CN105352898A - Turbidity compensation method for COD detection based on spectrometry - Google Patents

Turbidity compensation method for COD detection based on spectrometry Download PDF

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CN105352898A
CN105352898A CN201510661778.1A CN201510661778A CN105352898A CN 105352898 A CN105352898 A CN 105352898A CN 201510661778 A CN201510661778 A CN 201510661778A CN 105352898 A CN105352898 A CN 105352898A
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turbidity
cod
testing liquid
absorption spectrum
absorbance
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CN105352898B (en
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王晓萍
胡映天
文一章
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ZHEJIANG VEELANG ENVIRONMENT TECHNOLOGY Co.,Ltd.
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Zhejiang University ZJU
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry

Abstract

The invention discloses a turbidity compensation method for COD detection based on spectrometry. The method comprises the following steps: (1) acquiring the absorption spectrum of a to-be-measured liquid; (2) calculating the absorption spectrum of the to-be-measured liquid in the step (1) under the action of current turbidity; and (3) carrying out peak drop correction on the absorption spectrum of the to-be-measured liquid in the step (1). The turbidity compensation method introduces an impact factor KN(lambda) to characterize influence of turbidity substances on the light absorption effect of organic molecules and establishes a KN(lambda) model by using an approximate linear relation between KN(lambda) and the absorbance of a standard COD liquid and a negative exponential relation between the valley value of KN(lambda) and turbidity so as to correct and directly deduct peak drop in a turbidity baseline compensation method; and the established model has environmental adaptability, so precision and flexibility of COD measurement are improved.

Description

A kind of determining amount method detected based on spectroscopic methodology COD
Technical field
The present invention relates to water quality inspection technique field, particularly a kind of determining amount method detected based on spectroscopic methodology COD.
Background technology
In monitoring water environment, COD (chemical oxygen demand (COD)) is an important water-quality guideline, it reflects the pollution level of water body by reductive organic matter.In " water environment quality standard " (GB3838-2002), national standard such as " Drinking Water source quality standard " (CJ3020-93), " drinking water sanitary standard " (GB5749-2006) etc., all clear and definite regulation has been made to COD concentration limits, therefore to COD accurate, easily and fast detect extremely important.
At present, the detection method of COD has chemical method and physical method, wherein chemical method mainly dichromate titration (GB11914-89) and permanganate method (GB11892-89), these methods also exist Measuring Time long, need to consume reagent, there is secondary pollution, the shortcoming such as use cost is high.Physical method mainly refers to ultraviolet-visible (UV-VIS) absorption spectroscopy, have in real time, fast, online, original position, agent of being excused from an examination, low cost, the advantage such as highly reliable, non-secondary pollution, be the study hotspot in home and abroad environment monitoring field always.
But, utilize UV-VIS absorption spectroscopy to carry out the physical method of COD detection, there are larger technological difficulties.This is because the affect wave band of different component on absorption spectrum often exists overlap (i.e. cross sensitivity) in water, make forecasting process there is interference mutually, cause prediction deviation.Turbidity as water body can affect the prediction of COD; because the suspended particle existed in actual water sample can produce turbid phenomenon (i.e. water turbidity) to the scattering of light, absorption; although the absorption peak of COD is at ultraviolet band; but turbidity can affect the full wave absorption characteristic of UV-VIS and have comparatively overdamp effect in ultraviolet region to light, and therefore determining amount is particularly important.
Although turbidity has been subjected to as the important factor in order that COD measures and has paid attention to widely, and determining amount is also proposed by many scholars, and it is less that the specific algorithm for determining amount is mentioned.The determining amount method be suggested at present, roughly can be divided into two classes: one is revise COD predicted value with the variation relation of turbidity relative to the predicated error of actual value by setting up COD; Two is the method correction absorption spectrums by deduction turbidity baseline.Although first kind method is simple, does not fundamentally eliminate impact that turbidity brings but only considered data value maps relation, and needing a large amount of test experiments and Data support.For Equations of The Second Kind method, current most of ways are all the simple operation on doing mathematics, do not consider the mechanism that influences each other of material composition in water, so compensation result still exists relatively large deviation relative to the actual absorption spectrum curve without turbidity solution.Therefore, we need to find a kind of more excellent determining amount method, can revise the deviation in Equations of The Second Kind method, improve the prediction accuracy of COD.
Summary of the invention
The invention provides a kind of determining amount method detected based on spectroscopic methodology COD, effectively improve COD accuracy of detection, and use flexible, strong adaptability.
Based on the determining amount method that spectroscopic methodology COD detects, comprise the following steps:
(1) absorption spectrum of testing liquid is obtained;
(2) absorption spectrum during the current turbidity effect of the testing liquid in calculation procedure (1);
(3) carry out peak to the absorption spectrum of the testing liquid in step (1) and fall correction, detailed process is as follows:
3-1, by turbidity standard and the mixing of COD standard solution, obtain many group COD concentration is identical, turbidity value is different mixed solution as sample solution;
3-2, by formula (1), the factor of influence K of sample solution in calculation procedure 3-1 n(λ),
A(λ)＝K N(λ)A COD(λ)+A tur(λ)(1)
Wherein, the absorbance that A (λ) is sample solution, A cOD(λ) and A tur(λ) absorbance of COD titer corresponding to sample solution and turbidity standard is respectively, K n(λ) be factor to affect;
3-3, K according to all sample solutions calculated in step 3-2 n(λ), each K is obtained n(λ) valley is K, sets up variation model K (t) of valley K with turbidity by negative exponential curve matching;
3-4, according to trough valley K both sides K nlinear approximate relationship between the COD titer absorbance having an identical COD with sample solution, simulates K nwith the variation model K of wavelength n(λ);
3-5, by K n(λ) formula (1) is substituted into, the absorbance spectrum computing formula after can being compensated by inverse operation:
A' COD(λ)＝(A'(λ)-A tur'(λ))/K N(λ)(2)
Wherein, A' cOD(λ) be the absorbance after testing liquid determining amount, A'(λ) be the absorbance of testing liquid, A tur' (λ) be the turbidity absorbance of testing liquid under current turbidity, K n(λ) for simulating the variation model of the factor to affect obtained;
According to variation model K (t) in the current turbidity value of testing liquid and step 3-3, obtain the valley K of testing liquid, then obtain the K of testing liquid according to step 3-4 n(λ);
By the K of testing liquid n(λ) the A'(λ of the testing liquid, obtained in step (1)) and step (2) in the A of testing liquid that calculates tur' (λ) substitute in formula (2), the A' of the absorbance after being compensated cOD(λ).
In theory, langbobier law meets sumproperties:
I = I 0 e - k C O D C L · e - k t u r T L
Wherein, K cODand K turbe respectively the absorption coefficient of COD and turbidity, C and T is respectively COD concentration (mg/L) and turbidity (NTU), and L is light path.Then the absorbance of the mixed solution of turbidity standard and the mixing of COD standard solution should equal turbidity and COD absorbance contribution sum separately, that is:
A = - l n I I 0 = k C O D C L + k t u r T L = A C O D + A t u r
A, A cODand A turbe respectively the absorbance of mixed solution, COD titer and turbidity standard, should meet at different wave length place:
A(λ)＝A COD(λ)+A tur(λ)(3)
But in fact because the suction-operated of turbidity particle to organic molecule makes molecule coplanarity be deteriorated, cause sterically hindered, the conjugated system of molecule is destroyed, and makes it reduce the absorption of light.If do direct baseline deduction according to formula (3) absorption spectrum curve to mixed solution, there is peak and fall in the curve of spectrum obtained, and degree difference falls in the peak at different wave length place, therefore the not each materials absorbed light degree contribution of the absorbance of mixed solution simply adding and.
Therefore, need to carry out peak to the absorption spectrum of testing liquid and fall correction, at this, the present invention introduces a factor to affect K with wavelength variations n∈ [0,1], characterizes the impact of turbidity material on COD optical absorption, obtains formula (1), K nless show impact larger, K nclose to 1 be without impact:
A(λ)＝K N(λ)A COD(λ)+A tur(λ)(1)
Wherein, A (λ) is the total absorbance moving revised sample solution through peak, A cOD(λ) and A tur(λ) absorbance of COD titer and turbidity standard is respectively, K n(λ) be factor to affect.
According to above theory, use the absorption spectrum calculating K of the sample solution that formula (1) is right n(λ), and known through experiment, K near the absorption peak that there is the COD titer of identical COD concentration with sample solution n(λ) be just trough, at its both sides K nand between the absorbance of standard C OD solution, there is approximate linear relationship respectively, the larger K of absorbance of standard C OD solution nless, this shows that the centre wavelength of turbidity material to Potassium Hydrogen Phthalate molecule generation energy level transition has the greatest impact, and diminish at this wavelength both sides energy level transition probability, the impact of turbidity on Potassium Hydrogen Phthalate also diminishes gradually;
In addition, turbidity is larger, larger on the impact of COD optical absorption, K nvalley also reduce thereupon.Therefore, K is set up by carrying out negative exponential curve matching nvalley, just can by the current turbidity calculating K of water sample to be measured with the variation model of turbidity n(λ) valley, recycling trough both sides K nand the linear approximate relationship between COD titer absorbance, simulates K nwith the model K of wavelength variations n(λ), thus, by K n(λ) substitute into formula (1) namely can be compensated by inverse operation after absorbance spectrum:
A' COD(λ)＝(A'(λ)-A tur'(λ))/K N(λ)(2)
In order to reduce the storage capacity of system data, preferably, in step (2), the computing method of absorption spectrum during the current turbidity effect of testing liquid are as follows:
2-1, obtain the absorption spectrum of the different turbidity standard of multiple turbidity;
2-2, be normalized by the every bar absorption spectrum in step 2-1, formula is as follows:
ψ ( λ ) = A N ( λ ) - A min A m a x - A m i n ,
Wherein, A n(λ) be the absorption spectrum of turbidity standard, A maxand A minbe maximal value and the minimum value of absorbance, ψ (λ) is the curve of spectrum after normalization, and λ is wavelength;
2-3, the normalization curve of spectrum that step 2-2 calculates to be averaging, to obtain normalization spectrum as the curve of spectrum of standard turbidity;
The absorbance of the some wavelength points of absorption spectrum on visible light wave range of testing liquid in 2-4, obtaining step (1), calculates the absorbance that obtains relative to corresponding wavelength place scaling, and ask the mean value of scaling to characterize the current turbidity of this testing liquid;
2-5, by the mean value of the scaling in step 2-4 with entirety is multiplied, and obtains absorption spectrum during the current turbidity effect of this testing liquid.
Due to always limited to the spectra collection experimental quantities of standard turbidity solution in prior art, therefore can only obtaining the standard absorption curve of spectrum of discrete turbidity, also current turbidity can only be similar on discrete turbidity value when deducting turbidity baseline.In addition, for the standard absorption spectroscopic data storing different turbidity, data volume is huge.
And the present invention only need store average normalization curve of spectrum data for calculating testing liquid, without the need to storing the concrete spectroscopic data of different turbidity, greatly reduces the data volume of storage.
And pass through at visible light wave range corresponding wavelength place, calculate the scaling of water sample absorption spectrum to be measured relative to normalization spectrum to characterize turbidity, and with scaling and normalization spectrum be multiplied dynamic similation current turbidity independent role time absorption spectrum curve.The method applicability of this dynamic similation turbidity curve of spectrum is strong, obtaining the known turbidity curve of spectrum, improve precision and dirigibility without the need to turbidity measurements being quantized on certain specific turbidity value.
In order to improve the precision that COD measures further, preferably, in step (3), substitute into the A (λ) of formula (1) and substitute into the A'(λ of formula (2)) for move revised absorption spectrum through peak, peak moves correction and comprises the following steps:
4-1, the preparation known turbidity of many groups and the turbidity standard of COD concentration and the mixed solution of COD titer, and gather the absorption spectrum of each mixed solution;
The blue shift size of each mixed solution in 4-2, calculation procedure 4-1, sets up by curve the mathematical model that blue shift size changes with turbidity;
4-3, mathematical model by step 4-2, according to the current turbidity value of the testing liquid calculated in step (2), calculate the blue shift of testing liquid; The blue shift of the standard turbidity value calculation sample solution of solution per sample;
4-4, the absorption spectrum of sample solution and testing liquid is done corresponding movement according to the blue shift calculated in step 4-3, the absorption spectrum that peak moves revised sample solution and testing liquid must be arrived.
Known by experiment, if using the absorption spectrum curve of current turbidity as baseline, and direct baseline deduction is done to the absorption spectrum of testing liquid, all there is skew to shortwave direction and blue shift in the curve obtained compared with corresponding standard C OD solution absorption spectra curve.
Therefore, can set up by curve the model that blue shift size changes with turbidity, the size of this model prediction blue shift can be utilized after turbidity is calculated to water sample to be measured, and curve of spectrum entirety is done corresponding movement.Because the Component comparison of actual water sample is complicated, the blue shift impact that in different water sample, the interaction of material inside produces may be very little with titer not identical even blue shift deviation, but still mark experiment can be built by the method according to the concrete water sample of actual conditions to locality, set up model that blue shift changes with turbidity and utilize this model to carry out moving peak correction.
The present invention utilizes priori experiment and data to set up the relation of blue shift size and turbidity, predicts blue shift and moves peak correction to spectrum entirety, repaired the blue shift defect in direct deduction turbidity bias control method in compensation process with this.In addition, different blue shift models is set up to different water environments, there is certain water environment adaptability.
The carrying out of conveniently testing, has been convenient to move peak correction, and further preferably, preferably, described turbidity standard adopts formal hydrazine turbidity standard, and COD standard solution adopts Potassium Hydrogen Phthalate COD standard solution.Now blue-shifted phenomenon is that the hydrogen bond produced by the strong polar molecule hydrazine in turbidity standard formal hydrazine and the carboxyl in Potassium Hydrogen Phthalate causes, and because hydrogen bond can affect n-π * energy level transition, makes R be with absorption peak generation blue shift.Along with the increase of turbidity, the concentration of hydrazine increases, and the interference of hydrogen bond increases, and blue shift size is also in rising trend.
In order to fall in correction at peak, improve the accuracy revised, preferably, in step (3), the COD of the sample solution of configuration is 30 ~ 70mg/L.
In order to make the accuracy of the absorbance of the current turbidity of acquisition improve, preferably, in step 2-4, the wavelength coverage of described visible spectrum is 400 ~ 600nm.
In order to obtain variation model K exactly n(λ), preferably, in step 3-4,
Described linear approximate relationship is in 265 ~ 280nm and 280 ~ 300nm in wavelength coverage.In above-mentioned scope, trough valley K both sides K nbetween the COD titer absorbance that there is identical COD with sample solution, there is obvious linear relationship.
Beneficial effect of the present invention:
Determining amount method of the present invention introduces factor to affect K n(λ) characterize the impact of turbidity material on organic molecule optical absorption, utilize K nwith linear approximate relationship and the K of COD titer absorbance n(λ) valley, with the negative exponent variation relation of turbidity, sets up K n(λ) model, revises the peak directly deducted in turbidity bias control method and fall, and the foundation of model has environmental suitability, improves precision and the dirigibility of COD measurement.
Accompanying drawing explanation
Fig. 1 is that COD concentration is 50mg/L and the abosrption spectrogram of the different mixed solution of turbidity.
Fig. 2 is the abosrption spectrogram of different turbidity standard.
Fig. 3 is the turbidity abosrption spectrogram of different turbidity standard after normalization.
Fig. 4 is blue shift size under different turbidity and curve figure.
Fig. 5 is the abosrption spectrogram after COD concentration is identical, turbidity is different mixed solution directly deducts standard turbidity baseline.
Fig. 6 is the K of wavelength mixed solution of different turbidity within the scope of 250-330nm n(λ) with the variation diagram of wavelength.
Fig. 7 is K nvalley with the change of turbidity and curve figure thereof.
Fig. 8 is wavelength K within the scope of 265-280nm nwith the variation diagram of COD standard solution absorbance.
Fig. 9 is the abosrption spectrogram of testing liquid after determining amount.
Embodiment
In the present embodiment, turbidity standard adopts formal hydrazine titer, and COD standard solution adopts Potassium Hydrogen Phthalate COD standard solution.
The determining amount method detected based on spectroscopic methodology COD of the present embodiment, comprises the following steps:
(1) by turbidity standard and the mixing of COD standard solution, obtaining COD concentration is 50mg/L, turbidity value is respectively 0, the mixed solution of 5NTU, 10NTU, 20NTU, 30NTU, 40NTU and 50NTU as testing liquid, Fig. 1 is the abosrption spectrogram of above-mentioned several testing liquid.
(2) absorption spectrum in calculation procedure (1) during the current turbidity effect of all testing liquids, the computing method of absorption spectrum during current turbidity effect are as follows:
2-1, acquisition turbidity are respectively the absorption spectrum of the turbidity standard of 5NTU, 10NTU, 20NTU, 30NTU, 40NTU and 50NTU, as shown in Figure 2;
2-2, be normalized by the every bar absorption spectrum in step 2-1, obtain the turbidity abosrption spectrogram after normalization, as shown in Figure 3, normalized formula is as follows:
ψ ( λ ) = A N ( λ ) - A min A m a x - A min - - - ( 1 )
A n(λ) be the absorption spectrum of turbidity standard, A maxand A minbe maximal value and the minimum value of absorbance, ψ (λ) is the curve of spectrum after normalization, and λ is wavelength;
2-3, the normalization curve of spectrum that step 2-2 calculates to be averaging, to obtain normalization spectrum, as the curve of spectrum of standard turbidity;
The absorbance of the some wavelength points of absorption spectrum on visible light wave range of testing liquid in 2-4, obtaining step (1), calculates the absorbance that obtains relative to corresponding wavelength place scaling, and ask the mean value of scaling to characterize the current turbidity of this testing liquid;
2-5, by the mean value of the scaling in step 2-4 with entirety is multiplied, the current turbidity effect of this testing liquid time absorption spectrum.
Fig. 1 illustrates the absorption spectrum curve of different turbidity (5,10,20,30,40,50NTU) titer.Can find out that the curve shape of different turbidity is roughly the same, along with the increase curve of turbidity is in overall amplification, Fig. 2 illustrates the normalized curve of the curve of spectrum after formula (1) process in Fig. 1, find that the normalization curve of spectrum of different turbidity overlaps substantially, can by its averaged spectrum as normalization linear function characterize the normalization absorption spectrum of turbidity standard.
(3) carry out peak to the absorption spectrum of all testing liquids in step (1) and move correction, detailed process is as follows:
3-1, the preparation known turbidity of many groups and the turbidity standard of COD concentration and the mixed solution of COD titer, and gather the absorption spectrum of each mixed solution;
The blue shift size of each mixed solution in 3-2, calculation procedure 3-1, set up by curve the mathematical model that blue shift size changes with turbidity, fitting result is as shown in Figure 4;
3-3, mathematical model by step 3-2, according to the current turbidity value of the testing liquid calculated in step (2), calculate the blue shift of testing liquid;
3-4, the absorption spectrum of testing liquid in step (1) is done corresponding movement according to the blue shift calculated in step 3-3.
Blue-shifted phenomenon is that the hydrogen bond produced by the strong polar molecule hydrazine in turbidity standard formal hydrazine and the carboxyl in Potassium Hydrogen Phthalate causes, and because hydrogen bond can affect n-π * energy level transition, makes R be with absorption peak generation blue shift.Along with the increase of turbidity, the concentration of hydrazine increases, and the interference of hydrogen bond increases, and blue shift size is also in rising trend.As shown in Figure 4, illustrate the blue shift situation under different turbidity, represent with the point of black in the drawings.Curve is the result of these points being carried out to negative exponential curve matching.As we can see from the figure, along with turbidity becomes large, blue shift amplitude becomes large, slows down final almost constant when blue shift increases to its change with turbidity to a certain degree.
(4) carry out peak to the absorption spectrum moving revised all testing liquids in step (3) through peak and fall correction, detailed process is as follows:
4-1, by turbidity standard and the mixing of COD standard solution, obtaining COD value is 50mg/L, and turbidity value is respectively 0, the mixed solution of 5NTU, 10NTU, 20NTU, 30NTU, 40NTU and 50NTU is as sample solution;
4-2, by formula (2), the factor of influence K of sample solution in calculation procedure 4-1 n(λ),
A(λ)＝K N(λ)A COD(λ)+A tur(λ)(2)
Wherein, A (λ) is for sample solution is through moving the revised absorbance in peak, and process is identical with testing liquid, A cOD(λ) and A tur(λ) the COD titer respectively corresponding to sample solution and the absorbance of turbidity standard, K n(λ) be factor to affect;
4-3, K according to each sample solution calculated in step 4-2 n(λ), as shown in Figure 6, each K n(λ) valley is K, sets up variation model K (t) of valley K with turbidity, as shown in Figure 7 by curve;
4-4, according to trough valley K both sides K nand turbidity is the linear approximate relationship between the COD titer absorbance of zero, simulates K nwith the variation model K of wavelength n(λ), linear approximate relationship as shown in Figure 8;
4-5, by K n(λ) formula (3) is substituted into, the absorbance spectrum computing formula after can being compensated by inverse operation:
A' COD(λ)＝(A'(λ)-A tur'(λ))/K N(λ)(3)
Wherein, A' cOD(λ) be the absorbance after determining amount, A'(λ) for moving the absorbance of revised testing liquid through peak, A tur' (λ) be the turbidity absorbance of testing liquid under current turbidity, K n(λ) for simulating the variation model of the factor to affect obtained.
4-6, to substitute in step 4-3 according to the current turbidity value of testing liquid, obtain the valley K of testing liquid, then obtain the K of testing liquid according to the linear approximate relationship in step 4-4 n(λ), by the K of testing liquid n(λ), the A'(λ of the testing liquid obtained in step (1)), and the A of the testing liquid calculated in step (2) tur' (λ) substitute into formula (3), the A' of the absorbance after being compensated cOD(λ).
Fig. 5 ~ 8 illustrate factor to affect K n(λ) Changing Pattern, Fig. 5 illustrates 50mg/LCOD and different turbidity (0,5,10,20,30,40,50NTU) the absorption spectrum of mixed solution after directly deducting turbidity standard absorbance, it is comparatively obvious that deviation falls in the blue shift of absorption peak and peak, and turbidity more large deviation is larger.Fig. 6 represents K near COD titer absorption peak (280nm) nwith the change curve of wavelength, COD absorption peak place K in figure n(λ) there is valley, along with COD absorbance declines to peak value both sides, K nrise gradually final close to 1.Fig. 7 is K under different turbidity n(λ) valley, represents with the point of black in the drawings, and curve is the result of it being carried out to negative exponential curve matching.As can be seen from the figure, along with turbidity increases, K n(λ) valley reduces, and it is slack-off gradually to reduce speed.Fig. 8 illustrates within the scope of 265-280nm, K nwith the change of COD titer absorbance, as can be seen from the figure, K nbe the absorbance of the COD standard solution of 0 with turbidity be approximately linear variation tendency, COD standard solution absorbance is larger, K nless.
Fig. 9 represent determining amount after absorption spectrum.As can be seen from the contrast of Fig. 1 and Fig. 9, along with turbidity increases before compensating, the absorption peak of COD at 280nm place is submerged consequently None-identified gradually, and turbidity add the blue shift that brings and peak falls all comparatively obvious; After compensating, the absorption spectrum of mixed liquor almost overlaps with the absorption spectrum of COD titer, and the peak at 280nm place displays, and compensation effect is better.

Claims (7)

1., based on the determining amount method that spectroscopic methodology COD detects, it is characterized in that, comprise the following steps:
(1) absorption spectrum of testing liquid is obtained;
(2) absorption spectrum during the current turbidity effect of the testing liquid in calculation procedure (1);
(3) carry out peak to the absorption spectrum of the testing liquid in step (1) and fall correction, detailed process is as follows:
3-1, by turbidity standard and the mixing of COD standard solution, obtain many group COD concentration is identical, turbidity value is different mixed solution as sample solution;
3-2, by formula (1), the factor of influence K of sample solution in calculation procedure 3-1 n(λ),
A(λ)＝K N(λ)A COD(λ)+A tur(λ)(1)
Wherein, the absorbance that A (λ) is sample solution, A cOD(λ) and A tur(λ) the COD titer respectively corresponding to sample solution and the absorbance of turbidity standard, K n(λ) be factor to affect;
3-3, K according to all sample solutions calculated in step 3-2 n(λ), each K is obtained n(λ) valley is K, sets up variation model K (t) of valley K with turbidity by negative exponential curve matching;
3-4, according to trough valley K both sides K nlinear approximate relationship between the COD titer absorbance having an identical COD with sample solution, simulates K nwith the variation model K of wavelength n(λ);
3-5, by K n(λ) formula (1) is substituted into, the absorbance spectrum computing formula after can being compensated by inverse operation:
A' COD(λ)＝(A'(λ)-A tur'(λ))/K N(λ)(2)
Wherein, A' cOD(λ) be the absorbance after testing liquid determining amount, A'(λ) be the absorbance of testing liquid, A tur' (λ) be the turbidity absorbance of testing liquid under current turbidity, K n(λ) for simulating the variation model of the factor to affect obtained;
According to variation model K (t) in the current turbidity value of testing liquid and step 3-3, obtain the valley K of testing liquid, then obtain the K of testing liquid according to step 3-4 n(λ);
By the K of testing liquid n(λ) the A'(λ of the testing liquid, obtained in step (1)) and step (2) in the A of testing liquid that calculates tur' (λ) substitute in formula (2), the A' of the absorbance after being compensated cOD(λ).
2. as claimed in claim 1 based on the determining amount method that spectroscopic methodology COD detects, it is characterized in that, in step (2), the computing method of absorption spectrum during the current turbidity effect of testing liquid are as follows:
2-1, obtain the absorption spectrum of the different turbidity standard of multiple turbidity;
2-2, be normalized by the every bar absorption spectrum in step 2-1, formula is as follows:
ψ ( λ ) = A N ( λ ) - A min A m a x - A min ,
Wherein, A n(λ) be the absorption spectrum of turbidity standard, A maxand A minbe maximal value and the minimum value of absorbance, ψ (λ) is the curve of spectrum after normalization, and λ is wavelength;
2-3, the normalization curve of spectrum that step 2-2 calculates to be averaging, to obtain normalization spectrum as the curve of spectrum of standard turbidity;
The absorbance of the some wavelength points of absorption spectrum on visible light wave range of testing liquid in 2-4, obtaining step (1), calculates the absorbance that obtains relative to corresponding wavelength place scaling, and ask the mean value of scaling to characterize the current turbidity of this testing liquid;
2-5, by the mean value of the scaling in step 2-4 with entirety is multiplied, and obtains absorption spectrum during the current turbidity effect of this testing liquid.
3. as claimed in claim 1 or 2 based on the determining amount method that spectroscopic methodology COD detects, it is characterized in that, in step (3), substitute into the A (λ) of formula (1) and substitute into the A'(λ of formula (2)) for move revised absorption spectrum through peak, peak moves correction and comprises the following steps:
4-1, the preparation known turbidity of many groups and the turbidity standard of COD concentration and the mixed solution of COD titer, and gather the absorption spectrum of each mixed solution;
The blue shift size of each mixed solution in 4-2, calculation procedure 4-1, sets up by curve the mathematical model that blue shift size changes with turbidity;
4-3, mathematical model by step 4-2, according to the current turbidity value of the testing liquid calculated in step (2), calculate the blue shift of testing liquid; The blue shift of the standard turbidity value calculation sample solution of solution per sample;
4-4, the absorption spectrum of sample solution and testing liquid is done corresponding movement according to the blue shift calculated in step 4-3, the absorption spectrum that peak moves revised sample solution and testing liquid must be arrived.
4. as claimed in claim 1 or 2 based on the determining amount method that spectroscopic methodology COD detects, it is characterized in that, described turbidity standard adopts formal hydrazine turbidity standard, and COD standard solution adopts Potassium Hydrogen Phthalate COD standard solution.
5., as claimed in claim 1 or 2 based on the determining amount method that spectroscopic methodology COD detects, it is characterized in that, in step (3), the COD of the sample solution of configuration is 30 ~ 70mg/L.
6., as claimed in claim 2 based on the determining amount method that spectroscopic methodology COD detects, it is characterized in that, in step 2-4, the wavelength coverage of described visible spectrum is 400 ~ 600nm.
7. as claimed in claim 1 or 2 based on the determining amount method that spectroscopic methodology COD detects, it is characterized in that, in step 3-4, described linear approximate relationship is in 265 ~ 280nm and 280 ~ 300nm in wavelength coverage.
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