General pharmaceutical plants only need to detect COD ammonia nitrogen two indicators, so please equipped with HJ-200 COD meter and HJ-09N ammonia nitrogen detector, or HJ-20B COD ammonia nitrogen two-in-one detector can be.
Reagents needed:Ammonia nitrogen reagent3-2-1 Potassium sodium tartrate solution preparation
Weighing 250g of potassium sodium tartrate (KNaC4H4O6-4H2O) dissolved in 500mL of water, heated and boiled for 20 minutes to remove the ammonia, let cooled and volume to 500ml.
3-2-2. Preparation of NaCl reagent solution
Weigh 80 g of sodium hydroxide, dissolve in 250 mL of water and cool sufficiently to room temperature. Another 35g of potassium iodide (KI) and 50g of mercury iodide (HgI2) were dissolved in 250mL of water, stirred until fully dissolved, and then this solution was injected into the fully cooled sodium hydroxide solution with stirring, diluted with water to 500mL, and left to stand for more than 5 hours. Carefully pour out the upper layer of clear night for use.
3-2-3. Preparation of sodium thiosulfate solution
Water samples such as residual chlorine, should be added to the appropriate amount of 0.35% sodium thiosulfate solution, every 0.5ml can remove 0.25mg residual chlorine. Weigh 2.5g sodium thiosulfate (Na2S2O3) dissolved in 200mL of water, and weigh 1.5g disodium ethylenediaminetetraacetic acid and 2.5g sodium hydroxide (NaOH) dissolved in 200mL of water, and then the two solutions are mixed, stirred, and diluted to 500mL.
3-2-4. Ammoniacal nitrogen standard solution preparation
According to the concentration of ammonia nitrogen in the field water samples. To choose the appropriate standard solution range, the full range of the value of the configuration of the standard solution. For example, if the concentration of ammonia nitrogen in the water sample is known to be between 5-10mg/L, then the calibration range can be selected to block 0-12mg/L, and the standard nitrogen solution can be configured to be 12mg/L. In principle, it should be ensured that the concentration of ammonia nitrogen in the water sample is within the selected range.
Weighing 3.819g by 100 ℃ drying over the excellent pure ammonium chloride (NH4Cl) dissolved in water, transferred to 1000mL volumetric flask, diluted with water to the standard line and mixed. The concentration of this standard solution is 1000mg / L, other concentrations of standard solution to 1000mg / L standard solution is obtained by sequential dilution.
3-2-5. Ammonium standard solution
5.00ml of ammonium standard storage solution in a 500ml volumetric flask, diluted with water to the standard line. This solution contains 0.010mg ammonium per milliliter.? COD reagentNote: Please use analytically pure or superior sulfuric acid, which is a colorless transparent liquid. Because sulfuric acid is absorbent, the reagent should be sealed and stored immediately after configuration, and not exposed to air for a long time.
3-1-1 Preparation of reagents:
Water samples should be pretreated before analysis. The pre-treated water sample can only be tested on the instrument. Use the original two specialized reagents during the pretreatment process.
The two special reagents are packed and shipped in solid form,*** there are two packing specifications:
Oxidation C1 reagent: C1-200; catalytic C2 reagent: C2-200.
C1-200 reagent: Pour the whole bottle of the powdered crystalline reagent into a beaker, and add 200 ml of 28.6% sulphuric acid (28.6%). Configuration of sulfuric acid: take 60 ml of concentrated sulfuric acid dissolved in 140 ml of distilled water), stirring constantly until all dissolved.
C2-200 reagent: dissolve the whole bottle of powdered crystal reagent, all in 1000mL of analytically pure sulfuric acid, stir constantly or leave overnight until all reagent is dissolved. Note: Complete dissolution of the catalyst takes approximately 1-2 days.
3-1-2 Preparation of masking agent (for water samples with high chlorine content):
For water samples with high chlorine content can be avoided through the addition of mercuric sulphate masking agent to avoid interference, in general, when the COD value of 50mg/L or more, the concentration of chloride ions more than 2,000mg/L or more, you can use the dilution method, dilute the water samples with distilled water to make the chlorine ions less than 2,000mg/L, and then analyze. L, and then analyze.
Masking agent preparation: weigh 20g of analytically pure mercuric sulfate in a 100ml beaker, add about 80ml of distilled water, and then add 10ml of concentrated sulfuric acid to make it dissolve, shake well, and then move into a 100ml volumetric flask, and dilute with distilled water to the scale.
3-1-3 Preparation of standard solution: (can also be purchased, the market has different specifications of COD standard solution)
Standard solution, also known as the standard substance, is a simulation of the natural freshwater constituent matrix, using a special process, in the specified environment to accurately formulate and become. Its chemical oxygen demand (COD) concentration is known. Users can get it by purchasing or preparing it by themselves according to the requirements. The standard solution is mainly used for the following purposes:
① To calibrate the curve of COD meter;
② To check the accuracy of COD meter;
③ To confirm and evaluate the analyzing process of the operator;
④ To carry out the quality control for the whole measuring process of the instrument.
Standard storage solution: 5000mg/L standard material, as a storage solution. When used according to the need to use measuring instruments to dilute step by step, you can get a different concentration of the standard use of the solution, in the specified conditions of storage, standby. Strictly comply with the instructions and requirements of prudent operation.
Standard use solution 1: accurately measure 10mL of standard storage solution, transfer to a 100mL volumetric flask, dilute with distilled water to the scale and mix. The concentration of COD in this solution is 500mg/L. It is used for testing and calibrating instruments.
Standard Use Solution 2: Measure 20mL of Standard Use Solution 1 accurately, transfer it to 100mL volumetric flask, dilute it with distilled water to the scale line and mix well. The concentration of COD in this solution is 100mg/L. It is used for testing and calibrating the instrument.
Standard solution can also be prepared in accordance with the following methods:
Based on the "GB 11914-89 water quality determination of chemical oxygen demand dichromate method" in the method of preparation, note: the accuracy and uncertainty of the prepared standard solution, mainly depends on the preparation process of each link in the error.
Standard solution preparation method:
Weighing in 105 ℃ under the condition of drying for 2 hours and cooling of potassium hydrogen phthalate (HOOCC6H4COOK) 0.4251g all dissolved in distilled water, and diluted to 1000mL, mixing, the solution of the theoretical COD value of 500mg/L.
Weighing the benchmark pre-drying 2h l05 ~ 110 ℃ and drying, the standard solution of the method of dichromate, the method of preparation:
Weighing pre-drying 2h l05 ~ 110 ℃, the benchmark of the method of dichromate. 110 ℃ drying 2h benchmark or superior pure potassium hydrogen phthalate (HOOCC6H4COOK) 0.4251g dissolved in a small amount of water, transferred to 500mL volumetric flask, diluted to the mark with water, shaking well, the COD value of the solution for the 1000mg / L.