GB/T 5918-1997 Determination of mixing uniformity of compound feed

This standard specifies two methods for measuring the mixing uniformity of compound feed, namely the chloride ion selective electrode method and the methyl violet method. This standard is applicable to the quality inspection of various compound feeds, and is also applicable to the testing of mixing uniformity in mixers and feed processing technology. GB/T 5918-1997 Determination of mixing uniformity of compound feed GB/T5918-1997 Standard download decompression password: www.bzxz.net

GB/T 5918—1997bzxZ.net
Mixed uniformity is an important indicator of the quality of compound feed products. The measurement of the difference in the content of each component in the finished product can not only reflect the quality of the finished feed, but also be used to evaluate the rationality of the mixing equipment and processing technology. From the date of implementation of this standard, it will replace GB5918—86. This standard adopts the chloride ion selective electrode method to replace the precipitation method to determine the mixed uniformity of compound feed, and makes textual modifications to the methyl violet method; in "Sample Collection and Preparation", the provision of "For pellet feed and coarse powdered feed, the sample should be crushed before taking the sample" is added.
This standard is proposed by the Ministry of Domestic Trade of the People's Republic of China. This standard is under the jurisdiction of the National Feed Industry Standardization Technical Committee. The drafting unit of this standard: Wuxi University of Light Industry. The main drafters of this standard: Wang Xidong, Zhang Xiaoming, Yuan Xinhua. 66
1 Scope
National Standard of the People's Republic of China
Determination of mixing homogeneity for formula feed
Determination of mixing homogeneity for formula feedGB/T 5918—1997
Replaces GB591886
This standard specifies two methods for determining the mixing homogeneity of formula feed, namely the chloride ion selective electrode method and the methyl violet method. This standard is applicable to the quality inspection of various compound feeds, and is also applicable to the testing of mixing homogeneity in mixers and feed processing technology. 2 Chloride ion selective electrode method
2.1 Principle of the method
This method determines the content of chloride ions by the selective response of the potential of the fluoride ion selective electrode to chloride ions in the solution, and reflects the mixing homogeneity of the feed by the difference in the content of fluoride and chloride ions in the feed. 2.2 Instrument
2.2.1 Chloride ion selective electrode.
2.2.2 Double salt bridge calomel electrode.
2.2.3 Acidity meter or potentiometer: accuracy 0.2mV. 2.2.4 Magnetic stirrer.
2.2.5 Beaker: 100mL, 250ml.
2.2.6 Pipette: 1mL.5mL, 10mL.
2.2.7 Volumetric flask: 50ml.
2.2.8 Analytical balance: graduation value 0.0001g. 2.3 Reagents and solutions
The reagents and water used in this standard, unless otherwise specified, refer to analytical reagents and grade 3 water specified in GB/T6682. 2.3.1 Nitric acid (GB626-78) solution: concentration (HNO,) is about 0.5mol/L, take 35mL of concentrated nitric acid and dilute to 1000ml with water.
2.3.2 Potassium nitrate (GB64777) solution: The concentration (KNO) is about 2.5 mol/L. Weigh 252.75 g potassium nitrate into a beaker, add water and heat to dissolve, dilute with water to 1000 mL. 2.3.3 Fluoride ion standard solution: Weigh 8.2440 g sodium chloride (GB1253-89) after calcination at 500C for 1 hour and cool into a beaker, add water and heat to dissolve, transfer to a 1000 ml volumetric flask, dilute with water to the mark, shake well, and the solution contains 5 mg/mL chloride ions. 2.4 Collection and preparation of samples
2.4.1 The samples required for this method are finished compound feeds and must be collected and prepared separately. 2.4.2 Take at least 10 representative samples from each batch of feed. The quantity of each sample should be based on the average daily feed intake of livestock and poultry. 50g of early broiler feed is sampled; 100g of late broiler feed and laying hen feed is sampled; and 500g of growing and finishing pig feed is sampled. The distribution of samples must take into account the representativeness of the depth, number of bags or material flow in all directions. However, each sample must be sampled from a concentrated point. No turning or mixing is allowed during sampling. 2.4.3 Mix each of the above samples thoroughly in the laboratory, and take 10g of samples from them by quartering for measurement. For granular feed and powdered feed approved by the State Administration of Technical Supervision on March 31, 1997 and implemented in accordance with 199770-01, the samples need to be crushed before taking samples. 2.5 Determination steps 2.5.1 Drawing of standard curve GB/T 5918--1997
Pipette 0.1, 0.2, 0.4, 0.61.22.0, 4.0, 6.0mL of fluoride ion standard solution (2.3.3) and add them into 50mL volumetric flasks respectively. Add 5mL nitric acid solution (2.3.1) and 10mL potassium nitrate solution (2.3.2), and dilute to the scale with water. Shake well to get 0.50.1.00.2.003.00, 6.00, 10.00, 20.0 0, 30.00mg/50mL chloride ion standard series, pour them into 100ml dry beaker, put a magnetic stir bar, use chloride ion selective electrode as indicator electrode, double salt bridge calomel electrode as reference electrode, stir with magnetic stirrer for 3min (constant speed), read the indicated value (mV) on the acidity meter or potentiometer, use the potential value (mV) of the solution as the vertical axis and the chloride ion concentration as the horizontal axis, draw the standard curve on the semi-logarithmic coordinate paper. 2.5.2 Determination of sample
Weigh 10g of sample (accurate to 0.0002g) and place it in a 250mL beaker, accurately add 100ml. water, stir for 10min, let it stand for 10min, and filter with dry medium-speed qualitative filter paper. Pipette 10mL of the sample filtrate into a 50mL volumetric flask, add 5mL of nitric acid solution (2.3.1) and 10mL of potassium nitrate solution (2.3.2), dilute to the mark with water, shake well, measure according to the standard curve operation steps, read the potential value, and obtain the corresponding value of chloride ion content from the standard curve. 2.5.3 Calculation of mixing uniformity
The corresponding value of chloride ion content measured each time is X.,XX..X1o, and its average value X, standard deviation S and coefficient of variation CV are calculated according to formula (1) to formula (4).
The standard deviation S is:
XX++X+X+..+
(X, -x)2+(X, x) +(X,- X)2+.... +(Xi。-X)2101
Xi +X?+ X + ..... + Xio - 10x?10
The coefficient of variation CV is calculated from the average value X and the standard deviation S: CV(%) yun
× 100
If the chloride ion content in the feed is required, it can be calculated according to formula (5). (%)
Wherein: C—monofluoride ion (CI-) content; X
w××1000
X—chloride ion (CI-) content obtained from the standard curve, mg; W—weight of the sample during determination, g;
V—amount of sample filtrate used during determination, mL. 3 Methyl violet method
3.1 Principle of the method
This method uses methyl violet pigment as a tracer, adds it together with additives, and premixes it in the feed. Then the methyl violet content in the sample is determined by colorimetry. The difference in methyl violet content in the feed reflects the mixing uniformity of the feed. This method is mainly suitable for testing the mixing uniformity in mixers and feed processing technology. 3.2 Instruments
3.2.1 Spectrophotometer: with 5mm colorimetric dish. 68
3.2.2 Standard sieve: the basic size of the sieve hole is 100um. 3.3 Reagents
3.3.1 Methyl violet (biological dye).
3.3.2 Anhydrous ethanol (GB 678-90).
3.4 ​​Preparation and addition of tracers
GB/T 5918—1997
Mix and fully grind the methyl violet for determination so that it can all pass through a 100μm standard sieve. Add methyl violet in the additive adding stage at a dosage of 100,000th of the finished compound feed. 3.5 Collection and preparation of samples
The collection and preparation of samples are the same as those in 2.4.
3.6 Determination steps
Weigh 10g of the sample (accurate to 0.0002g), put it in a 100mL beaker, add 30mL of anhydrous ethanol, stir it from time to time, cover the beaker with a watch glass, filter it with filter paper (qualitative filter paper, medium speed) after 30 minutes, use anhydrous ethanol as blank to adjust the zero point, use a spectrophotometer, and use 5mm colorimetric blood to measure the absorbance of the filtrate at a wavelength of 590nm. The absorbance values ​​measured in each time are X1, X2, and XX1o, and their average value x, standard deviation S and coefficient of variation CV are calculated according to formula (1) to formula (4).
4 Precautions
a) When measuring 10 samples of the same batch of feed, the operation should be kept consistent as much as possible to ensure the stability and repeatability of the measured values. b) Since the methylation degree of each batch of methyl violet is different, the color tone may be different. Therefore, the methyl violet used to measure the mixing uniformity must be from the same batch and mixed well to maintain the comparability of the measured values ​​of each sample in the same batch of feed. c) If pigment-containing ingredients such as first powder and locust leaf powder are added to compound feed, the methyl violet method cannot be used to determine the mixing uniformity.
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