食品添加剂磷酸测重金属？ 我完全按照下面的标准做的(英文版的国标) 2 de termination of heavy metals(Pb) 2.4 summary: when PH is 3~4, the heavy metals reatct with H2S, form suspension of PbS, compare it with the standard. 2.5 R eagent : acetic acid Ammonia solution(1+1) Na2S--- glycerin solution(s glycerin is solvent): W eigh 5g Na2S, dissolved in 10 mL water and 30 mL glycerin . T he solution should be protected from light in the brown bottle. A nd it ’ s valid for 1 month. Pb standard solution: 10 μ g Pb/ mL: weight 0.799g lead nitrate ,dissolve with 50mL nitric acid(1+9), put in volumetric flask(working volume is 500 mL), dilute until the volume is 500 mL. take 1 mL solution from the volumetric flask, put in another volumetric flask(working volume is 100 mL), dilute until the volume is 100 mL. 2.6 steps: Heavy metals, as Pb ≤ 10 ppm 3.3.1prepare sample solution:weigh 10 g H3PO4, put in volumetric flask(working volume is 50 mL),dilute with water until the volume is 50mL. 3.3.2determination of heavy metals(Pb) ：take 25 mL sample solution, put in the colorimetric tube, adjust PH with ammonia solution until PH is 3~4(use special PH indicator paper ). A dd 10 mL Na2S--- glycerin solution, and dilute to the scale mark , shake the colorimetric tube gently. W ait for 10 minutes, and compare with the standard. T he standard: take 5 mL sample solution and 4 mL Pb standard solution, put in the colorimetric tube, do the test in the same way. 3.3.3 calculate: W 4 means the content of heavy metals(Pb) , w/w % file:///C:/DOCUME%7E1/ADMINI%7E1/LOCALS%7E1/Temp/ksohtml/wps_clip_image1.wmffile:///C:/DOCUME%7E1/ADMINI%7E1/LOCALS%7E1/Temp/ksohtml/wps_clip_image2.wmffile:///C:/DOCUME%7E1/ADMINI%7E1/LOCALS%7E1/Temp/ksohtml/wps_clip_image1.wmf V----- the volume of Pb standard solution m----- weight of H3PO4, m is about 10 g. 但是,标准是黑色沉淀,样品有白色的浑浊样,这算超标吗?查看更多2个回答 . 2人已关注
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