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食品加工中亚硫酸盐添加及检测作者：郑倩来源：《现代食品·上》2017年第05期摘要：随着社会的不断发展进步，社会各界对食品的安全问题越来越重视。
在食品加工中，亚硫酸盐具有贮藏保鲜、抗氧化、漂白等积极作用，因此有添加的可行性，并在较长的时间内都发挥着重要的作用，但亚硫酸盐在食品加工的毒性作用同样不可忽视，再加上一些商家急功近利造成人为添加剂量过大，极易对人体神经、器官、呼吸系统产生危害。
因此检测食品加工领域内的亚硫酸盐显得尤为重要，本文从科学的角度分析了亚硫酸盐的作用和危害，并阐述了当前常规的亚硫酸盐检测方法，展望了新型的检测方法。
关键词：亚硝酸盐；食品加工；检测方法Abstract：With the continuous development and progress of society， all circles of society pay more and more attention to the safety of food. The role of self-evident sulphite in food processing，such as storage， anti-oxidation， bleaching and other positive effects， so it is feasible to add and haa played an important role in a long time， but the toxicity of sulfite in food processing is also not to be ignored， plus some businesses quick cause artificially added dose too large， extremely easy to cause harm to human organs， nerves， respiratory system. Therefore the detection of sulfite in food processing in the field is particularly important in the scientific analysis of effects and harm of sulfite in this paper， and expounds the conventional detection method of sulfite， the prospect of new testing method.Key words：Nitrite； Food processing； Detection method中图分类号：TS207.3；TS202.31 食品加工中亚硝酸盐的毒害作用对呼吸系统：二氧化硫会对人们的呼吸系统黏膜产生刺激作用，触发呼吸道类的疾病，造成肺部器官的功能性障碍和损害，如引发支气管炎、哮喘、肺气肿；对神经系统：由于亚硫酸盐的化合物二氧化硫会产生一定神经性损害，尤其是对脑细胞造成损伤，极易影响神经中枢，并随着二氧化硫的浓度而愈严重，导致神经元平均放电频率降低、记忆力减弱、学习能力下降等；对循环系统：会使心肌细胞超微结构产生一定程度的恶化，如心肌线粒体肿胀、闰盘扩张、毛细血管扩张、心脏收缩力下降、血管环舒张等；对生殖系统：最新研究发现，亚硫酸盐如今已扩大至对生殖系统的影响，如导致睾丸细胞和脂质损伤，降低精子产生的速率和质量，阻碍胚胎的生长发育。
食品中亚硫酸盐添加剂的测定方法分析目的分析食品中亚硫酸盐添加剂的测定方法。
方法每种样品均采用三种方法处理后进行检测，研究组用四氯汞钠做吸收剂，对照A组用甲醛做吸收剂，对照B组用淀粉指示液。
结果研究组的结果明显优于对照A组及对照B组；同时研究组样品在加入四氯汞钠后，应用微波提取1.5h和用溶液直接浸泡4h所测得的结果相似；测定样品的相对标准偏差介于 2.6%~3.1%之间，且回收率介于91.00%~99.00%之间；研究组线性方程式为y=0.0325x+0.0015，相关系數为R2=0.9996。
结论采用四氯汞钠吸收-超声快速提取法测定食品中亚硫酸盐添加剂含量，其过程操作方便快捷，且重现性较好，可直接用于食品检测亚硫酸盐的实际操作中。
标签：食品；亚硫酸盐；四氯汞钠；盐酸副玫瑰苯胺法目前食品生产过程中存在着大量使用眼硫酸钠作为防腐剂、漂白剂和抗氧化剂的情况，而亚硫酸钠的毒性会直接破坏食品中的营养素[1]。
1资料与方法1.1试验试剂与仪器研究组：将称取13.5g氯化汞与6.0g氯化钠混合，加水溶解并稀释制成1000mL的混合溶液，将配置好的溶液过夜沉淀以备用；对照A 组：吸取0.55mL甲醛且无聚合沉淀，其甲醛溶液比例需为36%，加水溶解以稀释的同时混匀至100mL以备用；对照B组：将称取的1g可溶解性淀粉兑水调和成糊状，之后将100mL沸水缓慢倾入并加以搅拌，溶液煮沸后放冷备用，可用时再配用。
三组均采用相同的试验仪器，即苏州江东精密仪器有限公司生产的KQ-250DB型数控超声波清洗器，日本岛津公司制造的UV-2450紫外分光光度计。
其中甲醛和盐酸副玫瑰苯胺均为上海中剂化工生产的分析纯试剂。
1.2样品的测定固定样品检验需经粉碎机粉碎且经过筛处理，液体或水溶性样品则直接进行溶解处理。
分别称取5.0~10.0g样品放入容量瓶中备用。
研究组抽取两份样品，分别加入10mL四氯汞钠溶液和2mL氢氧化钠溶液，待溶液稀释5min后再加入2mL硫酸溶液，分别进行浸泡4h和超声处理1.5h后水稀释至100mL；对照A组及对照B组的测定方法与研究组相同。
食品中亚硫酸盐的测定GB/T5009.34-2003第一法盐酸副玫瑰苯胺法1、范围本标准规定了食品中亚硫酸盐的测定的方法本标准适用于食品中亚硫酸盐残留量的测定。
本标准检出浓度为1mg／kg 2、原理亚硫酸盐与四氯汞钠反应生成稳定的络合物，再与甲醛及盐酸副玫瑰苯胺作用生成紫红色，与标准系列比较定量。
3、试剂3.1四氯汞钠吸收液：称取13.6g氯化高汞及6.0g氯化钠，溶于水中并稀释至1000mL放置过夜，过滤后备用。
3.2 1.2 % 氨基磺酸铵溶液(12g/L)3.3甲醛溶液（2g/L）：吸取0.55 mL无聚合沉淀的甲醛（36%），加水稀释至100 mL，混匀。
3.4淀粉指示液：称取1g可溶性淀粉，用少许水调成糊状，缓缓倾入100 mL沸水中，搅拌煮沸，放冷备用，此溶液临用时配制。
3.5亚铁氰化钾溶液：称取10.6g亚铁氰化钾，加水溶解并稀释至100 mL 3.6乙酸锌溶液：称取22g乙酸锌溶于少量水中，加入3mL冰乙酸，加水稀释至100 mL。
3.7盐酸副玫瑰苯胺溶液：称取0.1g盐酸副玫瑰苯胺（C19H18N2CL.4H2O:p-rosanilinehydrochlo-ride）于研钵中，加少量水研磨使溶解并稀释至100 mL。
取出20mL，置于100 mL容量瓶中，加盐酸（1+1）充分摇匀后使溶液由红变黄，如不变黄再滴加少量盐酸至出现黄色，再加水稀释至刻度，混匀备用。
3.8碘溶液[c(1/2I2)=0.100 mol/L]。
3.9硫代硫酸钠标准溶液[c(Na2S2O3·5H2O)=0.100 mol/L]。
3.10二氧化硫标准溶液：称取0.5g亚硫酸氢钠，溶于200 mL四氯汞钠吸收液中，放置过液，上清液用定量滤纸过滤备用。
吸取10.0 mL亚硫酸氢钠-四氯汞钠溶液于250mL碘量瓶中，加100 mL水，准确加入20.00 mL碘溶液（0.1mol/L），5 mL冰乙酸，摇匀，放置于暗处，2min后迅速以0.100mol/L 硫代硫酸钠标准溶液滴定至淡黄色，加0.5 mL淀粉指示剂，继续滴定至无色。
AOAC:食品中亚硫酸盐测定方法一简介1 理论样品和挥发盐酸一起加热可使样品中的亚硫酸盐转化为二氧化硫。
溶液里面通入的氮气流可携带二氧化硫通过冷凝器，在3%过氧化氢溶液中被氧化为硫酸。
硫酸可被标准氢氧化纳滴定，而样品中含有的亚硫酸盐量与硫酸量是相对应的。
硫酸可转化为硫酸钡，通过重量法进行验证。
2 应用此方法适用于亚硫酸盐含量高于10ppm的新鲜和经过处理的食品，对存在挥发性硫化合物的物质也适用。
但本方法不能用于检测干洋葱、韭菜和卷心菜。
二装置a蒸馏装置b滴定管10mlc烧瓶带有螺帽d冷凝水可用甲醇水溶液，比例为甲醇：水=20：40，温度小于15℃e微量移液器100-1000微升三试剂和溶液1 试剂a盐酸12N，试剂级b过氧化氢30%ACS级c乙醚无水d乙醇无水e氮气高纯度，使用调节装置保持气流速度为200ml/minf氯化钡试剂级g氢氧化钠溶液0.01Nh水去离子水，18兆欧姆，用蒸馏水配置，使用前用250-300ml/m的氮气流冲15分钟脱氧，密闭保存。
I甲醛合次硫酸钠（HMS）j一水合磷酸氢二钠k D型甘露醇l甲基红2 溶液a 4N盐酸：加30ml12N盐酸至60ml去离子水中，搅拌均匀。
b甲基红指示剂：溶解250mg甲基红试剂于100ml乙醇中。
c 0.010N氢氧化钠：先配成1mol/l的氢氧化钠溶液,使用前再稀释至0.01ml/l的溶液。
1ml/l 氢氧化钠溶液的配置：称取110g NaOH，溶于100mL水中，摇匀，倒入聚乙烯容器中，密闭放置至溶液清亮。
用塑料管吸取54ml的上层清液，注入1000mL新沸过的冷水（煮沸一段时间后加盖冷却）中摇匀。
称取7.5g、于105—110℃烘至质量恒定的基准邻二甲酸氢钾，称准至0.0001 g，溶于80ml无CO2的水中，加2滴酚酞指示液（10 g/L），用配制好的NaOH 溶液滴定至溶液呈粉红色同时作空白试验。
氢氧化钠标准溶液浓度按下式计算：MC（NaOH）= －－－－－－－－－（V—V0）×0.2042式中：C（NaOH）——氢氧化钠标准溶液之物质的浓度，mol/L；V——消耗氢氧化钠的量，mL；V0——空白试验消耗氢氧化钠的量，mL；M——邻苯二甲酸氢钾的质量，g；0.2042——邻苯二甲酸氢钾的摩尔质量。
食品中亚硫酸盐的离子色谱法测定分析宋莲芳【摘要】作为食品添加剂,亚硫酸盐被广泛的应用于食品中,解离成亚硫酸,亚硫酸有一定的漂白性,具有漂白、脱色、防腐等作用,很多国家都严格控制食品中亚硫酸的残留量.当前,二氧化硫滥用的现象比较严重,给食品安全带来了严重的安全威胁,目前检测食品中的亚硫酸盐主要有蒸馏后碘滴定法、盐酸副玫瑰苯胺法、氢氧化钠滴定法等,但是这些测定方法都存在着一定的不足,本文使用离子色谱法对食品中的亚硫酸盐进行测定.【期刊名称】《生物技术世界》【年(卷),期】2016(000)002【总页数】1页(P57-57)【关键词】食品;亚硫酸盐;离子色谱法测定【作者】宋莲芳【作者单位】中粮生物化学（安徽）股份有限公司,安徽蚌埠233010【正文语种】中文【中图分类】TS201亚硫酸盐有着十分广泛的用途，在农业上，可以作为抑制剂，能够提高小麦、水稻、玉米、棉花等农作物的产量，在食品工业中，可以作为防腐剂。
为了检测食品中亚硫酸盐，本次研究利用离子色谱法测定食品中的亚硫酸盐，经过测定，可以发现离子色谱法的灵敏度比较高、测定结果的可靠性强，可以用在食品中亚硫酸盐的检测中。
1.1 准备设备与试剂本次研究使用的美国戴安公司的ICS2000离子色谱仪，并配合使用KOH淋洗液发生器、温控电导检测器、电子天平、德国莱驰的M200刀式混和研磨仪。
从国家计量科学院标准物质研究中心购买硫酸盐。
超纯水、NaHSO3、H3PO4、H2O2、优级纯。
1.2 色谱条件色谱柱为IonPac AS18阴离子分析柱，规格为25cm×0.4cm。
色谱柱的温度要达到40℃。
流速为每分钟1.00ml。
25μl进样量，30mmol/L 氢氧化钾溶液的流动相［1］。
1.3 测定方法1.3.1 选择样品将选择的固体检测试样进行研磨，如饼干、坚果等，使其与半固体勺浆、液体试样等进行混合均匀，称取其中的5g，将其放入200mL的蒸馏瓶中，然后加入18mL水，10mL15%的H3PO4，与水蒸气连接进行蒸馏工作。
AOAC:食品中亚硫酸盐测定方法一简介1 理论样品和挥发盐酸一起加热可使样品中的亚硫酸盐转化为二氧化硫。
溶液里面通入的氮气流可携带二氧化硫通过冷凝器，在3%过氧化氢溶液中被氧化为硫酸。
硫酸可被标准氢氧化纳滴定，而样品中含有的亚硫酸盐量与硫酸量是相对应的。
硫酸可转化为硫酸钡，通过重量法进行验证。
2 应用此方法适用于亚硫酸盐含量高于10ppm的新鲜和经过处理的食品，对存在挥发性硫化合物的物质也适用。
但本方法不能用于检测干洋葱、韭菜和卷心菜。
二装置a蒸馏装置b滴定管10mlc烧瓶带有螺帽d冷凝水可用甲醇水溶液，比例为甲醇：水=20：40，温度小于15℃e微量移液器100-1000微升三试剂和溶液1 试剂a盐酸12N，试剂级b过氧化氢30%ACS级c乙醚无水d乙醇无水e氮气高纯度，使用调节装置保持气流速度为200ml/minf氯化钡试剂级g氢氧化钠溶液0.01Nh水去离子水，18兆欧姆，用蒸馏水配置，使用前用250-300ml/m的氮气流冲15分钟脱氧，密闭保存。
I甲醛合次硫酸钠（HMS）j一水合磷酸氢二钠k D型甘露醇l甲基红2 溶液a 4N盐酸：加30ml12N盐酸至60ml去离子水中，搅拌均匀。
b甲基红指示剂：溶解250mg甲基红试剂于100ml乙醇中。
c 0.010N氢氧化钠：先配成1mol/l的氢氧化钠溶液,使用前再稀释至0.01ml/l的溶液。
1ml/l 氢氧化钠溶液的配置：称取110g NaOH，溶于100mL水中，摇匀，倒入聚乙烯容器中，密闭放置至溶液清亮。
用塑料管吸取54ml的上层清液，注入1000mL新沸过的冷水（煮沸一段时间后加盖冷却）中摇匀。
称取7.5g、于105—110℃烘至质量恒定的基准邻二甲酸氢钾，称准至0.0001 g，溶于80ml无CO2的水中，加2滴酚酞指示液（10 g/L），用配制好的NaOH 溶液滴定至溶液呈粉红色同时作空白试验。
氢氧化钠标准溶液浓度按下式计算：MC（NaOH）= －－－－－－－－－（V—V0）×0.2042式中：C（NaOH）——氢氧化钠标准溶液之物质的浓度，mol/L；V——消耗氢氧化钠的量，mL；V0——空白试验消耗氢氧化钠的量，mL；M——邻苯二甲酸氢钾的质量，g；0.2042——邻苯二甲酸氢钾的摩尔质量。
47.3.43AOAC Official Method990.28Sulfites in FoodsOptimized Monier–Williams MethodFirst Action1990Final Action1994(Applicable of determination of≥10ppm(µg/g)sulfites in foods. Applicable in presence of other volatile sulfur compounds;not ap-plicable to dried onions,leeks,and cabbage.)Results of the interlaboratory study supporting the acceptance of the method:Hominy,9.17ppm(µg/g)sulfites:s r=1.33;s R=1.42;RSD r=14.5%;RSD R=15.5%Fruit juice,8.05ppm(µg/g)sulfites:s r=1.36;s R=1.62;RSD r=16.9%;RSD R=20.1%Protein(seafood),10.41ppm(µg/g)sulfites:s r=1.47;s R=2.77;RSD r=14.1%;RSD R=26.6%A.PrincipleMethod measures free sulfite plus reproducible portion of bound sulfites,such as carbonyl addition products,in foods.Test portion is heated with refluxing HCl(ca1M)to convert sulfite to SO2.Stream of N2introduced below surface of refluxing solution sweeps SO2 through water-cooled condenser and,via bubbler attached to con-denser,with3%H2O2solution,where SO2is oxidized to H2SO4. Sulfite content is directly related to generated H2SO4,which is deter-mined by titration with standardized NaOH solution.For verifica-tion,sulfate can be determined gravimetrically as BaSO4.B.Apparatus(a)Distillation apparatus.—(Note:In this method,back pres-sure inside apparatus is limited to unavoidable pressure due to height of3%H2O2solution above tip of bubbler(F).Keep back pressure as low as possible to avoid loss of SO2through e thin film of stopcock grease on sealing surfaces of all joints except joint between separatory funnel and flask.Clamp together each joint to ensure complete seal throughout analysis.)Assemble apparatus(Figure 990.28A),which includes(1)inlet adapter(A)with hose connector (Kontes183000).Adapter provides means of applying head pres-sure above e of pressure-equalizing dropping funnel is not recommended because condensate,perhaps containing SO2,is deposited in funnel and side arm.(2)Separatory funnel(B),≥100mL capacity.(3)Round-bottom flask(C),1L,with three24/40 tapered joints.(4)Gas inlet tube(D)(Kontes179000)of sufficient length to permit introduction of N2within2.5cm of bottom of flask.(5)Allihn condenser(E)(Kontes431000-2430),jacket length 300mm.(6)Bubbler(F),fabricated from glass according to dimen-sions in Figure990.28B.(7)Vessel(G),ca2.5cm id and18cm deep.(b)Buret.—10mL(Kimble Glass,Inc.,No.17124-F)with over-flow tube and hose connections for Ascarite tube or equivalent air-scrubbing apparatus to permit maintenance of CO2-free atmo-sphere over standardized0.010M NaOH.(c)Chilled water circulator.—Chill condenser with coolant, such as methanol-water(20+40,v/v),maintained at≤15°C.Circu-lating pump,Neslab Coolflow33(Neslab Instruments,Inc.,PO Box 1178,Portsmouth,NH03801,USA),or equivalent,is suitable.C.Reagents(a)Aqueous hydrochloric acid.—4M.For each analysis,prepare 90mL solution by adding30mL HCl to60mL deionized(18meg-ohm)water.(b)Methyl red indicator.—Dissolve250mg methyl red in 100mL ethanol.(c)Standardized titrant.—0.010M NaOH.Certified reagent may be used(Fisher SO-5-284).Standardize solution with reference standard potassium acid phthalate.(d)Hydrogen peroxide solution.—3%.For each analysis,dilute 3mL ACS reagent grade30%H2O2to30mL with deionized (18megohm)water.Just prior to use,add3drops methyl red indica-tor and titrate with0.010M NaOH to yellow end point.If end point is exceeded,discard solution.(e)Nitrogen.—High purity,used with regulator to maintain flow of200mL/min.To guard against oxygen in N2gas,use GC-type trap (Oxy-Purge N[Alltech-Applied Science Laboratories,Inc.],or equivalent).Alternatively,oxygen-scrubbing solution,such as alkaline pyrogallol,in gas-washing bottle(Kimble Glass,Inc.)may be used. Prepare trap as follows:(1)Add4.5g pyrogallol to trap.(2)Purge trap with N2for2–3min.(3)Prepare KOH solution by adding65gFigure990.28A—Apparatus for optimized Monier-Williams method:A,inlet adapter;B,separatory funnel; C,round-bottom flask;D,gas inlet tube;E,Allihn con-denser;F,bubbler;G,vessel.KOH to85mL H2O.(Caution:Heat is generated.)(4)Add KOH so-lution to trap while atmosphere of N2is maintained in trap.D.Test Sample Preparation(a)Solids.—Transfer50g food,or quantity that contains 500–1500µg SO2,to food processor or blender.Add100mL etha-nol–water(5+95,v/v)and briefly grind mixture.Continue grinding or blending only until food is chopped into pieces small enough to pass through standard taper24/40joint of flask(C).(b)Liquids.—Mix50g test portion,or quantity that contains 500–1500µg SO2with100mL ethanol-water(5+95,v/v). (Note:Carry out test sample preparation and analysis as quickly as possible to avoid loss of labile forms of sulfite.)E.System PreparationUsing apparatus assembled as shown in Figure990.28A,position flask(C)in heating mantle controlled by power-regulating device (rheostat),and add400mL H2O to flask.Close stopcock of separa-tory funnel(B)and add90mL4M HCl to separatory funnel.Begin N2flow at200±10mL/min.Initiate condenser coolant flow at this time.To vessel(G)add30mL3%H2O2,which has been titrated to yellow end point with0.010M NaOH.After15min,apparatus and water will be thoroughly deoxygenated and prepared test portion may be introduced into system.F.Sample Introduction and DistillationRemove separatory funnel(B)and quantitatively transfer test por-tion in aqueous ethanol to flask(C).Wipe tapered joint clean with laboratory tissue,quickly apply stopcock grease to outer joint of separatory funnel,and return separatory funnel to flask.Nitrogen flow through3%H2O2solution resumes as soon as separatory funnel is reinserted into appropriate joint in flask.Examine each joint to be sure that it is sealed.Use rubber bulb equipped with valve to apply head pressure above HCl in separatory funnel.Open stopcock in separatory funnel and let HCl flow into flask.Continue to maintain sufficient pressure above acid solution to force solution into flask.Stopcock may be closed,if necessary,to pump up pressure above acid,and then opened again. Close stopcock before last2–3mL drain out of separatory funnel to guard against escape of SO2into separatory funnel.Apply power to heating e power setting that causes 80–90drops/min of condensate to return to flask from condenser. Let contents of flask boil1.7h,and then remove vessel(G).G.Determination(a)Titration.—Immediately titrate contents of vessel(G)with0.010M NaOH to yellow end point that persists≥pute sul-fite content,expressed inµg SO2/g food(ppm),as follows:SO2,µg/g(ppm)=32031000.×××V MweightBwhere32.03=milliequivalent weight of SO2;V B=volume(mL)of NaOH of molarity M required to reach end point;1000=factor to convert milliequivalents to microequivalents;weight=weight,g,of test portion introduced into1L flask.(b)Gravimetric determination.—Optional.Following titration, rinse contents of vessel(G)into400mL beaker.Add4drops1M HCl and excess of filtered10%BaCl2solution,and let mixture stand overnight.Wash precipitate by decantation3times with hot water through weighed Gooch crucible.Wash with20mL alcohol and 20mL ether,and dry at105–110°C.SO2,µg/g(ppm)=mg BaSOg test portion4×27446.(c)Blank determination.—Determine blank on reagents both by titration and gravimetrically,and correct results accordingly.H.Recovery AssaysTo become familiar and proficient with method before routine use,analyze food test portions containing known amounts of sulfite. Perform analysis in manner that precludes any loss of sulfite by oxi-dation or reaction with components in food.Since sulfites are reac-tive with air and food matrixes and lack stability,fortify portions with stable source of sulfite,not sodium sulfite or similar salts.So-dium hydroxymethylsulfonate(HMS),which is bisulfite addition product of formaldehyde and is structurally similar to some com-bined forms of sulfite in foods,is useful for preparing stable fortified test materials.For analysis,transfer50g prepared test sample of sulfite-free food to Monier-Williams flask.Add aliquot of aqueous solution of HMS sodium salt.Analyze solution immediately.HMS recoveries of≥80%from food matrixes fortified at10µg/g are recommended to ensure accurate analytical data. Reference:JAOAC72,470(1989).CAS-7446-09-5(sulfur dioxide)Figure990.28B—Enlarged diagram of bubbler for Monier-Williams apparatus(lengths in mm).。
食品中亚硫酸盐的测定方法探索杨胜元（贵州省黔南州食品药品检验所贵州都匀市 558000）摘要：将食品中的亚硫酸盐经超声充分溶解于水中，用库伦法原理，通过定硫仪测定，即可计算出食品中二氧化硫的含量。
探索实现优越的检验技术。
关键词：食品亚硫酸盐库伦法定硫仪探索新技术Determination of sulfite in food explorationYANG Sheng-Yuan（The Food and Drug Inspection of Qiannan, Guizhou,Duyun,558000）Abstract：The sulfite in food by ultrasound fully dissolved in water, using the Kulun method, the sulfur analyzer, we can calculate the content of sulfur dioxide in food. Exploration of superior test technology. Keyword：Food Sulfite Coulomb's law Sulphur analyzer Explore new technologies1. 引言鉴于现行《食品中亚硫酸盐的测定》（GB/T5009.34—2003）中的盐酸副玫瑰苯肼法和蒸馏法的复杂以及有毒且危险过程；流动注射化学发光法也过于繁琐和危险，现对食品中亚硫酸盐库伦法试验进行探索，快速、准确且安全的测量食品中的亚硫酸盐。
2. 实验部分2.1原理食品中各种形态的亚硫酸通过超声溶解于水中，生成SO32-，而立即被电解液中的I2(Br2)氧化成H2SO4，结果溶液中的I2(Br2)减少而I(Br)增加，破坏了电解液的平衡状态，指示电极间的电位升高，仪器自动判断启动电解，并根据指示电极上的电位高低，控制与之对应的电解电流的大小与时间，使电解电极上生成的I2(Br2)与SO32-反应所消耗的数量相等，从而使电解液重新回到平衡状态，重复些过程，直到试验结束。
AOAC亚硫酸盐测定方法（自己翻译）AOAC:食品中亚硫酸盐测定方法一简介1 理论样品和挥发盐酸一起加热可使样品中的亚硫酸盐转化为二氧化硫。
溶液里面通入的氮气流可携带二氧化硫通过冷凝器，在3%过氧化氢溶液中被氧化为硫酸。
硫酸可被标准氢氧化纳滴定，而样品中含有的亚硫酸盐量与硫酸量是相对应的。
硫酸可转化为硫酸钡，通过重量法进行验证。
2 应用此方法适用于亚硫酸盐含量高于10ppm的新鲜和经过处理的食品，对存在挥发性硫化合物的物质也适用。
但本方法不能用于检测干洋葱、韭菜和卷心菜。
二装置a蒸馏装置b滴定管10mlc烧瓶带有螺帽d冷凝水可用甲醇水溶液，比例为甲醇：水=20：40，温度小于15℃e微量移液器100-1000微升三试剂和溶液1 试剂a盐酸12N，试剂级b过氧化氢30%ACS级c乙醚无水d乙醇无水e氮气高纯度，使用调节装置保持气流速度为200ml/minf氯化钡试剂级g氢氧化钠溶液0.01Nh水去离子水，18兆欧姆，用蒸馏水配置，使用前用250-300ml/m的氮气流冲15分钟脱氧，密闭保存。
I甲醛合次硫酸钠（HMS）j一水合磷酸氢二钠k D型甘露醇l甲基红2 溶液a 4N盐酸：加30ml12N盐酸至60ml去离子水中，搅拌均匀。
b甲基红指示剂：溶解250mg甲基红试剂于100ml乙醇中。
c 0.010N氢氧化钠：先配成1mol/l的氢氧化钠溶液,使用前再稀释至0.01ml/l的溶液。
1ml/l 氢氧化钠溶液的配置：称取110g NaOH，溶于100mL水中，摇匀，倒入聚乙烯容器中，密闭放置至溶液清亮。
用塑料管吸取54ml的上层清液，注入1000mL新沸过的冷水（煮沸一段时间后加盖冷却）中摇匀。
称取7.5g、于105—110℃烘至质量恒定的基准邻二甲酸氢钾，称准至0.0001 g，溶于80ml无CO2的水中，加2滴酚酞指示液（10 g/L），用配制好的NaOH 溶液滴定至溶液呈粉红色同时作空白试验。
47.3.43AOAC Official Method990.28Sulfites in FoodsOptimized Monier–Williams MethodFirst Action1990Final Action1994(Applicable of determination of≥10ppm(µg/g)sulfites in foods. Applicable in presence of other volatile sulfur compounds;not ap-plicable to dried onions,leeks,and cabbage.)Results of the interlaboratory study supporting the acceptance of the method:Hominy,9.17ppm(µg/g)sulfites:s r=1.33;s R=1.42;RSD r=14.5%;RSD R=15.5%Fruit juice,8.05ppm(µg/g)sulfites:s r=1.36;s R=1.62;RSD r=16.9%;RSD R=20.1%Protein(seafood),10.41ppm(µg/g)sulfites:s r=1.47;s R=2.77;RSD r=14.1%;RSD R=26.6%A.PrincipleMethod measures free sulfite plus reproducible portion of bound sulfites,such as carbonyl addition products,in foods.Test portion is heated with refluxing HCl(ca1M)to convert sulfite to SO2.Stream of N2introduced below surface of refluxing solution sweeps SO2 through water-cooled condenser and,via bubbler attached to con-denser,with3%H2O2solution,where SO2is oxidized to H2SO4. Sulfite content is directly related to generated H2SO4,which is deter-mined by titration with standardized NaOH solution.For verifica-tion,sulfate can be determined gravimetrically as BaSO4.B.Apparatus(a)Distillation apparatus.—(Note:In this method,back pres-sure inside apparatus is limited to unavoidable pressure due to height of3%H2O2solution above tip of bubbler(F).Keep back pressure as low as possible to avoid loss of SO2through e thin film of stopcock grease on sealing surfaces of all joints except joint between separatory funnel and flask.Clamp together each joint to ensure complete seal throughout analysis.)Assemble apparatus(Figure 990.28A),which includes(1)inlet adapter(A)with hose connector (Kontes183000).Adapter provides means of applying head pres-sure above e of pressure-equalizing dropping funnel is not recommended because condensate,perhaps containing SO2,is deposited in funnel and side arm.(2)Separatory funnel(B),≥100mL capacity.(3)Round-bottom flask(C),1L,with three24/40 tapered joints.(4)Gas inlet tube(D)(Kontes179000)of sufficient length to permit introduction of N2within2.5cm of bottom of flask.(5)Allihn condenser(E)(Kontes431000-2430),jacket length 300mm.(6)Bubbler(F),fabricated from glass according to dimen-sions in Figure990.28B.(7)Vessel(G),ca2.5cm id and18cm deep.(b)Buret.—10mL(Kimble Glass,Inc.,No.17124-F)with over-flow tube and hose connections for Ascarite tube or equivalent air-scrubbing apparatus to permit maintenance of CO2-free atmo-sphere over standardized0.010M NaOH.(c)Chilled water circulator.—Chill condenser with coolant, such as methanol-water(20+40,v/v),maintained at≤15°C.Circu-lating pump,Neslab Coolflow33(Neslab Instruments,Inc.,PO Box 1178,Portsmouth,NH03801,USA),or equivalent,is suitable.C.Reagents(a)Aqueous hydrochloric acid.—4M.For each analysis,prepare 90mL solution by adding30mL HCl to60mL deionized(18meg-ohm)water.(b)Methyl red indicator.—Dissolve250mg methyl red in 100mL ethanol.(c)Standardized titrant.—0.010M NaOH.Certified reagent may be used(Fisher SO-5-284).Standardize solution with reference standard potassium acid phthalate.(d)Hydrogen peroxide solution.—3%.For each analysis,dilute 3mL ACS reagent grade30%H2O2to30mL with deionized (18megohm)water.Just prior to use,add3drops methyl red indica-tor and titrate with0.010M NaOH to yellow end point.If end point is exceeded,discard solution.(e)Nitrogen.—High purity,used with regulator to maintain flow of200mL/min.To guard against oxygen in N2gas,use GC-type trap (Oxy-Purge N[Alltech-Applied Science Laboratories,Inc.],or equivalent).Alternatively,oxygen-scrubbing solution,such as alkaline pyrogallol,in gas-washing bottle(Kimble Glass,Inc.)may be used. Prepare trap as follows:(1)Add4.5g pyrogallol to trap.(2)Purge trap with N2for2–3min.(3)Prepare KOH solution by adding65gFigure990.28A—Apparatus for optimized Monier-Williams method:A,inlet adapter;B,separatory funnel; C,round-bottom flask;D,gas inlet tube;E,Allihn con-denser;F,bubbler;G,vessel.KOH to85mL H2O.(Caution:Heat is generated.)(4)Add KOH so-lution to trap while atmosphere of N2is maintained in trap.D.Test Sample Preparation(a)Solids.—Transfer50g food,or quantity that contains 500–1500µg SO2,to food processor or blender.Add100mL etha-nol–water(5+95,v/v)and briefly grind mixture.Continue grinding or blending only until food is chopped into pieces small enough to pass through standard taper24/40joint of flask(C).(b)Liquids.—Mix50g test portion,or quantity that contains 500–1500µg SO2with100mL ethanol-water(5+95,v/v). (Note:Carry out test sample preparation and analysis as quickly as possible to avoid loss of labile forms of sulfite.)E.System PreparationUsing apparatus assembled as shown in Figure990.28A,position flask(C)in heating mantle controlled by power-regulating device (rheostat),and add400mL H2O to flask.Close stopcock of separa-tory funnel(B)and add90mL4M HCl to separatory funnel.Begin N2flow at200±10mL/min.Initiate condenser coolant flow at this time.To vessel(G)add30mL3%H2O2,which has been titrated to yellow end point with0.010M NaOH.After15min,apparatus and water will be thoroughly deoxygenated and prepared test portion may be introduced into system.F.Sample Introduction and DistillationRemove separatory funnel(B)and quantitatively transfer test por-tion in aqueous ethanol to flask(C).Wipe tapered joint clean with laboratory tissue,quickly apply stopcock grease to outer joint of separatory funnel,and return separatory funnel to flask.Nitrogen flow through3%H2O2solution resumes as soon as separatory funnel is reinserted into appropriate joint in flask.Examine each joint to be sure that it is sealed.Use rubber bulb equipped with valve to apply head pressure above HCl in separatory funnel.Open stopcock in separatory funnel and let HCl flow into flask.Continue to maintain sufficient pressure above acid solution to force solution into flask.Stopcock may be closed,if necessary,to pump up pressure above acid,and then opened again. Close stopcock before last2–3mL drain out of separatory funnel to guard against escape of SO2into separatory funnel.Apply power to heating e power setting that causes 80–90drops/min of condensate to return to flask from condenser. Let contents of flask boil1.7h,and then remove vessel(G).G.Determination(a)Titration.—Immediately titrate contents of vessel(G)with0.010M NaOH to yellow end point that persists≥pute sul-fite content,expressed inµg SO2/g food(ppm),as follows:SO2,µg/g(ppm)=32031000.×××V MweightBwhere32.03=milliequivalent weight of SO2;V B=volume(mL)of NaOH of molarity M required to reach end point;1000=factor to convert milliequivalents to microequivalents;weight=weight,g,of test portion introduced into1L flask.(b)Gravimetric determination.—Optional.Following titration, rinse contents of vessel(G)into400mL beaker.Add4drops1M HCl and excess of filtered10%BaCl2solution,and let mixture stand overnight.Wash precipitate by decantation3times with hot water through weighed Gooch crucible.Wash with20mL alcohol and 20mL ether,and dry at105–110°C.SO2,µg/g(ppm)=mg BaSOg test portion4×27446.(c)Blank determination.—Determine blank on reagents both by titration and gravimetrically,and correct results accordingly.H.Recovery AssaysTo become familiar and proficient with method before routine use,analyze food test portions containing known amounts of sulfite. Perform analysis in manner that precludes any loss of sulfite by oxi-dation or reaction with components in food.Since sulfites are reac-tive with air and food matrixes and lack stability,fortify portions with stable source of sulfite,not sodium sulfite or similar salts.So-dium hydroxymethylsulfonate(HMS),which is bisulfite addition product of formaldehyde and is structurally similar to some com-bined forms of sulfite in foods,is useful for preparing stable fortified test materials.For analysis,transfer50g prepared test sample of sulfite-free food to Monier-Williams flask.Add aliquot of aqueous solution of HMS sodium salt.Analyze solution immediately.HMS recoveries of≥80%from food matrixes fortified at10µg/g are recommended to ensure accurate analytical data. Reference:JAOAC72,470(1989).CAS-7446-09-5(sulfur dioxide)Figure990.28B—Enlarged diagram of bubbler for Monier-Williams apparatus(lengths in mm).。
