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Method for measuring chemical oxygen demand by using gaseous molecular absorption spectrum process

An absorption spectrometry, chemical oxygen demand technology, applied in the field of chemical analysis, can solve the problems of inaccurate determination of titration end point, liquid turbidity, inaccurate measurement results, etc., achieve high measurement efficiency, eliminate artificial errors, and solve chromaticity and turbidity. degree of interference

Inactive Publication Date: 2016-11-09
上海北裕分析仪器股份有限公司
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  • Abstract
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Problems solved by technology

[0010] In the above two processes, it is necessary to judge the amount of oxidant through titration experiments. However, samples such as waste water samples are often dark in color and the liquid is turbid. When the above titration method is used, the titration end point cannot be accurately judged. problems, resulting in inaccurate measurement results
[0011] In addition, even in the current general standard documents: such as, "GB11914-89 Determination of Chemical Oxygen Demand in Water Quality Potassium Dichromate Method", "HJ / T399-2007 Determination of Chemical Oxygen Demand in Water Quality by Rapid Digestion Spectrophotometry" and Teaching materials: For example, the rules and precautions of the measurement method are introduced in articles such as "Water and Wastewater Monitoring and Analysis Methods (Fourth Edition)". However, it is still unavoidable to detect in a liquid environment during the measurement process of the above method Therefore, it is still unavoidable that the color and turbidity of the water body will affect the operation process, detection process, and the accuracy of the detection results.

Method used

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  • Method for measuring chemical oxygen demand by using gaseous molecular absorption spectrum process

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Experimental program
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Embodiment 1

[0067] Embodiment one, sodium nitrite method

[0068] 1. Draw the standard curve:

[0069] Prepare a standard sodium nitrite solution with a concentration of 0.012mol / L; draw 0.00, 0.50, 1.00, 2.00, 3.00, 4.00ml of the standard solution into the volumetric flask one by one, add water to 100ml, and transfer the standard sodium nitrite solution through a peristaltic pump , concentrated sulfuric acid and ethanol are introduced into the gas-phase molecular absorption spectrometer, after the generated gas is mixed with the carrier gas, the absorbance of each standard solution is measured in turn, and the calibration curve is drawn with the absorbance and the corresponding amount of sodium nitrite.

[0070] 2. Sample testing:

[0071] Take 3ml of water sample to the digestion tube, add 1ml of 0.120mol / L potassium dichromate acidic solution (the solution can also be 0.010mol / L, 0.050mol / L, 0.100mol / L, 0.160mol / L, 0.200mol / L, 0.350mol / L, 0.500mol / L 1:9-20 sulfuric acid solution, th...

Embodiment 2

[0081] Embodiment two, precision and accuracy test

[0082] 1. Precision

[0083] Six water samples with known chemical oxygen demand were measured by the method standard sample of the above-mentioned embodiment 1, the relative standard deviation of repeatability was 0.6%, and the relative standard deviation of reproducibility was 0.9%.

[0084] 2. Accuracy

[0085] Six water samples with known chemical oxygen demand were measured using the method standard sample of the above-mentioned embodiment 1, and the relative errors were 0.1%.

[0086] The water sample selected in the above-mentioned embodiment, when it adopts titration method to measure, its COD is 110mg / L.

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Abstract

A provided method for measuring chemical oxygen demand by using a gaseous molecular absorption spectrum process is characterized in that the chemical oxygen demand of a to-be measured sample is determined according to the residual amount of a strong oxidant after being used to oxidize the to-be measured sample, wherein the residual amount is obtained by employing gas-phase molecular absorption spectroscopy. The finally detected substance of the method is a gaseous substance, the method is completely not influenced by water body color and turbidity, and accordingly, the precision of a measurement result is guaranteed.

Description

technical field [0001] The invention relates to the field of chemical analysis, in particular to a method for testing chemical oxygen demand by using gas-phase molecular absorption spectrometry. Background technique [0002] Chemical oxygen demand (COD) is an important index indicating the organic pollution of water bodies, reflecting the degree of water pollution by reducing substances, and it is also one of the comprehensive indicators of the relative content of organic matter. [0003] The so-called chemical oxygen demand (COD) is the amount of oxidant consumed when a certain strong oxidant is used to treat water samples under certain conditions. It is an indicator of the amount of reducing substances in water. The reducing substances in water include various organic substances, nitrite, sulfide, ferrous salt, etc., but the main ones are organic substances. Therefore, chemical oxygen demand (COD) is often used as an index to measure the content of organic substances in ...

Claims

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Application Information

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IPC IPC(8): G01N21/33
CPCG01N21/33
Inventor 卢文武曲明昕于静阳纯泉王文雷张琤陈凡赵勇赵建姚逸覃志桥陈健
Owner 上海北裕分析仪器股份有限公司
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