HG/T 2156-1991 Determination of anionic surfactants in industrial circulating cooling water - Methylene blue spectrophotometric method
Some standard content:
Chemical Industry Standard of the People's Republic of China
Determination of anionic surfactants in industrial circulating cooling water - Methylene blue spectrophotometric method
HG/T 2156--91
This standard refers to the international standard 1S07875/1:1984 "Water quality - Determination of surfactants - Part 1: Determination of anionic surfactants by methylene blue spectrophotometric method". Subject content and scope of application
This standard specifies the method for determining anionic surfactants in industrial circulating cooling water. This standard is applicable to the determination of anionic surfactants (collectively referred to as methylene blue active substances) in industrial circulating cooling water with a content of 0.05~~2.0mg/L.
This standard is not applicable to the determination of anionic surfactants when the concentration (mg/I.) of anionic substances such as organic sulfates or sulfonates and cationic substances such as quaternary ammonium compounds exceeds 15% and 8% of the concentration of linear alkylbenzene sodium sulfonate, respectively. 2 Reference standards
GB603 Preparation of preparations and products used in chemical reagent test methods GB6682 Laboratory water specifications
3 Method summary
Cationic dye methylene blue reacts with anionic surfactants (collectively referred to as methylene blue active substances) to form a blue ion association complex, which is extracted with chloroform and the absorbance is measured at 652nm. The concentration of the anionic surfactant is obtained from the working curve. 4 Reagents and materials
In the analytical method, except for special provisions, only analytically pure reagents and grade 3 water that meets the requirements of GB6682 should be used. The preparations and products used in the test are prepared in accordance with the provisions of GB603. 4.1 Sodium hydroxide (GB629) solution: 40g/L; 4.2 Sulfuric acid (G625)
4.3 Sulfuric acid (GB625) solution: 1+35;
4.4 Chloroform (GB682);
Methanol (GB 683);
Sodium dihydrogen phosphate dihydrate (GB1267): Hydrochloric acid (GB622)-Z alcohol (GB679) solution: 3+17;47
Formaldehyde (GB685) solution: 1+99;
4.9 Sodium linear alkylbenzene sulfonate stock solution: 1.00mg/mml. Weigh 0.100g of linear alkylbenzene sulfonate sodium standard (its alkyl carbon chain is between Co and C13, the average carbon number is 12, and the average relative molecular mass is 344.4), accurately to 0.001g, dissolve in 50mL of water, transfer all to a 100mL volumetric flask, dilute to the mark with water, shake well and store in a 4C refrigerator, the validity period is two months. 4.10 Linear alkylbenzene sulfonate sodium standard solution: 10.0gg/ml. Approved by the Ministry of Chemical Industry of the People's Republic of China on September 16, 1991 688
Implementation on January 1, 1992
HG/T 215691
Pipette 10.00mL linear alkylbenzene sulfonate sodium stock solution (4.9) into a 1000mL volumetric flask, dilute to the mark with water, shake well. Prepare on the same day.
4.11 Methylene blue (HGB3394) solution:
Weigh 50.0g sodium dihydrogen phosphate dihydrate (4.6) accurately to 0.1g, dissolve in 300mL water, transfer to a 1000mL volumetric flask, slowly add 6.8ml sulfuric acid (4.2), shake to hook; weigh another 30.0mg methylene blue (HGB3394) accurately to 0.1g, dissolve in 50mL water, transfer to the above volumetric flask, dilute to scale with water, shake well. Store in a brown bottle. 4.12 Washing solution:
Weigh 50.0g sodium dihydrogen phosphate dihydrate (4.6) accurately to 0.1g, dissolve in 300mL water, transfer to a 1000mL volumetric flask, slowly add 6.8ml sulfuric acid (4.2), dilute to scale with water, shake to hook. 4.13 Phenolic acid (GB10729) indicator: 10.0g/L ethanol solution. 4.14 Glass wool or absorbent cotton:
After extracting with chloramine (4.4) in Soxhlet extractor (5.3) for 4 hours, take out and dry, and store in a clean glass bottle for later use. 5 Instruments and equipment
5.1 Spectrophotometer
5.2 Separatory funnel: 250mlL. It is best to use a polytetrafluoroethylene piston; 5.3 Soxhlet extractor.
Note: The glassware III used should be thoroughly washed with water before use, then cleaned with hydrochloric acid ethanol solution (4.7), and finally rinsed with water. 6 Vegetable samples
6.1 The sampling bottle should be a clean glass bottle that has been cleaned with methanol (4.5). 6.2 If the sample cannot be measured in time, the sample should be handled as follows. 6.2.1 If the storage period of the sample is within 24 hours, the sample can be stored in a 4°C refrigerator. 6.2.2 If the storage period is within 4 days, formaldehyde solution (4.8) can be added. 6.2.3 If the storage period is within 8 days, the water sample needs to be saturated with oxygen (4.4). 7 Analysis steps
7.1 Drawing of working curve
7.1.1 Take 10 component liquid funnels (5.2), add 100.99, 97, 95, 93.91, 89, 87, 85 and 80 mL of water respectively, and then transfer 0, 1.00, 3.00, 5.00, 7.00, 9.00, 11.00, 13.00, 15.00 and 20.00 ml of linear alkylbenzene sulfonate sodium standard solution (4.10) respectively, and shake well.
7.1.2 Add 1 drop of phenolic acid indicator (4.13), add sodium hydroxide solution (4.1) drop by drop until the aqueous solution turns pink, then add sulfuric acid solution (4.3) until the pink color just disappears.
7.1.3 Add 25.0 mL of methylene blue solution (4.11), shake and then add 10 mL of fluoroform (4.4), shake vigorously for 30 seconds, and let stand to separate. 7.1.4 Place the chloroform layer in a second separatory funnel that has been pre-filled with 50 mL of washing solution (4.12). Repeat the extraction twice, using 10 mL of chloroform (4.4) each time. Collect each chloroform extract into the second separatory funnel, shake vigorously for 30 seconds, and let stand to separate. Pass the chloroform layer through glass wool or absorbent cotton (4.14) and collect it in a 50 mL volumetric flask: extract the washing solution twice with chloroform (4.4) (5 mL each time), and this chloroform layer is also added to the volumetric flask. Dilute to the mark with fluoroform (4.4), shake well, and prepare for determination. 7.1.5 Using the blank test solution as reference, measure the absorbance at 652am with a 10mm colorimetric III. 7.1.6 Use the measured absorbance as the ordinate and the corresponding linear alkylbenzene sulfonate sodium content (grid) as the abscissa to draw a working curve. 7.2 Sample volume
The sample volume can be selected according to Table 1.
HG/T 2156-91
Table 1 Selection of sample volume
Expected methylene blue active substance concentration, mg/L0. 05~2. 0
Sample volume, mi.
When the expected methylene blue active substance concentration exceeds 2mg/mL, select the sample volume according to the above table and dilute with water to 100mL. 7.3 Determination
7.3.1 If there is suspended matter in the water sample, the water sample should be filtered through medium-speed qualitative filter paper before determination. 7.3.2 Transfer the sample to the separator and operate according to steps 7.1.2-~7.1.5. Check the content of linear alkylbenzene sodium sulfonate from the working curve (7.1).
7.33 If the blue color in the water phase becomes lighter or disappears, it means that the concentration of methylene blue active substance in the water sample exceeds the expected amount, so that all the added methylene blue is reacted. The sample should be discarded and a smaller sample should be re-analyzed. 7.3.4 If the content of anionic surfactant in the water sample is low, the total amount of cyanoform used for extraction can be reduced to 25mL. The extraction amounts for the three extractions are 10, 5 and 5mL respectively, and then 3-~4mL chloroform is used to extract the wash solution. At this time, the detection limit can reach 0.02mg/L. 7.3.5 The same batch of oxyform, methylene blue solution and washing liquid shall be used for the drawing and determination of the working curve. 7.3.6 When rapid analysis is required, the simplified method of single extraction can be used. The efficiency of single extraction is about 90% of the extraction efficiency of this method. 8 Expression of analysis results
The content X of methylene blue active substance (calculated as linear sodium alkylbenzene sulfonate with an average relative molecular mass of 344.4) in the sample expressed in mg/L is calculated according to formula (1):
Wherein: m is the content of linear sodium alkylbenzene sulfonate obtained from the working curve.ugV is the volume of the sample, mL.
The result shall be expressed with three significant figures when ≥1mg/L; and with two significant figures when <1mg/L. 9 Allowable difference
The repeatability r has a stable relationship with the content of methylene blue active substance X in water: r0.044
The reproducibility has a linear relationship with X:
Additional instructions: bzxz.net
R 0. 035 + 0.011X
This standard was proposed by the Department of Science and Technology of the Ministry of Chemical Industry of the People's Republic of China. This standard is under the technical jurisdiction of Tianjin Chemical Industry Research Institute. This standard was drafted by Nanjing Institute of Chemical Technology. The main drafters of this standard are Wang Zhenpu, Yao Cheng, Qian Yuehong and Shen Yongcun. 590
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