GB/T 11446.6-2013 English PDF (GBT11446.6-2013)

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GB/T 11446.6-2013: Test method for SiO2 in electronic grade water by spectrophotometer
GB/T 11446.6-2013
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 31-030
L 90
Replacing GB/T 11446.6-1997
Test method for SiO2 in electronic grade water by
spectrophotometer
ISSUED ON: DECEMBER 31, 2013
IMPLEMENTED ON: AUGUST 15, 2014
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine of PRC;
Standardization Administration of PRC.
Table of Contents
Foreword ... 3 
1 Scope ... 5 
2 Normative references ... 5 
3 Terms and definitions ... 5 
4 Principles of the method ... 5 
5 Disturbing factors ... 6 
6 Reagents ... 6 
7 Instruments and utensils ... 7 
8 Sampling ... 8 
9 Operation procedures ... 8 
10 Detection limit and relative deviation ... 10 
11 Report ... 10 
Test method for SiO2 in electronic grade water by
spectrophotometer
1 Scope
This Part of GB/T 11446 specifies the spectrophotometric test method for silicon
dioxide, in electronic grade water.
This Part applies to the determination of silicon dioxide, in electronic grade
water, where the detection limit is 1 μg/L.
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) is applicable to this standard.
GB/T 11446.1-2013 Electronic grade water
GB/T 11446.3-2013 Generic rules for test methods of electronic grade water
3 Terms and definitions
The terms and definitions as defined in GB/T 11446.3-2013, as well as the
following terms and definitions, are applicable to this document.
4 Principles of the method
Soluble silicon in water reacts with ammonium molybdate, in an acidic medium
(pH = 1 ~ 2), to produce yellow silicon copper heteropoly acid
(NH4)2H6[Si(MO2O7)6]·H2O. The reducing agent 1-amino-2-naphthol-4-sulfonic
acid is used, to reduce the yellow silicon molybdenum heteropoly acid, to silicon
molybdenum blue. Then measure the absorbance of silicon molybdenum blue,
by a spectrophotometer; calculate the amount of soluble silicon in the water.
The insoluble silicon in water can be dissolved in hydrofluoric acid, for the
determination of total silicon.
5 Disturbing factors
5.1 Phosphate and arsenate, etc. generate the corresponding blue heteropoly
acid, under the measurement conditions. The oxalic acid, tartaric acid and other
hydroxy acids can be used, to eliminate the interference from arsenic and
phosphorus.
5.2 When measuring total silicon in water, use hydrofluoric acid to convert
insoluble silicon into soluble silicon. However, hydrofluoric acid has a negative
interference, then saturated boric acid is added to eliminate it.
5.3 Whether the laboratory air is purified or not, has a greater impact on the
analysis results. The measurement shall be performed in a grade 100 clean
room.
5.4 The water sample shall be analyzed as soon as possible. The longer the
storage time, the greater the possibility of contamination.
6 Reagents
6.1 Blank water
EW-I electronic grade water, which is specified in GB/T 11446.1-2013.
6.2 Silicon standard solution
6.2.1 1 mg/mL silica standard stock solution
Accurately weigh 1.0000 g of silicon dioxide (reference), which is sintered to
constant weight, at 800 °C, as well as 3.0 g of anhydrous sodium carbonate
(superior grade pure), in a platinum crucible. Mix well. Heat them at 1000 °C,
to melt completely. After cooling, dissolve the melt in water. Dilute to 1 L. Store
in a plastic bottle. The solution shall be transparent. If turbid, it shall be prepared
again.
6.2.2 10 μg/mL silica standard working solution
Dilute the silica standard stock solution (see 6.2.1), step by step, to prepare this
solution.
6.2.3 1 μg/mL silica standard working solution
Pipette 10.00 mL of silica standard working solution (see 6.2.2). Place it in a
100 mL volumetric flask, to make the volume reach to the mark.
6.3 Ammonium molybdate solution (100 g/L)
1-amino-2-naphthol-4-sulfonic acid reducing agent solution. Shake well.
Then let it stand for 10 min.
c) Take the blank solution as a reference. Use a 1 cm liquid tank. Use a
spectrophotometer, to make measurement, at a wavelength of 815 nm.
d) Use the absorbance as the ordinate AND silica concentration as the
abscissa, to draw a working curve.
9.2 Deduction of reagent blank
9.2.1 Determination of reagent blank
Inject 50 mL and 43 mL of blank water, into two polyethylene beakers,
respectively. According to the range of silica content in the water sample to be
tested, add the single reagent and double reagent, according to the steps b) ~
d) of 9.1.1 or 9.1.2, respectively. Use the blank water as the reference, for the
determination. The difference, between the measured absorbances of the two
solutions, is the reagent blank's absorbance.
Single reagent: Add 1.0 mL of hydrochloric acid (1+1), 3.0 mL of ammonium
molybdate (10%), 2.0 mL of oxalic acid (10%), 2.0 mL of reducing agent,
sequentially, to a beaker, which contains 50 mL of blank water. Solution's
absorbance is A1.
Double reagent: Add 1.0 mL of hydrochloric acid (1+1), 6.0 mL of ammonium
molybdate (10%), 4.0 mL of oxalic acid (10%), 4.0 mL of reducing agent,
sequentially, to a beaker, which contains 43.0 mL of blank water. The
absorbance value of the solution is A2.
9.2.2 Determination of total silicon
In a polyethylene cup, add 2.5 mL of saturated boric acid AND 1.0 mL of
hydrofluoric acid (1+1). After shaking well, add 39.5 mL of blank water.
According to the range of silica content in the water sample to be tested, follow
the steps b) ~ d) of 9.1.1 or 9.1.2, to add reagents. Use the blank water as a
reference, for measurement, to measure the absorbance value of the solution
A3. The absorbance value of hydrofluoric acid plus boric acid is A3 - A1.
9.2.3 Determination of soluble silicon
The reagent blank is A2 - A1. When measuring total silicon, the reagent blank is
A2 + A3 - 2A1.
9.3 Water sample determination
9.3.1 Determination of soluble silicon