Improvement on Determining Total Volatile Bases in Tobacco Leaves by AA Ⅱ Automatic Analyzer

There were three disadvantages in determining the total volatile bases in tobacco leaves with AA Ⅱ 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 iodidepotassium iodate and the buffer solution of potassium phosphate respectively, to further the baseline steady.The quency: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 NH₃) and its correlation coefficient was 0.999 6.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 AA Ⅲ automatic analyzer developed on the basis of the improvements was broadly applied in Chinese tobacco industry.