杏脯/杏干中二氧化硫检测方案(二氧化硫)

智能文字提取功能测试中

APPLICATION NOTEF&F-K-004-2014/A2 SO2 DETERMINATION IN DRIED APRICOTSMONIER-WILLIAMS METHOD Sulphur Determination in Dried Apricotsaccording to the Monier-Williams method Reference： AOAC 990.28 Sulfites in Foods- Optimized Monier-Williams MethodTested with VELP Scientifica UDK 149 Automatic Kieldahl distillation unit (Code F30200140) Introduction Sulphites， in various forms， have been added to foods as preservatives agents and for other purposes for centuries.Their use became an issue of concern when some sensitive individuals exhibited adverse reactions to sulphite residuesin foods. This fact lowers the concentration which was considered safe for human consumption and increases thenumber of control analyses to be performed. Therefore analytical methods were developed to monitor these compoundsat the regulatory limit of 10 ppm. Based on a 60-year database， the Monier-Williams procedure still remains the reference method (Fazio et al.， 1989). Sulphur Dioxide Determination in Dried Apricots One of the most commonly used methods for this analysis is the sulphur dioxide distillation from complex matrixesfollowed by iodine titration. This steam distillation considerably shortens the time required， without affecting the results. This method shows comparable results to the ones obtained by using the Monier-Williams technique. Chemicals ●e Starch solution 1 % lodine solution 0.02 N ● Hydrochloric acid (HCI)7% Sample Standard FAPASDried apricots (water/fruit slurry)Ref. NumberT2095QCQuantity100 gAnalyteSulphur dioxideAssigned value1483 mg/kgSatisfactory range1325-1641 mg/kg Sample Preparation Homogenize the sample avoiding unnecessary exposure to air. Weigh up to 10 g (±1 mg) of sample into a standard 250 ml test tube. Distillation and Titration Prepare the receiving solution in a 250 ml Erlenmeyer flask， adding 75 ml of distilled water 10 drops of starch solution：and 6 drops of iodine solution 0.02 N. The receiving solution color is light blue. Distill the sample according to the following parameters (set in a customizable method) H2O (dilution water)： 50 ml HHCI (7%)： 30 ml* . Distillation time： 6 minutes ● Steam power：50 % ● Set no automatic distillation residues discharge at the end of the distillation. Prepare some blanks with all the chemicals， without the sample. Titrate the distillate with iodine solution 0.02 N in order to get the solution back to light blue. It was found that using always the same amount of iodine reagent (6 drops) in the starting solution， titration is facilitatedand accuracy is increased. * added with acid pump kit (Code A00000220) Typical Results on Dried Apricots Record the ml of titration solution for the calculation using the formula：mg/kg SO2 = (ml sample- ml blank) * Mso2 *N *1000 msample*2 ml sample： titrant volume used for sampleml blank： average of titrant volume used for blanksMso2： SO2 molecular weight (64.06 g/mol)N： normality titrant solution (0.02N) msample： sample quantity (g) Sample quantity (g) mg SO2 mg/kg SO2 10.752 14.5 1346.5 10.465 14.0 1340.6 10.737 14.5 1348.4 10.419 14.0 1340.3 10.238 13.6 1332.8 Average ±SD% 1341.7±6.1 RSD%* 0.5 Expected SO2 content： 1325-1641 mg/kg *RSD%=(Standard Deviation * 100) / Average The complete procedure was verified by dosing 10 ml of sodium bisulphite standard solution containing 23.57 mg SO2. Conclusion The obtained results are reliable and reproducible in accordance with the expected values. with a low relative standarddeviation (RSD <1%). that means high repeatability of the results. Benefits of UDK 149 Automatic Kjeldahl distillation unit are： High level of precision and reproducibility Maximum productivity and full automation Worldwide official method Reliable and easy method Time saving Moderate running costs Copyright ◎ VELP Scientifica. All rights reserved.No part of this publication may be reproduced or transmitted in any form or for any purpose without the express permission of VELP.VELP Scientifica， Italy Tel： + Fax： + www.velp.com 利用VELP UDK 系列全自动二氧化硫测定仪测定食品中的硫含量