Method for measuring concentration of particulate matter suspension

Abstract

The invention discloses a method for measuring the concentration of a particulate matter suspension, and belongs to the technical field of particulate matter suspension detection and analysis. The measuring method comprises the following steps that a to-be-measured particulate matter suspension is poured into a cuvette, the OD value of the to-be-measured particulate matter suspension under different incident wavelengths is measured, and the OD value weight of the minimum wavelength is w1 = O1 / (O1 + pO2M + qO3N); the OD value weight of the intermediate wavelength is w2 = pO2M / (O1 + pO2M + qO3N); the OD value weight of the maximum wavelength is w3 = qO3N / (O1 + pO2M + qO3N); the final OD value of the particulate matter suspension is O = w1O1 + w2O2 + w3O3; and determining the concentration of the particulate matter suspension according to the final OD value. According to the measurement method, the problem of low OD reading at high concentration is solved, and the problem of jumping between dilution data and non-dilution data is also avoided.

Description

Technical Field

[0001] The invention relates to the technical field of particle suspension detection and analysis, and in particular to a method for measuring the concentration of a particle suspension. Background Art

[0002] The information disclosed in the background of the invention is only intended to enhance the understanding of the overall background of the invention and should not be necessarily regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] The concentration of a particle suspension refers to the content of particles per unit volume. Common particle suspensions include ink, muddy water, correction fluid, etc., in addition to various microbial culture fluids. The concentration of a particle suspension is generally determined by spectrophotometry. The principle of this detection method is that when a light beam passes through a suspension, its transmittance is reduced due to scattering or absorption. When the concentration of the suspension is low, the transmittance of light obeys the Beer-Lambert law. The concentration of particles is proportional to the optical density (OD value) within a certain range and inversely proportional to the transmittance.

[0004] The spectrophotometric method is simple and fast, but it can only directly measure the concentration of the particle suspension with an OD value not exceeding 1.0 more accurately. When the concentration of the particle is high, due to the secondary reflection of light, the Beer-Lambert law will no longer apply, and the reading of the OD value will be significantly lower than the actual value, and the higher the concentration, the greater the deviation. Therefore, for a suspension with a high OD value, it is necessary to dilute it until the OD value falls within the above range to measure it more accurately. The operation is cumbersome, and the readings of the diluted and non-diluted values ​​will jump, with poor stability and accuracy. In addition, the process of opening the cover for sampling and diluting the microbial culture solution may cause pollution and interfere with the growth conditions of the microorganisms, and this operation is completely unacceptable for anaerobic microorganisms.

[0005] Therefore, how to provide a method for determining the concentration of a particle suspension based on spectrophotometry with high accuracy and without the need for dilution is an urgent problem to be solved. Summary of the invention

[0006] In view of this, the present invention provides a method for measuring the concentration of a particle suspension. The measurement method provided by the present invention can directly and accurately detect the concentration of the liquid without dilution when the actual OD value of the particle suspension is far greater than 1.0, thereby greatly improving the efficiency and accuracy of the detection.

[0007] The present invention provides a method for measuring the concentration of a particle suspension, comprising the following steps:

[0008] Measure the OD value of the particle suspension to be tested at different incident wavelengths, where the minimum incident wavelength is wavelength 1; the middle incident wavelength is wavelength 2; and the maximum incident wavelength is wavelength 3;

[0009] The OD value weight of wavelength 1 is: w1 = O1 / (O1+pO2 M +qO3 N );

[0010] The OD value weight of wavelength 2 is: w2 = pO2 M / (O1+pO2 M +qO3 N );

[0011] The OD value weight of wavelength 3 is: w3 = qO3 N / (O1+pO2 M +qO3 N );

[0012] The final OD value of the particle suspension is: O = w1O1 + w2O2 + w3O3; the concentration of the particle suspension is determined according to the final OD value;

[0013] Among them, O1 is the OD value corresponding to wavelength 1; O2 is the OD value corresponding to wavelength 2; O3 is the OD value corresponding to wavelength 3;

[0014] p and q are real numbers, ≥0; M and N are real numbers, ≥0.

[0015] Preferably, the wavelength spacing between wavelength 1 and wavelength 2 and the wavelength spacing between wavelength 2 and wavelength 3 are greater than 200 nm.

[0016] Furthermore, the wavelength intervals between wavelength 1 and wavelength 2 and between wavelength 2 and wavelength 3 are 200-300 nm and 250-600 nm, respectively.

[0017] Furthermore, wavelength 1 is 550-650 nm, wavelength 2 is 750-950 nm, and wavelength 3 is 1000-1800 nm.

[0018] Furthermore, wavelength 1 is 600 nm, wavelength 2 is 850 nm, and wavelength 3 is 1200 nm.

[0019] Preferably, the specific values ​​of p, q, M and N are calibrated by preliminary experiments of the particles to be measured, so that the minimum wavelength has the maximum weight at low concentrations and the maximum wavelength has the maximum weight at high concentrations.

[0020] Furthermore, p=4, q=8, M=2, N=3.

[0021] Preferably, the particle suspension includes one or more of microbial culture fluid, mud or ink.

[0022] Preferably, the optical path length of the cuvette used in the measurement process is 1 cm, 5 mm or 2 mm.

[0023] Furthermore, O1, O2 and O3 are OD values ​​actually measured at wavelength 1, wavelength 2 and wavelength 3 respectively, which are converted into OD values ​​after the optical path length is 600 nm and 1 cm.

[0024] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0025] The present invention provides a method for measuring the concentration of a particle suspension by utilizing the different weights of the OD values ​​of the incident wavelength at different concentrations. The method not only solves the problem of low OD readings at high concentrations, but also avoids the problem of jumps between diluted data and non-diluted data. The method has high accuracy, is easy to operate, and has low detection cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their description are used to explain the present invention and do not constitute an improper limitation of the present invention. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 The OD in Table 1 in Example 1 of the present invention is 600 The scatter plot and linear fitting curve were made with the theoretical value as the horizontal axis and the final OD value as the vertical axis;

[0028] Figure 2 The OD in Table 2 in Example 2 of the present invention is 600 The scatter plot and linear fitting curve are drawn with the theoretical value as the horizontal axis and the final OD value as the vertical axis. DETAILED DESCRIPTION

[0029] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0030] The present invention provides a method for measuring the concentration of a particle suspension, comprising the following steps:

[0031] Measure the OD value of the particle suspension to be tested at different incident wavelengths, where the minimum incident wavelength is wavelength 1; the middle incident wavelength is wavelength 2; and the maximum incident wavelength is wavelength 3;

[0032] The OD value weight of wavelength 1 is: w1 = O1 / (O1+pO2 M+qO3 N );

[0033] The OD value weight of wavelength 2 is: w2 = pO2 M / (O1+pO2 M +qO3 N );

[0034] The OD value weight of wavelength 3 is: w3 = qO3 N / (O1+pO2 M +qO3 N );

[0035] The final OD value of the particle suspension is: O = w1O1 + w2O2 + w3O3; the concentration of the particle suspension is determined according to the final OD value;

[0036] Among them, O1 is the OD value corresponding to wavelength 1; O2 is the OD value corresponding to wavelength 2; O3 is the OD value corresponding to wavelength 3;

[0037] p and q are real numbers, ≥0; M and N are real numbers, ≥0.

[0038] The present invention finds that when a spectrophotometer is used to measure an OD value, at a lower concentration, the OD value measured by a smaller incident wavelength is closer to the actual value, and as the concentration increases, the OD value reading of the smaller wavelength is significantly lower than the actual value, and the higher the concentration, the greater the deviation. As the concentration increases, the weight of the smaller wavelength data decreases, while the weight of the higher wavelength data increases, so the present invention allocates different weights to the OD values ​​of different incident wavelengths, so that the calculation result of the measured OD value is closer to the actual OD value, solves the problem of low OD reading at high concentration, and avoids the problem of data jump caused by concentration dilution.

[0039] In the present invention, OD value, optical density, absorbance, and absorbance value are synonymous.

[0040] In the present invention, the wavelength spacing between wavelength 1 and wavelength 2 and the wavelength spacing between wavelength 2 and wavelength 3 are above 200nm. This design is to make the difference between the wavelengths larger, thereby improving the accuracy of the measurement. Further, the wavelength spacing between wavelength 1 and wavelength 2 and between wavelength 2 and wavelength 3 is 200-300 and 250-600nm, respectively. In one or more embodiments of the present invention, wavelength 1 is 550-650nm, wavelength 2 is 750-950nm, and wavelength 3 is 1000-1800nm. Most preferably, wavelength 1 is 600nm, wavelength 2 is 850nm, and wavelength 3 is 1200nm. 600nm is selected because it is the existing commonly used OD value wavelength value, the OD value at a wavelength of 850nm is close to 1 / 2 of 600nm, and the OD value at a wavelength of 1200nm is close to 1 / 4 of 600nm.

[0041] In the present invention, the optical path of the cuvette used in the measurement process is 1 cm, 5 mm or 2 mm. In the present invention, O1, O2 and O3 are the OD values ​​actually measured at wavelength 1, wavelength 2 and wavelength 3 respectively, converted into OD values ​​after the optical path of 600 nm and 1 cm.

[0042] The measurement method of the present invention can also be combined with optical path weighting to achieve secondary weighting to further increase the accuracy of the test. The specific test method is as follows:

[0043] First, use a cuvette with an optical path of 1 cm to detect the absorbance of the object under test at the following three incident wavelengths: 600nm, 850nm, and 1200nm. Then, use the above weighted formula to calculate the wavelength-weighted OD value of 1cm optical path, which is recorded as X1.

[0044] Then the same method was used to detect and calculate the weighted OD values ​​of the three incident wavelengths under the conditions of 5mm and 2mm optical path, which were recorded as X2 and X3;

[0045] Finally, X1, X2 and X3 are weighted twice, the maximum optical path (e.g. 1 cm) is optical path 1; the middle optical path (e.g. 5 mm) is optical path 2; the minimum optical path (e.g. 2 mm) is optical path 3;

[0046] The OD value weight w1' of optical path 1 is: w1'=X1 / (X1+bX2 E +cX3 F );

[0047] The OD value weight w2' of optical path 2 is: w2'=bX2 E / (X1+bX2 E +cX3 F );

[0048] The OD value weight w3' of optical path 3 is: w3'=cX3 F / (X1+bX2 E +cX3 F );

[0049] The final calculated OD value of the particle suspension (denoted as X) is: X = w1'X1 + w2'X2 + w3'X3;

[0050] In the present invention, the specific values ​​of p, q, M and N are calibrated by the preliminary experiments of the particles to be measured, so that the minimum wavelength has the maximum weight at low concentrations, and the maximum wavelength has the maximum weight at high concentrations. The two parameters p and q determine at what concentration the weights of wavelengths 2 and 3 exceed the previous wavelength. The two parameters M and N determine the speed at which the weights of the corresponding wavelengths increase, and the larger the power value, the faster the increase. In general, M and N can take positive integers, and more accurate parameters can be obtained by numerical fitting. Preferably, p=4, q=8, M=2, and N=3 are used in the present invention. These are empirical constants given based on observed data, and the error in this case is small enough.

[0051] In the present invention, the particle suspension includes one or more of microbial culture fluid, mud or ink, and may also be other suspensions. The present invention preferably uses microbial culture fluid, such as yeast culture fluid, Escherichia coli culture fluid, and the like.

[0052] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0053] Example 1

[0054] This embodiment provides a method for measuring the concentration of a particle suspension.

[0055] Prepare BMGY medium suitable for culturing yeast: Take a 300 ml conical flask, add 400 μl glycerol, 10 ml 1M pH=6.0 potassium phosphate buffer, and 80 ml distilled water, and seal the bottle mouth with tin foil. Place it in a high-pressure steam sterilizer and sterilize it at 121°C for 20 minutes. Then, add 10 ml of the yeast nitrogen base medium mother solution with a concentration of 134 g / L that has been filtered and sterilized to the above medium in a clean bench.

[0056] Take 100 microliters of yeast from the preserved yeast strain and add it to the above BMGY medium. Place it in a constant temperature shaking incubator and culture it at 30°C and 260 rpm for 24 hours. Dilute the yeast stock solution with water and add it to a quartz cuvette with a 1 cm optical path. Then use a spectrophotometer to detect the absorbance of the yeast stock solution at a wavelength of 600 nanometers. Then multiply the absorbance by the dilution factor to measure the OD of the yeast stock solution. 600 It is 14.9.

[0057] Take different volumes of the above yeast stock solution and mix it with distilled water to make the total volume of the two 5 ml, and you can get different concentrations of yeast solutions numbered 1-14 in Table 1. The OD of the yeast stock solution has been measured above. 600 The OD value of each yeast solution can be calculated based on the content of yeast stock solution in each yeast solution. 600 Theoretical value. Take 3 ml of the above 14 different concentrations of yeast solution and add them to a 1 cm optical path quartz cuvette, put it into the cuvette hole of the spectrophotometer, and detect the absorbance values ​​at incident wavelengths of 600 nanometers, 800 nanometers, and 1200 nanometers. According to Lambert-Beer's law and Mie scattering theory, the absorbance value is inversely proportional to the square of the incident wavelength, so when converting the absorbance value of 850 nanometers to 600 nanometers, it is necessary to multiply by 2, and when converting the absorbance value of 1200 nanometers to 600 nanometers, it is necessary to multiply by 4. The absorbance value of 600 nanometers and the converted absorbance values ​​of 850 nanometers and 1200 nanometers are set as O1, O2, and O3 respectively.

[0058] According to the experimental data, p=4, q=8, M=2, N=3, w1=O1 / (O1+4O2 2 +8O3 3 ), w2=4O2 2 / (O1+4O2 2 +8O3 3 ), w3=8O3 3 / (O1+4O2 2 +8O3 3 ). The final OD value = w1O1+w2O2+w3O3 can be calculated by multiplying O1, O2, O3 with coefficients w1, w2, w3 respectively.

[0059] The test and calculation results are shown in Table 1.

[0060] Table 1 Theoretical values ​​and OD values ​​of yeast solutions of different concentrations tested in Example 1

[0061]

[0062]

[0063] The OD in Table 1 600 A scatter plot is made with the theoretical value as the horizontal axis and the final OD value as the vertical axis, and a linear fit is performed on the scatter plot, such as Figure 1 As shown, the scatter plot conforms to the linear equation: y = 0.8836x + 0.2927, and the coefficient of determination R 2 =0.9908. From Table 1 and Figure 1It can be seen that when the yeast concentration is high, the reading at 600 nm wavelength is seriously low. The weighted method is used to give different absorbance values ​​of different detection wavelengths different weights at different concentrations, which solves the problem of low OD readings at high concentrations and the problem of jumps in the process of converting different wavelengths. The measurement method of this embodiment is effective.

[0064] Example 2

[0065] 100 μl of yeast was added to BMGY medium and placed in a constant temperature shaking incubator for 24 hours at 30°C and 260 rpm. The yeast stock solution was diluted with water and added to a quartz cuvette with a 1 cm optical path. The absorbance of the yeast stock solution at a wavelength of 600 nm was then measured using a spectrophotometer. The absorbance was then multiplied by the dilution factor to determine the OD of the yeast stock solution. 600 It is 21.3.

[0066] Take different volumes of the above yeast stock solution and mix it with distilled water to make the total volume of the two 5 ml, and you can get different concentrations of yeast solutions numbered 1-20 in Table 2. The OD of the yeast stock solution has been measured above. 600 The OD value of each yeast solution can be calculated from the content of yeast stock solution in each yeast solution. 600 Theoretical value. Take 3 ml of the above 20 different concentrations of yeast solution and add them to a 2 mm optical path quartz cuvette, put it into the cuvette hole of the spectrophotometer, and detect the absorbance values ​​at 600 nm, 800 nm, and 1200 nm under the condition of 2 mm optical path. According to Lambert-Beer's law and Mie scattering theory, the absorbance value is inversely proportional to the square of the incident wavelength, and the absorbance value is inversely proportional to the optical path. Therefore, when the absorbance value detected under the conditions of 600 nm incident wavelength and 2 mm optical path is converted into the absorbance value of 600 nm and 1 cm optical path, the absorbance value needs to be multiplied by 5; when converting the absorbance value of 850 nm incident wavelength and 2 mm optical path into the absorbance value of 600 nm and 1 cm optical path, it needs to be multiplied by 10; similarly, the absorbance value of 1200 nm needs to be multiplied by 20 when converted. The converted absorbance values ​​at 600 nm, 850 nm, and 1200 nm are designated as O1, O2, and O3, respectively.

[0067] According to the experimental data, p=4, q=8, M=2, N=3, w1=O1 / (O1+4O2 2 +8O3 3 ), w2=4O2 2 / (O1+4O2 2 +8O3 3 ), w3=8O3 3 / (O1+4O2 2 +8O33 ). The final OD value = w1O1+w2O2+w3O3 can be calculated by multiplying O1, O2, O3 with coefficients w1, w2, w3 respectively.

[0068] The test and calculation results are shown in Table 2.

[0069] Table 2 Theoretical values ​​and OD values ​​of yeast solutions of different concentrations tested in Example 1

[0070]

[0071] Taking the OD in Table 2 600 A scatter plot is made with the theoretical value as the horizontal axis and the final OD value as the vertical axis, and a linear fit is performed on the scatter plot, such as Figure 2 As shown, the scatter plot conforms to the linear equation: y = 1.0106x + 1.0516, and the coefficient of determination R 2 =0.9945. From Table 2 and Figure 2 It can be seen that the 1 cm optical path reading of yeast is more serious at high concentrations. The weighted method is used to give different incident wavelengths different weights at different concentrations, which solves the problem of low OD readings at high concentrations. At the same time, the use of short optical path cuvettes further increases the linear range of detection, and the accuracy of this measurement method is higher.

[0072] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for measuring the concentration of a particle suspension, characterized in that: The steps include: Measure the OD value of the particle suspension to be tested at different incident wavelengths, where the minimum incident wavelength is wavelength 1; the middle incident wavelength is wavelength 2; and the maximum incident wavelength is wavelength 3; The OD value weight of wavelength 1 is: w1 = O1 / (O1+pO2 M +qO3 N ); The OD value weight of wavelength 2 is: w2 = pO2 M / (O1+pO2 M +qO3 N ); The OD value weight of wavelength 3 is: w3 = qO3 N / (O1+pO2 M +qO3 N ); The final OD value of the particle suspension is: O = w1O1 + w2O2 + w3O3; the concentration of the particle suspension is determined according to the final OD value; Among them, O1 is the OD value corresponding to wavelength 1; O2 is the OD value corresponding to wavelength 2; O3 is the OD value corresponding to wavelength 3; p and q are real numbers, ≥0; M and N are real numbers, ≥0.

2. The measuring method according to claim 1, characterized in that: The wavelength interval between wavelength 1 and wavelength 2 and the wavelength interval between wavelength 2 and wavelength 3 are above 200 nm.

3. The measuring method according to claim 2, characterized in that: The wavelength intervals between wavelength 1 and wavelength 2 and between wavelength 2 and wavelength 3 are 200 to 300 nm and 250 to 600 nm, respectively.

4. The measuring method according to claim 1, characterized in that: Wavelength 1 is 550-650nm, wavelength 2 is 750-950nm, and wavelength 3 is 1000-1800nm.

5. The measuring method according to claim 4, characterized in that: Wavelength 1 is 600nm, wavelength 2 is 850nm, and wavelength 3 is 1200nm.

6. The measuring method according to claim 1, characterized in that: The specific values ​​of p, q, M and N are calibrated by preliminary experiments on the particles to be measured, so that the minimum wavelength has the maximum weight at low concentrations and the maximum wavelength has the maximum weight at high concentrations.

7. The measuring method according to claim 6, characterized in that: p=4, q=8, M=2, N=3.

8. The measuring method according to claim 1, characterized in that: The particle suspension includes one or more of microbial culture solution, mud or ink.

9. The measuring method according to claim 1, characterized in that: The optical path length of the cuvette used in the measurement process is 1 cm, 5 mm or 2 mm.

10. The measuring method according to claim 9, characterized in that: O1, O2 and O3 are the OD values ​​actually measured at wavelength 1, wavelength 2 and wavelength 3 respectively, converted into OD values ​​after the optical path length is 600nm and 1cm.

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