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目的建立测定原料乳中蛋白质的离子色谱法。方法用15%三氯乙酸沉淀原料乳中蛋白并抽滤得滤液,用硫酸—双氧水体系分别消解原料乳及滤液,用20mmol/L的甲烷磺酸作淋洗液,IonpacCS12A色谱柱,DS-6电导检测器测定原料乳及滤液中的NH4+-N含量,两者之差乘以转换系数即为蛋白质含量。结果蛋白质(以NH4+-N计)在0.2～10mg/L范围内线性良好,该方法的定量限为0.038g/100g,加标回收率为90.0%～105.0%,相对标准偏差(RSD)为1.06%～5.38%。结论本法简便、快速、准确,灵敏度及精密度高,适用于原料乳中蛋白质含量的测定。
Objective To establish a method for the determination of protein in raw milk by ion chromatography. Methods The protein in raw milk was precipitated by 15% trichloroacetic acid and the filtrate was filtered with suction. The raw milk and filtrate were digested with sulfuric acid-hydrogen peroxide system, and eluted with 20 mmol / L methanesulfonic acid as eluent, IonpacCS12A column, DS- Conductivity detector determination of raw milk and filtrate NH4 + -N content, the difference between the two multiplied by the conversion factor is the protein content. Results The results showed that the linearity was good with 0.2 ~ 10 mg / L NH4 + -N. The limit of quantitation was 0.038 g / 100 g, the recoveries were 90.0% ~ 105.0% and the relative standard deviations (RSDs) were 1.06 % ~ 5.38%. Conclusion This method is simple, rapid, accurate, sensitive and precise, suitable for the determination of protein content in raw milk.