the range of 0.40%-4.00%. The correlation coefficient was 0.9904. The relative standard deviation was 4.04%(n=11), the detection limit was 0.0009%, and the average recovery was 101.03%. Experimental results showed that the measurement accuracy and precision could meet the analysis requirement. No significant differences were observed between the detection results by infrared absorption method and those detected by inductively coupled plasma atomic emission spectrometry and barium sulfate gravimetric method. Sulfur content in ginkgo leaves from different regions was determined. The results showed that dry basis total sulfur content in ginkgo leaves from scenic zone and residential areas was lower, and which from heavy industrial area was higher. Dry basis total sulfur content from the same area in ginkgo fruit higher than shell, nuts was the lowest. The method has high sensitivity and repeatability which is suitable for the accurate analysis of sulfur in ginkgo biloba and ginkgo leaves.