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Background absorption correction method for CODcr measurement

A technology of background absorption and correction method, which is applied in the field of domestic sewage water quality monitoring, can solve problems such as large COD calculation value, reduced light transmittance, errors, etc., and achieve the effect of improving sensitivity

Inactive Publication Date: 2012-10-10
SHENZHEN SHIJI TIANYUAN ENVIRONMENTAL PROTECTION TECH
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  • Abstract
  • Description
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  • Application Information

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Problems solved by technology

The increase of suspended matter will increase the degree of scattering, the chromaticity of the sample will cause the decrease of light transmittance, and other interference components of the sample matrix will absorb part of the light, all of which will lead to the increase of the total absorbance, so that the calculated value of COD will be too large , in severe cases even get a wrong data

Method used

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  • Background absorption correction method for CODcr measurement
  • Background absorption correction method for CODcr measurement
  • Background absorption correction method for CODcr measurement

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0043] like figure 1 shown, one for COD Cr The measured background absorption correction method specifically includes the following steps:

[0044] S100. After the sample is pretreated 1, digested 2 and cooled, the absorbance in the vicinity of the two wavelength ranges of 440±20nm and 600±20nm is respectively tested by light detection 3, which is recorded as A 440 and A 600 ;

[0045] S200. According to characteristic absorbance balance formula 4: (A 440 -ΔA)+k×(A 600 -ΔA)=A 0 , to calculate the absorbance change ΔA caused by the background absorption; where, k is a proportional coefficient, A 0 is the standard total absorbance;

[0046] S300. According to the 440nm absorbance correction formula 5: A 0 440 =A 440 - ΔA and 600nm absorbance correction formula 6: A 0 600 =A 600 -ΔA, restore the characteristic absorbance A near the two wavelength ranges of 440±20nm and 600±20nm 0 440 and A 0 600 ;

[0047] S400. According to the characteristic absorbance A 0 4...

Embodiment 2

[0049] Pretreatment 1 is mainly adding diluent and chemical reagents to the sample, or adding only chemical reagents. Diluents include but are not limited to deionized water, distilled water, and acidic solutions; chemical reagents are mainly oxidizing agents, or oxidizing agents and catalysts or masking agents; oxidizing agents are potassium dichromate (K 2 Cr 2 o 7 ), catalysts include but not limited to silver sulfate (Ag 2 SO 4 ) or silver nitrate (AgNO 3 ), masking agents include but are not limited to mercury sulfate (HgSO 4 ) or silver sulfate (Ag 2 SO 4 ).

[0050] According to the actual application situation, you can choose the pretreatment 1 method of different process formulas. figure 2 In the shown embodiment, what diluent selects is deionized water, and what catalyst selects is silver sulfate (Ag 2 SO 4 ), the masking agent is mercury sulfate (HgSO 4 ), the oxidizing agent is potassium dichromate (K 2 Cr 2 o 7 ).

Embodiment 3

[0052] Digestion 2 methods can use high temperature digestion, high temperature airtight digestion and microwave digestion, etc. figure 2 The example shown uses high temperature closed digestion.

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Abstract

The invention provides a background absorption correction method for CODcr measurement. The background absorption correction method comprises the following steps of carrying out pretreatment, digestion and cooling of a sample, respectively detecting sample absorbance values at wavelengths of 440+ / -20nm and 600+ / -20nm, calculating an amount of absorbance variation caused by background absorption according to an absorbance balance formula, deducing characteristic absorbance values at wavelengths of 440+ / -20nm and 600+ / -20nm respectively according to a correction formula of absorbance at a wavelength of 440nm and a correction formula of absorbance at a wavelength of 600nm, and deducing a chemical oxygen demand (COD) value of the sample according to the characteristic absorbance values. The background absorption correction method for CODcr measurement can correct CODcr measurement interference caused by background absorption, effectively improve sensitivity, accuracy and repeatability of CODcr measurement, widen a linear range of and CODcr measurement, and especially improve technical indexes such as low-range measurement accuracy and the like.

Description

technical field [0001] The invention relates to the field of environmental protection including water quality monitoring or on-line monitoring of surface water / underground water / drinking water, on-line monitoring of continuous discharge of industrial waste water, and water quality monitoring of domestic sewage. Specifically, a method for COD Cr Measured background absorption correction method, especially involving a COD based on "440nm and 600nm dual-wavelength background absorption correction" Cr Measurement methods. Background technique [0002] Chemical Oxygen Demand (COD / Chemical Oxygen Demand) refers to the amount of oxidant consumed by the oxidation of organic matter that is susceptible to oxidant oxidation, expressed in mg / L of oxygen, and is an indicator to measure the degree of pollution of water quality by reducing substances. One of the most commonly used water quality pollution and evaluation indicators. Reducing substances, especially organic compounds, consu...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N21/31
Inventor 张利杨萍赖胜波万怡芳黄涛刘安刘敏敏缪震华
Owner SHENZHEN SHIJI TIANYUAN ENVIRONMENTAL PROTECTION TECH
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