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GB/T 4325.7-2013 English PDF (GBT4325.7-2013)

GB/T 4325.7-2013 English PDF (GBT4325.7-2013)

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GB/T 4325.7-2013: Methods for chemical analysis of molybdenum -- Part 7: Determination of iron content- 1, 10-phenanthroline spectrophotometry and inductively coupled plasma atomic emission spectrometry

This part of GB/T 4325 specifies the method for determining the content of iron in molybdenum. This part applies to the determination of iron content in molybdenum powder, molybdenum bar, molybdenum trioxide, ammonium molybdate. Method 1 measurement range: 0.0005% ~ 0.060%; method 2??s measurement range: 0.0002% ~ 0.100%.
GB/T 4325.7-2013
GB
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 77.120.99
H 63
Replacing GB/T 4325.6-1984
Method for chemical analysis of molybdenum - Part 7:
Determination of iron content - 1,10-phenanthroline
spectrophotometry and inductively coupled plasma
atomic emission spectrometry
ISSUED ON: MAY 09, 2013
IMPLEMENTED ON: FEBRUARY 01, 2014
Issued by: General Administration of Quality Supervision, Inspection and Quarantine of PRC;
Standardization Administration of PRC.
Table of Contents
Foreword ... 3
1 Scope ... 6
2 Normative references ... 6
3 General ... 6
4 Method 1 - Phenanthroline spectrophotometry ... 7
5 Method 2 - Inductively coupled plasma atomic emission spectrometry ... 12 6 Test report ... 15
Method for chemical analysis of molybdenum - Part 7:
Determination of iron content - 1,10-phenanthroline
spectrophotometry and inductively coupled plasma
atomic emission spectrometry
1 Scope
This part of GB/T 4325 specifies the method for determining the content of iron in molybdenum.
This part applies to the determination of iron content in molybdenum powder, molybdenum bar, molybdenum trioxide, ammonium molybdate. Method 1?€?s
measurement range: 0.0005% ~ 0.060%; method 2?€?s measurement range:
0.0002% ~ 0.100%.
2 Normative references
The following documents are essential to the application of this document. For the dated documents, only the versions with the dates indicated are applicable to this document; for the undated documents, only the latest version (including all the amendments) are applicable to this standard.
GB/T 6682 Water for analytical laboratory use - Specification and test
methods (ISO 3696)
GB/T 12806 Laboratory glassware - One-mark volumetric flasks (ISO 1042) GB/T 12808 Laboratory glassware - One-mark volumetric flasks (ISO 648)
GB/T 12809 Laboratory glassware - Principles of design and construction of volumetric glassware (ISO 384)
GB/T 12810 Laboratory glassware - Volumetric glassware - Methods for use and testing of capacity (ISO 4787)
3 General
3.1 Unless otherwise specified, only confirmed analytical reagents are used in the analysis; the water used is distilled or deionized water or water of equivalent 3 g of potassium iodide; after dissolving, use quick quantitative filter paper to filter in a separatory funnel; use water to dilute it to 500 mL; add 20 mL ~ 30 mL of trichloromethane (4.2.5); oscillate for 2 minutes; stand still for stratification; discard the organic phase; use trichloromethane (4.2.5) to repeatedly extract the water until the organic phase is colorless; put the water phase into the reagent bottle to prepare for use.
4.2.12 Citric acid solution (500 g/L). The purification steps are as follows: Weigh 250 g of citric acid; place it in a 1000 mL beaker; add 200 mL of water to dissolve it; use ammonia (4.2.4) to adjust to pH 7 (check with pH test paper); add 2.5 mL of sodium perchlorate solution (4.2.8), 2 g of hydroxylamine hydrochloride, 20 mL of o-phenanthroline solution (4.2.10); heat to boil it; cool it down; add 3 g of potassium iodide; after dissolving, use quick quantitative filter paper to filter it in a separatory funnel; use water to dilute it to 500 mL; use trichloromethane (4.2.5) to make extraction several times (20 mL each time, shaking for 2 min), until the organic phase is colorless; discard the organic phase; put the aqueous phase in the reagent bottle to prepare for use.
4.2.13 Citric acid-ammonia mixed solution: Pipette 150 mL of citric acid solution (4.2.12), 80 mL of ammonia (4.2.4), 70 mL of water; mix well to prepare for use. 4.2.14 Potassium iodide solution (300 g/L): Weigh 150 g of potassium iodide (excellent grade pure); place it in a 1000 mL beaker; add 400 mL of water to dissolve it; use ammonia (4.2.4) to adjust to pH 7 (check with pH test paper); add 15 mL of hydroxylamine hydrochloride solution (4.2.15); use water to dilute it to 500 mL; mix well to prepare for use.
4.2.15 Hydroxylamine hydrochloride solution (200 g/L). The purification steps are as follows: Weigh 50 g of hydroxylamine hydrochloride; place it in a 500 mL beaker; add 150 mL of water to dissolve it; use ammonia (4.2.4) to adjust to pH 7 (check with pH test paper); add 20 mL of phenanthroline solution (4.2.10); heat to boiling; cool it down; add 3 g of potassium iodide; after dissolving, use water to transfer to a separatory funnel and dilute to a volume of 250 mL; trichloromethane (4.2.5) to make extraction several times (20 mL each time, shaking for 2 min), until the organic phase is colorless; discard the organic phase; put the aqueous phase in the reagent bottle to prepare for use.
4.2.16 Disodium ethylenediaminetetraacetic acid (EDTA) solution (100 g/L): Weigh 10 g of EDTA (excellent grade pure); put it in a 250 mL beaker; add 90 mL of water and heat (50 ??C ~ 60 ??C) to dissolve; use ammonia water (4.2.4) to adjust to pH 7 (check with pH test paper); use water to dilute it to 100 mL; mix it uniformly to prepare for use.
4.2.17 Buffer solution: Pipette 100 mL of acetic acid (1 mol/L) and 100 mL of ammonia (1 mol/L); mix it uniformly to prepare for use.
70 mL; add 10 mL of trichloromethane (4.2.5); shake for 1 min; stand for stratification; put the organic phase into a dry 25 mL colorimetric tube; shake with 5 mL of trichloromethane (4.2.5) for 1 min; combine the organic phases in the colorimetric tube; add a small amount of anhydrous sodium sulfate (4.2.1); mix well.
4.5.4.1.4 Transfer part of the solution into a 1 cm cuvette; use trichloromethane (4.2.5) as a reference, to measure its absorbance with a spectrophotometer at a wavelength of 510 nm.
4.5.4.1.5 Subtract the absorbance of the blank made with the specimen. Find the corresponding iron content from the working curve.
4.5.4.2 Specimen with nickel content greater than 0.01%
4.5.4.2.1 Place the sample (4.5.1) in a 150 mL beaker; use 5 mL of water to moisten it; add 5 mL of nitric acid (4.2.3), 4 mL of sulfuric acid (4.2.2); heat to dissolve and evaporate it, until white sulfuric acid smoke is produced; remove and cool it; use water to rinse the watch glass and the wall of beaker; repeat the generation of white smoke of sulfuric acid once again; remove and cool. 4.5.4.2.2 Use hydrochloric acid (4.2.7) to rinse the watch glass and beaker wall (about 20 mL); place the beaker at a low temperature and heat until the solution is clear; remove it; cool to room temperature; use hydrochloric acid (4.2.7) to transfer it in a 125 mL separatory funnel; control its volume to be about 40 mL. 4.5.4.2.3 Add 20 mL of ethyl acetate (4.2.6); shake for 2 min; stand for stratification; discard the aqueous phase; add 10 mL of hydrochloric acid (4.2.7); gently shake for 30 seconds; let it stand for stratification; discard the aqueous phase. Add 20 mL of citric acid-ammonia mixed solution (4.2.13) in the organic phase and shake for 1 min. After standing for stratification, put the aqueous phase into a 150 mL beaker; add 10 mL of citric acid-ammonia mixed solution (4.2.13) and repeat the back extraction once; combine the water phase in a 150 mL beaker; discard the organic phase. Place the beaker on the electric stove to heat and boil for 1 min ~ 2 min; take it off and cool; proceed the following according to 4.5.4.1.2 ~ 4.5.4.1.5.
4.6 Drawing of working curve
Pipette 0 mL, 0.50 mL, 1.00 mL, 2.00 mL, 3.00 mL, 4.00 mL, 5.00 mL, 6.00 mL of iron standard solution (4.2.19); put them into eight 150 mL beakers; add 30 mL of citric acid-ammonia mixed solution (4.2.13); use sulfuric acid (4.2.2) to adjust the pH to 7; proceed the following steps according to 4.5.4.1.2 ~ 4.5.4.1.4; measure the absorbance. Subtract the absorbance of the reagent blank. Draw a working curve with iron content as the abscissa and absorbance as the ordinate.
5 Method 2 - Inductively coupled plasma atomic
emission spectrometry
5.1 Method summary
The sample is dissolved with nitric acid and hydrogen peroxide; under selected conditions, the emission intensity is measured with an ICP-AES instrument at a wavelength of 238.2 nm to calculate the element content. The molybdenum matrix is added to offset the influence of molybdenum.
5.2 Reagents
5.2.1 Hydrogen peroxide (?? = 1.10 g/mL).
5.2.2 Nitric acid (?? = 1.42 g/mL), excellent grade pure.
5.2.3 Hydrochloric acid (1 + 1), excellent grade pure.
5.2.4 Molybdenum trioxide, spectrally pure.
5.2.5 Ammonium molybdate, spectrally pure.
5.2.6 Iron standard storage solution: Weigh 0.1429 g of iron trioxide (mass fraction ??? 99.9%); place it in a 250 mL beaker; add 10 mL of hydrochloric acid (5.2.3); heat and dissolve at a low temperature; use water to transfer it to a 1000 mL volumetric flask and dilute to the mark; mix well. This solution 1 mL contains 100 ??g of iron.
5.2.7 Iron standard solution: Pipette 10.00 mL of iron standard stock solution (5.2.6); place it in a 100 mL volumetric flask; use water to dilute it to the mark; mix well. 1 mL of this solution contains 10 ??g of iron.
5.3 Apparatus
Plasma emission spectrometer: resolution < 0.006 nm (at 200 nm).
5.4 Analytical procedures
5.4.1 Sample
Weigh the sample according to Table 3, accurate to 0.0001 g.

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