CN115453043A - Long-acting stable liquid calcium indicator - Google Patents
Long-acting stable liquid calcium indicator Download PDFInfo
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- CN115453043A CN115453043A CN202211000421.5A CN202211000421A CN115453043A CN 115453043 A CN115453043 A CN 115453043A CN 202211000421 A CN202211000421 A CN 202211000421A CN 115453043 A CN115453043 A CN 115453043A
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- G01N31/00—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods
- G01N31/22—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using chemical indicators
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N31/00—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods
- G01N31/16—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using titration
- G01N31/162—Determining the equivalent point by means of a discontinuity
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Abstract
The application relates to the technical field of metal content determination, and particularly discloses a long-acting stable liquid calcium indicator, which comprises an indicating component A and a diluting component B; the indicating component A is prepared by compounding calcein, phenol red and thymolphthalein; the diluent component B is a mixed solution of glycerol and triethanolamine; the liquid calcium indicator is prepared by adding 1g of calcein, 0.15g of phenol red and 1g of thymolphthalein into 100mL of glycerol-triethanolamine mixed solution by mass and mixing; compared with a solid calcium indicator, the liquid calcium indicator obviously prolongs the storage period, and the newly prepared liquid calcium indicator can be placed at normal temperature for 63 days without deterioration and can accurately indicate a titration end point; in addition, the addition amount of the liquid calcium indicator can be accurately controlled, particularly, the liquid calcium indicator can be accurately added by a pipette, but the solid calcium indicator cannot be accurately controlled.
Description
Technical Field
The application relates to the technical field of metal content determination, in particular to a long-acting stable liquid calcium indicator.
Background
Limestone (CaCO) 3 ) Or slaked lime Ca (OH) 2 The dispersion liquid is often used as an absorption liquid of the smoke. The flue gas generated in the production is directly and continuously introduced into the absorption liquid, orThe absorption liquid is directly sprayed into the flue gas to make the limestone or hydrated lime and NO in the flue gas 2 、Cl 2 、HF、F 2 、SO 2 And SO 3 The toxic and harmful gases are chemically reacted to generate Ca (NO) 2 ) 2 、Ca(NO 3 ) 2 、CaCl 2 、CaF 2 、CaSO 3 And CaSO 4 And the calcium-containing compound can remove toxic and harmful gases in the smoke. Along with NO and NO in limestone or slaked lime and flue gas 2 、Cl 2 、HF、F 2 、SO 2 And SO 3 And the reaction of toxic and harmful gases proceeds, the effective calcium content in the limestone or slaked lime dispersion liquid is reduced. In order to ensure effective treatment of flue gas, it is often necessary to measure the effective calcium content of limestone or slaked lime dispersion during actual treatment.
At present, the analysis methods for measuring the calcium content mainly include Ethylene Diamine Tetraacetic Acid (EDTA) titration method, potassium permanganate method, tribromoazoarsine dual-wavelength spectrophotometry method, atomic absorption spectrometry, potentiometric titration method, inductively coupled plasma atomic emission spectrometry and the like. The EDTA titration method has the advantages of wide and common application range, large calcium concentration (content) detection range (0.1-99.90%), simple operation, high reliability of analysis results, less material consumption and the like. When the calcium content of limestone or slaked lime is determined by EDTA titration, it is usually necessary to add an indicator to the solution to be tested of the sample.
When the disodium Ethylene Diamine Tetraacetic Acid (EDTA) titration method is used for detecting calcium, common indicators comprise a calcium indicator and calcein. The calcium indicator is also called calcium red and NN indicator, is a black powder, and is commonly used for measuring the content of calcium ions. At a pH of 12 to 14, the calcium indicator is blue, and forms a wine red complex with calcium ions, and can indicate a titration end point according to the difference of the two colors, but other ions which influence/interfere with the detection accuracy are small in concentration during titration, and when the concentration of other ions which influence/interfere with the detection accuracy in the liquid to be detected exceeds the allowable concentration, other ions which influence/interfere with the detection accuracy in the liquid to be detected need to be removed before titration, so that the operation is complicated and the time is long. The method comprises the steps that calcein and calcium ions in water can generate a yellow-green fluorescent complex, when the pH value is larger than 13, calcium in a liquid to be detected is titrated by an EDTA titration method, the complexing ability of EDTA and calcein is larger than that of calcium and calcein, therefore, EDTA can continuously capture calcein in a fluorescent yellow-green complex, after EDTA completely captures calcein in the fluorescent yellow-green complex, yellow-green fluorescence in the liquid to be detected disappears, the liquid to be detected is changed into a brownish red color, namely, the titration end point is reached, and the concentration of other ions which are allowed by calcein to influence/interfere detection accuracy is higher than that of a calcium indicator. In the related art, since an aqueous solution of a calcium indicator and calcein is unstable, in an analysis experiment, the aqueous solution is often mixed with potassium nitrate (or potassium sulfate, sodium chloride, potassium chloride, etc.) in a certain proportion to prepare a solid calcium indicator for use. However, in the practical application process, it is found that solid potassium nitrate powder (including potassium sulfate, sodium chloride, potassium chloride and other powder) has extremely strong water absorption and air absorption, so that the solid calcium indicator can easily absorb substances such as acidic gas, acidic moisture, oxygen, organic gas and the like in the air, and the substances directly react with indicating components (calcein, phenol red and thymolphthalein) adsorbed on the surface layer of the solid potassium nitrate powder, thereby not only affecting the judgment of the titration end point color, but also causing problems such as lagging or advancing of the titration end point; moreover, the newly prepared solid calcium indicator has a short storage period, and can be invalid after being generally placed for 2-3 weeks at normal temperature; in addition, the adding amount of the solid calcium indicator cannot be accurately controlled due to the small adding mass of the solid calcium indicator, the adding mass cannot be kept equal due to manual uncontrollable reasons, the color depth of the end point is inconsistent due to the uncertainty of the using amount of the indicator, the judgment of the titration end point is difficult to master, the generated complex is unstable, and the accuracy and the precision of a detection result are not high. Based on the above statements, the present application provides a long-lasting stable liquid calcium indicator.
Disclosure of Invention
In order to solve the problems that the storage period of the solid calcium indicator is short, the dosage is quantitative and troublesome, the discoloration of a terminal point is not sharp, the accuracy of a detection result is not high and the like in the related technology, the application provides the long-acting stable liquid calcium indicator.
The application provides a long-acting stable liquid calcium indicator, which adopts the following technical scheme:
a long acting stable liquid calcium indicator comprising an indicator component a and a diluent component B; the indicating component A is prepared by compounding calcein, phenol red and thymolphthalein; the diluent component B is a mixed solution of glycerol and triethanolamine.
By adopting the technical scheme, the diluent in the liquid calcium indicator is a glycerol-triethanolamine mixed solution, wherein the concentrated glycerol (glycerol) and the aqueous solution are neutral, the concentrated triethanolamine and the aqueous solution are medium-weak alkaline, and the glycerol and the triethanolamine can absorb acidic gases, some organic gases, oxygen, acidic moisture and other substances in the air. Substances such as acid gas, some organic gas, oxygen and acid moisture in the air of the detection chamber can be absorbed and diluted by glycerol and triethanolamine in the liquid calcium indicator, so that the concentration of the substances in the liquid calcium indicator is very low, and the substances cannot react with or slowly react with indicating components A (calcein, phenol red and thymolphthalein) in the liquid calcium indicator.
Preferably, the mass ratio of the calcein to the phenol red to the thymolphthalein is 1.
Preferably, the glycerol-triethanolamine mixed solution is prepared by compounding 95 volume percent of glycerol and 5 volume percent of triethanolamine.
Preferably, the mass concentration of the glycerol and the triethanolamine is 98wt%.
By adopting the technical scheme, the triethanolamine in the liquid calcium indicator is used for preventing the acid gas, the acid moisture and the oxygen from reacting with the indicating component A (calcein, phenol red and thymolphthalein) in the liquid calcium indicator, the existence of a small amount of triethanolamine in the liquid calcium indicator enables the liquid calcium indicator to become weakly alkaline, when the triethanolamine in the liquid calcium indicator contacts with the acid gas, the acid moisture, some organic gases, oxygen and the like in the air, the triethanolamine in the liquid calcium indicator can be subjected to a neutralization reaction with the acid gas and the acid moisture, the acid gas, the acid moisture and the oxygen are prevented from reacting with the indicating component A (calcein, phenol red and thymolphthalein) in the liquid calcium indicator, and the indicating component A (calcein, phenol red and thymolphthalein) cannot rapidly generate other substances to be invalid.
The more the triethanolamine content in the liquid calcium indicator is, the better the triethanolamine content is, the more the triethanolamine content is, the stronger the alkalinity of the liquid calcium indicator is, the alkalescence of the liquid calcium indicator is changed into the medium-strong alkalinity, the property of the indicating component A (calcein, phenol red and thymolphthalein) can be changed under the medium-strong alkalinity for a long time, the indicating component A cannot be preserved for a long time, and the accuracy and precision of a detection value can be influenced; the applicant finds that when the volume content of the triethanolamine in the mixed solution of the glycerol and the triethanolamine is 5%, the liquid calcium indicator can be stored for the longest time, can keep the properties unchanged within 63 days in a normal-temperature environment, does not need to be prepared again during use, and does not affect the accuracy and precision of detection values.
Preferably, the liquid calcium indicator is prepared by adding and mixing 1g of calcein, 0.15g of phenol red and 1g of thymolphthalein to a 100 mL-volume glycerol-triethanolamine mixed solution.
By adopting the technical scheme, the liquid calcium indicator adopts the glycerol-triethanolamine mixed liquid of calcein, phenol red and thymolphthalein, can effectively ensure that the color change of the titration end point of the calcium-containing liquid to be detected is sharp, the color chromaticity of the calcium-containing liquid to be detected is kept consistent, the color change of the titration end point can be quickly and simply judged, and the operation is simple. The method can effectively avoid that the color change of the calcium indicator in the calcium-containing liquid to be detected is not sharp at the titration end point; or when an operator adds a calcium indicator into the calcium-containing liquid to be detected, the quality of the calcium indicator cannot be kept equal due to manual uncontrollable reasons, so that the color and the chroma in the calcium-containing liquid to be detected are different, the titration end point is difficult to accurately judge, and the titration error (end point error) is increased, thereby improving the detection accuracy and precision. Compare with the calcium indicator who uses the potassium nitrate solid as the diluent, the method in this application, it is more difficult rotten than the calcium indicator who uses the potassium nitrate solid as the diluent at normal atmospheric temperature, effective live time is longer moreover, and it is more convenient to use, operates simpler, and the color change of the calcium-containing liquid that awaits measuring when closing on titrating the terminal point is more acute, and the accuracy of detection is higher with the degree of accuracy.
In summary, the present application has the following beneficial effects:
the liquid calcium indicator adopts a glycerol-triethanolamine mixed solution as a diluent, and a small amount of triethanolamine exists, so that the liquid calcium indicator is alkalescent, can neutralize acid gas and acid moisture in the liquid calcium indicator for a long time, and can keep the liquid calcium indicator alkalescent or neutral for a long time; the mixed liquid of glycerol and triethanolamine can prevent the reaction of oxygen and moisture with the indicating component or the reaction is slow. The applicant finds that the diluent of the liquid calcium indicator adopts 95 volume percent of glycerol (glycerin) and 5 volume percent of triethanolamine, so that the liquid calcium indicator can be stored for a long time (at least 63 days), has unchanged properties, and does not affect the purposes of accuracy and precision of detection values.
The application of the liquid calcium indicator obviously prolongs the storage period compared with a solid calcium indicator, the newly prepared liquid calcium indicator can be placed at normal temperature for 63 days without deterioration, and can accurately indicate a titration end point, in addition, the adding amount of the liquid calcium indicator can be accurately controlled, a specific available pipette is accurately added, and the solid calcium indicator cannot be accurately controlled.
Detailed Description
The present application will be described in further detail with reference to examples.
Examples
Example 1
A long-acting stable liquid calcium indicator comprises an indicating component A and a diluting component B; wherein the indicating component A is prepared by compounding calcein, phenol red and thymolphthalein, and the mass ratio of the calcein to the phenol red to the thymolphthalein is 1;
the dilution component B is a mixed solution of glycerol and triethanolamine, and is specifically obtained by compounding 95% of glycerol by volume and 5% of triethanolamine by volume, wherein the mass concentration of the glycerol and the triethanolamine is 98wt%;
the liquid calcium indicator is prepared by mixing 1g of calcein, 0.15g of phenol red and 1g of thymolphthalein by mass and adding 100mL of glycerol-triethanolamine mixed solution.
The preparation method of the liquid calcium indicator comprises the following steps: (1) Respectively adding 95ml of glycerol and 5ml of triethanolamine into a glass beaker, and uniformly stirring to obtain a glycerol-triethanolamine mixed solution; (2) Putting 1g of calcein, 0.15g of phenol red and 1g of thymolphthalein into a glass beaker filled with a glycerol-triethanolamine mixed solution, putting the glass beaker into an ultrasonic oscillator, and oscillating by ultrasonic waves until the calcein, the phenol red and the thymolphthalein are completely dissolved to obtain the prepared liquid calcium indicator.
Comparative example
Comparative example 1
The preparation method of the national standard solid calcium indicator comprises the following steps: putting 1g of calcein, 0.15g of phenolphthalein, 1g of methyl thymol blue and 100g of potassium nitrate (analysis purity) into a mortar made of an agate material, and manually grinding the materials into fine powder by using a grinding handle made of the agate material to obtain the national standard solid calcium indicator.
Comparative example 2
The solid calcium indicator comprises an indicating component A and a diluting component C; the indication component A is obtained by compounding calcein, phenol red and thymolphthalein, the mass ratio of the calcein to the phenol red to the thymolphthalein is 1.15;
the solid calcium indicator is prepared by adding and mixing 1g of calcein, 0.15g of phenol red and 1g of thymolphthalein to 100g of solid potassium nitrate powder.
The preparation method of the solid calcium indicator comprises the following steps: placing 1g of calcein, 0.15g of phenol red, 1g of thymolphthalein and 100g of potassium nitrate (analytical purity) into a mortar made of an agate material, and manually grinding the materials into fine powder by using a grinding handle made of the agate material to obtain the solid calcium indicator.
1. A national limestone component analysis standard substance (GBW 03106) is adopted, the standard calcium oxide value is 51.61%, and a control test of the liquid calcium indicator in the embodiment 1 and the national standard solid calcium indicator in the comparative example 1 is carried out according to a GB/T5762-2012 detection method.
1. On the 7 th day of detection and preparation, the control of the accuracy and the precision of the calcium standard substance detected by the two calcium indicators is shown in the table 1.
Table 1:
2. on the 21 st day of detection and preparation, the accuracy and precision of the calcium-containing standard substance are compared by the two calcium indicators, and the results are shown in table 2.
Table 2:
as can be seen from the data in tables 1 and 2: the detection time is respectively 7 days and 21 days after the two calcium indicators are prepared; the national limestone component analysis standard substance (GBW 03106) is detected, and a control experiment is carried out to detect the accuracy and precision of the average measured value and the standard value (GBW 03106) of the two calcium indicators on the 7 th day and the 21 st day after the preparation respectively.
From the first control experiment on day 7 it can be seen that:
(1) The difference (absolute error) between the average value and the standard value is small, the liquid calcium indicator is only 0.038%, the national standard solid calcium indicator is only 0.043%, and the difference between the difference (absolute error) between the average value and the standard value of the two calcium indicators is only 0.005%.
(2) The average measured value has small relative error (accuracy), the liquid calcium indicator is only 0.074%, the national standard solid calcium indicator is only 0.083%, and the difference of the relative errors (accuracies) of the two calcium indicators is only 0.009%.
(3) The standard deviation (precision) of the average measured value is small, the liquid calcium indicator is only 0.053%, the national standard solid calcium indicator is only 0.058%, and the difference of the standard deviation (precision) of the two calcium indicators is only 0.005%.
From the second control experiment on day 21 it can be seen that:
(1) The difference (absolute error) between the average value and the standard value of the national standard solid calcium indicator is large, the difference (absolute error) between the average value and the standard value of the liquid calcium indicator is small, the liquid calcium indicator is 0.043%, the difference between the liquid calcium indicator and the standard value of the first control experiment on the 7 th day is very small, only 0.005%, and is 13% higher; while the difference between 0.155 percent of the national standard solid calcium indicator and 0.043 percent of the difference of the first control experiment on the 7 th day is 0.112 percent which is higher than 260 percent; the difference between the mean value of the two calcium indicators and the standard value (absolute error) was also large, 0.112%.
(2) The relative error (accuracy) of the average measured value of the national standard solid calcium indicator is large, the difference (absolute error) between the average value and the standard value of the liquid calcium indicator is small, the difference between the average value and the standard value of the liquid calcium indicator is 0.083%, and the difference is very small and only 0.009%, which is 12% higher than the difference of 0.074% of the first control experiment on the 7 th day; while the national standard solid calcium indicator is 0.30 percent, and the difference value of 0.083 percent with the first control experiment on the 7 th day is 0.217 percent and is higher than 261 percent; the difference in relative error (accuracy) between the two calcium indicators was also large, 0.217%.
(3) The standard deviation (precision) of the average measured value of the national standard solid calcium indicator is large, the difference (absolute error) between the average value and the standard value of the liquid calcium indicator is small, the liquid calcium indicator is 0.056 percent, the difference with 0.053 percent of the first control experiment on the 7 th day is very small, only 0.003 percent, and is 5.7 percent higher; the national standard solid calcium indicator is 0.18 percent, and the difference of 0.058 percent of the difference value of the first control experiment on the 7 th day is 0.122 percent and is higher than 210 percent; the difference in standard deviation (precision) between the two calcium indicators was also large, 0.124%.
In summary, the following steps:
(1) The second control experiment of the liquid calcium indicator on the 21 st day after preparation is compared with the first control experiment on the 7 th day after preparation; the differences of the average measured value and the standard value (absolute error), the relative error (accuracy) and the standard deviation (precision) are small and are only 13%, 12% and 5.7% respectively, which indicates that the prepared liquid calcium indicator can be stored for a long time at normal temperature, the property is unchanged within 21 days, and the accuracy and precision of the detected value are not influenced.
(2) Comparing the second control experiment of the national standard solid calcium indicator on the 21 st day after preparation with the first control experiment of the national standard solid calcium indicator on the 7 th day after preparation; the difference (absolute error) between the average measured value and the standard value, the relative error (accuracy) and the standard deviation (precision) are greatly different and are respectively higher than 260%, 261% and 210%, which indicates that the prepared national standard solid calcium indicator cannot be stored for a long time, the property changes after 21 days, the accuracy and precision of the detection value are obviously reduced, and the accuracy and precision of the detection value are influenced.
3. The accuracy and precision of the calcium-containing standard substance detected by the two calcium indicators are compared under different days of detection, and the results are shown in table 3.
Table 3:
note: the average value in table 3 is the average of 6 measurements.
As can be seen from the data in table 3; the liquid calcium indicator can keep the property unchanged within 63 days, does not influence the accuracy and precision of a detection value, and does not need to be prepared again. And the national standard solid calcium indicator can only keep the property unchanged within 21 days, does not influence the accuracy and precision of a detection value, does not need to be prepared again, and has the storage time shorter than the storage time of the liquid calcium indicator by 42 days.
2. A national limestone component analysis standard substance (GBW 03106) is adopted, the standard calcium oxide value is 51.61%, and a control test of the national standard solid calcium indicator in the comparative example 1 and the solid calcium indicator in the comparative example 2 is carried out according to a GB/T5762-2012 detection method.
1. The accuracy and precision of the calcium-containing standard substance detected by the two solid calcium indicators are compared under different days of detection, and the results are shown in table 4.
Table 4:
note: the average value in table 4 is the average of 6 measurements.
As can be seen from the data in table 4; the two solid calcium indicators can only keep the properties unchanged within 21 days, do not influence the accuracy and precision of the detection value, do not need to be prepared again, are shorter than the storage time of a liquid calcium indicator by 42 days for 63 days, show that the prepared national standard solid calcium indicator is the same as the solid calcium indicator, can not be stored for a long time, the properties can be changed after 21 days, the accuracy and precision of the detection value can be obviously reduced, and the accuracy and precision of the detection value are influenced.
The difference (absolute error) and relative error (accuracy) between the average measured value and the standard value, and the absolute error and relative error of the standard deviation (precision) are small, wherein the absolute errors are respectively: 0.002%, 0.004%, 0.002%, 0.001%, 0.002%, 0.004%, 0.002% on day 7, relative errors are respectively: day 7 4.76%, 4.94%, 3.51%, day 14 1.23%, 1.27%, 0.99%, day 21 1.30%, 1.34%, 1.12%, indicating no significant difference between the two solid calcium indicators.
2. The two solid calcium indicators were compared with the significance difference test t values of the control tests at 7 th day, 14 th day and 21 st day of preparation.
When the confidence P =95% and the degree of freedom f =6, t is calculated National standard And t This application The data obtained are shown in Table 5.
t af The value is in the country with confidence P =95% and degree of freedom f =6Value of t specified by home when t National standard And t This application Greater than t af When the value is in the range of t, the significant difference exists, which indicates that the two solid calcium indicators can not be used for indicating the titration endpoint National standard And t This application Less than t af The absence of significant differences indicates that the two solid calcium indicators can be used to indicate the endpoint of the titration.
Table 5:
| preparation time | 7 days | 14 days | 21 days |
| t national standard | 1.64 | 1.82 | 1.92 |
| t this application | 1.66 | 1.81 | 1.92 |
| taf value | 2.57 | 2.57 | 2.57 |
From the data in table 5, it can be seen that: the two solid calcium indicators are respectively prepared on the 7 th day and the 14 th day,T calculated after significant difference test of control test on day 21 National standard And t This application Data well below t af The value data, i.e., the absence of significant differences, indicates that the two solid calcium indicators can be used to indicate the titration endpoint, and that the two solid calcium indicators are formulated at days 7, 14, and 21 with t between them National standard And t This application The difference between the data is 0.02, 0.01 and 0.00 respectively, which shows the significant difference (t) of the two solid calcium indicators National standard And t This application ) Extremely small and much less than t af The value is obtained.
3. The storage period of the finally prepared liquid calcium indicator was measured by changing the contents by volume of glycerol and triethanolamine in example 1 without changing other factors, and the results are shown in table 6.
Table 6:
| triethanolamine volume fraction/%) | 0 | 2.5 | 5 | 7.5 | 10 | 12.5 |
| Glycerol volume content/%) | 100 | 97.5 | 95 | 92.5 | 90 | 87.5 |
| Shelf life of liquid calcium indicator | 35 days | For 49 days | 63 days | For 49 days | 35 days | 21 days |
As can be seen from the data in table 6; when the volume content of triethanolamine in the mixed solution of glycerol and triethanolamine is 5%, the liquid calcium indicator can be stored for the longest time, has unchanged properties within 63 days, does not affect the accuracy and precision of detection values, and does not need to be prepared again.
The specific embodiments are merely illustrative of the present application and not restrictive, and those skilled in the art who review this disclosure may make modifications to the embodiments as needed without any inventive contribution, but fall within the scope of the claims of the present application.
Claims (5)
1. A long-acting stable liquid calcium indicator, characterized in that it comprises an indicator component a and a diluent component B; the indicating component A is prepared by compounding calcein, phenol red and thymolphthalein; the diluent component B is a mixed solution of glycerol and triethanolamine.
2. The long-term stable liquid calcium indicator according to claim 1, wherein the mass ratio of calcein, phenol red and thymolphthalein is 1.
3. The long-acting stable liquid calcium indicator according to claim 1, wherein the glycerol-triethanolamine mixture is prepared by mixing 95 vol.% glycerol and 5 vol.% triethanolamine.
4. The long-term stable liquid calcium indicator according to claim 3, wherein the glycerol and the triethanolamine are present at a mass concentration of 98wt%.
5. The long-term stable liquid calcium indicator according to any one of claims 1 to 4, wherein the liquid calcium indicator is prepared by mixing calcein with a mass of 1g, phenol red with a mass of 0.15g, and thymolphthalein with a volume of 100mL of glycerol-triethanolamine mixture.
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