A colorimetric method for real-time sensitive direct measurement of dye intermediate concentration

Abstract

The present application relates to the technical field of chemical analysis, and discloses a colorimetric method for directly and sensitively measuring the concentration of dye intermediates in real time, wherein the reliability of transmittance or reflectance is first ensured by controlling the colorimetric detection conditions of the instrument at the source, the most sensitive index is further selected from traditional three-stimulus values XYZ, and low-sensitivity data information is stripped from the traditional three-stimulus values by defining local three-stimulus values, so that the sensitivity and stability between the three-stimulus values and the concentration change are greatly improved, a quantitative model between the local three-stimulus values and the concentration is established, the most sensitive and accurate color spectrum response is obtained, the whole colorimetric quantitative process does not need any pretreatment operation on the sample, the relative error is small, the robustness is good, the analysis time is short, the universality is strong, and there is no secondary pollution risk. The method can be used for real-time monitoring and regulation in the production process, is conducive to improving the dye production efficiency, realizes pollution reduction and efficiency increase, and provides a reference for the quantification of other chemical substances.

Description

Technical Field

[0001] This invention relates to the field of chemical analysis technology, and in particular to a colorimetric method for real-time and sensitive direct measurement of the concentration of dye intermediates. Background Technology

[0002] Dye intermediates are important raw materials for dye production. The accuracy of the raw material formulation concentration has a great impact on the efficiency of subsequent dye production and the total amount of pollutants generated. Real-time monitoring of their concentration is conducive to achieving refined production, timely detection of abnormalities in the production process, and convenient effective intervention and control, thereby improving the efficiency of subsequent dye production, reducing the total amount of pollutants generated, and achieving pollution reduction and efficiency improvement.

[0003] Colorimetry is an important method for the quantitative detection and analysis of organic compounds, but it still faces several major challenges in the monitoring of dye intermediates: 1. There is currently a lack of methods for real-time and accurate quantification of dye intermediate concentrations based on colorimetric indicators; 2. Due to the high concentration of dye intermediates, which are generally tens or even hundreds of grams per liter, the tristimulus values ​​X, Y, and Z of high-concentration samples show little difference with concentration, resulting in low detection sensitivity and large measurement errors.

[0004] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a colorimetric method for real-time sensitive direct measurement of dye intermediate concentration, which aims to solve the current lack of colorimetric methods for real-time accurate direct measurement of dye intermediate concentration, and the problems of low sensitivity and large measurement error when using traditional tristimulus values ​​for direct detection.

[0006] The technical solution of the present invention is as follows:

[0007] A colorimetric method for real-time, sensitive, and direct measurement of dye intermediate concentration, comprising the following steps:

[0008] Preparation of standard samples: Find the historical lowest and highest concentration values ​​of the dye intermediate from the historical database, and denote them as C. min C max ; in [C L C H Within the concentration range of ], n standard samples of different concentrations are prepared at uniform concentration intervals, where C L ≤0.7C min C H ≥1.3C max n is greater than or equal to 6;

[0009] Sensitive colorimetric determination: A spectrophotometer is used to scan and test the standard samples of different concentrations. By adjusting the optical path, the transmittance or reflectance τ(λ) of the standard samples is kept within the range of [0.02%, 97%] to ensure that reliable and quantitative response data of the test samples are obtained.

[0010] Optimal colorimetric index selection: X(λ), Y(λ), and Z(λ) of standard samples at different concentrations are measured within the wavelength range [λ1, λ2], forming three variation curves, defined as follows: Among them, S λ Let λ be the relative spectral density of the illuminant, and τ(λ) be the transmittance or reflectance of the standard sample. The tristimulus values ​​are for the isoenergetic spectrum. λ1 = 380nm, λ2 = 740nm;

[0011] From the three variation curves X(λ), Y(λ), and Z(λ), identify the maximum characteristic peak of each curve and compare their magnitudes. Select the index M(λ) with the largest maximum characteristic peak as the subsequent quantitative index, where M is X, Y, or Z. Based on the quantitative index, construct the M(λ)-λ distribution curve of the standard sample. Measure the M(λ)-λ distribution curves of different standard concentrations at different wavelengths six times consecutively, calculate the standard deviation curve σ(λ)-λ at each concentration, find the wavelength range where the M(λ)-λ distribution curves of different concentrations intersect with the 6σ(λ)-λ curves, find the intersection band, and set it as λ3-λ4. Integrate M(λ) for each distribution curve corresponding to different concentrations within [λ3,λ4] to obtain the local tristimulus value pM of the standard sample at different concentrations, i.e. in,

[0012] Quantitative model fitting: By plotting ln(pM)-C and performing least-squares linear fitting, the quantitative model equation ln(pM)=a*C+b is obtained, where a and b are the parameter values ​​obtained by linear fitting; C is the different concentrations of the standard sample; and ln(pM) is the natural logarithm of the local tristimulus value of the standard sample at that concentration obtained according to the above steps.

[0013] Quantification of the test sample: Under the same colorimetric detection conditions as the standard sample, the local tristimulus value of the test sample is measured. The local tristimulus value is substituted into the quantitative model equation to obtain the actual concentration of dye intermediate in the test sample.

[0014] The colorimetric method for real-time sensitive direct measurement of dye intermediate concentration, wherein in the step of adjusting the optical path length so that the transmittance or reflectance τ(λ) of the standard sample is in the range of [0.02%, 97%], the optical path length is 1mm-10cm.

[0015] Beneficial Effects: This invention proposes a real-time, sensitive, and direct colorimetric method for measuring the concentration of dye intermediates. By constructing local tristimulus values, low-sensitivity data information is extracted from traditional tristimulus values, significantly improving the sensitivity between tristimulus values ​​and concentration changes. A quantitative model equation between local tristimulus values ​​and concentration is established, yielding sensitive and accurate chromatographic responses. The entire colorimetric quantitative process requires no sample pretreatment, exhibits small relative errors, good stability, short analysis time, strong universality, and no risk of secondary contamination. This method can be used for real-time monitoring and control of production processes, improving dye production efficiency and achieving pollution reduction and efficiency enhancement; it also provides a reference for the quantification of other chemical substances. Attached Figure Description

[0016] Figure 1 This is a graph showing the X(λ)-λ distribution curves of standard samples with different concentrations in Example 1 of the present invention.

[0017] Figure 2 This is a Y(λ)-λ distribution curve of standard samples with different concentrations in Example 1 of the present invention.

[0018] Figure 3 This is a Z(λ)-λ distribution curve of standard samples with different concentrations in Example 1 of the present invention.

[0019] Figure 4 This is a comparison chart of the quantitative fitting effects of the traditional tristimulus value X and the local tristimulus value pX in Embodiment 1 of the present invention. Detailed Implementation

[0020] This invention provides a colorimetric method for real-time, sensitive direct measurement of dye intermediate concentration. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0021] The main reasons for inaccurate colorimetric quantification in existing technologies include: transmittance or reflectance exceeding the instrument's accurate quantification range, or failure to select the most sensitive tristimulus index. Furthermore, the integration of traditional tristimulus values ​​within the 380-780nm range leads to the integration of data with low recognition, poor sensitivity, and low reliability, thereby reducing the overall sensitivity and accuracy of the index.

[0022] To overcome the aforementioned problems encountered by photometric methods in detecting the concentration of dye intermediates, this invention provides a real-time, sensitive, and direct colorimetric method for measuring the concentration of dye intermediates, comprising the following steps:

[0023] S10. Preparation of standard samples: Find the historical lowest and highest concentration values ​​of the dye intermediate from the historical data database, and denote them as C. min C max ; in [C L C H Within the concentration range of ], n standard samples of different concentrations are prepared at uniform concentration intervals, where C L ≤0.7C min C H ≥1.3C max n is greater than or equal to 6;

[0024] In this embodiment, the historical record database is a database formed by recording the concentrations of sample dye intermediates during the company's long-term production process. In this embodiment, a database with concentrations at [0.7C] is selected. min 1.3C max The preparation of standard samples with different concentrations within the concentration range of [ ] is to ensure that the concentration range of the standard samples is wider than the concentration boundary range of the actual test sample, thereby reducing the quantitative error of the test sample. In this embodiment, except for the different concentrations of the dye intermediate to be tested, the composition of other background solutions in the standard samples is consistent with the actual test solution system. As an example, assume C min =1%, C max =10%, then C L ≤0.7%, C H ≥13%, then in [C L C H Within the concentration range of ], according to uniform concentration intervals (C) H -C L Prepare n standard samples of different concentrations, where n is an integer greater than or equal to 6, preferably an integer between 6 and 20.

[0025] S20. Sensitive colorimetric determination: The standard samples of different concentrations are scanned and tested using a spectrophotometer. The transmittance or reflectance τ(λ) of the standard samples is adjusted to be within the range of [0.02%, 97%].

[0026] In this embodiment, the optical path range of the spectrophotometer is 1mm-10cm. By adjusting the appropriate optical path, the transmittance or reflectance τ(λ) of the standard sample can be within the range of [0.02%, 97%]. S30. The optimal colorimetric index is preferably: X(λ), Y(λ), and Z(λ) of standard samples of different concentrations are measured within the wavelength range of [λ1, λ2], forming three variation curves, which are defined as follows: Among them, S λ Let λ be the relative spectral density of the illuminant, and τ(λ) be the transmittance or reflectance of the standard sample. The tristimulus values ​​are for the isoenergetic spectrum. λ1 = 380 nm, λ2 = 740 nm; Find the maximum characteristic peak of each curve from the three variation curves X(λ), Y(λ), and Z(λ) and compare their magnitudes. Select the index M(λ) with the largest maximum characteristic peak as the subsequent quantitative index, where M is X, Y, or Z; Based on the quantitative index, construct the M(λ)-λ distribution curve of the standard sample. Measure the M(λ)-λ distribution curves of different standard concentrations at different wavelengths six times consecutively, calculate the standard deviation curve σ(λ)-λ at each concentration, find the band range where the M(λ)-λ distribution curves of different concentrations intersect with the 6σ(λ)-λ curves, find the intersection band, and set it as λ3-λ4. Integrate M(λ) for each distribution curve corresponding to different concentrations within [λ3, λ4] to obtain the local tristimulus value pM of the standard sample at different concentrations, i.e. in,

[0027] In this embodiment, taking the maximum absorption peak of the X(λ) curve as an example, the M(λ)-λ distribution curve of the standard sample is constructed based on the quantitative index. The M(λ)-λ distribution curves of different standard concentration components at different wavelengths are measured six times consecutively, and the standard deviation curves σ(λ)-λ at each concentration are calculated. The wavelength range where the M(λ)-λ distribution curves of different concentrations intersect with the 6σ(λ)-λ curves is found. The intersection band is identified and set as λ3-λ4. The X(λ) of each distribution curve corresponding to different concentrations is integrated within [λ3,λ4] to obtain the local tristimulus value pX of the standard sample at different concentrations. Similarly, taking the maximum value of the absorption peak of the Y(λ) curve as an example, the local tristimulus values ​​pY of the standard samples at different concentrations are obtained. Taking the maximum value of the absorption peak of the Z(λ) curve as an example, the local tristimulus values ​​pZ of the standard samples at different concentrations are obtained.

[0028] S40. Quantitative model fitting: By plotting ln(pM)-C and performing least-squares linear fitting, the quantitative model equation ln(pM)=a*C+b is obtained, where a and b are the parameter values ​​obtained by linear fitting; C is the different concentrations of the standard sample; and ln(pM) is the natural logarithm of the local tristimulus value of the standard sample at that concentration obtained according to the above steps.

[0029] S50. Quantification of the test sample: Under the same colorimetric detection conditions as the standard sample, the local tristimulus value of the test sample is measured. The local tristimulus value is substituted into the quantitative model equation to obtain the actual concentration of the dye intermediate in the test sample.

[0030] This invention controls the colorimetric detection conditions of the instrument at the source, first ensuring the reliability of transmittance or reflectance, and then selecting the most sensitive index from the traditional tristimulus values ​​XYZ. Furthermore, by defining local tristimulus values, low-sensitivity data is removed from the traditional tristimulus values, significantly improving the sensitivity between tristimulus values ​​and concentration changes. Simultaneously, local integration avoids single-measurement errors, improving the stability and robustness of the method. This invention establishes a quantitative model between local tristimulus values ​​and concentration, obtaining the most sensitive and accurate chromatographic response. The entire colorimetric quantitative process requires no sample pretreatment, has small relative errors, short analysis time, strong universality, and no risk of secondary contamination. The method of this invention can be used for real-time monitoring and control of production processes, which is beneficial for improving dye production efficiency and achieving pollution reduction and efficiency improvement; and it also provides a reference for the quantification of other chemical substances.

[0031] The standard curve and fitting operations of this invention only need to be involved in the initial model building or periodic model calibration stages. When determining the concentration of the actual intermediate to be tested after the modeling is completed, the above process is not required, which helps to simplify the detection steps, shorten the detection time, and improve the detection efficiency.

[0032] The present invention will be further explained and illustrated below through specific embodiments:

[0033] Example 1

[0034] A colorimetric method for real-time, sensitive, and direct measurement of dye intermediate concentration specifically includes the following steps:

[0035] a. Standard sample preparation: The historical minimum and maximum concentration boundary values ​​of the dye intermediate to be tested are obtained by statistically analyzing the company's long-term production history data, and denoted as C. min =2%, C max=9%, and 13 standard samples of different concentrations were uniformly prepared within the concentration range of [0%, 12%]. Except for the concentration of the intermediate to be tested, the composition of the background solution in the standard samples was consistent with that of the actual test system. The main component was sulfuric acid with a concentration of 4%. The 13 concentrations of the standard samples were 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, and 12%.

[0036] b. Sensitive colorimetric measurement: Adjust the appropriate optical path size to 5 mm within the range of 1 mm to 10 cm, and use a spectrophotometer to scan and test the standard samples of different concentrations, so that the reflectance τ(λ) is within the range of [0.02%, 97%].

[0037] c. Optimal colorimetric index selection: X(λ), Y(λ), and Z(λ) of standard samples at different concentrations are measured within the wavelength range of [λ1, λ2] (λ1 = 380 nm, λ2 = 740 nm), forming a... Figures 1-3 The three variation curves shown are defined as follows: Among them, S λ Let λ be the relative spectral density of the illuminant, and τ(λ) be the reflectance of the standard sample. The tristimulus values ​​are for the isoenergetic spectrum;

[0038] By comparing the three curves, identify the largest characteristic peak of each curve, compare their magnitudes, and select the index X(λ), Y(λ), or Z(λ) with the largest value as the subsequent quantitative index. Figures 1-3 It can be seen that within the range [λ1, λ2], the maximum values ​​of X(λ), Y(λ), and Z(λ) with a minimum concentration of 1% are obtained, and their magnitudes are: X(λ)max > Y(λ)max > Z(λ)max. Therefore, the index X(λ) with the largest value is selected as the subsequent quantitative index. Based on this quantitative index, the M(λ)-λ distribution curve of the standard sample is constructed. The M(λ)-λ distribution curves of different standard concentrations at different wavelengths are measured six times consecutively, and the standard deviation curve σ(λ)-λ at each concentration is calculated. The wavelength range where the M(λ)-λ distribution curves of different concentrations intersect with the 6σ(λ)-λ curves is found. The intersection band is set as λ3-λ4 (570nm-680nm). Within [λ3, λ4], the X(λ) of each distribution curve corresponding to different concentrations is integrated to obtain the local tristimulus value pX of the standard sample at different concentrations.

[0039] d. Quantitative model fitting: Plotting ln(pX)-C, such as... Figure 4As shown, and after linear fitting, the quantitative model equation is obtained as ln(pX)=-46.378C+3.3314,R 2 =0.9999, the average relative error absolute value =1.2%, as shown in Table 1.

[0040] e. Quantification of the test sample: Under the same colorimetric detection conditions as the standard sample, the local tristimulus value of the test sample was measured and substituted into the equation fitted in step d above to obtain the actual concentration of the dye intermediate in the test sample. The average spiked recovery rate at the two concentrations of 2% and 9% was 99.8% and the relative standard deviation was 0.33%.

[0041] In contrast. Figure 4 Table 1 shows the comparison effect of using the traditional tristimulus index X for modeling and quantification. It can be seen that the average absolute value of the relative error of the ln(pX)-C quantification method of this invention is reduced by 32.4% compared with the traditional ln(X)-C fitting quantification method.

[0042] Table 1 Comparison of the quantitative fitting effects of traditional tristimulus value X and local tristimulus value pX.

[0043]

[0044] This invention controls the colorimetric detection conditions of the instrument from the source, first ensuring the reliability of transmittance or reflectance, and then selecting the most sensitive index from the traditional tristimulus values ​​XYZ. Moreover, by defining local tristimulus values, low-sensitivity data information is removed from the traditional tristimulus values, which greatly improves the sensitivity between tristimulus values ​​and concentration changes. A quantitative model between local tristimulus values ​​and concentration is established to obtain the most sensitive and accurate chromatographic response. The entire colorimetric quantitative process does not require any sample pretreatment, has small relative error, short analysis time, strong universality, and no risk of secondary pollution.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A colorimetric method for real-time, sensitive, and direct measurement of the concentration of dye intermediates, characterized in that, Including the following steps: Preparation of standard samples: Find the historical lowest and highest concentration values ​​of the dye intermediate from the historical database, and denote them as C. min C max ; in [C L C H Within the concentration range of ], n standard samples of different concentrations are prepared at uniform concentration intervals, where C L ≤0.7C min C H ≥1.3C max n is greater than or equal to 6; Sensitive colorimetric determination: A spectrophotometer is used to scan and test the standard samples of different concentrations. The transmittance or reflectance of the standard samples is adjusted by changing the optical path length. Within the range of [0.02%, 97%], to ensure that reliable and quantifiable response data of the sample to be tested are obtained; Selection of optimal colorimetric parameters: Determination of standard samples of different concentrations within the wavelength range [λ1, λ2]. This results in three variation curves, defined as follows: ; ; ;in, The relative spectral density of the illuminant. The transmittance or reflectance of the standard sample. The tristimulus values ​​are for the isoenergetic spectrum. λ1=380nm, λ2=740nm; Find the maximum characteristic peak of each of the three curves X(λ), Y(λ), and Z(λ) and compare their sizes. Select the index M(λ) with the largest maximum characteristic peak as the subsequent quantitative index. M(λ) can be X(λ), Y(λ), or Z(λ). Based on the quantitative indicators, the M(λ)-λ distribution curves of the standard samples were constructed. The M(λ)-λ distribution curves of different standard concentrations at different wavelengths were measured six times consecutively. The standard deviation curves σ(λ)-λ at each concentration were calculated. The wavelength range where the M(λ)-λ distribution curves of different concentrations intersect with the 6σ(λ)-λ curves was found. The intersection band was identified and designated as λ3-λ4. Within [λ3, λ4], the M(λ) of each distribution curve corresponding to different concentrations was integrated to obtain the local tristimulus values ​​pM of the standard samples at different concentrations. ,in, ; Quantitative model fitting: By plotting ln(pM)-C and performing least-squares linear fitting, the quantitative model equation ln(pM)=a*C+b is obtained, where a and b are the parameter values ​​obtained by linear fitting; C is the different concentrations of the standard sample; and ln(pM) is the natural logarithm of the local tristimulus value of the standard sample at that concentration obtained according to the above steps. Quantification of the test sample: Under the same colorimetric detection conditions as the standard sample, the local tristimulus value of the test sample is measured. The local tristimulus value is substituted into the quantitative model equation to obtain the actual concentration of dye intermediate in the test sample.

2. The colorimetric method for real-time sensitive direct measurement of dye intermediate concentration according to claim 1, characterized in that, By adjusting the optical path length, the transmittance or reflectance of the standard sample can be adjusted. In steps within the range of [0.02%, 97%], the optical path length is 1mm-10cm.

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