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1、INTERNATIONAL STANDARD INTERNATIONAL ORGANIZATION FOR STANDARDIZATION .MEXflYHAPOAHAFI OPI-AHM3AUMA l-IO CTAHAAPTM3ALWiM*ORGANISATION INTERNATIONALE DE NORMALISATION Meat and meat products - Determination of nitrate content (Reference method) Viandes et produits ;i base de viande - De termination de
2、 la teneur en nitrates (Me thode de re f repeat the same treatment with another 15 ml portion of water. Carry ou t two independent deter minati ons, beginning different test portions taken from the sa me test sample with 8.10 Calibration curve 8.10.1 Pipette respectively into four 100 ml one-mark vo
3、lumetric flasks (6.3) 10 ml of water and 10 ml of each of the three sodium nitrite standard solutions (5.6), containing 2,5 rug, 5,0 ,ug and IO,0 ,ug of nitrite per millilitre. After this portio completely fill the n has run into the column as well, ,eservoir wi th water. 8.10.2 To each flask add wa
4、ter to obtain a volume of about 60 ml and proceed as described in 8.8.2 to 8.8.4. 3 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/27/2007 02:09:23 MDTNo reproduction or networking perm
5、itted without license from IHS -,-,- IS0 3091-1975 (E) 8.10.3 Draw the calibration curve by plotting the measured absorbances against the concentrations, in micrograms per millilitre, of the standard sodium nitrite solutions. 9 EXPRESSION OF RESULTS NaN02 is the nitrite content of the sample, expres
6、sed as milligrams of sodium nitrite per kilogram and determined according to IS0 2918. Take as the result the arithmetic mean of the two determinations, provided that the requirement for repeatability (see 9.2) is satisfied. Express the result to the nearest 1 mg per kilogram of product. 9.1 Method
7、of calculation and formula 9.2 Repeatability Calculate the nitrate content of the sample, expressed as milligrams of potassium nitrate per kilogram, using the formula : 10 000 KN03 = 1,465 cx- mxV - NaN02 The difference between the results of two determinations carried out simultaneously or in rapid
8、 succession, by the same analyst, shall not be greater than 10 % of the mean value. where 10 TEST REPORT m is the mass, in grams, of the test portion; V is the volume, in millilitres, of the aliquot portion of the eluate (see 8.8.1); c is the concentration of sodium nitrite, in micrograms per millil
9、itre, read from the calibration curve, that corresponds with the absorbance of the solution prepared from the test portion (see 8.8.4); The test report shall show the method used and the result obtained; it shall also mention all operating conditions not specified in this International Standard, or
10、regarded as optional, as well as any circumstances that may have influenced the result. The report shall include all identification of the sample. details necessary for complete Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical St
11、andards 1/9972545001 Not for Resale, 04/27/2007 02:09:23 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 3091-1975 (E) Dimensions in millimetres Reservoir kapaci ty 40 Rubber stopper db Laumlum column Rubber tubing -a7 I Effluent t$ ext. 7 to 8 $ int. O/I to 0,6 NOTE -
12、A flexible connection may be used between the bottom of the column and the effluent capillary tube, in order to allow adjustment of the height of the capillary tube and thus of the flow rate. F I G U R E - Apparatus for nitrate reduction 5 Copyright International Organization for Standardization Pro
13、vided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/27/2007 02:09:23 MDTNo reproduction or networking permitted without license from IHS -,-,- This page intentionally left blank Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/27/2007 02:09:23 MDTNo reproduction or networking permitted without license from IHS -,-,-