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HJ 670-2013: Water quality. Determination of orthophosphate and total phosphorus. Continuous flow analysis(CFA) and Ammonium molybdate spectrophotometry
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Water quality. Determination of orthophosphate and total phosphorus. Continuous flow analysis(CFA) and Ammonium molybdate spectrophotometry
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HJ 670-2013
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Basic data | Standard ID | HJ 670-2013 (HJ670-2013) | | Description (Translated English) | Water quality. Determination of orthophosphate and total phosphorus. Continuous flow analysis(CFA) and Ammonium molybdate spectrophotometry | | Sector / Industry | Environmental Protection Industry Standard | | Classification of Chinese Standard | Z16 | | Classification of International Standard | 13.060 | | Word Count Estimation | 12,166 | | Quoted Standard | GB/T 11893; HJ/T 91; HJ/T 164 | | Regulation (derived from) | Ministry of Environmental Protection Notice No. 63 of 2013 | | Issuing agency(ies) | Ministry of Ecology and Environment | | Summary | This standard specifies the determination of total phosphorus in water and continuous flow of phosphate - molybdate spectrophotometry. This standard applies to surface water, groundwater measurement, sewage and industrial effluent phosphate and total phos | HJ 670-2013: Water quality. Determination of orthophosphate and total phosphorus. Continuous flow analysis(CFA) and Ammonium molybdate spectrophotometry
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Water quality.Determination of orthophosphate and total phosphorus.Continuous flow analysis (CFA) and Ammonium molybdate spectrophotometry
National Environmental Protection Standard of the People's Republic
Determination of water quality phosphate and total phosphorus
Continuous flow-ammonium molybdate spectrophotometry
Water quality-Determination of orthophosphate and total
phosphorus-Continuous flow analysis (CFA) and Ammonium molybdate
2 0 1 3 - 1 0 - 2 5 released
2 0 1 4 - 0 1 - 0 1 implementation
Ministry of Environmental Protection released
Content
Foreword. II
1 Scope.1
2 Normative references.1
3 Terms and Definitions..1
4 Principle of the method 1
5 interference and elimination..2
6 Reagents and materials..3
7 instruments and equipment..4
8 samples..4
9 Analysis step 5
10 Results calculation and representation..5
11 Precision and Accuracy..6
12 Quality Assurance and Quality Control 6
13 Notes.7
Foreword
To implement the Environmental Protection Law of the People's Republic of China and the Law of the People's Republic of China on Water Pollution Prevention and Control, to protect the environment,
This standard is formulated to ensure human health and to regulate the determination of phosphate and total phosphorus in water.
This standard specifies the continuous flow-ammonium molybdate spectrophotometric method for the determination of phosphate and total phosphorus in water.
This standard is the first release.
This standard was formulated by the Science and Technology Standards Department of the Ministry of Environmental Protection.
This standard is mainly drafted by. Suzhou Environmental Monitoring Center Station.
This standard is verified by. Jiangyin Environmental Monitoring Station, Taihu Basin Water Environment Monitoring Center, and Jilin City Environmental Protection Monitoring
Station, Tianjin Water Environment Monitoring Center and Yellow River Basin Water Environment Monitoring Center and Suzhou Environmental Monitoring Center Station.
This standard was approved by the Ministry of Environmental Protection on October 25,.2013.
This standard has been implemented since January 1,.2014.
This standard is explained by the Ministry of Environmental Protection.
Water quality - Determination of phosphate and total phosphorus - Continuous flow - Ammonium molybdate spectrophotometric method
1 Scope of application
This standard specifies the continuous flow-ammonium molybdate spectrophotometric method for the determination of phosphate and total phosphorus in water.
This standard applies to the determination of phosphate and total phosphorus in surface water, groundwater, domestic sewage and industrial wastewater.
When the detection optical path is 50mm, the detection limit of the method for determining phosphate (in terms of P) is 0.01mg/L, and the measurement range is
0.04~1.00mg/L; the detection limit of total phosphorus (in P) is 0.01mg/L, and the measurement range is 0.04~5.00mg/L.
2 Normative references
The contents of this standard refer to the terms in the following documents. For undated references, the valid version applies to this
standard.
GB 11893 Determination of total phosphorus in water - Ammonium molybdate spectrophotometric method
HJ/T 91 Surface Water and Wastewater Monitoring Technical Specifications
HJ/T 164 Technical Specifications for Groundwater Environmental Monitoring
3 Terms and definitions
The following terms and definitions apply to this standard.
Phosphate (orthophosphate)
Refers to the sum of orthophosphates (including PO43-, HPO42-, H2PO4-) in the samples measured under the conditions specified in this standard.
In P.
4 Principle of the method
4.1 Working principle of continuous flow analyzer
The sample and the reagent enter the chemical reaction module under the push of the peristaltic pump, and continuously flow in the closed pipeline, and are pressed by the bubble.
They are regularly spaced at regular intervals and mixed and reacted in a specific order and proportion. After the color development is completed, they enter the flow detection cell.
Photometric detection.
4.2 Principle of chemical reaction
4.2.1 Determination of phosphate
The orthophosphate in the sample reacts with ammonium molybdate to form a phosphorus molybdenum heteropoly acid in an acidic medium in the presence of a cerium salt, and the combination
The material was immediately reduced by ascorbic acid to form a blue complex, and the absorbance was measured at a wavelength of 880 nm. See the workflow diagram, see
figure 1.
4.2.2 Determination of total phosphorus
The sample was added with potassium persulfate solution, and subjected to ultraviolet digestion and acidic hydrolysis at 107 ° C ± 1 ° C. All forms of phosphorus were completely oxidized.
For the determination of normal phosphate and orthophosphate, see 4.2.1. Refer to the work flow chart, as shown in Figure 2.
1 Peristaltic pump 2 Mixed reaction ring 3 Dialyzer (unit) 4 Heating bath (circle) 40 °C
5 Flow detection cell 50mm 880nm 6 Degassing S Sample 0.8ml/min G Air
R1 acid reagent I0.32ml/min (6.12) R2 surfactant solution 0.80ml/min (6.19) W waste liquid
R3 ammonium molybdate solution 0.23ml/min (6.16) R4 ascorbic acid solution 0.23ml/min (6.18)
Figure 1 Flow chart of continuous flow-ammonium molybdate spectrophotometric determination of phosphate
1 peristaltic pump 2 mixed reaction ring 3 dialyzer (unit) 4 heating bath (circle) 107 ° C, 40 ° C
5 UV digestion device 6 bubble removal 7 flow detection cell 50mm 880nm S sample 0.80ml/min
R1 potassium persulfate digestion reagent 0.32ml/min (6.15) R2 acid reagent II 0.16ml/min (6.13) G air
R3 alkali reagent 0.16ml/min (6.14) R4 surfactant solution 0.80ml/min (6.19) W waste liquid
R5 ammonium molybdate solution 0.23ml/min (6.16) R6 ascorbic acid solution 0.23ml/min (6.18) ReS secondary injection 1.00ml/min
Figure 2 Flow chart of continuous flow-ammonium molybdate spectrophotometric determination of total phosphorus
5 interference and elimination
5.1 Arsenic, chromium and sulfur in the sample will interfere with the determination. For the elimination method, see GB 11893.
5.2 The turbidity or chromaticity of the sample will interfere with the measurement and can be eliminated by the dialysis unit. See Figure 1, 2 (3).
5.3 High concentrations of organic matter in the sample will consume potassium persulfate oxidant, making the determination of total phosphorus lower, which can be diluted
Samples to eliminate the effects.
5.4 When the sample contains more solid particles or suspended solids, it should be shaken, sampled, diluted properly, and then homogenized.
After injection.
6 reagents and materials
Analytically pure reagents in accordance with national standards were used for analysis, unless otherwise stated.
Deionized water with a rate of less than 0.5 μS/cm (25 ° C).
6.1 Sulfuric acid (H2SO4). ρ(H2SO4) = 1.84 g/ml.
6.2 Sodium hydroxide (NaOH).
6.3 Potassium persulfate (K2S2O8).
6.4 Ammonium molybdate ((NH4)6Mo7O24·4H2O).
6.5 Potassium bismuth tartrate (K(SbO)C4H4O6·1⁄2H20).
6.6 Ascorbic acid (C6H8O6).
6.7 Potassium dihydrogen phosphate (KH2PO4). excellent grade, dried at 105 ° C ± 5 ° C constant weight, stored in a desiccator.
6.8 Sodium pyrophosphate (Na4P2O7·10H2O). sealed and stored.
6.9 Pyridoxal 5-phosphate (C8H10NO6P·H2O). purity greater than 95%. Store at 2 ° C ~ 8 ° C sealed.
6.10 Sodium (di)dodecyl sulfate sodium diphenoxide (FFD6). commercial solution, ω = 45~47%.
6.11 Sodium hypochlorite (NaClO). a commercial solution containing 100~140g/L of available chlorine.
6.12 Acid Reagent I.
14 ml of sulfuric acid (6.1) was slowly added to about 800 ml of water. After cooling, add 2ml FFD6 (6.10), add
Dilute water to 1000 ml and mix.
6.13 Acid Reagent II.
A quantity of 160 ml of sulfuric acid (6.1) was slowly added to about 800 ml of water. After cooling, add 2ml FFD6 (6.10), add
Dilute water to 1000 ml and mix.
6.14 Alkali reagent.
Weigh 160g of sodium hydroxide (6.2) dissolved in an appropriate amount of water, after cooling, add 2ml of FFD6 (6.10), dilute to 1000ml with water,
And mix well.
6.15 potassium persulfate digestion reagent
Add.200 ml of sulfuric acid (6.1) to an appropriate amount of water, add 12 g of potassium persulfate (6.3), dissolve and cool to room temperature.
Dilute to 1000 ml with water and mix. The solution is stored at room temperature and protected from light for 1 month.
6.16 Ammonium molybdate solution
Measure 40 ml of sulfuric acid (6.1) dissolved in 800 ml of water. After cooling, add 4.8 g of ammonium molybdate (6.4) and add 2 ml of FFD6.
(6.10), dilute to 1000ml with water and mix. The solution was stored at 4 ° C and was stable for 1 month.
6.17 Potassium tartrate storage solution
Weigh 0.30g of bismuth potassium tartrate (6.5), dissolve in 80ml of water, dilute to 100ml with water and mix well, in brown with stopper
In the glass bottle. The solution was stored at 4 ° C and was stable for 2 months.
6.18 Ascorbic acid solution
Weigh 18g ascorbic acid (6.6), dissolve in 800ml of water, add 20ml potassium bismuth tartrate stock solution (6.17),
Dilute to 1000 ml with water and mix well in a brown stoppered glass bottle. The solution was stored at 4 ° C and was stable for 7 days.
6.19 Surfactant solution
Add 2 ml of FFD6 (6.10) in 1000 ml of water and mix. The solution was stored at 4 ° C and was stable for 7 days.
6.20 Standard stock solution of potassium dihydrogen phosphate. ρ(P)=1000mg/L
Weigh 4.390g of potassium dihydrogen phosphate (6.7), dissolve in an appropriate amount of water, transfer to a 1000ml volumetric flask, add 2.5ml
Sulfuric acid (6.1), make up to volume with water and mix and store in a stoppered glass reagent bottle. The solution can be stored for 6 months at 4 °C.
Or buy a commercially available certified standard solution directly.
6.21 Potassium dihydrogen phosphate standard intermediate solution. ρ(P) = 100.0mg/L
Measure 10.00 ml of potassium dihydrogen phosphate standard stock solution (6.20) in a 100 ml volumetric flask, dilute to volume with water and mix. The solution
The solution can be stored for 3 months at 4 °C.
6.22 Potassium dihydrogen phosphate standard use solution I. ρ (P) =10.0 mg/L
Measure 10.00 ml of potassium dihydrogen phosphate standard intermediate solution (6.21) in a 100 ml volumetric flask, dilute to volume with water and mix. The solution
The solution can be stored for 1 month at 4 °C.
6.23 Potassium dihydrogen phosphate standard use solution II. ρ (P) = 2.50mg/L
The appropriate amount of potassium dihydrogen phosphate standard stock solution (6.20) was weighed and prepared by dilution with water. Available at the time of use.
6.24 Standard stock solution of sodium pyrophosphate. ρ(P) =500mg/L
Weigh 3.600g sodium pyrophosphate (6.8), dissolve in an appropriate amount of water, transfer to a 1000ml volumetric flask, and dilute and mix with water.
uniform. The solution can be stored for 3 months at 4 °C.
6.25 Standard use solution of sodium pyrophosphate (test hydrolysis efficiency). ρ(P) = 2.50mg/L
A suitable amount of sodium pyrophosphate stock solution (6.24) was weighed and prepared by dilution with water. Available at the time of use.
6.26 Standard stock solution of pyridoxal 5-phosphate. ρ(P) =500mg/L
Weigh 0.8561 g (100% by purity) of pyridoxal 5-phosphate (6.9), dissolve in an appropriate amount of water, and transfer to.200 ml.
In a measuring flask, make up to volume with water and mix in a brown stoppered glass bottle. The solution can be stored for 3 months at 4 °C.
6.27 Standard use solution of pyridoxal 5-phosphate (test UV digestion efficiency). ρ(P) = 2.50mg/L
An appropriate amount of pyridoxal 5-phosphate stock solution (6.26) was weighed and prepared by dilution with water. Available at the time of use.
6.28 Cleaning solution (sodium hypochlorite solution).
A suitable amount of a commercially available sodium hypochlorite solution (6.11) was weighed and diluted with water to a solution having an effective chlorine content of about 1.3%.
7 Instruments and equipment
7.1 Continuous Flow Analyzer. Autosampler (with homogenous components), chemical analysis unit (ie chemical reaction module, by
Multi-channel peristaltic pump, manifold, pump tube, mixed reaction ring, UV digestion device, dialyzer, heating coil, etc.), test list
Element (detection pool optical path is 50mm), data processing unit.
7.2 Analytical balance. Accuracy is 0.0001g.
7.3 Common instruments and equipment used in general laboratories.
8 samples
Samples were collected and stored in accordance with the relevant regulations of HJ/T 91 and HJ/T 164.
Prior to sampling, all vessels in contact with the sample were rinsed with water and the samples were collected in cleaned polyethylene or glass vials. use
The water sample for the determination of phosphate is sampled and stored in the dark at 0-4 ° C for 24 h. Water sample for determination of total phosphorus, after collection
Sulfuric acid (6.1) should be added immediately to pH ≤ 2, and stored at room temperature for 24 hours; frozen at -20 ° C for 1 month.
Note. For samples with less phosphorus (phosphate or total phosphorus concentration ≤ 0.1mg/L), polyethylene bottles should not be stored, except for cryopreservation.
9 Analysis steps
9.1 Instrument Commissioning
Install the analysis system, set the operating parameters, and operate the instrument according to the instrument manual. After starting the machine, first replace the reagent with water, check
Check the tightness of the flow path and the smoothness of the liquid flow. After the baseline is stabilized (about 20 min), the system starts to enter the reagent.
After the baseline is stabilized again, proceed to 9.2~9.4.
The determination of phosphate is generally carried out using a phosphate analysis module, see Figure 1, which can also be determined using an analytical module for total phosphorus.
See 13.7 for the method.
9.2 Calibration
9.2.1 Preparation of the calibration series
Phosphate calibration curve. separately take appropriate amount of potassium dihydrogen phosphate standard use solution (6.22), dilute to volume with water until
100 ml, a standard series of 6 concentration points was prepared. The phosphate concentrations were. 0.00 mg/L, 0.05 mg/L, 0.10 mg/L,
0.25 mg/L, 0.50 mg/L and 1.00 mg/L.
Total phosphorus calibration curve. separately take appropriate amount of potassium dihydrogen phosphate standard solution (6.21, 6.22), dilute to 100ml with water,
A standard series of 6 concentration points was prepared. The total phosphorus concentrations were. 0.00 mg/L, 0.05 mg/L, 0.50 mg/L, 1.00 mg/L,
2.50 mg/L and 5.00 mg/L.
Note. When analyzing clean surface water, the linear range can be appropriately reduced.
9.2.2 Drawing of the calibration curve
Measure the appropriate amount of standard series solution (9.2.1), place it in the sample cup, and sample and measure according to the procedure. Test
The fixed signal value (peak height) is the ordinate, and the corresponding phosphate or total phosphorus mass concentration (in P) is plotted on the abscissa.
curve.
9.3 Determination
The measurement of the sample was carried out under the same conditions as in the drawing of the calibration curve.
Note. If the sample phosphate or total phosphorus content exceeds the calibration curve range, the appropriate amount of sample should be diluted and measured on the machine.
9.4 Blank test
Replace the sample with experimental water and perform a blank test in accordance with step 9.3.
10 Calculation and representation of results
10.1 Calculation of results
The mass concentration of phosphate or total phosphorus (in terms of P, mg/L) in the sample is calculated according to formula (1).
Yaf
ρ −= × (1)
In the formula.
Ρ--the mass concentration of phosphate or total phosphorus in the sample, mg/L;
y -- determine the signal value (peak height);
a -- the intercept of the calibration curve equation;
b -- the slope of the calibration curve equation;
f -- dilution factor.
10.2 Results are expressed
When the measurement result is less than 1.00mg/L, the result is retained to the second place after the decimal point; when it is greater than or equal to 1.00mg/L, the knot
If you keep three significant digits.
11 Precision and accuracy
11.1 Precision
Six laboratories tested the uniform samples with phosphate concentrations of 0.10mg/L, 0.50mg/L, and 0.90mg/L.
The relative standard deviations in the room are. 0.5%~4.1%, 0.3%~1.6%, 0.4%~2.4%; the relative standard deviation between laboratories
The differences were. 5.4%, 1.2%, 1.7%; the repeatability limits were. 0.01 mg/L, 0.02 mg/L, 0.03 mg/L; reproducibility
The limits are. 0.02 mg/L, 0.02 mg/L, 0.05 mg/L.
Six laboratories tested the uniform samples with total phosphorus concentrations of 0.50 mg/L, 2.5 mg/L, and 4.5 mg/, respectively.
The relative standard deviations in the room are. 0.8%~3.8%, 0.4%~1.9% and 0.2%~1.2%; the relative standard deviation between laboratories
They were. 1.8%, 3.1%, 2.7%; the repeatability limits were. 0.03 mg/L, 0.08 mg/L, 0.09 mg/L; reproducibility limit
They were. 0.04 mg/L, 0.23 mg/L, and 0.36 mg/L, respectively.
11.2 Accuracy
11.2.1 Phosphate
6 laboratory-certified reference materials with phosphate concentrations of 0.30 mg/L ± 0.02 mg/L and 0.70 mg/L ± 0.04 mg/L
The measured values were. 0.0%~2.7%, 0.0%~2.2%, and the relative error final values were. 1.3%±2.2%,
0.9% ± 1.9%.
Phosphate concentrations in the six laboratories ranged from 0.05 mg/L to 0.29 mg/L, from 0.21 mg/L to 0.43 mg/L, and from 0.52 mg/L to 0.72 mg/L.
The three actual samples were tested by spiked recovery. The recoveries of the spiked samples were 94.5%~109% and 99.3%~104%, respectively.
95.0%~104%; the final values of the spiked recovery were. 100%±12%, 102%±3.6%, and 99.1%±6.8%.
11.2.2 Total phosphorus
Six laboratories conducted standard substances with total phosphorus concentrations of 0.22 mg/L ± 0.01 mg/L and 1.58 mg/L ± 0.06 mg/L.
The relative errors are. 0.5%~2.3%, 0.0%~1.3%; the relative error final values are. 1.2%±1.5%, 0.5%
±1.0%.
The total phosphorus concentration in 6 laboratories was 0.15mg/L~1.33mg/L, 1.15mg/L~1.61 mg/L, 1.97 mg/L~4.16 mg/L.
The three actual samples were spiked and recovered. The recoveries were 96.0%~105% and 92.8%~104%.
95.6%~103%; the final values of the spiked recovery were. 100%±6.7%, 98.6%±7.9%, 100%±5.8%.
12 Quality Control and Quality Assurance
12.1 Blank test
At least 2 blank samples shall be measured for each batch of samples, and the blank value shall not exceed the method detection limit. Otherwise, you should find out the reason and re
The sample can only be determined after analysis until it is qualified.
12.2 Calibration validity check
A calibration curve must be drawn for each batch of samples. The correlation coefficient of the calibration curve is γ ≥ 0.995.
For each sample analyzed, a calibration curve intermediate concentration solution is used for calibration verification, and the measurement results are relatively biased.
The difference should be ≤ 5%, otherwise the calibration curve should be redrawn.
12.3 Precision Control
At least 10% of the parallel samples should be determined for each batch of samples. When the number of samples is less than 10, at least one parallel sample should be determined.
When the phosphate or total phosphorus concentration of the sample is ≤0.04mg/L, the relative deviation of the parallel samples is ≤25%; when the phosphate or total phosphorus is concentrated
When the degree is >0.04 mg/L, the relative deviation of the parallel samples is ≤10%.
12.4 Accuracy Control
Each batch of samples must be subjected to 10% spiked recovery samples. When the number of samples is less than 10, at least one spiked recovery should be determined.
Sample, spiked recovery should be controlled between 80~120%.
Or each batch of samples with at least one known concentration of quality control samples, the test results should be within the range of uncertainty given.
12.5 System Performance Check
Regularly use the sodium pyrophosphate standard use solution (6.25) to verify the hydrolysis efficiency of the method, using pyridoxal 5-phosphate standard
The digestion efficiency of the solution (6.27) verification method is generally 1 time in 2 weeks.
Calibrate the system (9.2) first. Then, parallel analysis of sodium pyrophosphate standard use solution (6.25) or pyridoxal 5-phosphate standard
Calculate the hydrolysis or digestion efficiency R,R according to formula (2) using solution (6.27) and potassium dihydrogen phosphate standard solution (6.23).
Should be greater than 90%.
100%R ρρ= × (2)
In the formula.
R--hydrolysis or digestion efficiency, %;
ρ1--Sodium pyrophosphate standard use solution (6.25) or pyridoxal 5-phosphate standard use solution (6.27), mg/L;
The measurement result of the standard use solution of ρ2--potassium dihydrogen phosphate (6.23), mg/L.
Note. For the total phosphorus analysis module, when the test result of the certified reference material is lower than the lower limit of the uncertainty range, the above test is required.
13 Precautions
13.1 All glassware must be soaked in dilute or dilute nitric acid.
13.2 To reduce baseline noise, the reagents should be kept clear and the reagents should be filtered if necessary. Reagent and ambient temperature affect analysis
As a result, the temperature of the reagent stored in the refrigerator should be used after reaching room temperature, and the room temperature fluctuation during the analysis does not exceed ±5 °C.
13.3 After the analysis is completed, the filter in the flow detection tank should be removed and placed in the dryer to prevent dust and moisture.
13.4 Pay attention to the cleaning of the flow path. After the analysis is completed every day, all the flow paths should be washed with water for 30 minutes. Weekly cleaning solution (6.28)
The line was cleaned for 30 min and then washed with water for 30 min.
13.5 The dialysis membrane should be kept moist. In order to prevent the dialysis membrane from rupturing, it can be added in every liter of cleaning water when the cleaning system is analyzed.
Enter 1 drop of FFD6 (6.10).
13.6 When the concentration of the sample analyzed in the same batch fluctuates greatly, a blank can be inserted between the sample and the sample to reduce the concentration of the high concentration sample.
The effect of low concentration samples.
13.7 Phosphate determination The total phosphorus analysis module can be utilized.
The specific operation is as follows. first disconnect the secondary sample tube of the total phosphorus analysis module, and then directly connect the phosphate sample tube to the total phosphorus
Analyze the secondary inlet of the module, and replace the R3 reagent pump tube (alkali reagent) of the total phosphorus module with the phosphate module R1 reagent pump.
Tube (acid reagent I).
Adjust the infusion pump tube and air pump tube before the disconnected total phosphorus module secondary sample tube to the non-injection state, that is, open
The pump cover is in a relaxed state; the oxidation unit such as ultraviolet digestion is in a closed state.
13.8 Different types of flow analyzers can be selected with reference to this standard to select the appropriate instrument conditions.
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