铁皮石斛多糖含量测定不确定度分析

Uncertainty Evaluation in Determination of Polysaccharides in Dendrobium officinale

采用硫酸苯酚比色法测定铁皮石斛中多糖的含量,建立相应的数学模型,并分析该方法测定结果不确定度的主要来源,对测定结果的合成标准不确定度和扩展不确定度进行了量化。干燥的粉末状样品经乙醇回流脱去游离糖后,用纯水提取其中的多糖,利用分光光度计测定多糖含量,外标法定量。结果显示:待测样品多糖含量为29.9%,扩展不确定度为0.31%,测定结果可以表示为(29.9±0.31)%,k=2。分析结果表明:该方法测定结果不确定度的主要来源是标准溶液的配制过程,所以,在测定过程中应特别注意标准物质的称量和稀释过程;该方法相对不确定度为5.14×10-3,因而可以认为该方法适用于铁皮石斛中多糖含量的检测。

Concentration of polysaccharides in Dendrobium officinale was determinated by phenol-sulfuric acid colorimetry, and a mathematical model was established. The main sources of determination uncertainty were analyzed. The combined standard uncertainty and the expanded uncertainty were calculated. The dried sample powder was prepared by ethanol reflux extraction to re- move the free sugar, and the polysaccharides were extracted by water, and then the quantization was carried out by the external standard method. The result showed that the polysaccharides content was 29.90% and its expanded uncertainty was 0.31%. The mathematical expression of the result was （ 29.90 ±0. 31 ） , k = 2. The evaluation indicated that the uncertainty caused by the preparation process of standard solution had a significant contribution to synthetic uncertainty. Therefore, special attention should be paid to the preparation and dilution process of standard solution. The calculation of relative uncertainty of model was 5.14× 10 ^-3 and the result showed that this method was suitable for the determination of polysaceharides in Dendrobium officinale.