Determination of Sulphur Dioxide in White Sugar 白糖二氧化硫测定
1.0 Principle of Method 方法原理
An alkaline solution of the sample is treated with acid bleached rosaniline and formaldehyde. 一分样品的碱性溶液用酸漂白的玫瑰苯胺和甲醛处理。
The colour of the sulphur dioxide/rosaniline complex is determined photometrically at a wavelength of 570 nm. 二氧化硫/玫瑰苯胺络合物的颜色以波长570 nm进行光学测定。
2.0 Apparatus 仪器
Variable wavelength spectrophotometer, 1cm cells. Volumetric flask, 100 cm3. AutoPipettes, two x 0.2 cm3, and a 0.4 cm3. Graduated Test tubes, 150 x 19 mm. 不同波长的紫外分光光度计，1 cm 比色皿 容量瓶，100 cm3. 自动移液器，2 个 0.2 cm3, 1个0.4 cm3. 刻度试管，150 x 19 mm
Rosaniline hydrochloride solution (saturated). 盐酸玫瑰苯胺溶液（已达饱和的） Supplied by OSS WARNING: this is a suspected carcinogen 由OSS提供 警告：这是一种疑似致癌物。 Reagent 1. Sodium hydroxide solution (0.1M) 试剂 1 氢氧化钠溶液(0.1M) Dissolve 4.0g of sodium hydroxide (BDH AnalaR) in D.W. and make up to 1000cm3 把4.0g的氢氧化钠（英国BDH公司AnalaR标准）溶解在脱盐水中，直到1000cm3 Reagent 2. Bleached rosaniline.
WARNING: This is a suspected Carcinogen 试剂 2 漂白玫瑰苯胺 警告：这是一种疑似致癌物。 Pipette 20 cm3 of saturated rosanilinehydrochloride into a 500 cm3 volumetric flask. Add 30 cm3 of conc.hydrochloric acid and make up to the mark with D.W. Mix and allow thesolution to stand for at least 1 hour before use. (Store in a brownglass reagent bottle. 将20 cm3的饱和盐酸玫瑰苯胺移液到500 cm3的量杯中。加入30 cm3的浓盐酸用脱盐水加到记号处。混合并在使用之前让溶液静置至少1小时。（保存在棕色玻璃试剂瓶里） Reagent 3. Formaldehyde solution,. 0.2% 试剂 3 甲醛溶液，0.2% Pipette 5 cm3 of 40% formaldehyde into a 1000 cm3 volumetric flask. Make up to the mark with D.W. and mix. 将5 cm3的40%甲醛移液到一个1000 cm3容量瓶里。用脱盐水加到记号处，并混合。
1. Dissolve 1g of sugar in D.W. to approximately 8 cm3 in a graduated test tube. 在一个 刻度试管中，将1g糖溶解于大约8 cm3脱盐水中。 0-5 mg SO2/kg use 4g sugar. 5-15 mg SO2/kg use 2g sugar. 15-30 mg SO2/kg use 1g sugar. 0-5 mg SO2/kg 用4g糖 5-15 mg SO2/kg用2g糖 15-30 mg SO2/kg用1g糖。 2. Add 0.4 cm3 of 0.1M sodium hydroxide into the flask and makeup to the 10 ml mark on the test tube with D.W. Mix well. 在刻度试管中加入0.4 cm3的0.1M氢氧化钠，并用脱盐水定容到10ml处。充分混合。 Reagent 1. Use Autopipette 试剂 1 使用自动移液器。 3. Add 0.2 cm3 of the 0.2% bleached rosaniline solution and mix. 加入0.2 cm3 的 0.2%漂白玫瑰苯胺溶液，混合。 Reagent 2. Use Autopipette 试剂 2 使用自动移液器 4. Add, 0.2 cm3 of the 0.2% formaldehyde solution and mix. 加入0.2 cm3的0.2%甲醛溶液，混合。 Reagent 3. Use Autopipette 试剂 3 使用自动移液器 5. Stand at room temperature for 30 ± 5 min. 在室温下静置30 ± 5分钟。 6. Measure the absorbance of the test solution in a 1 cm cell, at 570 nm wavelength against a D.W. blank. 7. 用1 cm的比色皿，测量测试溶液的吸收率，570 nm 波长对照空白脱盐水 Note the absorbance, A. 记录消光值，A.
5.0 Calculation of Results 结果计算
Using the formula supplied with the standard absorption curve,determine the amount of sulphur dioxide in the test solution from theabsorbance measured. 用标准消光曲线提供的公式，从测量的吸收率来测定测试溶液中二氧化硫的量。
The amount of sulphur dioxide in the sugar sample is then amount ofsulphur dioxide calculated from the formula or curve divided by theweight of sample used. 在样品糖中二氧化硫的量是由所用样品重量分成的公式或曲线计算出的二氧化硫的量。
5.1 Worked Example 举例
If the calculated amount of SO2 from the formula is 7.32 and the sample weight = 4g then mg/kg of SO2 in sugar sample = 7.32 = 1.834 如果从公式中计算的SO2 的量是7.32，并且样品重量 = 4g 那么mg/kg 的样品糖中 SO2 = 7.32 = 1.834
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