JP2012026912A - Salinity concentration measuring instrument and salinity concentration measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a salinity concentration measuring instrument and a salinity concentration measuring method capable of measuring salinity concentration with high accuracy by easily and automatically calculating a dilution magnification with high accuracy.SOLUTION: The salinity concentration measuring instrument includes: soluble solid content concentration measuring means for measuring the soluble solid content concentration of an undiluted solution and a diluted solution of a sample; dilution magnification calculating means for calculating a dilution magnification on the basis of the soluble solid content concentration of the undiluted solution and the diluted solution; electrical conductivity measuring means for measuring the electrical conductivity of the diluted solution; and salinity concentration calculating means for calculating the salinity concentration of the undiluted solution on the basis of the dilution magnification and the electrical conductivity.

Description

  The present invention relates to an apparatus and method for measuring a salinity concentration in a sample, and more particularly to an apparatus and a method capable of easily diluting a sample and measuring the salinity concentration with high accuracy.

  As a salinometer for measuring the salinity of a sample, an electric conductivity type salinity meter that converts the measured value of the electric conductivity of the sample into a salinity based on the linear relationship between the salinity and electric conductivity is known. (Patent Document 1).

  However, in a sample having a high salinity concentration, the salinity concentration and the electric conductivity are not in a linear relationship, so that a high concentration salinity cannot be measured using an electric conductivity type salinity meter. In addition, when the sample contains a lot of ions other than sodium ions, the conductivity increases due to those ions, and when the sample contains a lot of organic substances such as amino acids and oils, the organic substances adhere to the electrodes due to the adhesion. Since the conductivity decreases, the salt concentration cannot be determined accurately.

  Therefore, in the case of high salinity samples and samples containing various ions and organic substances, dilute the sample stock solution at the specified dilution factor, measure the salt concentration of the diluted solution, and multiply the measured salt concentration value by the dilution factor. Thus, a method for obtaining the salt concentration of the stock solution has been performed. However, even if the influence of ions other than sodium ions and organic substances is reduced by dilution, there is a problem that the salt concentration cannot be obtained accurately if the accuracy of the dilution factor is low. Further, in order to increase the accuracy of the dilution ratio, a high-precision precision balance and a high-performance dispenser must be used, and there is a problem that skill is required for these operations.

JP 2006-349450 A

  The present invention has been made to solve the above-described problems, and an object of the present invention is to determine a dilution ratio simply and automatically with high accuracy, and thereby to measure a salinity concentration with high accuracy. And providing a method for measuring salinity.

  To achieve the above object, the salinity concentration measuring device according to the present invention is based on soluble solid concentration measuring means for measuring the soluble solid concentration of the sample stock solution and the diluted solution, and the soluble solid content concentration of the stock solution and the diluted solution. A dilution ratio calculating means for calculating the dilution ratio of the diluted liquid, an electric conductivity measuring means for measuring the electric conductivity of the diluted liquid, and a salinity concentration calculating means for calculating the salt concentration of the stock solution based on the dilution ratio and the electric conductivity. With.

  The salt concentration measurement method according to the present invention includes a step of measuring a soluble solid content concentration of a sample stock solution, a step of diluting the stock solution to create a diluted solution, and a step of measuring the soluble solid content concentration of the diluted solution. The step of calculating the dilution ratio of the diluted solution based on the soluble solid content concentration of the stock solution and the diluted solution, the step of measuring the electrical conductivity of the diluted solution, and the salt concentration of the stock solution based on the dilution rate and the electrical conductivity Including the process of calculating.

  According to the present invention, it is possible to provide a salinity concentration measuring apparatus and a salinity concentration measuring method capable of obtaining a dilution ratio simply and automatically with high accuracy and thereby measuring the salinity concentration with high accuracy.

It is a schematic block diagram of the salt concentration measuring apparatus in embodiment of this invention. The relationship between Brix measurement value and dilution concentration is shown for various samples. The relationship between a dilution rate and a salt concentration measurement value is shown about various samples. The relationship between the salt concentration conversion value of the undiluted solution calculated from the salt concentration measurement value of the diluted solution at various dilution ratios and the dilution ratio for various samples is shown. It is a flowchart which shows the salt concentration measuring method in embodiment of this invention. It shows the value converted into the salt concentration of the stock solution when the dilution rate is calculated from the ratio of the Brix measurement values of the stock solution and the diluted solution. The error of the dilution rate at the time of calculating a dilution rate from the ratio of a Brix value is shown.

  Referring to FIG. 1, a salinity concentration measuring apparatus 10 according to an embodiment of the present invention has an opening 14 in a housing 12, and a sample for placing a sample stock solution S and a diluent S ′ in the opening 14. A placement surface 16 is provided.

  The salinity concentration measuring apparatus 10 includes a prism 18, a light source 20, a light detection unit 22, and a soluble solid content concentration calculation unit 24 as means for measuring the Brix value (%) of the sample stock solution S and the diluent S ′. The Brix value (%) represents the concentration of soluble solids in the solution, as is well known.

  The prism 18 forms at least a part of the sample mounting surface 16 so as to form a boundary surface with the sample stock solution S or the diluted solution S ′. The light source 20 makes light incident on the boundary surface between the sample stock solution S or the diluted solution S ′ and the prism 18 from the prism 18 side. The light detection unit 22 receives light from the light source 20 reflected by the boundary surface between the sample stock solution S or dilution solution S ′ and the prism 18. For the light detection unit 22, a photoelectric sensor having a plurality of light receiving elements such as a one-dimensional image sensor or a two-dimensional image sensor is used. The prism 18, the light source 20, and the light detection unit 22 may be equivalent to the prism, the light source, and the light detection unit used in a general refractometer.

  The soluble solid content concentration calculator 24 calculates the Brix values of the stock solution S and the diluted solution S ′ from the output of the light detector 22. Here, the “dilution ratio” is defined as the weight (g) of the sample diluent divided by the weight (g) of the sample stock solution contained in the diluent.

  The salinity concentration measuring apparatus 10 further includes a first electrode 26, a second electrode 28, and an electric conductivity calculator 34 as means for measuring the electric conductivity of the diluent S '.

  The first electrode 26 and the second electrode 28 are provided on the sample placement surface 16 so as to be in contact with the sample diluent S ′ while being separated from each other. A voltage is applied between the first electrode 26 and the second electrode 28 by a power supply means (not shown). The current and voltage between the first electrode 26 and the second electrode 28 are measured by a current voltage detection means (not shown). The electrical conductivity calculator 34 calculates the electrical conductivity of the diluent S ′ based on the detected current and voltage.

  The salinity concentration measuring apparatus 10 includes a processing circuit 38 connected to a light source 20, a light detection unit 22, a first electrode 26, and a second electrode 28 via an interface 36. The processing circuit 38 includes an arithmetic control unit 40, a data storage unit 42, an operation unit 44, and a display unit 46.

  The calculation control unit 40 includes a dilution rate calculation unit 48, a dilution rate determination unit 50, and a salt concentration calculation unit 52 in addition to the soluble solid content concentration calculation unit 24 and the electrical conductivity calculation unit 34 described above. The dilution factor calculation unit 48 calculates the dilution factor from the Brix value based on the following consideration.

Table 1 shows the results of measuring the refractive indexes of the stock solution and the diluted solutions of various dilution concentrations for various samples, and converting those refractive indexes into Brix values. Here, “dilution concentration (%)” is defined as the weight (g) of the sample stock solution contained in 100 g of the diluent, and is dilution concentration (%) = 100 / dilution ratio. Sample dilutions are made by adding pure water to the sample stock solution while strictly measuring the weight so that the dilution concentrations are 5%, 10%, 15%, 20%, 25%, 50%, and 75%. It is a thing.

  Referring to FIG. 2 in which Table 1 is plotted with the Brix measurement value on the horizontal axis and the dilution concentration on the vertical axis, the Brix measurement value varies depending on the sample, but the Brix measurement value and the dilution concentration of each sample are generally linearly related. You can see that Since the Brix measurement value is 0% when the dilution concentration is 0%, it can be assumed that the Brix measurement value and the dilution concentration are in a proportional relationship. Based on this assumption, the dilution rate can be calculated regardless of the sample by dividing the Brix measurement value of the stock solution by the Brix measurement value of the diluent.

  Referring to FIG. 1 again, the dilution rate determination unit 50 determines whether the dilution rate is in a range suitable for salinity concentration measurement. The range of the dilution rate suitable for the salinity concentration measurement is determined based on the following considerations.

Table 2 measures the electrical conductivity of the stock solution and the same dilution factor of various dilutions as in Table 1 for the same various samples as in Table 1, and determines the salinity of each stock solution and dilution from those electrical conductivities. The calculated results are shown. As in Table 1, the sample diluent is purely added to the sample stock solution while the weight is strictly measured so that the dilution concentrations are 5%, 10%, 15%, 20%, 25%, 50%, and 75%. It was created by adding water.

  Referring to FIG. 3 in which Table 2 is plotted with the dilution factor as the horizontal axis and the salinity concentration measurement value as the vertical axis, a curve showing the relationship between the dilution factor and the salinity concentration measurement value is obtained for some samples (eg, yakiniku). In the case of soy sauce, boiled paste, etc.), the slope changes greatly when the dilution factor is around 2 times. In addition, although the salt concentration should be lower as the dilution factor is larger, in some samples (for example, Tamari soy sauce, white soy sauce, saikokomi soy sauce, etc.), the salt concentration measurement value of the diluted solution with a dilution factor of 1.33 Is higher than the measured salt concentration of the stock solution.

  FIG. 4 is a graph showing the salt concentration converted value of the stock solution obtained by multiplying the measured value of salt concentration in Table 2 by the dilution factor with the dilution factor as the horizontal axis. It turns out that the salt concentration conversion value of the stock solution calculated | required using the dilution liquid whose dilution rate is 5 times or less is remarkably small. This is considered to be the influence of components other than salt contained in the sample.

  On the other hand, the salt concentration conversion value of the stock solution obtained using a dilution solution having a dilution ratio of 15 to 20 times is smaller than the salt concentration conversion value of the stock solution obtained using a dilution solution having a dilution ratio of 10 times. is there. This is presumably because the electrical conductivity could not be measured accurately due to excessive dilution.

  Therefore, the appropriate range of the dilution rate for measuring the salinity concentration with high accuracy is preferably 5 to 15 times. In FIG. 4, since the salt concentration conversion value of the stock solution is substantially constant when the dilution rate is in the range of 8 to 12 times, the appropriate range of the dilution rate is more preferably 8 to 12 times.

  Referring to FIG. 1 again, the salinity concentration calculator 52 calculates the salinity of the diluent S ′ from the electrical conductivity of the diluent S ′, and the salinity of the stock solution S from the salinity of the diluent S ′ and the dilution factor. Calculate the concentration.

  The data storage unit 42 stores various calculation formulas in advance and temporarily stores data being measured. More specifically, the data storage unit 42 includes a critical angle calculation formula, a refractive index calculation formula, a refractive index to Brix conversion formula, a dilution rate calculation formula, an electrical conductivity calculation formula, and a salinity calculation. The formula is stored in advance.

  The conversion formula from the refractive index to the Brix value can be created based on, for example, a relational expression between the refractive index and the Brix value determined by ICUMSA (International Sugar Analysis Standardization Committee).

As described above, the calculation formula for the dilution rate is preferably the Brix value of the stock solution / the Brix value of the diluted solution. Alternatively, the calculation formula for the dilution rate may be based on a relational expression between the Brix value and the dilution concentration obtained from the regression analysis of the measurement results performed in advance. This relational expression is preferably a linear function expression (y = ax + b), but may be a quadratic function expression (y = ax ² + bx + c) or the like in consideration of the nonlinear term.

  The operation unit 44 is operated by the user when measuring the Brix value of the stock solution S and the diluted solution S ′, and when measuring the electrical conductivity of the diluted solution S ′, and sends a signal to the arithmetic control unit 40.

  The display unit 46 displays the calculated salt concentration of the stock solution S, and displays an error message when the dilution factor is not within the appropriate range.

  With reference to FIG. 5, the salt concentration measuring method in the embodiment of the present invention will be described.

  In step S101, a Brix value indicating the soluble solid content concentration of the stock solution S is measured. The sample stock solution S is extended to the sample mounting surface 16 so as to cover the boundary surface with the prism 18. When the user operates the operation unit 44, a signal is sent from the arithmetic control unit 40 to the light source 20, and the light source 20 is turned on. The light from the light source 20 enters the boundary surface between the stock solution S and the prism 18 (arrow a in FIG. 1), and a part of the light is reflected at the boundary surface according to the refractive index of the stock solution S, and the reflected light is detected by light. The light is received by the unit 22 (arrow b in FIG. 1).

  The soluble solid content concentration calculation unit 24 uses the critical angle calculation formula and the refractive index calculation formula stored in advance in the data storage unit 42 to output the critical angle from the prism 18 to the stock solution S from the output of the light detection unit 22. And the refractive index of the stock solution S is determined from the critical angle and the known refractive index of the prism 18 based on Snell's law. Next, the refractive index of the stock solution S is converted into a Brix value using a conversion formula from a refractive index stored in advance in the data storage unit 42 to a Brix value. The refractive index and Brix value of the stock solution S are stored in the data storage unit 42.

  In step S103, a sample diluent S 'is prepared. The diluted solution S ′ can be prepared by adding pure water to the stock solution S used in step S <b> 101 on the sample placement surface 16. Alternatively, the diluted solution S ′ may be prepared by diluting the same stock solution S used in step S101 with another container. In any case, the diluting solution S ′ can be easily prepared without using a special tool and without measuring the weight of the stock solution S and the pure water added to the stock solution S.

  In step S105, the Brix value of the diluent S 'is measured. Similarly to step S <b> 101, when the user operates the operation unit 44, the light source 20 is turned on, and the light reflected by the boundary surface between the diluent S ′ and the prism 18 is received by the light detection unit 22. The soluble solid content concentration calculation unit 24 uses the critical angle calculation formula and the refractive index calculation formula stored in advance in the data storage unit 42 to output the prism 18 to the diluent S ′ from the output of the light detection unit 22. The critical angle is detected, and the refractive index of the diluent S ′ is obtained from the critical angle and the refractive index of the prism 18. Next, similarly to step S101, the refractive index of the diluent S 'is converted into a Brix value using a conversion formula from a refractive index stored in advance in the data storage unit 42 to a Brix value. The refractive index and the Brix value of the diluent S ′ are stored in the data storage unit 42.

  In step S107, the dilution ratio from the stock solution S to the diluent S 'is calculated. Preferably, when the Brix value of the diluent S ′ is measured in step S105, the dilution factor calculator 48 automatically calculates the dilution factor. The dilution rate is calculated from the Brix values of the stock solution S and the diluted solution S ′ using a dilution rate calculation formula stored in advance in the data storage unit 42. Preferably, the dilution ratio is calculated by dividing the Brix value of the stock solution S by the Brix value of the diluent S ′.

  In step S109, it is determined whether the dilution factor is within a predetermined appropriate range. As described above, the appropriate range of the dilution ratio is preferably 5 to 15 times, more preferably 8 to 12 times in order to measure the salinity of the sample stock solution using the sample diluent.

  If the dilution factor determination unit 50 determines that the dilution factor is not within the proper range, an error message is displayed on the display unit 46 in step S111, and the process returns to step S103 to adjust the dilution factor.

  When the dilution rate is less than the predetermined appropriate range, the calculation control unit 40 causes the display unit 46 to display an error message (for example, “HHH” or “High”) indicating that the dilution concentration is too high. Thereby, it is possible to inform the user that it is necessary to further add pure water to the diluent S ′ to reduce the dilution concentration.

  When the dilution factor exceeds the predetermined range, the calculation control unit 40 displays an error message (for example, “LLL” or “Low”) indicating that the dilution concentration is too low. The user can be informed that the stock solution S needs to be added to the liquid S ′ to increase the dilution concentration.

  On the other hand, when the dilution rate determination unit 50 determines that the dilution rate is within the appropriate range, the dilution rate is displayed on the display unit 46 and stored in the data storage unit 42, and the process proceeds to step S113.

  In step S113, the electrical conductivity of the diluent S 'is measured. The measurement of electrical conductivity is started when the user gives an instruction using the operation unit 44. However, if it is determined in step S109 that the dilution factor is not in the proper range, the measurement of electrical conductivity is not started even if the user instructs. This can prevent the electrode from being damaged by the sample having a high salt concentration.

  When it is determined that the dilution ratio is within the appropriate range and the user instructs measurement of electrical conductivity, an alternating voltage is applied between the first electrode 26 and the second electrode 28, and the first electrode The current and voltage between 26 and the second electrode 28 are measured. The electrical conductivity calculator 34 calculates the electrical conductivity of the diluent S ′ from the measured current and voltage using the electrical conductivity calculation formula stored in advance in the data storage unit 42. The calculated electrical conductivity of the diluted solution S ′ is stored in the data storage unit 42.

  In step S115, the salinity of the diluent S 'is calculated. The salinity concentration calculating unit 52 calculates the salinity concentration of the diluent S ′ from the electrical conductivity of the diluent S ′ calculated in step S <b> 113, using the salinity concentration calculation formula stored in advance in the data storage unit 42. The calculated salt concentration of the diluted solution S ′ is stored in the data storage unit 42.

  In step S117, the salt concentration of the stock solution S is calculated. The salinity concentration calculation unit 52 calls the dilution rate and the measured salt concentration value of the diluent S ′ from the data storage unit 42 and multiplies them to calculate the salt concentration of the stock solution S. The calculated salt concentration of the stock solution S is displayed on the display unit 46 and stored in the data storage unit 42.

  The refractive index and Brix value of the stock solution S, the refractive index and Brix value of the diluent S ′, the dilution factor, the measured electric conductivity and salt concentration of the diluent S ′, and the stock solution S stored in the data storage unit 42 at each step. The converted salinity value can be transmitted to another device via the interface 36.

Example FIG. 6 shows the salt concentration conversion value of the stock solution when the dilution ratio is calculated from the ratio of the Brix measurement values of the stock solution and the diluted solution for various samples.

  More specifically, the dilution ratio was calculated by dividing the measured Brix value of the stock solution in Table 1 by the measured Brix value of the diluted solution having a dilution concentration of 10% in Table 1. Subsequently, the electrical conductivity of the diluted solution having the dilution concentration of 10% was measured to calculate the measured salt concentration of the diluted solution, and this salt concentration measured value was multiplied by the dilution factor to convert it to the salt concentration of the stock solution.

  The solid line in FIG. 6 shows the stock solution salinity conversion value when the dilution ratio is calculated as the ratio of the Brix value of the stock solution and the dilution solution, and the broken line is the conventional method, that is, the dilution concentration is exactly 10%. Assuming that the dilution factor is 10 times, the value converted into the salt concentration of the stock solution is shown. As shown in the figure, even when the dilution ratio is calculated as a ratio of Brix values, a salinity concentration almost equal to the conventional method of preparing a diluted solution by strictly measuring the weight% ratio is obtained.

  FIG. 7 shows the error of the dilution factor obtained in the first embodiment with respect to the diluted solution having a dilution rate of 10 times prepared by strictly measuring the weight% ratio. The dilution factor in Example 1 for calculating the dilution factor as the ratio of the Brix value of the stock solution and the diluted solution was 9.41 to 10.91 times.

  On the other hand, when the weight is measured with an accuracy of ± 0.2 g and diluted 10 times, the actual dilution factor is 8.17 to 12.75 times. When the weight is measured with an accuracy of ± 0.1 g and diluted 10 times, the actual dilution factor is 9.00 to 11.22 times.

  As shown in the figure, it can be seen that in the first example in which the dilution rate is calculated as the ratio of the Brix value, the dilution rate can be obtained with higher accuracy than when the diluted solution is prepared by weight measurement with an accuracy of ± 0.1 g. Therefore, by calculating the dilution ratio as the ratio of Brix values, it can be seen that the salinity concentration of the sample stock solution can be measured with higher accuracy than using the diluted solution prepared by weight measurement with an accuracy of ± 0.1 g.

  According to the salinity concentration measuring apparatus and the salinity concentration measuring method, since the dilution rate can be obtained from the Brix value indicating the soluble solid content concentration of the stock solution and the diluted solution, the dilution work by strict weight measurement is unnecessary, and the salinity concentration Measurement can be performed easily.

  Since it can be determined whether or not the dilution ratio of the diluent is within a predetermined range, the dilution ratio can be easily adjusted to a range suitable for the measurement of the salinity concentration, and thereby the salinity concentration can be accurately measured. it can.

  By setting the ratio of the Brix measurement values of the stock solution and the diluted solution as the dilution rate, the dilution rate can be calculated in the same manner for all the samples, so that the measuring apparatus and the measuring method can be simplified.

  Although the salinity concentration measuring apparatus and the salinity concentration measuring method according to the embodiment of the present invention have been described above, the present invention is not limited to this. For example, the configuration of each part of the salinity concentration measuring device can be replaced with an arbitrary configuration having the same function.

DESCRIPTION OF SYMBOLS 10 Salinity concentration measuring apparatus 12 Case 14 Opening 16 Sample mounting surface 18 Prism 20 Light source 22 Light detection part 24 Soluble solid content concentration calculation part 26 First electrode 28 Second electrode 34 Electrical conductivity calculation part 36 Interface 38 Process Circuit 40 Operation control unit 42 Data storage unit 44 Operation unit 46 Display unit 48 Dilution factor calculation unit 50 Dilution factor determination unit 52 Salinity concentration calculation unit S Sample stock solution S 'Sample dilution solution

Claims (8)

A soluble solids concentration measuring means for measuring the soluble solids concentration of the sample stock solution and the diluted solution;
A dilution ratio calculating means for calculating a dilution ratio of the diluent based on the soluble solid content concentration of the stock solution and the diluent;
Electrical conductivity measuring means for measuring the electrical conductivity of the diluent;
A salinity concentration measuring device comprising: a salinity concentration calculating means for calculating a salinity concentration of the stock solution based on the dilution factor and the electric conductivity.   The salt concentration measuring apparatus according to claim 1, wherein the dilution rate calculating means calculates the dilution rate by dividing the soluble solid content concentration of the stock solution by the soluble solid content concentration of the diluted solution.   The salinity concentration calculating means calculates the salinity concentration of the stock solution by converting the electrical conductivity into the salinity concentration of the diluent and multiplying the salt concentration of the diluent by the dilution factor. The salinity concentration measuring apparatus according to 1.   The salt concentration measurement according to any one of claims 1 to 3, further comprising a dilution rate determination means for determining whether or not the dilution rate is in a predetermined range, wherein the predetermined range is 5 to 15 times. apparatus. Measuring the soluble solids concentration of the sample stock solution;
Diluting the stock solution to create a diluted solution;
Measuring the soluble solids concentration of the diluent;
Calculating the dilution ratio of the diluent based on the soluble solid content concentration of the stock solution and the diluent; and
Measuring the electrical conductivity of the diluent;
Calculating the salt concentration of the stock solution based on the dilution factor and the electrical conductivity.   The salt concentration measurement method according to claim 5, wherein in the step of calculating the dilution rate, the dilution rate is calculated by dividing the soluble solid content concentration of the stock solution by the soluble solid content concentration of the dilution solution. The step of calculating the salinity is
Converting the electrical conductivity into a salt concentration of the diluent;
The salt concentration measuring method according to claim 5, further comprising: multiplying the salt concentration of the diluted solution by the dilution factor to calculate the salt concentration of the stock solution.   The salt concentration measuring method according to any one of claims 5 to 7, further comprising a step of determining whether or not the dilution ratio is within a predetermined range, wherein the predetermined range is 5 to 15 times.

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