亚硝酸盐对粗蛋白质测定的影响及其测定方法的改进研究
发布时间：2018-07-20 13:00
【摘要】：本试验将从盐酸溶液浓度的标定方法、蒸馏仪器的选择、饲料中亚硝酸盐含量等方面对饲料中粗蛋白质含量测定时产生的影响以及饲料中亚硝酸盐含量测定方法的比较及改进进行研究。凯氏定氮法是食品和饲料中测定粗蛋白质应用最广泛也是最经典的方法,其中盐酸溶液浓度的标定是凯氏定氮法中至关重要的一步,盐酸溶液浓度的标定方法分为无水碳酸钠法和硼砂法。无水碳酸钠标定法需要在270℃~300℃干燥至恒重,操作较费时费事,且指示剂颜色不易把握;而硼砂标定法中只说是干燥的硼砂,并未说明干燥程度以及如何干燥。蒸馏装置是凯氏定氮法中的重要仪器,分为半微量蒸馏装置和全自动凯氏定氮仪等类型,不同蒸馏装置对测定结果的影响尚无报道。试验表明:无水碳酸钠须在270℃~300℃干燥至恒重才可标定盐酸。380℃干燥至恒重的硼砂在标定盐酸时计算式中的硼砂分子式要按无水硼砂计算;100℃干燥的硼砂不可以用于盐酸标定;正常室温密闭存放的硼砂更适于北方地区实验室进行盐酸标定(因为南方湿度较大)。全自动凯氏定氮仪较半微量蒸馏装置测定准确性更好。亚硝酸钠存在于饲料原料及配合饲料中,尤其在鱼粉、肉骨粉及青绿饲料中含量较大,目前没有试验研究表明饲料中亚硝酸盐对其粗蛋白质含量测定是否产生影响,但是通过人为向标准样品硫酸铵中加入一定浓度梯度的亚硝酸钠后,发现测出的硫酸铵中的氮含量减少,损失的氮含量与亚硝酸钠的添加量呈现一定的线性关系。向牛血清白蛋白和饲料中加入亚硝酸钠后会出现同样的线性关系。试验表明:亚硝酸盐的存在会对凯氏定氮法测定粗蛋白质时产生一定的副作用,会与部分含氮化合物反应,降低蛋白含量的真实值,严重影响粗蛋白质测定的准确性。草酸是最简单的有机二元酸之一,结构简式HOOCCOOH。NO2-中的N为+3价,所以既有氧化性,又有还原性,在酸性介质中呈现较强的氧化能力。与很弱的草酸、乙酸均可反应。可能的反应为:2NO2-+2H+=NO+NO2↑+H2O。向加有不同浓度梯度亚硝酸钠的硫酸铵混合物中分别加入0.1mol/l、0.5mol/l、1mol/l的草酸溶液,待反应充分后加入浓硫酸。经过试验结果分析得出:草酸溶液的加入不能消除亚硝酸钠对粗蛋白质测定的影响,所测出的硫酸铵中的氮含量与亚硝酸钠的添加量仍然呈现一定的线性关系。为了对饲料中亚硝酸盐含量进行有效的检测,首先要确定比较可靠、准确的测定方法。饲料中亚硝酸盐的测定方法分别为GB/T 13085—2005版和GB 13085—91版两种。试验采用两版国标法对同一样品进行检测,分别对两种方法的准确度和精确度进行比较。同时对2005版前处理方法进行改进,探讨用于青绿饲料的测定。试验表明:亚硝酸盐国标检测方法中2005版的精确度和准确度均高于1991版,用2005版测定青绿饲料中亚硝酸盐时加入1g活性炭可提高亚硝酸盐的回收率,增强其测定的准确性。
[Abstract]:This experiment will study the influence of the determination of the concentration of hydrochloric acid solution, the selection of the distillation instrument, the content of nitrite in the feed and the comparison and improvement of the method for determining the content of nitrite in feed. The Kjeldahl method is the application of the determination of crude protein in food and feed. The calibration of hydrochloric acid solution concentration is the most important step in Kjeldahl method. The calibration method of hydrochloric acid solution concentration is divided into anhydrous sodium carbonate method and borax method. The calibration method of anhydrous sodium carbonate should be dried at 270 ~300 C to constant weight, the operation is time-consuming and difficult, and the color of the indicator is not easy to grasp. The borax calibration method is only a dry borax, which does not indicate the degree of drying and how to dry. The distillation unit is an important instrument in the Kjeldahl method, which is divided into a semi micro distillation unit and a full automatic Kjeldahl nitrogen meter. The effects of different distillation units on the results have not yet been reported. The test shows that the anhydrous sodium carbonate must be at 270 ~300 The borax molecular formula in the calculation formula of hydrochloric acid.380 C drying to constant weight can be calibrated by drying to constant weight at centigrade to calibrate the borax molecular formula in the formula for hydrochloric acid to be calculated according to the anhydrous borax. The borax drying at 100 C can not be used for hydrochloric acid demarcation, and the borax stored in the normal room temperature is more suitable for the laboratory in the north area to carry out hydrochloric acid calibration (because the humidity in the south is larger). The accuracy of the Full Automatic Kjeldahl nitrogen meter is better than that in the semi microdistillation unit. Sodium nitrite is found in feed materials and compound feed, especially in fish meal, meat and bone meal and green feed. No experimental study has shown whether nitrite has an effect on the determination of its crude protein content in the feed, but by human direction. After adding a certain concentration gradient of sodium nitrite in the standard sample ammonium sulfate, it is found that the nitrogen content in the ammonium sulfate is reduced. The loss of nitrogen content is linearly related to the addition of sodium nitrite. The same linear relationship will appear after the addition of sodium nitrite to bovine serum albumin and feed. There will be a certain side effect on the determination of crude protein by Kjeldahl nitrogen method, which will react with some nitrogen compounds and reduce the true value of protein content, which seriously affects the accuracy of crude protein determination. Oxalic acid is one of the simplest organic dicaric acids, and the N in simple structure HOOCCOOH.NO2- is +3 price, so it has both oxidation and reduction. It can react with very weak oxalic acid and acetic acid. The possible reaction is that 2NO2-+2H+=NO+NO2 +H2O. adds 0.1mol/l, 0.5mol/l, 1mol/l to oxalic acid in the mixture of ammonium sulphate with different concentration gradient sodium nitrite, after the reaction is sufficient to add sulfuric acid. The analysis shows that the addition of sodium nitrite can not eliminate the effect of sodium nitrite on the determination of crude protein, and the nitrogen content in ammonium sulfate is still linear with the addition of sodium nitrite. In order to detect the content of nitrite in the feed, the first must determine a more reliable and accurate method. The determination method of nitrite in the material is GB/T 13085 - 2005 and GB 13085 - 91. The test uses two edition of national standard to test the same sample. The accuracy and accuracy of the two methods are compared respectively. At the same time, the pretreatment method of 2005 edition is improved and the determination of green fodder is discussed. The experiment shows that: nitrite The accuracy and accuracy of the 2005 edition of the 2005 edition of the acid salt national standard were all higher than that of the 1991 version. The addition of 1G activated carbon to nitrite in green feed could improve the recovery of nitrite and enhance the accuracy of the determination.
【学位授予单位】：东北农业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S816.17
本文编号：2133598
[Abstract]:This experiment will study the influence of the determination of the concentration of hydrochloric acid solution, the selection of the distillation instrument, the content of nitrite in the feed and the comparison and improvement of the method for determining the content of nitrite in feed. The Kjeldahl method is the application of the determination of crude protein in food and feed. The calibration of hydrochloric acid solution concentration is the most important step in Kjeldahl method. The calibration method of hydrochloric acid solution concentration is divided into anhydrous sodium carbonate method and borax method. The calibration method of anhydrous sodium carbonate should be dried at 270 ~300 C to constant weight, the operation is time-consuming and difficult, and the color of the indicator is not easy to grasp. The borax calibration method is only a dry borax, which does not indicate the degree of drying and how to dry. The distillation unit is an important instrument in the Kjeldahl method, which is divided into a semi micro distillation unit and a full automatic Kjeldahl nitrogen meter. The effects of different distillation units on the results have not yet been reported. The test shows that the anhydrous sodium carbonate must be at 270 ~300 The borax molecular formula in the calculation formula of hydrochloric acid.380 C drying to constant weight can be calibrated by drying to constant weight at centigrade to calibrate the borax molecular formula in the formula for hydrochloric acid to be calculated according to the anhydrous borax. The borax drying at 100 C can not be used for hydrochloric acid demarcation, and the borax stored in the normal room temperature is more suitable for the laboratory in the north area to carry out hydrochloric acid calibration (because the humidity in the south is larger). The accuracy of the Full Automatic Kjeldahl nitrogen meter is better than that in the semi microdistillation unit. Sodium nitrite is found in feed materials and compound feed, especially in fish meal, meat and bone meal and green feed. No experimental study has shown whether nitrite has an effect on the determination of its crude protein content in the feed, but by human direction. After adding a certain concentration gradient of sodium nitrite in the standard sample ammonium sulfate, it is found that the nitrogen content in the ammonium sulfate is reduced. The loss of nitrogen content is linearly related to the addition of sodium nitrite. The same linear relationship will appear after the addition of sodium nitrite to bovine serum albumin and feed. There will be a certain side effect on the determination of crude protein by Kjeldahl nitrogen method, which will react with some nitrogen compounds and reduce the true value of protein content, which seriously affects the accuracy of crude protein determination. Oxalic acid is one of the simplest organic dicaric acids, and the N in simple structure HOOCCOOH.NO2- is +3 price, so it has both oxidation and reduction. It can react with very weak oxalic acid and acetic acid. The possible reaction is that 2NO2-+2H+=NO+NO2 +H2O. adds 0.1mol/l, 0.5mol/l, 1mol/l to oxalic acid in the mixture of ammonium sulphate with different concentration gradient sodium nitrite, after the reaction is sufficient to add sulfuric acid. The analysis shows that the addition of sodium nitrite can not eliminate the effect of sodium nitrite on the determination of crude protein, and the nitrogen content in ammonium sulfate is still linear with the addition of sodium nitrite. In order to detect the content of nitrite in the feed, the first must determine a more reliable and accurate method. The determination method of nitrite in the material is GB/T 13085 - 2005 and GB 13085 - 91. The test uses two edition of national standard to test the same sample. The accuracy and accuracy of the two methods are compared respectively. At the same time, the pretreatment method of 2005 edition is improved and the determination of green fodder is discussed. The experiment shows that: nitrite The accuracy and accuracy of the 2005 edition of the 2005 edition of the acid salt national standard were all higher than that of the 1991 version. The addition of 1G activated carbon to nitrite in green feed could improve the recovery of nitrite and enhance the accuracy of the determination.
【学位授予单位】：东北农业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S816.17
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