折光率测定尿素含量的方法研究

Study on refractive index method for determination of urea concentration

【目的】建立简便、快速、准确、可靠的尿素含量测定方法。【方法】参照折光率仪的工作原理,建立测定溶液中尿素含量的折光率法,并将其与2种标准方法(对二甲氨基苯甲醛(PDAB)比色法和H2SO4消化比色法)的测定结果进行比较,通过对比分析、相关分析和校验研究,评价25℃恒温条件下折光率法测定溶液中尿素含量的准确性和可靠性。【结果】折光率与溶液中尿素含量呈极显著线性正相关,相关系数达0.9999以上。折光率法与PD-AB比色法、H2SO4消化比色法测定结果均呈极显著线性正相关(r值均在0.9999以上,标准误分别为0.2193和0.2487),测定结果无统计学差异(t值分别为1.7486和1.3231)。折光率法测定尿素的平均回收率为96.68%～101.18%,最小检测限为0.5g/kg,最大检测限为600g/kg,测定的尿素浓度范围远大于PDAB比色法和H2SO4消化比色法。【结论】用折光率法可直接测定溶液中尿素的含量,且该方法具有分析速度快、测定效率高、检测尿素浓度范围广、不需任何化学试剂和无污染等优点,可以替代PDAB比色法和H2SO4消化比色法,适用于尿素或包膜尿素企业及教学科研部门批量分析测定溶液中的尿素含量。

[Objective] The purpose of the study is to establish a simple,rapid,accurate and reliable method to determine urea concentration.[Method] Referred to operating principle of refractive index,the contrast and correlation analysis as well as verification method were applied to evaluate the accuracy and reliability of refractive index method（RIM） to determine urea concentration in solution under the condition of 25 ℃ by taking paradimethylaminobenzal dehydedmaba（PDAB） colorimetric and H2SO4 digestive colorimetric method as standard.[Result] There was a significantly and positive correlation between refractive index value（RIV） and urea concentration in the solution,and the linear correlation coefficient was more than 0.999 9.Urea content tested by use of the RIM,i.e.the urea concentration measured by RIV regression equations（standard curve） of urea standard solution,was significantly linearly positive correlated to the urea concentration measured by PDAB colorimetric method and H2SO4 digestive colorimetric one respectively（r value being more than 0.999 9,SE less than 0.219 3 and 0.248 7 separately）.There was no statistic difference between measurement results by RIM and the two standard methods respectively（t value less than 1.748 6 and 1.323 1）.The average recovery rate of urea was between 96.68% and 101.18%,and the test range was from 0.5 g/kg to 600 g/kg by use of refractive index method,much greater than PDAB colorimetric and H2SO4 digestive colorimetric method.[Conclusion] The refractive index is able to be used to measure the concentration of urea in solution directly and the method possesses advantages,such as fast analysis,high efficiency,without any chemical reagent consumption and pollution-free.Therefore,RIM is suitable for urea enterprises,coated urea enterprises,slow or controlled release urea enterprises,institute and universities to measure the urea concentration in batch.