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Method for determining COD (Chemical Oxygen Demand) value by laboratory microwave digestion method

A microwave digestion method and laboratory technology, applied in the field of COD determination, can solve the problems of long time-consuming, low efficiency and inapplicability of boiling reflux

Inactive Publication Date: 2015-01-28
ZHENGZHOU YU CHI TESTING TECH
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Problems solved by technology

[0004] In the existing oxygen consumption measurement process, because the boiling reflux takes a long time (two hours), the measurement
[0005] The efficiency in the determination process is low, it is not suitable for the detection of a large number of water samples, and a large amount of circulating water is used in the analysis process, which wastes resources; although the spectrophotometric method is more convenient, compared with the titration reaction, the accuracy of the photometric method is slightly worse

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  • Method for determining COD (Chemical Oxygen Demand) value by laboratory microwave digestion method

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Embodiment Construction

[0021] The present invention will be further described below in conjunction with specific embodiments.

[0022] Experiment overview:

[0023] This method is applicable to various types of water samples containing COD (chemical oxygen demand) value greater than 50mg / L; the upper limit of determination for undiluted water samples is 1000mg / L. This method is not suitable for chlorine-containing water samples with a chloride ion concentration greater than 1000mg / L (after dilution).

[0024] Experimental principle:

[0025] In a strong acidic solution, potassium dichromate is used to oxidize the reducing substances in the water sample, and microwave digestion is carried out in a closed (sealed) state. Excessive potassium dichromate uses ferrous iron as an indicator, and ferrous sulfate Ammonium drips back. Calculate the COD value of the water sample according to the amount of ammonium ferrous sulfate.

[0026] Instruments and medicines required for the experiment

[0027] (1) ...

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Abstract

The invention relates to a method for determining a COD (Chemical Oxygen Demand) value, in particular to a method for determining the COD value by a laboratory microwave digestion method. The method particularly comprises the following steps: 1) pretreatment of a water sample, 2) sample introduction and dosing, 3) digestion, 4) cooling, 5) titration, and 6) calculation: oxidizing a reducing substance in the water sample with potassium dichromate in a strongly acidic solution, carrying out microwave digestion in a closed (sealed) state, taking a ferroin indicator solution as an indicator for excessive potassium dichromate, carrying out back titration with ammonium ferrous sulfate, and working out the COD value of the water sample according to dosage of ammonium ferrous sulfate. The experiment efficiency can be improved, the experiment accuracy can be ensured, and resources are saved.

Description

technical field [0001] The invention relates to a method for measuring COD, in particular to a method for measuring COD value by a laboratory microwave digestion method. Background technique [0002] At present, there are existing methods for measuring chemical oxygen demand (also known as oxygen consumption and COD) in water. One is [0003] Add a known amount of potassium dichromate solution, and use silver as a catalyst in a strong acid medium, choose the boiling reflux method, use ferrous iron as an indicator, and titrate the unreduced potassium dichromate in water with ferrous ammonium sulfate The mass concentration converted into oxygen consumption. The other is to add a known amount of potassium dichromate solution to the sample, use silver sulfate as a catalyst in a strong sulfuric acid medium, and measure the COD value by spectrophotometry after high temperature digestion. [0004] In the existing oxygen consumption measurement process, because the boiling...

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Application Information

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IPC IPC(8): G01N31/16G01N1/44G01N21/79
Inventor 孙世民李晓玥秦继磊焦英九蒋松钰张芳
Owner ZHENGZHOU YU CHI TESTING TECH
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