The Effect Of Nitrite On Determination Of Crude Protein And The Improvement Of The Method Of Nitrite Determination

The concentration of hydrochloric acid solution from the test calibration method was studied from the calibration method、choosing the distillation equipment、feed and other effects of nitrite content generated when the dietary crude protein content was measured and comparisons and improved method for the determination of nitrite in feed.Kjeldahl method is widely used in measuring crude protein and it is the most classic, in which the concentration of hydrochloric acid solution Calibration Kjeldahl method is a crucial step, the concentration of hydrochloric acid solution is divied into no calibration method water,sodium carbonate and borax Law Act. Anhydrous sodium carbonate calibration method requires270℃ ~ 300℃drying to constant weight, the more time-consuming and cumbersome operation,and the indicator color is not easy to grasp; and the borax is just called dried borax in the borax calibration method.But it doesn’t explain how the degree of drying and how to dry. Distillation unit Kjeldahl method is an important instrument,it divided into semi-micro distillation unit and automatic Kjeldahl instrument, such as the type, the effects of different distillation unit of measurement results have not been reported. Experiments showed: anhydrous sodium carbonate must be dried between 270℃ ~ 300℃ to constant weight before calibration hydrochloric acid.From 380℃ drying to constant weight of borax in the calibration formula HCl in anhydrous borax,borax is calculated according to the formula; 100℃ drying borax can not be used for calibration of hydrochloric acid; properly stored airtight at room temperature is more suitable for the northern region of borax laboratory hydrochloric acid were calibrated(because the South humidity).Automatic Kjeldahl nitrogen analyzer accuracy better than the semi-micro determination of the distillation unit.Sodium nitrite was present in feed materials and compound feed, especially in fish meal,bone meal, and a large green feed content, there is no experimental studies which show that whether the feed crude protein content of nitrite in their determination impacts or not, but after adding a certain standard sample concentration gradient of ammonium sulfate sodium nitrite by man was found that the nitrogen content in ammonium sulfate lessens,and it shows some linear relationship between the addition of sodium nitrite nitrogen content and presentation of certain losses. After bovining serum albumin and feeding will appear the same linear relationship to sodium nitrite. Experiments show that: the presence of nitrite Kjeldahl method will produce the determination of crude protein certain side effects, will react with some nitrogen compounds,reduce the real value of the protein content, seriously affect the accuracy of the determination of crude protein.Oxalic acid, i.e. acetic acid, one of the simplest organic dibasic acid. The simple structure isHOOCCOOH. N+3 in NO2-is a positive trivalent, so both oxidation, but also reduction, showing a strong oxidizing power in acidic media. With weak acid, acetic acid can be reacted. Possible reaction: 2NO2-+2H+=NO+NO2↑+H2O. The mixture was added with ammonium sulfate to different concentrations of sodium nitrite were added to 0.1mol/l、0.5 mol/l、1mol/l oxalic acid solution until the reaction after addition of concentrated sulfuric acid sufficiently. After analyzing the test results obtained: adding oxalic acid solution can not eliminate the influence of sodium nitrite on the crude protein determination, the measured amount of ammonium sulfate is added sodium nitrite nitrogen content and still showing a linear relationship. So to find a way to eliminate the effect of nitrite on the determination of crude protein content has to be studied further experiments.In order to feed the nitrite content for effective detection, we must first determine a more reliable and accurate measurement method. Determination of nitrite in feed were GB/T13085-2005 and GB 13085-91 edition version of the two. Test uses two editions of the national standard method for testing the same sample, respectively for the accuracy and precision of the two methods were compared. While the 2005 edition of pretreatment methods is improved determination to explore for green feed. experiments showed:nitrite 2005 edition national standard test method precision and accuracy are higher than the 1991 version, 1g of activated carbon can improve the recovery of nitrite measured nitrite green feed with the 2005 edition, to enhance its determination accuracy. Nitrite in some common feed ingredients and feed content,such as soybean meal, rice bran, corn bran, cottonseed meal, broiler complete feed, pig feed full price,is lower,it meets feed hygiene standards allowable amount of nitrite.