双波长比色法测定不同产地和品种青稞中直链淀粉和支链淀粉的含量

Determination of amylase and amylopectin in hullessbarley from different habitats and varieties by dual-wavelength colorimetric method

利用一种更简便、准确的双波长比色法来测定不同产地和品种青稞中直链淀粉和支链淀粉的含量,以此代替以往复杂繁琐的样品前处理过程。根据双波长比色原理——若溶液中某溶质在两个波长下均有吸收,则两个波长的吸收差值与该溶质浓度成正比,以及根据直链淀粉和支链淀粉与碘试剂作用分别产生纯蓝色和紫红色的性质,用紫外分光光度计对两种淀粉与碘试剂的反应液进行全波长扫描（450~900nm）,用作图法在同一个坐标系里确定其各自的测定波长和参比波长。结果测得直链淀粉的测定波长和参比波长分别为560nm和506nm,支链淀粉的测定波长和参比波长分别为545nm和722nm。青稞中直链淀粉和支链淀粉分别在0.20~0.59mg和0.50~3.00mg范围内具有良好的线性关系（R2=0.9993和R2=0.9995）,平均加样回收率分别为91.14%和91.73%,RSD分别为1.70%和2.25%（n=9）。该方法简便、准确、稳定性和重现性好,适用于测定青稞中直链淀粉和支链淀粉的含量,可为青稞的质量控制提供依据。

A more simple,accurate dual-wavelength colorimetric method was developed to determine the contents of amylose and amylopectin in hullessbarley from different habitats and varieties. It was replaced the previous complicated sample pre-treatment process. The reaction solution that reacted by two ingredient of starch and iodine reagents were scanned from 450 nm to 900 nm by UV spectrophotometer to determine its detection wavelength and reference wavelength in the same coordinate system which according to the principle of the dual-wavelength colorimetry——the difference was proportional to the concentration of solute while there were two absorption peaks at two different wavelengths from the same solute in the solution,as well as characteristic of blue appearance that amylase encountered with iodine reagents and purple red as amylopectin. The results indicated that the detection wavelength and reference wavelength were 560 nm and 506 nm for amylase,545 nm and 722 nm for amylopectin,respectively. The method had good linear relationship within the ranges of 0.20 ~0. 59 mg for amylose（ R2= 0. 9993）, 0. 50 ~ 3. 00 mg for amylopectin（ R2= 0. 9995）, respectively. The average recoveries（n=9） were 91.14%（RSD=1.70%） for amylose and 91.73%（RSD=2.25%） for amylopectin. The assay demonstrated that the method had adequate simple,accurate,good stability and reproducibility. It was suitable for the determination of amylose and amylopectin contents in hullessbarley. In addition,it could be used to assist the quality evaluation of hullessbarley.