CN108037084B - Anti-interference measuring method suitable for photometric principle water quality automatic analyzer - Google Patents

Abstract

The invention discloses an anti-interference measurement method suitable for an automatic water quality analyzer based on the principle of photometry. According to the change of absorption spectrum characteristics, the influence of interfering substances on measurement and the shift of absorption spectrum are determined, and no interference (or minimum interference) is selected. ) as the optimal measurement wavelength, analyze the change of the absorption spectrum characteristics of the sample solution to be tested and the reference absorption spectrum characteristics, and calculate the final measurement result as the output indication value of the instrument for this measurement to achieve anti-interference.

Description

An anti-interference measurement method suitable for photometric principle water quality automatic analyzer

technical field

The invention belongs to the field of water quality detection, in particular to an anti-interference measurement method suitable for an automatic water quality analyzer based on the principle of photometry.

Background technique

The principle of photometric water quality automatic online analyzer has the advantages of simple structure, high sensitivity and good repeatability, and has been widely used in the field of environmental online monitoring. The principle of photometry The automatic water quality online analyzer is mainly based on Lambert Beer's law to achieve measurement, that is, when a beam of parallel monochromatic light passes through a solution containing a uniform light-absorbing substance, the absorbance of the solution is proportional to the concentration of the light-absorbing substance and the thickness of the absorbing layer. The available formulas are expressed as:

A=εbc

In the formula: A is the absorbance, which is a dimensionless quantity; ε is the molar absorption coefficient, which is related to the properties of the light-absorbing substance to be measured and the measurement wavelength set by the instrument, and the unit is L·mol ^-1 ·cm ^-1 ; b is the absorption liquid Layer thickness, in cm; c is the concentration of light-absorbing substances, in mol·L ^-1 .

The existing photometric principle The water quality automatic analyzer usually selects a specific absorption wavelength as the measurement wavelength according to the light absorption characteristics of the target substance to be measured. In this way, the molar absorption coefficient ε of the substance measured by the analyzer can be understood as a fixed value and can be Through the calibration calculation, the liquid layer thickness b is usually a fixed value after the analyzer is produced, (usually, the product of the molar absorption ε and the liquid layer thickness b is directly calculated by calibration as the instrument parameter). Therefore, after the instrument is calibrated, the concentration of the target substance to be measured can be calculated by measuring the corresponding relationship between the absorbance of the sample solution and the concentration of the sample solution.

In actual measurement, especially in the measurement of complex waters, in addition to the target substance to be measured, there are often interfering substances that also absorb at the selected measurement wavelength, affecting the measurement of the target substance to be measured. . The existing water quality automatic analyzer usually adopts the method of adding interfering ion masking reagents to reduce the influence of interfering ions. However, due to the different use environments of the analyzer, the types and contents of interfering ions are different, so the analyzer uses masking reagents to reduce the influence of interfering ions. It is more restrictive.

The content of the present invention has not found an obvious similar scheme. Chinese patent CN101329252A discloses a chemical oxygen demand detection method. The method measures the absorbance of the sewage sample to be measured in multiple wavebands to be measured, and calculates the absorbance in the wavebands to be measured. Taking the wavelength as the integral variable, the absorbance is integrated, the integrated value of the absorbance of the sewage sample to be measured in each waveband to be measured is calculated, and the chemical oxygen demand is calculated through the calculation. The patent adopts a multi-wavelength ultraviolet measurement method. , so that the measurement results can accurately measure the value of chemical oxygen demand in a large application range and reduce the measurement error. This patent aims to improve the measurement accuracy of the substance to be tested (i.e. chemical oxygen demand) through a certain measurement and calculation method, which is different from the method in this patent to suppress the influence of interfering substances in the sample to be tested by means of multi-wavelength measurement and calculation. Multi-wavelength measurement technology, but the data analysis and processing methods are different, and the goals achieved are also different. The doctoral dissertation "Key Technology Research of Multi-parameter Water Quality Detector Based on Micro Spectrometer" (Wei Kanglin) pointed out the method of eliminating background interference by multi-wavelength spectral analysis method (P68-). A mathematical model is established based on the ratio of wavelength, measurement wavelength and magnification factor to eliminate background interference (mainly refers to turbidity), and its measurement wavelength is still a fixed measurement wavelength, which is different from the measurement method of this patent that selects the best absorption wavelength according to the water sample spectrum. Master's thesis "Research on Data Processing Method and Technology of Water Quality Monitoring System Based on Distributed Ultraviolet-Visible Spectroscopy" (Tongo) pointed out the research on spectral global calibration algorithm based on total light scattering method (P33-), which mentioned the optimal wavelength Extraction, but its purpose is to establish the particle size distribution function of suspended particles in water based on the extraction of the optimal wavelength, thereby eliminating the influence of turbidity measurement in water, which is different from the selection of the optimal measurement wavelength in this patent to eliminate interference ion absorption The effect of the "best measurement wavelength" is different in essence.

The existing water quality automatic analyzer based on the principle of photometry mainly realizes the quantitative measurement of the substance to be tested according to Lambert Beer's law, that is, after the monochromatic light of a certain wavelength passes through the solution to be tested, the absorbance of the solution, the concentration of the light-absorbing substance and the thickness of the absorption layer proportional. The monochromatic light measurement wavelength of the existing water quality automatic analyzer is usually selected according to the absorption spectrum characteristics of the substance to be tested, and it is a fixed measurement wavelength (for example, the measurement wavelength of 697 nm is usually used to measure ammonia nitrogen by color development of salicylic acid, and the measurement wavelength of 697 nm is usually used by diphenyl carbon. The acyl dihydrazide colorimetric measurement of hexavalent chromium usually adopts the measurement wavelength of 540nm), this measurement method can better meet the measurement requirements in a simple water environment, but when there are interfering substances in the substance to be tested (that is, in the selected measurement At the wavelength, when the interfering substances also have absorption), due to the additivity of the absorbance of the multi-component system, the analyzer will have errors in the measurement, which will affect the measurement.

At present, the measurement reliability of water quality analyzers is poor, especially in the complex environment where there are interfering substances in the water sample to be tested, the measurement results of the instrument have large errors (the concentration of the interfering substances is about the same, the larger the error is), and it is difficult to meet the measurement requirements of complex water samples.

Existing water quality analyzers usually select a specific wavelength as the measurement wavelength of the instrument according to the absorption spectrum characteristics of the substance to be measured. In the case of simple water samples (when there is no interfering substance or the concentration of the interfering substance is low), the measurement requirements can be better met, but in the case of measuring complex water samples with interfering substances There is also absorption at the measurement wavelength, which will inevitably lead to an increase in the error of the measurement result and affect the applicability and reliability of the instrument. As shown in Figure 1, the absorption spectrum of substance A (target substance) at a concentration of Xmol/L is shown in Figure 1. Spectral curve 1, and the absorption spectrum of substance B (interfering substance) at a concentration of Ymol/L is shown in Figure 1 Spectral curve 2, when the solutions of the two substances are mixed, the absorption spectrum of the (sample solution) is like the spectral curve 3. In this way, the measurement result calculated by the absorbance measured at the selected specific wavelength must be too large, which leads to Error in measurement result.

In addition, in existing water quality analyzers, a specific wavelength (usually the maximum absorption wavelength of substance A, ie, 700 nm) is usually selected as the measurement wavelength according to the absorption spectrum characteristics of the target substance. However, due to the drift interference factor of the optical system of the analyzer, the measured absorption spectrum curve of the sample solution is shifted, which will inevitably lead to the error of the measurement result. As shown in Fig. 2, the absorption spectrum of the target substance A is shown as absorption spectrum 1 in Fig. 2, and 700 nm is selected as the measurement wavelength. In the actual measurement, due to the influence of interference, the absorption spectrum is shifted to the absorption spectrum 2 shown in the figure, which will inevitably lead to the change of the absorbance measured at 700 nm, resulting in the error of the final measurement result.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the deficiencies in the prior art. The present invention discloses a new anti-interference measurement method suitable for an automatic water quality analyzer based on the principle of photometry. The method is based on the absorption spectrum characteristics of the target substance to be measured by the analyzer. , select multiple measurement wavelengths within a certain wavelength range, select the measurement wavelength with no interference (or the least interference) as the optimal measurement wavelength, and calculate the measurement result based on the absorbance of the optimal measurement wavelength and the corresponding standard curve equation, thus To achieve the effect of eliminating (or reducing) the influence of interfering substances, to achieve the purpose of anti-interference measurement by the analyzer.

In order to solve the above-mentioned purpose, the technical scheme of the present invention is as follows:

An anti-interference measurement method suitable for a photometric water quality automatic analyzer, comprising the following steps:

S1, according to the absorption spectrum range of the measurement target substance A and the performance requirements of the instrument, select the wavelength range λ _a ~ λ _b that meets the performance requirements of the analyzer, where λ _a and λ _b are the absorption spectrum range of the measurement target substance A and meet the analytical requirements. The minimum and maximum wavelengths required by the performance _of the instrument; in the wavelength range, _{λ 1} , λ ₂ ... Recommended absorption wavelength in the standard analysis method of substance A); n is the number of selected measurement wavelengths;

S2, use standard solutions of target substance A with different concentrations to calibrate the water quality automatic analyzer, obtain the absorbance of solutions with different concentrations at the selected measurement wavelengths λ ₁ , λ ₂ ... λ _n respectively, and according to the measurement wavelengths λ ₁ , λ ₂ ... The corresponding relationship between the absorbance at λ _n and the concentration of the target substance A is obtained respectively. The standard curve equations under different measurement wavelengths are C _λ1 =f ₁ (A _λ1 ), C _λ2 =f ₂ (A _λ2 )...C _λn =f _n ( A _λn ), in which C ₁ , C ₂ . . . C _{ω are} standard solutions of different concentrations of target substance A, respectively; A _λ1 , _{A λ2} . A _λ1 ), f ₂ (A _λ2 ), ... f _n (A _λn ) are the concentrations C _λ1 , C _λ2 ... C _λn relative to A _λ1 , A _λ2 ... A _λn at the measurement wavelengths λ ₁ , λ ₂ ... λ _n respectively Fitting the obtained standard curve equation; ω is the number of standard solutions of different concentrations of standard substance A;

S3, select the absorption spectrum of the concentration C _j (1≤j≤ω) as the reference absorption spectrum, and record the full spectrum absorbance of the concentration C _j , wherein the measurement wavelengths λ ₁ , λ ₂ . . . corresponding to the target substance A of the concentration C _j The absorbances of λ _n are respectively A _1j , A _2j . . . A _nj ;

S4. Measure the sample solution to be tested, and record the full spectral absorbance of the sample solution to be tested; wherein, record the absorbances at the measurement wavelengths λ ₁ , λ ₂ ... λ _n of the sample solution to be tested as A' ₁ , A' ₂ ... A'_n;

S5, analyze the change of the absorption spectrum characteristics of the sample solution to be tested and the reference absorption spectrum characteristics: the absorbance of the sample solution to be tested measured at the selected wavelength and the absorbance of the reference absorption spectrum measured at the C _j concentration at the corresponding wavelength do a proportional calculation,

其中R％为水质自动分析仪的重复性要求，则干扰物质造成的影响在仪器测量性能指标要求范围内，则以最大吸收波长λ₁为本次测量的最佳测量波长，通过最大吸收波长λ₁测得的吸光度A'₁和最大吸收波长λ₁对应标准曲线方程C_λ1＝f₁(A_λ1)，计算得到水质浓度测量结果；S6, if

Among them, R% is the repeatability requirement of the automatic water quality analyzer. If the influence caused by the interfering substances is within the required range of the instrument's measurement performance index, the maximum absorption wavelength λ ₁ is the best measurement wavelength for this measurement. The maximum absorption wavelength λ _1. The measured absorbance A' ₁ and the maximum absorption wavelength λ ₁ correspond to the standard curve equation C _λ1 =f ₁ (A _λ1 ), and calculate the water quality concentration measurement result;

则进行以下计算判断：S7, if

Then make the following calculation and judgment:

并计算比值

S701, select MAX(K1, K2... _{Kn )} , record the wavelength corresponding to MAX ₍ K1, _K2 ... _{Kn )} as λ _m1 and the absorbance at the measured wavelength of λ _m1

and calculate the ratio

S702, calculate the deviation Δλ=λ _m1 -λ ₁ between λ _m1 and the maximum absorption wavelength λ ₁ of the standard substance A, and take λ _m2 =λ ₂ +Δλ; λ _m3 =λ ₃ +Δλ...λ _mn =λ _n +Δλ ;

待测样品溶液在λ_m3处的吸收光谱

待测样品溶液在λ_mn处的吸收光谱

并计算比值

S703, acquiring the absorption spectrum of the sample solution to be tested at λ _m2

The absorption spectrum of the sample solution to be tested at λ _m3

The absorption spectrum of the sample solution to be tested at λ _mn

and calculate the ratio

则表示P＞R％由吸收峰偏移导致，则采用

和λ₁波长下的标准曲线方程

计算水质浓度测量结果；S704, if

It means that P>R% is caused by the shift of the absorption peak, then the

and the standard curve equation at λ ₁ wavelength

Calculate the results of water concentration measurements;

则表明待测样品溶液中存在一定浓度干扰物质B而导致P＞R％，则在MIN(K₁、K₂…K_n)处测得的吸光度最接近目标物质浓度的真实吸光度，将MIN(K₁、K₂…K_n)对应的测量波长选取为最佳测量波长，通过MIN(K₁、K₂…K_n)对应的测量波长处的吸光度和相应的标准曲线方程，计算得水质浓度测量结果。S705, it is judged that if

It indicates that there is a certain concentration of interfering substance B in the sample solution to be tested, resulting in P>R%, then the absorbance measured at MIN (K ₁ , K ₂ ... K _n ) is closest to the true absorbance of the target substance concentration, and MIN ( _The measurement _wavelength corresponding to _{K 1} , _{K 2 .} measurement results.

Preferably, in step S03, taking the fixed wavelength spacing as the step, recording the full-spectrum absorbance of the concentration C _j ; in step S04, taking the wavelength spacing as the step, recording the full-spectrum absorbance of the sample solution to be tested.

The wavelength spacing is 0.5nm-5nm.

The measurement wavelengths λ ₂ ...λ _n are distributed on both sides of the maximum absorption wavelength.

The full spectrum absorbance of concentration C _j includes the absorbance of measured wavelengths λ ₁ , λ ₂ . . . λ _n at concentration C _j .

n≥3.

The beneficial effects of the present invention include:

Aiming at the problem of poor applicability and reliability of the instrument due to the influence of different interfering ions in different use environments (especially complex water environment), the invention is based on multi-wavelength measurement technology, combined with analysis According to the measurement requirements of the instrument product, through the calculation and logical judgment of the absorbance, the absorption spectrum of the solution to be tested is analyzed by spectral characteristics, so as to determine the interference of the interference substance on the absorption spectrum of the target substance, and then select the measurement wavelength with no interference (or the least interference). As the best measurement wavelength, and based on the measurement result of the best measurement wavelength as the output indication value of the current measurement of the instrument, the analyzer can widely eliminate (or reduce) the effect of interference ions, and the purpose of anti-interference measurement;

Step S06 ensures that the measurement performance of the method in simple measurement occasions is not lower than the existing conventional measurement technology, and step S07 better eliminates (or reduces) the impact of interfering ions on measurement in complex occasions; at the same time, step S0704 In view of the absorption peak shift, the shifted absorbance was selected and included in the original standard curve equation for calculation, which better eliminated the influence of absorption peak shift on the measurement and improved the reliability of the instrument measurement;

This method can be widely used in the measurement of water quality automatic analysis instruments based on the principle of photometry, and can better eliminate (reduce) the influence of interfering ions and the influence of absorption spectrum shift independently caused by the measurement error on the instrument measurement in use. The applicability and measurement reliability of the analyzer to different measurement situations.

Description of drawings

Fig. 1 is a schematic diagram of the influence of interfering ions;

Fig. 2 is a schematic diagram of absorption spectrum shift;

Fig. 3 is a schematic diagram of the selection of measurement wavelengths λ ₁ , λ ₂ ... λ _n ;

Fig. 4 is a schematic diagram of measurement wavelength selection range;

Figure 5 is a schematic diagram of the standard curve corresponding to different measurement wavelengths.

Detailed ways

The application of the method will be described in detail below with reference to the accompanying drawings.

The present invention solves the existing technical problems and realizes through the following technical solutions:

The present invention will be further described below in conjunction with the accompanying drawings. The following examples are only used to illustrate the technical solutions of the present invention more clearly, and cannot be used to limit the protection scope of the present invention.

In this embodiment, the repeatability requirement of the water quality analyzer is R%, and there is a solution to be tested containing target substance A of unknown concentration. The measurement method includes the following steps,

S1, according to the absorption spectrum range of the measurement target substance A and the performance requirements of the instrument, the wavelength range λ _a ~ λ _b selected to meet the performance requirements of the analyzer is drawn up as shown in Figure 3 . In the wavelength range, λ ₁ , λ ₂ ... λ _n are selected as the measurement wavelengths of the water quality automatic analyzer, where λ ₁ is the maximum absorption wavelength of the target substance, and the other selected wavelengths are usually distributed on both sides of the maximum absorption wavelength, and n is The number of measurement wavelengths, n=3 in this embodiment, that is, the measurement wavelengths in this embodiment are λ ₁ , λ ₂ and λ ₃ , where λ ₁ is the maximum absorption wavelength of the target substance A, and λ ₂ and λ ₃ are distributed in the maximum absorption wavelength. both sides of the wavelength. As shown in Figure 4, absorption spectrum 1 in Figure 4 is the absorption spectrum of the target substance, absorption spectrum 2 is the absorption spectrum of the interfering substance B, and absorption spectrum 3 is the absorption spectrum of the sample solution, that is, the target substance mixed with the interfering substance.

S2, use standard solutions of target substance A with different concentrations to calibrate the water quality automatic analyzer, obtain the absorbance of solutions with different concentrations at the selected measurement wavelengths λ ₁ , λ ₂ ... λ _n respectively, and according to the measurement wavelengths λ ₁ , λ ₂ ... The corresponding relationship between the absorbance at λ _n and the concentration of the target substance A is obtained respectively. The standard curve equations under different measurement wavelengths are C _λ1 =f ₁ (A _λ1 ), C _λ2 =f ₂ (A _λ2 )...C _λn =f _n ( A _λn ), wherein the standard solutions of different concentrations of the target substance A are C ₁ , C ₂ ... C _ω respectively; A λ ₁ , A _{λ 2} ... A _λn are the absorbance f ₁ ( A _λ1 ), f ₂ (A _λ2 ), ... f _n (A _λn ) are the concentrations C _λ1 , C _λ2 ... C _λn relative to A _λ1 , A _λ2 ... A _λn at the measurement wavelengths λ ₁ , λ ₂ ... λ _n respectively Fit the standard curve equation of gained; In this embodiment, the standard solutions of target substance A of different concentrations are 3 groups, and the standard curve equation and standard curve of gained are respectively as shown in Table 2 and Figure 5;

Table 2 Standard curve equations corresponding to different measurement wavelengths

S3, select the absorption spectrum of the concentration C _j (1≤j≤ω) as the reference absorption spectrum, and record the full spectrum absorbance of the concentration C _j , wherein the measurement wavelengths λ ₁ , λ ₂ . . . corresponding to the target substance A of the concentration C _j The absorbances at λ _n are respectively A _1j , A _2j . . . A _nj ; in this embodiment, the absorption spectrum of concentration C ₂ is selected as the reference absorption spectrum (spectral curve 4 in FIG. 4 ), and the full spectrum absorbance of concentration C ₂ is recorded , that is, with a certain wavelength interval (0.5nm-5nm) as the step, record the absorbance, wherein the absorbance at λ ₁ , λ ₂ and λ ₃ corresponding to the target substance A with concentration C ₂ are A ₁₂ , A ₂₂ and A ₃₂ respectively ;

S4, measure the sample solution to be tested, and record the full-spectrum absorbance of the sample solution to be measured, (sequentially record the absorbance with the wavelength of the selected step length in step 3), wherein, record the measurement wavelengths λ ₁ and λ ₂ of the sample solution to be tested The absorbances at λ _n are respectively A' ₁ , A' ₂ ...A'_n; in this embodiment, the absorbances at λ ₁ , λ ₂ and λ ₃ are respectively A' ₁ , A' ₂ , A'₃;

S5, analyze the change of the absorption spectrum characteristics of the sample solution and the reference absorption spectrum characteristics, and calculate the ratio of the absorbance measured at the selected wavelength of the sample solution to the absorbance measured at the C _{concentration} at the corresponding wavelength,

其中R％为水质自动分析仪的重复性要求，则表明样品溶液中没有干扰物质或干扰物质极少(干扰物质造成的影响在仪器测量性能指标要求范围内)时，如此，则以最大吸收波长λ₁为本次测量的最佳测量波长，通过该波长下测得的吸光度A'₁和对应标准曲线方程C_λ1＝f₁(A_λ1)，计算得到最终水质浓度测量结果；通过该波长下测得的吸光度A'₁和对应标准曲线方程C_λ1＝f₁(A_λ1)，计算水质浓度，是本领域技术人员的公知技术，本实施例不再详述。S6, if

Among them, R% is the repeatability requirement of the automatic water quality analyzer, which means that there are no interfering substances or very few interfering substances in the sample solution (the influence caused by the interfering substances is within the required range of the instrument’s measurement performance indicators). In this case, the maximum absorption wavelength is used. λ ₁ is the best measurement wavelength for this measurement, and through the measured absorbance A' ₁ at this wavelength and the corresponding standard curve equation C _λ1 =f ₁ (A _λ1 ), the final water quality concentration measurement result is obtained by calculation; The measured absorbance A' ₁ and the corresponding standard curve equation C _λ1 =f ₁ (A _λ1 ), calculating the water quality concentration is a well-known technique of those skilled in the art, and will not be described in detail in this embodiment.

则应进行如下判断：S7, if

The following judgment should be made:

并计算比值

S701, select MAX (K ₁ , K ₂ , K ₃ ), record the wavelength corresponding to MAX (K ₁ , K ₂ , K ₃ ) as λ _m1 and the absorbance at the measured wavelength of λ _m1

and calculate the ratio

S702, calculate the deviation Δλ=λ _m1 -λ ₁ between λ _m1 and the maximum absorption wavelength λ ₁ of the standard substance A, and take λ _m2 =λ ₂ +Δλ; λ _m3 =λ ₃ +Δλ;

和样品溶液在λ_m3处的吸收光谱

并计算比值

和

S703, acquiring the absorption spectrum of the sample solution at λ _m2

and the absorption spectrum of the sample solution at λ _m3

and calculate the ratio

and

则表明P＞R％由吸收峰偏移导致，如此则采用

和λ₁波长下的标准曲线方程

计算得到最终水质浓度测量结果。S704, if

It shows that P>R% is caused by the shift of the absorption peak, so the use of

and the standard curve equation at λ ₁ wavelength

Calculate the final water concentration measurement result.

则表明样品溶液中存在一定浓度干扰物质B而导致P＞R％，如此，则在MIN(K₁、K₂、K₃)处测得的吸光度必然最接近目标物质浓度的真实吸光度，故MIN(K₁、K₂、K₃)选取为仪器本次测量的最佳测量波长(即示例中的λ₃处)，如此，通过λ₃处的吸光度A'₃和相应的标准曲线方程

计算得到最终水质浓度测量结果。因为干扰物质B的存在，根据吸光度的加和性原则，在干扰物质B存在吸收的测量波长下(λ₁、λ₂、)的吸光度必然大于真实值，进而依据其标准曲线计算所得的测量浓度也必然大于真实值，而在λ₃的测量波长下，干扰物质B处几乎没有吸收，故在该测量波长下的吸光度必然最接近于真实值，依据其标准曲线计算所得的测量浓度c₃'必然最接近于物质A的真值浓度，且c₃'必然小于c₁'和c₂'，由此分析仪即可选定c₃'(所有测量波长的计算结果中最小的计算结果)作为仪器本次测量过程的最终测量结果输出(其最佳测量波长即为λ₃)，从而实现消除(或减少)干扰之目的。S705, it is judged that if

It indicates that there is a certain concentration of interfering substance B in the sample solution, which leads to P>R%. In this case, the absorbance measured at MIN (K ₁ , K ₂ , K ₃ ) must be closest to the true absorbance of the target substance concentration, so MIN (K ₁ , K ₂ , K ₃ ) are selected as the best measurement wavelengths for this measurement by the instrument (that is, at λ ₃ in the example), so, through the absorbance A' ₃ at λ ₃ and the corresponding standard curve equation

Calculate the final water quality concentration measurement result. Because of the existence of interfering substance B, according to the principle of additivity of absorbance, the absorbance at the measurement wavelength (λ ₁ , λ ₂ , λ 2 ) at which the interfering substance B absorbs must be greater than the true value, and then the measured concentration calculated based on its standard curve It must also be greater than the true value, and at the measurement wavelength of λ ₃ , there is almost no absorption at the interfering substance B, so the absorbance at this measurement wavelength must be the closest to the true value, and the measured concentration c ₃ ' calculated according to its standard curve must be closest to the true concentration of substance A, and c ₃ ' must be less than c ₁ ' and c ₂ ', so that the analyzer can select c ₃ ' (the smallest calculation result among all measured wavelengths) as the calculation result The instrument outputs the final measurement result of this measurement process (the optimal measurement wavelength is λ ₃ ), so as to achieve the purpose of eliminating (or reducing) interference.

The above are only the preferred embodiments of the present invention, it should be pointed out: for those of ordinary skill in the art, under the premise of not departing from the principles of the present invention, several improvements and modifications can also be made, and these improvements and modifications should also be regarded as It is the protection scope of the present invention.

Claims (6)

1. an anti-interference measuring method that is applicable to photometric principle water quality automatic analyzer, is characterized in that, comprises the following steps, S1, according to the absorption spectrum range of the measurement target substance A and the performance requirements of the instrument, select the wavelength range λ _a ~ λ _b that meets the performance requirements of the analyzer, and select λ ₁ , λ ₂ . . . λ _n in the wavelength range as the water quality The measurement wavelength of the automatic analyzer, where λ ₁ is the maximum absorption wavelength of the target substance A; S2, use standard solutions of target substance A with different concentrations to calibrate the water quality automatic analyzer, obtain the absorbance of solutions with different concentrations at the selected measurement wavelengths λ ₁ , λ ₂ ... λ _n respectively, and according to the measurement wavelengths λ ₁ , λ ₂ ... The corresponding relationship between the absorbance at λ _n and the concentration of the target substance A obtains the standard curve equations under different measurement wavelengths C _λ1 =f ₁ (A _λ1 ), C _λ2 =f ₂ (A _λ2 )...C _λn =f _n (A _λn ), in which the standard solutions of different concentrations of the _{target substance A are represented} by C ₁ , C ₂ . A _λ1 ), f ₂ (A _λ2 ), ... _{f n} (A _λn ) are the concentrations C _λ1 , C _λ2 ... C _λn relative to the absorbance A _λ1 , A _λ2 ... A at the measurement wavelengths λ ₁ , λ ₂ ... The standard curve equation obtained by fitting _λn ; S3, select the absorption spectrum of the concentration C _j (1≤j≤ω) as the reference absorption spectrum, and record the full spectrum absorbance of the concentration C _j , wherein the measurement wavelengths λ ₁ , λ ₂ . . . corresponding to the target substance A of the concentration C _j The absorbances of λ _n are respectively A _1j , A _2j . . . A _nj ; S4. Measure the sample solution to be tested, and record the full spectral absorbance of the sample solution to be tested; wherein, record the absorbance at the measurement wavelengths λ ₁ , λ ₂ ... λ _n of the sample solution to be tested as A' ₁ , A' ₂ ... A'_n; S5, analyze the change of the absorption spectrum characteristics of the sample solution to be tested and the reference absorption spectrum characteristics, and compare the absorbance of the sample solution to be tested at the selected wavelength with the absorbance of the reference absorption spectrum measured at the C _j concentration at the corresponding wavelength do a proportional calculation,

S6, if

Among them, R% is the repeatability requirement of the automatic water quality analyzer, and the influence caused by the interfering substances is within the required range of the instrument's measurement performance index. The maximum absorption wavelength λ ₁ is the best measurement wavelength for this measurement. The maximum absorption wavelength λ ₁ The measured absorbance A' ₁ and the maximum absorption wavelength λ ₁ correspond to the standard curve equation C _λ1 =f ₁ (A _λ1 ), and calculate the water quality concentration measurement result; S7, if

Then carry out the following steps to calculate and judge: S701, select MAX(K1, K2... _{Kn )} , record the wavelength corresponding to MAX ₍ K1, _K2 ... _{Kn )} as λ _m1 and the absorbance at the measurement wavelength of λ _m1

Calculate the ratio

S702, calculate the deviation Δλ=λ _m1 -λ ₁ between λ _m1 and the maximum absorption wavelength λ ₁ of the standard substance A, and take λ _m2 =λ ₂ +Δλ; λ _m3 =λ ₃ +Δλ...λ _mn =λ _n +Δλ; S703, acquiring the absorption spectrum of the sample solution to be tested at λ _m2

The absorption spectrum of the sample solution to be tested at λ _m3

The absorption spectrum of the sample solution to be tested at λ _mn

Calculate the ratio

S704, if

It means that P>R% is caused by the shift of the absorption peak, then the

and the standard curve equation at λ ₁ wavelength

Calculate the results of water concentration measurements; S705, it is judged that if

It indicates that there is a certain concentration of interfering substance B in the sample solution to be tested, resulting in P>R%, then the absorbance measured at MIN (K ₁ , K ₂ ... K _n ) is closest to the true absorbance of the target substance concentration, and MIN ( _The measurement _wavelength corresponding to _{K 1} , _{K 2 .} measurement results. 2. a kind of anti-interference measuring method that is applicable to photometric principle water quality automatic analyzer according to claim 1, is characterized in that, comprises the following steps, Step S03, taking the fixed wavelength spacing as the step length, recording the full spectrum absorbance of the concentration C _j ; Step S04, taking the wavelength interval as a step, recording the full-spectrum absorbance of the sample solution to be tested. 3. a kind of anti-interference measuring method that is applicable to photometric principle water quality automatic analyzer according to claim 2, is characterized in that, comprises the following steps, The wavelength spacing is 0.5nm-5nm. 4. The anti-interference measurement method suitable for the photometric principle water quality automatic analyzer according to claim 1, characterized in that the measurement wavelengths λ ₂ ... λ _n are distributed on both sides of the maximum absorption wavelength. 5. a kind of anti-interference measuring method suitable for photometric principle water quality automatic analyzer according to claim 2, is characterized in that, the full spectrum absorbance of described concentration C _j comprises measuring wavelength λ ₁ , λ ₂ ...... λ _n Absorbance at concentration C _j . 6 . The anti-jamming measurement method suitable for an automatic water quality analyzer based on the principle of photometry according to claim 1 , wherein n≧3. 7 .

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