摘要
用AAⅡ型自动分析仪测定烟叶中的总挥发碱存在 3种缺陷 :①测定结果不准确 ;②基线不稳定 ;③分析管路腐蚀严重。为了使AAⅡ型自动分析仪能够快速准确地测定烟叶中的总挥发碱 ,参考烟草行业标准YC/T 35 1996《烟草及烟草制品总挥发碱的测定》的测试原理 ,对AAⅡ型自动分析仪挥发碱检测模块进行了 4种改进 :①增设了蒸馏装置 ,使挥发碱的测定结果符合行业标准规定的要求 ;②用pH =8磷酸钾缓冲溶液替代NaOH溶液作蒸馏介质 ,克服了NaOH溶液腐蚀AAⅡ型自动分析仪分析管路的缺陷 ;③用水循环法代替气体冷却法 ,确保了基线稳定 ,使得标准溶液的工作曲线线性良好 ;④在碘酸钾 -碘化钾反应平衡体系中加入一定量的稀磷酸 (0 .0 75mL 85 %磷酸 + 10 0 0mL水 )和在磷酸钾缓冲液中加入一定量的甘油 (2 5 0mL甘油 + 10 0 0mL水 )使基线更加稳定。确定了改进后的AAⅡ型自动分析仪检测挥发碱的最佳参数。这些参数为 :进样速率 :30个样品 /h ;进样与清洗时间比 :1∶1;比色计增益参数 :35 ;蒸馏介质 :磷酸钾缓冲液 (pH =8) ;蒸馏温度 :140℃ ;反应体系 :碘化钾 (KI) -碘酸钾(KIO3 ) ;滤光片波长 :4 2 0nm。测定了标准溶液的工作曲线 ,在 0～ 65mg/L (以氨计算 )检测范围内为线性方程 ,其相关系数为r=0 .9996。
There were three disadvantages in determining the total volatile bases in tobacco leaves with AAⅡ automatic analyzer-inaccuracy of result, unsteadiness of baseline and heavy erosion of analytic tube. Modifications were made based on the principle of the industrial standard YC/T 35-1996, including: 1)adding a volatile base distiller; 2)using a buffer solution of potassium phosphate replacing the aqueous solution of hydroxide sodium as distilling medium to prevent the analytic tube from erosion; 3)using circulated water cooling in place of the air cooling to stabilize the baseline; 4)adding a fixed amount of dilute phosphorous acid ( 0.075 mL 85% phosphorous acid + 1 000 mL water) and glycerin ( 250 mL glycerin + 1 000 mL water ) to the reaction system of potassium iodide-potassium iodate and the buffer solution of potassium phosphate ?respectively, ?to further the baseline steady. ?The optimum operating parameters for determining the total volatile bases in tobacco leaves were as follows: injection frequency∶30 samples per hour; ratio of injection time to purging time:1∶1; gain factor of colorimeter:35; distilling medium: pH=8 buffer solution of potassium phosphate; distilling temperature: 140℃; reaction system: potassium iodide-potassium iodate; and wavelength of light filter: 420nm. The calibration curve of the standard solution was a linear equation in the range of 0 to 65mg/L (as NH 3) and its correlation coefficient was 0.9996. The coefficient of variation was below 2.0% and the recoveries of the volatile bases were in the range of 98.0% to 99.6%. The relative mean deviation of test results between the improved analyzer and the standard method was within \{0.08\}% to 5%, and was in conformity with the requirement of YC/T 35-1996. These improvements were adopted by German BRAN+LUEBBE Company and some domestic tobacco enterprises. The AAⅢ automatic analyzer developed on the basis of the improvements was broadly applied in Chinese tobacco industry.
出处
《烟草科技》
EI
CAS
2003年第1期4-8,共5页
Tobacco Science & Technology
关键词
AAⅡ型自动分析仪
检测
总挥发碱
改进
烟叶
AAⅡ automatic analyzer
Total volatile bases
Determination
Tobacco leaves
Improvement
