Some standard content:
National Standard of the People's Republic of China
Test methods for drinking natural mineral water
Methods for testing drinking natural mineral water
Part I General Principles
1.1 Content and scope of application
This standard specifies the test method for drinking natural mineral water. This standard is applicable to the test of drinking natural mineral water and its packaging water. 1.2. Terms and units
GB/T8538—1995
Generation H 8538. 1~8538.63—87
1.2.1 The terms and units used in the test methods are in accordance with the provisions of the national standards. 1.2.2 Except for color, flavor, brilliance, pH value, total colony count, total coliform group, and total beta radioactivity, which have their own specific units or are described in words, all the test results of this standard are generally expressed in ng/L, that is, each liter of water sample contains a certain number of grams of the substance. When the concentration is low, some items are also expressed in pg/1.
1.3 Reagents and concentration expression
1.3.1 Reagents used in this standard, if the specifications are not specified, are analytically pure (AR). If other specifications of reagents are required, such as high-grade pure, or special requirements for gas chromatography and atomic absorption spectrophotometry, they must be clearly specified according to specific experiments. 1.3.2 The concentrations of some reagents in this standard are expressed in moles/liter, mal/L, and their basic units must be indicated. 1.3.3 The concentration of the test solution prepared with liquid solutes is expressed as solute volume + solvent volume, such as 1 + 2 sulfuric acid solution, which means 1 volume of concentrated sulfuric acid mixed with 2 volumes of water.
1.3.4 The concentration of the test solution prepared with solid reagents is expressed in mass concentration. That is, the number of grams of solute per liter of solution. 1.3.5 When the solution does not indicate the type of reagent used to prepare it, it refers to aqueous solution. 1.3.6 Sulfuric acid, hydrochloric acid, and nitric acid refer to concentrated sulfuric acid, concentrated hydrochloric acid, and concentrated nitric acid. 1.4 Pure water
In general determination items, pure water is used when preparing reagents and diluting water samples. Pure water refers to the following distilled water or deionized water. Pure water with special requirements needs to be specifically explained. 1.4.1 Ordinary distilled water, prepared by distilling raw water with a distiller. 1.4.2 Redistilled water, prepared by redistilling distilled water with a full glass distiller. Be careful to prevent contamination caused by contact with rubber stoppers and rubber catheters
1.4.3 Deionized water, often prepared by passing ordinary distilled water through a cation resin exchange column. 1.4.4 Deionized distilled water: prepared by refilling deionized water with a full glass distiller. 1.5 Glass instruments
Hard glass bottles are best used for reagents and sampling devices. When reagents or water samples are corrosive to glass, or glass has adsorption to certain components of reagents and water samples, polyethylene bottles can be used. Bottle caps and stoppers should be selected to resist the corrosion of the solution contained in the container. Implementation on August 1, 1996
National Technical Supervision Commission approved on August 17, 1995
GB/T85381995
1.5.1 Washing of glass instruments: Glass instruments must be thoroughly cleaned before use. The general washing method is to first rinse the residue with tap water, then wash with detergent, then rinse thoroughly with tap water, and finally rinse three times with pure water. The preparation and use of commonly used washing solutions are as follows: 1.5.1.1 Chromium washing solution: weigh 10 (g 1.6 potassium dichromate into a beaker, add about 100 ml of water, slightly heat to dissolve it, cool it, and slowly add 1.6 concentrated sulfuric acid. Use a glass rod to stir the sulfuric acid continuously until the precipitation is just finished. When washing instruments with chromic acid, the instruments must be soaked for several minutes to hours. When the washing solution turns green-brown, it cannot be used again. Instruments washed with this washing solution should pay attention to the interference caused by adsorption on the organ wall. 1.5.1.2 Fertilizer and synthetic detergents: used to wash grease and organic matter. Instruments used to analyze organic matter should be baked at 300 ° C for several hours after washing.
1.5-1.3 Nitric acid: Determination of metal ions. Soak glass instruments in nitric acid of different concentrations. When washing glass instruments, prevent contamination from new ones. For example, the glass instruments used for zinc measurement cannot be rinsed with plain water after being soaked in acid, and cannot be rinsed with pure water for surface testing. The instruments used for iron measurement cannot be washed with a brush with a wire handle, etc. 1.5.2 Calibration of glass instruments: Volumetric flasks, burettes, non-divided pipettes, graduated pipettes, etc. should be calibrated in accordance with relevant national regulations. A set of colorimetric tubes must be used when preparing standard series. The height of the scales of each tube should be consistent, and the volume should be corrected when necessary. 1.6 Only instrument calibration
Instruments such as the balance and spectrophotometer used in each measurement item need to be calibrated regularly. 1.7 Constant weight
Except for soluble solids, it means that the difference in mass after two consecutive calcinations or baking is less than 0.2 mg. Regardless of whether it is weighed after baking or calcination, it must be placed in a desiccator (usually 30 minutes, and extended to 60 minutes in summer) to cool to room temperature before weighing. 1.8 Accurate weighing
refers to weighing with an accuracy of 0.000 1 g.
1.9 Pipetting and taking
Pipetting refers to using a graduated pipette or a non-divided pipette, and measuring refers to using a basic pipette. The two have different requirements for accuracy. 1.10 Volume adjustment
refers to diluting to the scale with pure water or other solvents in a basic bottle. 1.11 Selection of test method
If there are two or more test methods for the same item in a country, local areas can choose to use them according to different conditions, but the first method shall be the supplementary method.
Chapter 2 Collection and Preservation
2 Collection and Preservation
2.1 Determination range
This method is applicable to the collection and Preserve. 2.2 Sample container and washing
2.2.1 Sampling container
Grind hard glass bottle and high-pressure colorless polyethylene plastic bottle. 2.2.2 Container washing
2.2.2.1 Newly used hard glass bottle and polyethylene bottle must be soaked in nitric acid solution (1+1) for one night, and then cleaned by different washing methods.
2-2.2.2 Hard glass bottle should be washed with hydrochloric acid solution (1+1) first, and then rinsed with tap water. 2.2.2.3 Polyethylene plastic bottle can be washed with hydrochloric acid or nitric acid solution (1+1) according to the situation, or washed with sodium hydroxide solution (10g/L), and then rinsed with tap water.
GB/T8538-1995
2.2.2.4 Sample bottle used to hold microbiological test samples is preferably a 500ml wide-mouth bottle with a stopper. After washing the sample bottle, wrap the head and neck of the bottle with aluminum foil or kraft paper and other moisture-proof paper. Sterilize in a drying oven at 160°C for 2 hours or sterilize in a high-pressure steam sterilizer at 121°C for 15 minutes. 2.3 Sampling methods and requirements for various water sources
2.3.1 Sampling methods and requirements
Before sampling, rinse the sampling bottle and bottle stopper with the water collected at least three times (except for the water sample bottle for microbiological testing). When sampling, let the water flow slowly into the sample bottle. When sampling, leave 1% to 2% of space at the bottle mouth. After sampling, cover the bottle immediately, tighten the bottle mouth with gauze, and finally seal the mouth tightly with paraffin.
2.3.1.1 Sampling of natural springs Avoid sampling in stagnant pools, but choose to sample in the concentrated day bubble near the main spring mouth or the mainstream of the spring, in flowing but not urgent water. 2.3.1.2 For sampling of fountains or artesian wells, a clean guide can be used to drain a portion of the water from the gushing water. 2.3.1.3 For sampling of wells, pay attention to pumping water for a certain period of time. After pumping out about 2 to 3 times the volume of the non-simple storage water, it can be collected.
2.3.1.4 When taking parallel water samples, they must be collected at the same time under the same conditions, and the container materials should also be the same. 2.3.2 When sampling, it is necessary to measure the water temperature and pH value on site. Observe and describe the external physical properties of the water (color, taste, visible objects, etc.). For carbonated mineral water, the content of free CO, HCO, calcium and magnesium should be measured on site. 2.4 Recommended format of water sample label and water analysis sample submission form After sampling, the filled water sample label (see Table 1) should be attached to the water sample bottle. When submitting the sample, the sample submission form (see Table 2) should be filled out item by item. Special requirements should be noted in the remarks column.
Table 1 Water sample label
Well (spring) number
Sampling location
Sample depth
Sampling date
Chemical treatment method
Analysis items
Field measurement results
Heavy acid salt content (CaC(+mg/1.)
Acid content (CaCOs+mg/1)
Calcium (ng/l.)
2.5 Collection and preservation methods of water samples for food classification
Traffic CO (mR/1.）
Sample number
Ice source type
Sampler
The collection and preservation of various analytical water samples must comply with the following relevant regulations. For water samples that need to be added with protective agents, the specific regulations such as the purity, concentration, addition amount, addition order and addition method of the reagents must be strictly observed during sampling. The general technical requirements for sample preservation are shown in Table 3. The necessary cutting materials should be properly prepared before sampling. 2.5.1 Raw water sample
That is, the water sample without any protective reagent is used to determine the pH value, free CO), HCO, CO-, NO, NO, CI, SO, FBr\I-, H, B)z.Cr(V1), H, SiO), total decomposable solids and other items. Take 5000mL of water sample in a hard glass bottle or a polyethylene plastic bottle (water samples for the determination of boron and metasilicic acid must be taken in polyethylene plastic bottles). When taking raw water, it should be sent for inspection as soon as possible. 24s
Commissioning unit:
Sampling location
Sample collection period:
2.5-2 Acidified water sample
Water source description
GB/T 8538—1995
Table 2 Water analysis sample submission form
Physical properties
Stratum lithology Depth and depth of enclosure
Type,
Sample submitter:
Sample collection person,
Sampling date:
Sample submission period:
Analysis items
Chemical treatment method
Take a clean hard glass bottle or polyethylene plastic bottle with a volume of 1000mL, rinse it with the water sample to be tested, and add 5m l nitric acid solution (1+1), rotate the container to make the acid soak the inner wall, put in 1000ml of water sample to be tested (if the water sample is turbid, it must be filtered) spoon (the water sample plI value should be less than F=2), seal (the bottle should not be sealed with a rubber stopper or tape to prevent zinc and other pollution>, for the determination of Cu, Pb.Zn.Cd, Mn, total Fc.Ni.Co, total Cr, Li, Be, Sr, Ba, Ag, V, Ca, Mg, Al, K, Na and other items. Use a volume of 100~200mE. Take 100~200mL of water sample in a hard glass bottle or plastic bottle, add sulfuric acid solution (1+1) to acidify, make pH <2, for determination of As. 2.5.3 Alkalinization of water sample
Take 2000mL of water sample in a hard corrugated glass bottle with a volume of 2000mL, add 5ml of sodium hydroxide solution (400g/L) (or 2g of solid sodium hydroxide), stir, make the water sample pH ≥12. Seal and store at low temperature for determination of volatile phenols and amines. 2.5.4 Water sample for determination of Fe1 and Fe||t t||Take 250mL of water sample and put it in a polyethylene plastic bottle or hard glass bottle, add 2.5mL sulfuric acid solution (1+1) and (.5g ammonium sulfate, sow and seal.
2.5.5 Determination of sulfide in water sample
In a 500ml hard glass bottle, add 10mL zinc acetate solution (<200g/1.) and 1mL sodium hydroxide solution (Cc(Na0H)=1tm1ol/L), then fill it with water sample (almost full, leaving a little space). Cover the bottle stopper and shake it repeatedly. Seal. The exact amount of reagents added should be indicated on the water label!
2.5.6 Determination of organic gas pesticide residues in water samples Take 3-50 water samples and put them in hard glass bottles (plastic bottles are not allowed). Add sulfuric acid to acidify the water samples to make the pH of the water sample 2. Disassemble evenly, seal and store at low temperature.
2.5.7 Collection of water gas samples
2.5.7.1 Collection of escaped gas samples: The escaped gas in the water is generally collected by special equipment such as gas collecting pipes using the drainage gas collection method. As shown in Figure 1a, connect the nest The glass funnel 1 on the gas pipe 2 is sunk into the water. When the water surface rises above the spring clip 5, close the spring clip 5, then lift the lower bottle 3 filled with water to inject water into the gas pipe. When the water is full (no bubbles should be left), close the spring clips 6 and 7, fill the lower bottle 3 with water, and place it in the lower gas collecting pipe. Then move the funnel to the escape point of the escaping gas, open the spring tips 5 and 7, and the gas will enter the gas collecting pipe along the full funnel. After the water in the gas collecting pipe is drained, close the spring clips 5 and 7. Since the above-mentioned basket cannot ensure the complete sealing of the gas sample, after sampling, the gas sample should be immediately transferred to the gas collecting tank with a corrugated stopcock by the drainage gas collection method (the lubricant applied to the glass stopcock should be vacuum grease), and then sent to the laboratory for analysis. For sampling of escaping gases, a 250mL hard ground glass bottle is also used, with a glass funnel and a rubber stopper (a hole is drilled in the middle to insert the funnel and a small gap is provided on the edge for drainage). The sampling device is shown in Figure 1b. When sampling, first fill the glass bottle with water underwater, then immerse the bottle upside down in water (no air bubbles can be left in the bottle), plug the bottle mouth with a rubber stopper with a funnel inserted, and aim the funnel at the outlet of the underwater escaping gas. When the gas is about to fill the container (about 10mL of water sample should be retained in the glass bottle), remove the rubber stopper underwater, plug the glass bottle with the original bottle, take it out of the water, immediately seal the bottle mouth with wax, put the bottle in a wooden box, and send it to the laboratory for determination. 2.5.7.2 Collection and separation of dissolved gas samples: The dissolved gas samples are separated and collected on site by the vacuum method, and the sampling and separation device is shown in Figure 2. Bottle 2 is a 51.5mm glass bottle with two-hole rubber stoppers, each with two copper tubes inserted. The lower end of one of them is covered with a rubber glass ball 1. Make a mark at 3.000ml. of the bottle. Before separating the dissolved gas, check whether the vacuum bottle is airtight. Inject 40mL of water sample into the bottle, plug the bottle, clamp the spring clamp 5, open the spring clamp 6. Use a vacuum pump to exhaust the air in the ball, then close the spring clamp 6. Open the spring clamp 5. Vacuum the glass bottle (pump until the water in the bottle boils and bubbles, until it stops bubbling). Close the spring clamp 5 and turn the bottle. If the bottle is completely airtight, no bubbles will escape from the water surface. Otherwise, it indicates a leak. After finding out the cause, re-evacuate it. After checking the airtightness, the dissolved gas can be separated. Use a rubber tube (the tube should be filled with water to prevent air from entering the vacuum bottle) to introduce the water sample into the vacuum bottle through the rubber tube 4. When the volume of the water sample reaches the 3000mL mark, close the spring clamp 5 and unplug the rubber tube. Connect the gas collecting tube when returning. Drain the gas collecting device, open the spring clamp 6 to allow the atmosphere to enter the ball bladder. At this time, the dissolved gas is concentrated at the bottle neck. Open the spring clamp 5, lower the position of the lower bottle 8, and draw the dissolved gas at the bottleneck into the gas collecting tube (the size of the gas collecting tube is selected to match the amount of dissolved gas in the water sample). After the dissolved gas is completely drawn out, close the spring clamp 5 and close the stopcock on the gas collecting tube (the stopcock should be coated with commercial vacuum grease). After a single separation operation, the dissolved gas in the water cannot be completely separated and needs to be separated repeatedly. For this reason, use a vacuum pump to draw out the air in the ball bladder again, and the water sample in the bottle returns to the 3000ml mark. At this time, low pressure is formed in the bottle again. Then fill the bladder with air, and collect the separated free gas in the gas collecting tube by drainage gas collection method. Repeat separation for 3-5 times, and the separation can be basically complete. The gas collecting tube is sealed with paraffin wax, and the label of the gas sample bottle indicates the water source temperature, atmospheric temperature, atmospheric pressure at the time of sampling, dissolved gas volume and water volume used to separate dissolved gas.
Figure 1 Escaped gas sampling device
1 One end bucket; 2 Gas collecting tube 3 Bottle-Rubber tube 5.6.. Spring clip
GB/T 85381995
1 Rubber bladder + 2--Glass bottle; 3-Transfer stopper 14--Rubber tube 5.6 Spring fire: 7 Gas collecting belt; 8-Lower door bottle Table 3 General technical requirements for sample preservationWww.bzxZ.net
The recommended water sample preservation technology is only a general guide. It should be linked to the analytical method used, and both should be taken into account. Determination items
Luster turbidity
Alkalinity, membrane
HCO, CE
Al.Na,Ca.Mg.Total. Fe.Mn
Cu.Zn.Total Ct,Pl.,Cd,Mo.
Cn.Ni,Be,Ag.Ba,K,V
Treatment technology
2~5℃ Refrigeration
Acidification to pH2
Acidification with sulfuric acid to pH-<2
Acidification with nitric acid to pH<2
Add vegetable acid and sulfuric acid
Exclude oxygen in the atmosphere
Use oxidizing caustic soda to 1
Acidification with nitric acid to pH2. And add
potassium glycate to make its concentration
0. 5 k/t.
6 months
Measure as soon as possible
It is best to measure on site
It is best to measure on site
It is best to measure on site
Pay special attention to the sample
Do not let it be contaminated and
If pure nitric acid is added, it should
It is best to measure as soon as possible
Chronic
Chloride
Bromide
Iodide|| tt||Measurement Items
Ammonia Nitrate
Nitrite
Sulfate
Phosphate
Silicate
Oxide
Organic Oxide
Anion Alkali
Detergent
Rongbai (a)
Total 3
Pin-226
Total Colony Count
Eliminococcus
Note: 1) G
3 Chroma
Material"
CB/T 8538-1995
Continued Table 3
Silicon glass P polyethylene plastic.
Processing technology
Condensation, avoid direct sunlight
Acidify with sulfuric acid to pH~.2,
2~5℃ cold bottle
2---5 C cold energy
2--513 cooling
Add zinc acetate treatment, oxygenate sodium alkali
Acidify with sulfuric acid to pH<.2
When it is 100/L, use
sulfur to acidify to pHc_2
Acidify with sulfuric acid to pH<2 The sodium oxide is reduced to H12. Sodium hydroxide is added to alkalize to pH>12. 2~5℃. Use sulfuric acid to gel to pHI2. Add methyl chloride. Add 2-50℃ cooling. Add cyclohexane to 2~5℃ cooling. Acidify with hydrochloric acid to pH3. Part III. Test method. Book. Film. Determine as soon as possible. 12 months. Determine as soon as possible. On-site determination. Construction. Add the film immediately after taking the sample. Extraction agent used in the method. The so-called color refers to the degree of yellow or even yellowish brown color presented by soluble substances or colloidal substances contained in water. The color produced by the substance in the solution state is called "true color". \; The color produced by suspended matter is called "false color". Before the determination, the suspended matter in the water sample must be removed.
Usually, the platinum cobalt colorimetric method is used to determine clean natural water. This method is simple to operate. The color is stable, and the standard color series can be used for a long time if it is properly stored. However, chloroplatinic acid is too expensive, and it is not economical to use it. The chromium cobalt colorimetric method has cheap and easy-to-obtain reagents. The method has the same precision and accuracy as the sodium cobalt colorimetric method, but the standard color series has a shorter storage time. 3.1 Needle cobalt standard colorimetric method
3-1.1. Determination range
CB/T 8538—1995
The minimum detection color of this method is 5 degrees, and the determination range is 5~50 degrees. Even slight turbidity will interfere with the determination, so the turbid water sample is first centrifuged to make it clear, and then the supernatant is taken for determination. 3.1.2 Method Summary
Potassium chloroplatinate and cobalt fluoride are used to prepare a standard colorimetric column with the same yellow hue as natural water, which is used for visual colorimetric determination of water samples. The color of 1 mg of platinum and 0.5 mg of cobalt fluoride per liter of water is defined as a chromaticity unit, called 1 degree. 3.1.3 Reagents
3.1.3.1 Platinum cobalt standard solution: Weigh 1.246 potassium fluoroplatinate (K,PtCl,) and 1.000g cobalt fluoride (CoClg·6H,0), dissolve in 100mL pure water F, add 100ml hot acid, and adjust to 1000mL with pure water. The chromaticity of this standard solution is 500 degrees. 3.1.4 Instruments and Equipment
3.1.4.150ml set of high-type stoppered colorimetric tubes. 3.1.4.2 Centrifuge.
3.1.5 Analysis steps
3.1.5.1 Take 50ml of transparent water sample in a colorimetric tube. If the water sample is turbid, centrifuge it first and take the upper liquid for determination. If the color of the water sample is too high, take less water sample, dilute it with pure water and then do the colorimetric test. Multiply the result by the dilution factor. 3.1.5.2 Take 11 colorimetric tubes and add 0, 0.59, 1.00, 1.50, 2.00, 2.50, 3.00, 3.50, 4.00, 4.50, and 5.00ml of platinum cobalt standard solution respectively, add pure water to the scale and shake the spoon. The prepared standard color series are 0.5, 10.15, 20, 25, 30.35, 40, 45 and 50 degrees. This standard color series can be used for a long time, but the liquid should be prevented from evaporating and being contaminated. 3.1.5.3 In a well-lit place, place the water sample and the standard color series side by side, with white paper as the base, so that light can pass through the colorimetric tube from the bottom upwards, and observe the color from the tube mouth downwards vertically.
3.1.5.4 Record the degree of the color of the standard tube. 3.1.6 Sieve counter
C = (m/V) × 500
Where: m-color of water sample, degree:
m-amount of platinum cobalt standard solution.mL
V-volume of water sample.mL,
3.2 Chromium cobalt standard colorimetric method
3.2.1 Measurement range
The minimum detection color of the method is 5 degrees, and the measurement range is 5~50 degrees. Even slight turbidity is difficult to measure. The water sample must be centrifuged to make it clear, and then the supernatant is taken for measurement. ·（）
3.2.2 Method summary
Potassium dichromate and cobalt sulfate are used to prepare a standard color series with a yellow hue close to that of natural water, which is used for the quantitative colorimetric measurement of water samples. The color unit is the same as that of the platinum cobalt method.
3.2.3 Reagents
3.2.3.1 Dilute hydrochloric acid solution: Take 1mL hydrochloric acid (Pz=1.19g/ml.), add 10nml pure water. 3.2.3.2 Chrome cobalt standard solution (chrome cobalt color is 500 degrees): Weigh 0.0437 potassium dichromate (K,Cr(),) and 1.00g dry sulfur cobalt (CoS0,.7H,0)), dissolve in a little pure water, add 0.50mL sulfuric acid (p=1.84g/ml.), stir with a spoon, and dilute to 500ml with pure water.
3.2.4 Instruments and equipment
3.2.4.150ml. set of high-type stoppered colorimetric tubes. 3.2.4.2 Centrifuge.
3.2.5 Analysis steps
CB/T 8538-1995
3.2.5.1 Take 50mL of transparent water sample and put it into colorimetric tube. If the water sample is turbid, centrifuge it first and take the supernatant for determination. If the chromaticity of the water sample is too high, use less water sample. Dilute with pure water and then do the colorimetric test. Multiply the result by the dilution factor. 3.2.5.2 Take 11 other colorimetric tubes and add chromium-cobalt standard solution (3.2.3.2) 0, 0.50, 1.00, 1.50, 2.00, 2.50, 3.00, 3.5 (1, 4.10, 4.50 and 5.0) mL respectively, add pure water to the scale and shake the spoon. The chromaticity of chromium in each tube is 0, 5.10, 15.20, 25, 30+35.40, 45 and 50 degrees respectively. 3.2.5.3 Water sample determination method: Same as 3.1.5.3. 3.2.6 Calculation G = (m/V) X 500 Wherein: Chromaticity of water sample; Volume of chromium standard solution, mL; —— Volume of water sample, mL. 4 Odor and smell 4.1 Odor and taste of source water sample 4.1.1 Determination range This method is applicable to the determination of odor and taste of source water sample. 4.1.2 Analysis steps
Take 100ml of water sample and place it in a 250mL triangular flask. After shaking, smell the odor of the water from the flask, describe it with appropriate sentences, and record its intensity according to six levels.
At the same time, take a small amount of water and put it in your mouth (this water should be harmless to human health), do not swallow it, taste the water, describe it, and record its intensity according to six levels.
4.2 Odor and taste of raw water after boiling
4. 2. 1 Scope of measurement
This method is applicable to the determination of odor and taste of raw water after boiling. 4.2.2 Analysis steps
Heat the water sample in the above triangular flask until it boils, immediately remove the lower flask, and after it cools down slightly, describe the above smell and taste with appropriate words and sentences, and record its intensity according to six levels, see Table 1. 4 True
Intensity level of odor and taste
5 Visible to the naked eye
5.1 Analysis steps
Shake the water sample, observe directly, and record. 6 Turbidity
No odor
It is difficult for ordinary drinkers to detect,However, people who are sensitive to noise and taste may find that the user can just detect the environment. Generally, the user can already clearly detect a very obvious odor. There is a strong unpleasant or peculiar smell. Turbidity is an indicator that reflects the physical properties of natural water. It is used to indicate the clarity and turbidity of water. It is one of the main indicators for measuring the quality of water. GB/T85381995. The methods for measuring turbidity include transmission method, scattering method and scattering-transmission method. This standard adopts the scattering method. 6.1 Measurement range. The maximum detection accuracy of this method is 0.5 scattering turbidity unit (NIU). 6.2 Method recognition. The intensity of light scattered by the standard suspension of the tauermagne under the same conditions is compared with the intensity of light scattered by the water sample under certain conditions. The greater the intensity of the incident light, the higher the turbidity. 6.3 Reagents
6.3.1 Purified water turbidity reagent: Filter with a 0.2 μm membrane filter to reduce the turbidity to less than 0.02 NT0. 6.3.2 Fluorine oil standard reagent: Weigh 1.00 g of sulphuric acid [(NH2):·H2SO4] in a 100 mL volumetric flask and add purified water. This solution is called solution A.
Separately weigh 10.00 g of hexamethylenediamine (CH3PO4) in a 100 mL volumetric flask, add purified water to make the volume 100 mL, and this solution is called solution B.
Respectively take 5 μL of solution A and 5 μL of solution B in a 10 L volumetric flask, mix, and place at 25°C for 24 h. After that, add refined water to the chamber.
This solution can be used for about 10 minutes.
6.3.3 Formaldehyde standard solution: Dilute the Formaldehyde standard stock solution 10 times with refined water. This solution is 40NTU and should be diluted appropriately according to the situation when used.
6.4 Instruments and equipment
6.4.1 Scattering turbidity meter: Although they are all calibrated, turbidity meters with different designs will also get different readings. Therefore, the following design conditions must be required to reduce this difference: 6.4.1.1 Light source: The power supply voltage of the tungsten lamp used shall not be lower than 85% of the rated voltage and shall not exceed the rated voltage. 6.4.1.2 The total distance that the incident light and scattered light pass in the water sample tube shall not exceed 10cm. 6.4.1.3 The angle of light received by the photoelectric detector: The incident light path is concentrated at: 90\: not more than ±30°. 6.4.1.4 The maximum turbidity shall not exceed 40NTU6.5 Analysis steps
Operate according to the instrument manual. When the turbidity exceeds 40NTU, it can be diluted with turbidity-free purified water for determination. 6.6 Calculation
Calculate the result by multiplying the turbidity value displayed by the instrument by the dilution factor. 7 pH value
PH is one of the most important and most frequently analyzed items in water analysis and is an important parameter for evaluating water quality. When water is polluted, it may cause a large change in pH value. When the water contains a large amount of free carbon dioxide, the pH value of the water can be significantly reduced. The methods for determining pH value include potentiometer method and visual colorimetry, and the potentiometer method is more accurate. 7.1 Measurement range
The color, turbidity, free oxygen, oxidants, reducing agents and high salt content of water will not interfere with the determination. In a strong alkaline solution, the presence of a large amount of sodium ions will cause errors and make the readings lower. This method can be accurate to 0. 01 pH unit. 7.2 Method Summary
Use glass electrode as indicator electrode and saturated argon electrode as reference electrode to form a primary cell in solution. At 25°C, each unit of pH is equivalent to a 59.1mV electromotive force change. That is, for every 59.1mV change in electromotive force, the pH of the solution changes by one unit, and the pH value can be directly read on the instrument. The temperature difference is compensated on the instrument. 7.3 Reagents
GB/T 8538--1995
The following standard buffers must be prepared with water without carbon dioxide and stored in plastic bottles. Such solutions can be stable for 1 to 2 months. 7.3.1 Buffer A: Weigh 10.21g of potassium hydrogen phthalate (KHCH0.) dried at 105°C for 2h, drop it into pure water, and dilute to 1000mL. The pH value of this solution is 4.00 at 20°C. 7.3.2 Buffer B: Weigh 3.40 g of potassium monohydrogen phosphate (KHPO4) and 3.55 g of sodium hydrogen phosphate (NaHPO4) dried at 105°C for 2 h, dissolve in pure water, and dilute to 1000 mL. The pH value of this solution is 6.88 at 20°C. 7.3-3 Buffer C; Weigh 3.81 g of sodium tetraborate (NaBO4) and dissolve in pure water, and dilute to 1000 mL. The pH value of this solution is 9.22 at 20°C.
The pH values of the above two buffers vary slightly with temperature, and their changes are shown in Table 5. Table 5 pH values of standard buffers at different temperatures Standard buffer solution
Temperature,
7.4 Instruments and equipment
Acidity
7.5 Analysis steps
KHC, HO,
Na, HAO),
Follow the instructions of the acidometer used. The glass electrode should be soaked in pure water for 24 hours before use. First measure the standard buffer to calibrate the instrument scale, then rinse the electrode with pure water several times, then rinse with water sample 6 to 8 times, and then measure the water sample. The pH value of the water sample can be directly read from the instrument scale table 1:
7.6 Precision and accuracy
68 laboratories used this method to measure synthetic water with pH values of 8.6 and 7.7. The relative standard deviations were 1.9% and 2.7%, and the relative error was 0.
8 Total dissolved solids
B. Drying-weight method at 1105℃
8.1.1 Measurement range
This method specifies a range of 20~2000mg/L.
8.1.2 Extractor
Total dissolved solids is the total amount of inorganic mineral components dissolved in water. The water sample is filtered through a 0.45μm filter membrane to remove suspended matter, and a certain volume of filtrate is evaporated and dried at 105℃ to constant weight. The evaporation residue content can be measured. The dissolved solid content plus half of the bicarbonate content (bicarbonate decomposes and loses carbon dioxide during drying and is converted into carbonate) is the total dissolved solids. 8.1.3 Equipment
8. 1. 3. 1 Evaporation blood.
8.1.3.2 Oven: temperature control accuracy ± 1℃. 8. 1. 3. 3 Water bath.
8. 1. 3. 4
dryer,
8.1.3.5 Analytical weight 0.0001g. 8.1.4 Analytical steps
GB/T8538—1995
8.1.4.1 Place the cleaned evaporated blood in an oven at 105℃ for 1h. Then cool it to room temperature in a drying oven and weigh it. Repeat the drying, cooling and weighing until the weight is constant (the difference between two consecutive weighings is less than 0.0005, the same below). 8.1.4.2 Pipette an appropriate amount (so that the measured soluble quasi-solid is 2.5~200mg) of clear water (water samples containing volatiles should be filtered through a 0.45 tm filter membrane) into the evaporated blood of constant weight and evaporate it to dryness in a water bath. 8.1.4.3 Place the evaporated blood in an oven and dry it at 1(5°C) for 1 h, then take it out and cool it to room temperature in a desiccator and weigh it. Repeat the drying, cooling and weighing until the weight is constant.
8.1.5 Calculate the first
(m2 -mz) × 1 000
Total dissolved solids in water sample, mg/L4
Evaporated blood culture medium R:
Evaporated blood dissolved solids, F
Water sample volume, ml.
Concentration of monohydrate salt, mg/L.
8.1.6 Precision
The same experimental ratio was used to measure the groundwater sample 10 times in parallel, the average value was 164mg/L., and the relative standard deviation was 4.6%. 8.2180℃ dry weight method
8.2.1 Measurement range
The measurement range of this method is 20-~2000 m/1.
8.2.2 Summary
When permanent hardness exists in the water sample, the calcium and magnesium ions that constitute the permanent hardness of the water will form sulfate and chloride during evaporation. When the method of drying at 105°C (see 8.1.2) is used for determination, the crystal water contained in the sulfates of calcium and magnesium cannot be completely removed, which will cause the result to be biased high. The chlorides of calcium and magnesium will also affect the measurement accuracy due to their strong adsorption and mixing properties. Adding an appropriate amount of sodium carbonate to the water sample in advance so that the calcium and magnesium ions will form carbonate after evaporation and drying at 180°C will eliminate the above-mentioned influence. 8.2.3 Reagents
Sodium carbonate (Na,CO,).
8.2.4 Apparatus
8.1.3.
8.2.5 Analytical Procedure
8.2.5.1 Weigh (1.2-0.4% sodium carbonate (Na2C)) into clean evaporating blood, put into oven and dry at 180℃ for 2h. Take out and put into desiccator to cool to room temperature, weigh and repeat drying, cooling and weighing until constant weight (difference between two consecutive weighings is less than 0.0005, the same below). 8.2.5.2 Take appropriate clear water sample (see 8.1.4.2) into evaporating blood of constant weight and evaporate to dryness in water bath. 8.2.5.3 Dry the evaporating blood in oven at 180℃ for 2h, then take out and put into desiccator to cool to room temperature, weigh. Repeat drying, cooling and weighing until constant weight.
B. 2. 6 Calculation
Calculate according to formula 3) in 8.1.5.
8.2.7 Precision
The same laboratory measured the groundwater sample 8 times in parallel, and the average value was 261rg/1. The relative standard deviation was 4.3%. 9 Total hardness
9.1 Determination specification
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