Measurement cuvette and method for concentration of particulate suspension

Abstract

A measurement cuvette and method for the concentration of a particulate suspension. The cross section of the measurement cuvette is of an L-shaped structure, which is formed by removing a rectangular notch from a square, the difference between the length and width of the rectangular notch being between 1 mm and 4 mm; and the cuvette is made of a fully transparent material. The measurement method comprises the following steps: pouring into a cuvette a particulate matter suspension to be measured; and measuring the absorbance of the cuvette at different optical path lengths, wherein the maximum optical path length of the cuvette is an optical path length 1, an intermediate optical path length thereof is an optical path length 2, and the minimum optical path length thereof is an optical path length 3; the weight of an OD value of the optical path length 1 is: w1=X1 / (X1+bX2 E+cX3 F), the weight of an OD value of the optical path length 2 is: w2=bX2 E / (X1+bX2 E+cX3 F), and the weight of an OD value of the optical path length 3 is: w3=cX3 F / (X1+bX2 E+cX3 F); and a final OD value of the particulate suspension is: X=w1X1+w2X2+w3X3, X1 being the OD value corresponding to the optical path length 1, X2 being the OD value corresponding to the optical path length 2, and X3 being the OD value corresponding to the optical path length 3.

Description

A cuvette and method for measuring particle suspension concentration

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] The present invention claims priority to Chinese patent application No. 202310866504.0 filed with the State Intellectual Property Office of China on July 14, 2023, entitled “A cuvette and method for measuring the concentration of a particle suspension”, the entire contents of which are incorporated by reference into the present invention and constitute a part of the present invention for all purposes. Technical Field

[0003] The invention belongs to the technical field of particle suspension detection and analysis, and relates to a particle suspension concentration measurement cuvette and a measurement method. Background Art

[0004] The statements herein merely provide background information related to the present invention and do not necessarily constitute prior art.

[0005] The concentration of a particulate suspension refers to the amount of particulate matter per unit volume. Common examples of particulate suspensions include ink, muddy water, correction fluid, and various microbial culture solutions. Spectrophotometry is generally used to determine the concentration of a suspension. This method relies on the principle that when a light beam passes through a suspension, its transmittance is reduced due to scattering or absorption. When the suspension concentration is low, the transmittance of light obeys the Beer-Lambert law. Within a certain range, the concentration of particulate matter is directly proportional to the optical density (OD value) and inversely proportional to the transmittance.

[0006] The spectrophotometric method is simple and fast, but it can only directly measure the concentration of particulate suspensions with an OD value not exceeding 1.0 with relative accuracy. When the concentration of particulate matter is high, the Beer-Lambert law no longer applies due to the secondary reflection of light, and the OD reading is significantly lower than the actual value, and the higher the concentration, the greater the deviation. Therefore, for suspensions with high OD values, they need to be diluted until the OD value falls within the above range in order to be measured more accurately. The operation is cumbersome, and the diluted and undiluted readings will jump, with poor stability, affecting accuracy. The process of opening the lid for sampling and diluting the microbial culture solution may also cause contamination and interfere with the growth conditions of the microorganisms. This operation is completely unacceptable for anaerobic microorganisms.

[0007] Summary of the Invention

[0008] In response to the shortcomings of the prior art, the present invention provides a cuvette and method for measuring the concentration of a particle suspension. This method allows for direct and accurate detection of the liquid concentration even when the actual OD value of the particle suspension far exceeds 1.0, without requiring dilution, thereby significantly improving detection efficiency and accuracy.

[0009] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0010] In a first aspect, the present invention provides a cuvette for measuring the concentration of a particle suspension, wherein the cuvette has an L-shaped cross-section formed by removing a rectangular notch from a square, wherein the difference between the length and width of the rectangular notch is 1-4 mm;

[0011] The cuvette is made of fully transparent material.

[0012] In some embodiments, the cuvette is made of polystyrene.

[0013] In some embodiments, the height of the cuvette is 4-5 cm.

[0014] In some embodiments, the width of the square of the cross section of the cuvette is 0.8-1.2 cm.

[0015] Preferably, the width of the square of the cross section of the cuvette is 1 cm, the length of the rectangular notch is 7-9 mm, and the width is 5-6 mm.

[0016] In a second aspect, the present invention provides a method for measuring the concentration of a particle suspension, comprising the following steps:

[0017] The particle suspension to be tested is poured into the cuvette, and the absorbance at different optical path lengths of the cuvette is measured, wherein the maximum optical path length of the cuvette is optical path length 1; the middle optical path length is optical path length 2; and the minimum optical path length is optical path length 3;

[0018] The OD value weight of optical path 1 is: w1=X1 / (X1+bX2 E +cX3 F );

[0019] The OD value weight of optical path 2 is: w2=bX2 E / (X1+bX2 E +cX3 F );

[0020] The OD value weight of optical path 3 is w3=cX3 F / (X1+bX2 E +cX3 F );

[0021] The final OD value of the particle suspension is: X = w1X1 + w2X2 + w3X3;

[0022] Among them, X1 is the OD value corresponding to optical path 1; X2 is the OD value corresponding to optical path 2; X3 is the OD value corresponding to optical path 3;

[0023] b and c are real numbers, ≥0; E and F are real numbers, ≥0.

[0024] Where b and c are both real numbers greater than or equal to zero, with their specific values ​​determined by experimental data. These two parameters determine at what concentration the weights of pathlengths 2 and 3 exceed those of the preceding pathlength. E and F are positive real numbers, with their optimal values ​​determined by experimental data. These two parameters determine how quickly the weights of the corresponding pathlengths increase; larger exponents increase faster. Generally, E and F can be positive integers.

[0025] In some embodiments, the specific values ​​of b and c are calibrated by preliminary experiments of the substance to be tested, so that at low concentrations, the maximum optical path has the greatest weight, and at high concentrations, the minimum optical path has the greatest weight.

[0026] In some embodiments, the specific values ​​of E and F are calibrated by preliminary experiments of the substance to be tested, so that at low concentrations, the maximum optical path has the greatest weight, and at high concentrations, the minimum optical path has the greatest weight.

[0027] The values ​​of b, c, E and F are all calibrated by preliminary experiments of a certain substance to be measured. The principle is that at low concentrations, one centimeter of optical path (maximum optical path) has the greatest weight, and as the concentration increases, the weights of 5 mm or 4 mm (intermediate optical path) and 2 mm or 1 mm optical path (minimum optical path) gradually increase, so that at high concentrations, the optical path of 2 mm or 1 mm (minimum optical path) has the greatest weight. Integers are taken in the embodiments as empirical constants given based on observed data, and the errors in this case are already small enough. More accurate parameters can be obtained by numerical fitting. Once the values ​​of b, c, E and F are determined, they can be directly used for subsequent measurements of similar particles.

[0028] In some embodiments, when the particle suspension to be tested is detected by spectrophotometry, its absorbance is greater than 1.0.

[0029] The beneficial effects achieved by one or more embodiments of the present invention are as follows:

[0030] Using the cuvette and detection method of the present invention, when the concentration of the particle suspension to be tested is low, the one-centimeter optical pathlength has the highest weight. As the concentration increases, the weight of the one-centimeter optical pathlength decreases, while the weight of shorter optical pathlengths increases. The OD value of the particle suspension to be tested is the weighted average of the readings at each optical pathlength. This solves the problem of low OD readings at high concentrations and the problem of jumps between diluted and undiluted data. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings, which constitute a 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 descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0032] FIG1 is a schematic diagram of the cross-sectional structure of a cuvette used in the method for accurately measuring the concentration of particulate matter of the present invention. DETAILED DESCRIPTION

[0033] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0034] The present invention will be further described below with reference to the embodiments.

[0035] Example 1

[0036] Prepare LB medium suitable for culturing E. coli: To a 300 mL Erlenmeyer flask, add 1 g of peptone powder, 0.5 g of yeast extract, 1 g of sodium chloride powder, and 100 mL of distilled water. Seal the flask with tin foil. Sterilize in an autoclave at 121°C for 20 minutes before use.

[0037] Pipette 100 μL of E. coli from the stored strain and add it to the previously returned-to-room-temperature LB medium. Add the appropriate amount of antibiotics. Incubate the culture in a constant-temperature shaking incubator at 37°C and 220 rpm for 16 hours.

[0038] The above E. coli solutions were serially diluted with distilled water to obtain the E. coli solutions numbered 1-11 in Table 1, each with decreasing concentrations. Three milliliters of each of the 11 E. coli solutions of varying concentrations were added to a cuvette designed in the present invention, which was then placed in the cuvette well of a spectrophotometer. The wavelength was set to 600 nanometers, and the OD values ​​at three optical pathlengths of 1 cm, 5 mm, and 2 mm were measured, designated as X1, X2, and X3, respectively.

[0039] According to the experimental data, b=4, c=8, E=2, F=3, w1=X1 / (X1+4X2 2 +8X3 3 ), w2=4X2 2 / (X1+4X2 2 +8X3 3 ), w3=8X3 3 / (X1+4X2 2 +8X3 3 ). Multiplying X1, X2, X3 by the coefficients w1, w2, w3 respectively can calculate the final OD value = w1X1+w2X2+w3X3.

[0040] In addition, the particle suspension was diluted 2 times and 5 times respectively, and the OD value at 1 cm optical path was detected. Then the OD value was multiplied by the dilution factor to obtain the particle concentration detected by the dilution method, which was recorded as X 1-2 and X 1-5 .

[0041] The test and calculation results are shown in Table 1.

[0042] Table 1

[0043] As can be seen from Table 1, the weighted method is used to assign different weights to different optical pathlengths at different concentrations, which solves the problem of low OD readings at high concentrations and the problem of jumps between diluted data and undiluted data.

[0044] At low concentrations, the final OD reading is close to X1, and at high concentrations, close to X3. This solves the problem of low X1 readings at high concentrations and eliminates the need for dilution. If the concentration is high enough to be diluted to a certain degree, slightly lower concentrations will appear low, while slightly higher concentrations will not appear low. Microbial growth curves will show anomalies around this point.

[0045] Example 2

[0046] Prepare BMGY medium suitable for yeast cultivation: To a 300 ml Erlenmeyer flask, add 400 μl of glycerol, 10 ml of 1 M potassium phosphate buffer (pH 6.0), and 80 ml of distilled water. Seal the flask with tin foil. Sterilize the flask in an autoclave at 121°C for 20 minutes. Then, in a laminar flow hood, add 10 ml of filter-sterilized yeast nitrogen base stock solution at a concentration of 134 g / L.

[0047] 100 μL of yeast was taken from the stored yeast culture and added to the above BMGY medium. The culture was placed in a constant temperature shaking incubator at 30°C and 260 rpm for 24 hours.

[0048] The yeast solutions were serially diluted with distilled water to obtain the yeast solutions numbered 1-17 in Table 2, each with decreasing concentrations. Three milliliters of each of the 17 yeast solutions of varying concentrations were added to a cuvette designed in the present invention. The cuvette was then placed in the cuvette well of a spectrophotometer, with the wavelength set to 600 nanometers. The OD values ​​at three optical pathlengths, 1 cm, 4 mm, and 1 mm, were measured, designated as X1, X2, and X3, respectively.

[0049] According to the laboratory data, b=c=4,E=2,F=4, then w1=X1 / (X1+4X2 2 +4X3 4), w2=4X2 2 / (X1+4X2 2 +4X3 4 ), w3=4X3 4 / (X1+4X2 2 +4X3 4 ). Multiplying X1, X2, X3 by the coefficients w1, w2, w3 respectively can calculate the final OD value = w1X1+w2X2+w3X3.

[0050] In addition, the particle suspension was diluted 2.5 times and 10 times respectively, and the OD value at 1 cm optical path was detected. Then the OD value was multiplied by the dilution factor to obtain the particle concentration detected by the dilution method, which was recorded as X 1-2.5 and X 1-10 .

[0051] The test and calculation results are shown in Table 2.

[0052] Table 2

[0053] As shown in Table 2, using a weighted approach, which assigns different weights to different pathlengths at different concentrations, solves the problem of low OD readings at high concentrations and the jump between diluted and undiluted data. Furthermore, the low OD readings at 1 cm pathlength are more severe at high yeast concentrations, making this new method more effective.

[0054] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A cuvette for measuring the concentration of a particle suspension, characterized in that: Its cross section is an L-shaped structure formed by removing a rectangular notch from a square, and the difference between the length and width of the rectangular notch is 1-4 mm; The cuvette is made of fully transparent material.

2. The cuvette for measuring the concentration of a particle suspension according to claim 1, characterized in that: The material of the cuvette is polystyrene.

3. The cuvette for measuring the concentration of a particle suspension according to claim 1, characterized in that: The height of the cuvette is 4-5 cm.

4. The cuvette for measuring the concentration of a particle suspension according to claim 1, characterized in that: The width of the square of the cross section of the cuvette is 0.8-1.2 cm.

5. The cuvette for measuring the concentration of a particle suspension according to claim 4, characterized in that: The width of the square of the cross section of the cuvette is 1 cm, the length of the rectangular notch is 7-9 mm, and the width is 5-6 mm.

6. A method for measuring the concentration of a particle suspension, characterized in that: The steps include: Pour the particle suspension to be tested into the cuvette of any one of claims 1 to 5, and measure the absorbance of the cuvette at different optical path lengths, wherein the maximum optical path length of the cuvette is optical path length 1; the middle optical path length is optical path length 2; and the minimum optical path length is optical path length 3; The OD value weight of optical path 1 is: w1 = X1 / (X1+bX2 E +cX3 F ); The OD value weight of optical path 2 is: w2 = bX2 E / (X1+bX2 E +cX3 F ); The OD value weight of optical path 3 is w3=cX3 F / (X1+bX2 E +cX3 F ); The final OD value of the particle suspension is: X = w1X1 + w2X2 + w3X3; Among them, X1 is the OD value corresponding to optical path 1; X2 is the OD value corresponding to optical path 2; X3 is the OD value corresponding to optical path 3; b and c are real numbers, ≥0; E and F are real numbers, ≥0.

7. The method for measuring the concentration of a particle suspension according to claim 6, characterized in that: The specific values ​​of b and c are calibrated by preliminary experiments of the substance to be tested, so that at low concentrations, the maximum optical path has the maximum weight, and at high concentrations, the minimum optical path has the maximum weight.

8. The method for measuring the concentration of a particle suspension according to claim 6, characterized in that: The specific values ​​of E and F are calibrated by preliminary experiments of the substance to be tested, so that at low concentrations, the maximum optical path has the maximum weight, and at high concentrations, the minimum optical path has the maximum weight.

9. The method for measuring the concentration of a particle suspension according to claim 7 or 8, characterized in that: The values ​​of b, c, E, and F were obtained by data fitting.

10. The method for measuring the concentration of a particle suspension according to claim 6, characterized in that: When the particle suspension to be tested is detected by spectrophotometry, its absorbance is greater than 1.0.

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