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GB/T 1601-2023 PDF in English


GB/T 1601-2023 (GB/T1601-2023, GBT 1601-2023, GBT1601-2023)
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GB/T 1601-2023: PDF in English (GBT 1601-2023)

GB/T 1601-2023
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 65.100
CCS G 23
Replacing GB/T 1601-1993
Determination method of pH value for pesticides
ISSUED ON: SEPTEMBER 07, 2023
IMPLEMENTED ON: APRIL 01, 2024
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 5
3 Terms and definitions ... 5
4 Test method ... 5
Appendix A (Normative) pH standard buffer solution ... 8
Determination method of pH value for pesticides
1 Scope
This document describes determination method of pH value for pesticides.
This document applies to the determination of pH value for pesticide (technical
concentrate) and preparation.
2 Normative references
The following documents are referred to in the text in such a way that some or all of
their content constitutes requirements of this document. For dated references, only the
version corresponding to that date is applicable to this document; for undated references,
the latest version (including all amendments) is applicable to this document.
GB/T 8170-2008, Rules of rounding off for numerical values & expression and
judgment of limiting values
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
pH value
The negative logarithm of hydrogen ion activity expressed in mol/L.
3.2
pH standard buffer solution
Buffer solution prepared using pH reference reagent according to specified method.
4 Test method
Warning: Personnel using this document shall have practical experience in
laboratory work. This document does not address all safety concerns. It is the
user's responsibility to take appropriate safety and health measures.
4.1 General provisions
The judgment of the inspection results shall be carried out in accordance with the
provisions of 4.3.3 in GB/T 8170-2008.
4.2 Method summary
Use a pH meter to measure the pH of the aqueous sample solution or undiluted water-
based preparation.
4.3 Reagents and solutions
4.3.1 pH standard buffer solution: Either commercial pH standard buffer solution, or
self-prepared pH reference reagent can be used. The preparation process is carried out
in accordance with Appendix A.
4.3.2 pH reference reagents: potassium tetraoxalate dihydrate, potassium hydrogen
phthalate, disodium hydrogen phosphate, potassium dihydrogen phosphate, disodium
borate decahydrate, calcium hydroxide.
4.3.3 Water: distilled water or deionized water, which shall be re-boiled and cooled to
room temperature before use, with a pH value of 5.5 ~ 7.0.
4.4 Apparatus
4.4.1 pH meter: with temperature compensation function, available for at least two-
point calibration.
4.4.2 Electrode: stored according to instructions for use.
4.5 Test steps
4.5.1 Calibration of pH meter
According to the instructions for use of the pH meter, select an appropriate standard
buffer solution to calibrate the pH meter at least two points, so that the pH value of the
sample solution is between the two points.
4.5.2 Determination of pH value
4.5.2.1 Dilution method (applicable to all pesticide products)
4.5.2.1.1 Preparation of sample solution
Weigh 1.0 g (accurate to 0.001 g) of the sample; place it in a 100 mL stoppered
measuring cylinder containing 50 mL of water; then, use water to make up to 100 mL;
shake vigorously until the sample is fully mixed or dispersed; then, transfer to a 200
mL beaker; let stand for 1 minute.
4.5.2.1.2 Determination
Appendix A
(Normative)
pH standard buffer solution
A.1 Preparation of pH standard buffer solution
A.1.1 Oxalate pH standard buffer solution: Weigh 12.71 g (accurate to 0.001 g) of
potassium trihydrogen oxalate that has been baked to constant weight at 54 ℃ ± 3 ℃;
place it in a 1 000 mL volumetric flask; use water to dissolve it and dilute it to the mark;
shake well.
A.1.2 Potassium hydrogen phthalate pH standard buffer solution: Weigh 10.21 g
(accurate to 0.001 g) of potassium hydrogen phthalate that has been baked at 110 ℃ ±
5 ℃ to constant weight; place it in a 1 000 mL volumetric flask; add water to dissolve
and dilute to the mark; shake well.
A.1.3 Phosphate pH standard buffer solution: Weigh 3.55 g (accurate to 0.001 g) of
disodium hydrogen phosphate that has been baked at 115 ℃ ± 5 ℃ to constant weight
and 3.40 g (accurate to 0.001 g) of potassium dihydrogen phosphate that has been baked
at 115 ℃ ± 5 ℃ to constant weight; place them in a 1 000 mL volumetric flask; use
water to dissolve and dilute to the mark; shake well.
A.1.4 Disodium tetraborate pH standard buffer solution: Weigh 19.07 g (accurate to
0.001 g) of disodium tetraborate decahydrate; place it in a 1 000 mL volumetric flask;
use water to dissolve and dilute to the mark; shake well.
A.1.5 Calcium hydroxide pH standard buffer solution: At 25 °C, use carbon dioxide-
free water and excess calcium hydroxide to make a saturated solution through full
shaking; take the supernatant for use. Since the buffer solution is a saturated calcium
hydroxide solution at 25 °C; therefore, it shall be confirmed before use whether the
temperature of the solution is 25 °C. If not, adjust the temperature to 25 °C, and then
take the supernatant after dissolution and equilibrium. When storing, carbon dioxide in
the air shall be prevented from entering. Once turbidity occurs, discard it and re-prepare.
A.2 Temperature correction of pH value of pH standard buffer solution
The pH correction values of various pH standard buffer solutions under different
temperature conditions are shown in Table A.1.
......
 
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.