HJ 1226-2021

Determination of Sulfide in Water Quality Methylene Blue Spectrophotometric Method (English Version)

Standard No.

HJ 1226-2021

Language

Chinese, Available in English version

Release Date

2021

Published By

Professional Standard - Environmental Protection

Latest

HJ 1226-2021

Scope

This standard specifies the spectrophotometric determination of methylene grass contamination of sulfide in water. This standard is applicable to the determination of sulfur in surface water, ground water secondary chlorine and sewage, industrial wastewater and wash water. When the sampling volume is 200 ml and a 10mm nm light path colorimeter is used, the detection limit of the method is 0.01mgL and the lower determination limit is 0.04 mg/L; when a 30 mm light path colorimeter is used, the method detection limit is 0.003 mgL. The lower limit of determination is 0.012 mg/L. Note: The 30 mm area colorimeter is suitable for the lower area or the stool and the determination of Wang Benshou's Liang and seawater. The pretreatment method should be the "acidification-garlic drink-absorption" method.

Introduction

Background of Standard Revision and Technical Evolution

This standard replaces GB/T 16489-1996. The main revisions include: Optimization of method detection limit (10mm cuvette reduced to 0.01mg/L), Expansion of pretreatment methods (new acidification-distillation-absorption method), Strengthening of quality control (adding quality assurance chapter) and Safety specification (supplementing waste disposal requirements). The revision was led by the Environmental Standards Institute of the Ministry of Ecology and Environment in accordance with the requirements of the Environmental Protection Law of the People's Republic of China and other laws and regulations.

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Core Method Principle

Sulfides in the sample are acidified to generate hydrogen sulfide, which is separated by nitrogen purging or distillation, absorbed by sodium hydroxide solution and reacted with N,N-dimethyl-p-phenylenediamine to generate methylene blue, and the absorbance is measured at a wavelength of 665nm.

Components	Reaction Conditions	Products
S2?	Acidic Environment	H?S
H?S	NaOH Absorption	Na?S
Na?S+Color Developer	Fe3? Catalysis	Methylene Blue

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Comparison of Key Technical Parameters

Parameters	HJ 1226-2021	GB/T 16489-1996
Detection limit	0.003-0.01mg/L	0.005mg/L
Pretreatment method	2 types (air blowing/distillation)	Air blowing method only
Scope of application	Added seawater testing	Does not include seawater
Quality control requirements	12 specific clauses	No system regulations

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Key operating points

1. Sample fixation: Add zinc acetate solution (1mol/L) and antioxidant on site and store at 4℃ for ≤4 days
2. Interference elimination: Pretreatment is required when NO?? concentration is ＞2mg/L (in terms of N), and the allowable amount of SCN? is up to 900mg/L
3. Color development control: The pH value (1.5-2.0) of the color development reaction must be strictly controlled, and the reaction time is 10±0.5min
4. Equipment calibration: The spectrophotometer needs to be regularly calibrated for wavelength accuracy (±1nm) and absorbance linearity

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Implementation suggestions

• Seawater detection: A 30mm cuvette must be used in combination with the acidification-distillation method to avoid salinity interference
• High concentration samples: When the absorbance is greater than 0.8, it is recommended to dilute and then retest using a 10mm cuvette
• Quality control nodes: Each batch of samples should contain 10% parallel samples and spiked samples, and the recovery rate should be controlled at 60%-120%
• Safety protection: Operation of N,N-dimethyl-p-phenylenediamine should be carried out in a fume hood