CN112326576A - Continuous flow method for determining content of calcium carbonate in paper-making reconstituted tobacco - Google Patents
Continuous flow method for determining content of calcium carbonate in paper-making reconstituted tobacco Download PDFInfo
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- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 title claims abstract description 102
- 229910000019 calcium carbonate Inorganic materials 0.000 title claims abstract description 53
- 241000208125 Nicotiana Species 0.000 title claims abstract description 31
- 235000002637 Nicotiana tabacum Nutrition 0.000 title claims abstract description 31
- 238000000034 method Methods 0.000 title claims abstract description 26
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 86
- 239000000523 sample Substances 0.000 claims abstract description 55
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims abstract description 33
- 239000012488 sample solution Substances 0.000 claims abstract description 23
- 239000000835 fiber Substances 0.000 claims abstract description 18
- 239000000243 solution Substances 0.000 claims abstract description 18
- 239000012224 working solution Substances 0.000 claims abstract description 16
- 239000000945 filler Substances 0.000 claims abstract description 15
- 238000001914 filtration Methods 0.000 claims abstract description 12
- 238000010790 dilution Methods 0.000 claims abstract description 11
- 239000012895 dilution Substances 0.000 claims abstract description 11
- 238000004537 pulping Methods 0.000 claims abstract description 10
- 238000001035 drying Methods 0.000 claims abstract description 5
- NLKNQRATVPKPDG-UHFFFAOYSA-M potassium iodide Chemical compound [K+].[I-] NLKNQRATVPKPDG-UHFFFAOYSA-M 0.000 claims description 33
- 238000002156 mixing Methods 0.000 claims description 22
- 239000002245 particle Substances 0.000 claims description 22
- 239000003153 chemical reaction reagent Substances 0.000 claims description 21
- 239000000203 mixture Substances 0.000 claims description 21
- JLKDVMWYMMLWTI-UHFFFAOYSA-M potassium iodate Chemical compound [K+].[O-]I(=O)=O JLKDVMWYMMLWTI-UHFFFAOYSA-M 0.000 claims description 15
- 239000001230 potassium iodate Substances 0.000 claims description 15
- 229940093930 potassium iodate Drugs 0.000 claims description 15
- 235000006666 potassium iodate Nutrition 0.000 claims description 15
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 15
- 239000000047 product Substances 0.000 claims description 12
- 239000000706 filtrate Substances 0.000 claims description 11
- 238000005259 measurement Methods 0.000 claims description 10
- 239000012086 standard solution Substances 0.000 claims description 9
- 239000011550 stock solution Substances 0.000 claims description 8
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- 238000003756 stirring Methods 0.000 claims description 5
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- 238000005520 cutting process Methods 0.000 claims description 2
- 238000001514 detection method Methods 0.000 abstract description 22
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- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 239000013043 chemical agent Substances 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
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- SNICXCGAKADSCV-JTQLQIEISA-N (-)-Nicotine Chemical compound CN1CCC[C@H]1C1=CC=CN=C1 SNICXCGAKADSCV-JTQLQIEISA-N 0.000 description 1
- 241000196324 Embryophyta Species 0.000 description 1
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical class C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
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Abstract
The invention discloses a continuous flow method for measuring the content of calcium carbonate in paper-making reconstituted tobacco. Drying a sample to be detected, adding an excessive hydrochloric acid solution, fully reacting, filtering, and decoloring with active carbon to obtain a sample solution; the residual H in the sample solution was measured with a continuous flow analyzer+And calculating the corresponding calcium carbonate observed value to obtain the calcium carbonate content in the sample. The invention improves the prior continuous flow analysis technology, adds an on-line dilution channel before the sample solution enters the dialyzer, and leads the highest CaCO corresponding to the standard working solution3The content reaches 125.00mg, and the linear correlation coefficient reaches r2>0.999, the detection range is obviously improved, and the detection method can simultaneously meet the requirements of determining fiber pulping, filler finished product pulp, paper forming and the like of the paper-making reconstituted tobaccoThe need for multiple samples. The method is simple, convenient, rapid and accurate to operate, is very suitable for measuring a large number of samples, and has good application and popularization prospects.
Description
Technical Field
The invention belongs to the technical field of detection of physical and chemical indexes of paper-making reconstituted tobacco, and particularly relates to a method capable of sampling different nodes in the production process of the paper-making reconstituted tobacco and accurately determining the calcium carbonate content of different samples (including fiber pulping, filler finished product pulp and finished paper) obtained by sampling.
Background
The calcium carbonate is an important filler of the paper-making reconstituted tobacco, the content of the calcium carbonate affects the physical indexes of the reconstituted tobacco sheet base and the product, such as ash content, quantification, filling value, balanced water content, tensile strength, bulk and the like, and the smoking quality of tar, CO release amount, total particulate matters, smoke, nicotine and the like, and the calcium carbonate plays a role in reducing the cost. However, the calcium carbonate as the filler has extremely small particle size and cannot be completely retained in the pulp fibers, and the lost fine filler enters a sewage system along with the thick white water, so that the environment is polluted and great waste is caused. In order to improve the problem of calcium carbonate retention rate in the production process of paper-making reconstituted tobacco, the content of calcium carbonate in the paper-making reconstituted tobacco needs to be quickly and accurately determined. At present, according to the GB/T742-2008 'determination (900 ℃) of paper, paperboard and pulp residues (ash content)' requirements in the industry, an ash content index is used for evaluation, and because the index contains two parts of ash content brought in by tobacco raw materials and added calcium carbonate, the evaluation of the actually added calcium carbonate content has no practical significance, and the method is tedious and time-consuming, and cannot meet the requirement of monitoring the calcium carbonate retention rate in the reconstituted tobacco production process.
The continuous flow analysis technology can realize continuous detection of samples and improve the detection work efficiency due to the advantages of online mixing and dilution, continuous sample introduction, real-time data processing and the like. In the prior art, although a continuous flow method is used for detecting the content of calcium carbonate in a finished cigarette paper product, the situation that the content of calcium carbonate exceeds the concentration range of a standard solution is easy to occur when the calcium carbonate is directly applied to detection of reconstituted tobacco by a paper-making method. In addition, the prior art also has the condition of test result deviation caused by the difference of the decoloring effect.
Disclosure of Invention
The invention aims to provide a method for simply, conveniently, quickly and accurately measuring the content of calcium carbonate in paper-making reconstituted tobacco, aiming at the defects of the prior art. The method is realized by improving the continuous flow analysis technology, and can simultaneously meet the sampling requirements of different nodes in the production process of the paper-making reconstituted tobacco.
The purpose of the invention is realized by the following technical scheme.
All percentages used in the present invention are mass percentages unless otherwise indicated.
A continuous flow method for determining the content of calcium carbonate in paper-making reconstituted tobacco adopts the following steps:
(1) taking 0.5g of a sample to be detected, placing the sample at 105 ℃ for drying for 2h, transferring the sample into a 150mL beaker, adding 4.5mL of hydrochloric acid solution with the concentration of 0.5mol/L, stirring the mixture by using a glass rod until fibers are dispersed and no bubbles overflow, adding 95.5mL of pure water, fully mixing the mixture, filtering the mixture by using qualitative filter paper, adding 3g of activated carbon particles with the particle size of 400 meshes into the filtrate, oscillating the mixture for 15 minutes for decolorization, and filtering the mixture by using the qualitative filter paper to obtain a sample solution for later use;
(2) analyzing the sample solution with a continuous flow analyzer to obtain residual H+Corresponding calcium carbonate instrumental observations:
concentration of reagent: potassium iodate solution: 5g/L, potassium iodide solution: 50 g/L;
a flow path is provided: mixing the sample solution with dilution water through a 5-turn mixing ring, then mixing with a potassium iodate reagent through the 5-turn mixing ring, and then entering the upper layer of a dialyzer; the lower layer of the dialyzer is a potassium iodate reagent, and the mixed solution obtained by dialysis and the potassium iodide reagent undergo a color reaction and then enter a continuous flow analyzer after passing through 10 circles of mixing rings; the sample solution is pumped by a black/black pump tube at the flow rate of 0.32 mL/min; an ash/ash pump pipe for dilution water is used, and the flow rate is 1.02 mL/min; a purple/purple pump tube is used for a potassium iodate reagent, and the flow rate is 2.50 mL/min; the potassium iodide reagent is pumped by an orange/white pump tube at the flow rate of 0.23 mL/min; an orange/orange pump tube is used for secondary sample introduction, and the flow rate is 0.42 mL/min;
detecting wavelength by the analyzer: 420 nm; detecting speed: 20 samples/h; sample introduction/cleaning time ratio: 1: 1; sample introduction time is 90 s; baseline correction: opening; carrying out factor passing: 1.06 percent;
(3) drawing a standard working curve: preparing and calibrating HCl standard stock solution with concentration of 0.5mol/L, transferring 1.0, 2.0, 3.0, 4.0 and 5.0mL of the standard stock solution, and diluting to 100mL to obtain corresponding CaCO3Standard working solution with contents of 25.00mg, 50.00mg, 75.00mg, 100.00mg and 125.00mg respectively;
analyzing the standard working solution by the same method as the step (2), drawing a standard working curve, setting the linear regression equation y to 5.0583x-0.0826 and obtaining the correlation coefficient r2＝1；
(4) And (4) calculating a result: the residual H in the sample solution+Substituting the observed value of the corresponding calcium carbonate instrument into the formula (1) for calculation to obtain the calcium carbonate content in the sample;
in the formula:
CaCO3-the content of calcium carbonate in the sample in mass percent (%);
50-mass of calcium carbonate consumed by the reaction per millimole of hydrochloric acid in milligrams per millimole (mg/mmol);
C1the exact concentration of 0.5mol/L HCl standard solution in moles per liter (mol/L);
V1-the volume of 0.5mol/L HCl standard solution added in milliliters (mL);
C2residual H in the sample solution+Corresponding calcium carbonate instrumental observations in milligrams (mg);
g-sample mass in milligrams (mg);
the average value of two parallel measurements is used as the final measurement result, the accuracy is 0.1%, and the difference between the absolute values of the two parallel measurements should not exceed 0.4%.
The sample to be detected is as follows: cutting the reconstituted tobacco into strips as samples to be detected; or 1000mL of fiber pulping or filler finished product pulp is placed in a clean tray, the liquid level is kept flat, and the fiber pulping or filler finished product pulp is dried to constant weight at 100 ℃ and is used as a sample to be detected for later use.
Compared with the prior art, the invention has the following advantages:
1. the invention realizes that a detection method can simultaneously meet the requirements of determining various samples such as fiber pulping, filler finished product pulp, paper forming and the like of the paper-making reconstituted tobacco by improving the existing continuous flow analysis technology.
2. An on-line dilution channel is added before the sample solution enters the dialyzer to realize secondary sample introduction, so that the highest CaCO corresponding to the standard working solution3The content reaches 125.00mg, and the linear correlation coefficient can reach r2>0.999, the detection range is obviously improved. The condition that the prior art exceeds the range of a standard curve is effectively solved, the detection limit is 0.189mg, and the quantification limit is 0.63 mg. The coefficient of variation of 3 samples tested 6 times in succession was in the range 0.57-1.24%. The average recovery of 3 samples ranged from 98.3 to 100.1%.
3. The influence of 3 factors and 4 levels of the particle size of the activated carbon, the using amount of the activated carbon and the treatment time of the activated carbon on the detection result is compared through orthogonal experimental design, the influence degree of each factor on the detection result and the experimental cost are comprehensively considered, and the optimal conditions for using the activated carbon are determined as follows: the grain size of the activated carbon is 400 meshes, the dosage of the activated carbon is 3g, and the treatment time of the activated carbon is 15 min.
4. The method is simple, convenient, rapid and accurate, is very suitable for measuring mass samples, and has good application and popularization prospects.
Drawings
FIG. 1 is a schematic view of a continuous flow analyzer flow path arrangement prior to modification;
FIG. 2 is a schematic view of a continuous flow analyzer flow path arrangement of the present invention;
FIG. 3 is a standard operating curve;
FIG. 4 shows a typical process flow for producing paper-making reconstituted tobacco and a distribution diagram of calcium carbonate measurement sampling points.
Detailed Description
The present invention is further described in detail with reference to the drawings and examples, which are not intended to limit the technical scope of the present invention, and all changes and equivalents which come within the spirit of the teachings of the present invention shall fall within the scope of the present invention.
Example 1-detection of calcium carbonate content in finished paper of paper-making reconstituted tobacco.
1. Principles of experiment, materials and methods
1.1 principle of the experiment
Reacting a paper-making reconstituted tobacco sample with an excessive HCl solution with a known accurate amount, adding activated carbon particles into the filtrate, oscillating, decoloring and filtering, and performing continuous flow method by using potassium iodate and potassium iodide and residual H in the sample solution+To detect the remaining H+And the content of calcium carbonate in the paper-making reconstituted tobacco sample is calculated.
1.2 materials and instruments
Potassium iodate (AR, shanghai rungi chemical agents ltd); potassium iodide (AR, shanghai chemical agents, ltd.); hydrochloric acid (AR, west longridge chemical plant, guangdong, Shantou, Guangdong); calcium carbonate (working standard reagent (volume), peer trace element research institute); activated carbon granules (Shanghai chemical Co., Ltd., China medicine).
METLER AE200 analytical balance (sensory: 0.0001g, METLER TOLEDO, Switzerland); BRAN LUEBBE AA3 continuous flow analyzer (BRAN LUEBBE, Germany); JA5002 balance (sensory 0.01g, shanghai balance instrument factory); 101A-2 drying box (Shanghai city laboratory instruments general factory); SX2-4-10 box-shaped resistance furnace (China, Huaguang electric furnace factory in Changsha);
millipore AQUELIX5 water purifier (MERCK Millipore, USA).
All samples of the paper-making reconstituted tobacco are collected from the tobacco-reconstituted limited responsibility company in Yunnan province.
1.3 sample treatment and analysis
At sampling point W as shown in FIG. 4AAnd (4) taking the paper-making reconstituted tobacco to form paper to obtain a sample A. Weighing0.5g (to the nearest 0.01g) of sample A thin strip (about 0.5 cm. times.2.5 cm) baked at 105 ℃ for 2 hours was placed in a 150mL beaker, 4.5mL of 0.5mol/L hydrochloric acid solution was added, the mixture was stirred sufficiently with a glass rod until the fibers were dispersed and no air bubbles overflowed, 95.5mL of pure water was added, the mixture was filtered with qualitative filter paper after sufficient mixing, 3g of activated carbon particles having a particle size of 400 mesh were added to the filtrate, the mixture was shaken for 15 minutes, qualitative filtration was performed with filter paper, and the filtrate was collected as sample A solution for use.
1.4 apparatus conditions
FIG. 1 shows a flow path design of a conventional continuous flow analyzer. The flow path design after adding the in-line dilution tunnel of the present invention is shown in fig. 2.
Reagent: potassium iodate solution: 5g/L, potassium iodide solution: 50 g/L;
flow path arrangement of the main reagents: mixing the sample solution with dilution water through a 5-turn mixing ring, then mixing with a potassium iodate reagent through the 5-turn mixing ring, and then entering the upper layer of a dialyzer; the lower layer of the dialyzer is a potassium iodate reagent. The interfering substances in the mixture of sample solution and potassium iodate reagent were removed by a 12 inch dialyzer. Carrying out color reaction on the mixed solution obtained by dialysis and a potassium iodide reagent, and then feeding the mixed solution into a continuous flow analyzer after passing through 10 turns of mixing rings; the sample solution is pumped by a black/black pump tube at the flow rate of 0.32 mL/min; an ash/ash pump pipe for dilution water is used, and the flow rate is 1.02 mL/min; a purple/purple pump tube is used for a potassium iodate reagent, and the flow rate is 2.50 mL/min; the potassium iodide reagent is pumped by an orange/white pump tube at the flow rate of 0.23 mL/min; an orange/orange pump tube is used for secondary sample introduction, and the flow rate is 0.42 mL/min;
other analysis conditions were: detection wavelength: 420 nm; detecting speed: 20 samples/h; sample introduction/cleaning time ratio: 1: 1; sample introduction time is 90 s; baseline correction: opening; carrying out factor passing: 1.06 percent.
1.5 standard working solution: preparing and calibrating HCl standard stock solution with concentration of 0.5mol/L, transferring 1.0, 2.0, 3.0, 4.0 and 5.0mL of the standard stock solution, and diluting to 100mL to obtain corresponding CaCO3Standard working solution with contents of 25.00mg, 50.00mg, 75.00mg, 100.00m g and 125.00mg respectively;
analyzing the standard working solution by the same method as the step 1.4, drawing a standard working curve, setting a linear regression equation y to be 5.0583x-0.0826,coefficient of correlation r21 is ═ 1; as shown in fig. 3.
1.6 calculation of results
The residual H in the solution of the sample A+Substituting the observed value of the corresponding calcium carbonate instrument into the formula (1) for calculation to obtain the calcium carbonate content in the sample;
in the formula:
CaCO3(%) -content of calcium carbonate in the sample in mass percent (%);
50-mass of calcium carbonate consumed by the reaction per millimole of hydrochloric acid in milligrams per millimole (mg/mmol);
C1the exact concentration of 0.5mol/L HCl standard solution in moles per liter (mol/L);
V1-the volume of 0.5mol/L HCl standard solution added in milliliters (mL);
C2residual H in the sample solution+Corresponding calcium carbonate instrumental observations in milligrams (mg);
g is sample mass in milligrams (mg).
The average value of two parallel measurements is used as the final measurement result, the accuracy is 0.1%, and the difference between the absolute values of the two parallel measurements should not exceed 0.4%.
Example 2-detection of calcium carbonate content in filler finished pulp of paper-making reconstituted tobacco.
Example 1 was repeated with the following differences: at sampling point W as shown in FIG. 4BAnd pouring 1000mL of filler finished product slurry into a clean tray, keeping the liquid level flat, and placing the filler finished product slurry into a 100 ℃ oven to be dried to constant weight to obtain a sample B. Weighing 0.5g (accurate to 0.01g) of sample B strips (about 0.5cm multiplied by 2.5cm) baked at 105 ℃ for 2h, putting the strips into a 150mL beaker, adding 4.5mL of 0.5mol/L hydrochloric acid solution, stirring the mixture sufficiently by a glass rod until the fibers are dispersed and no bubbles overflow, adding 95.5mL of pure water, filtering the mixture by qualitative filter paper after mixing sufficiently, adding 3g of activated carbon particles with the particle size of 400 meshes into the filtrate, and oscillating the mixture for 1Decolorized for 5 minutes, filtered with qualitative filter paper, and the filtrate was collected as sample B solution for use.
Example 3-detection of calcium carbonate content in paper-making reconstituted tobacco fiber pulping.
Example 1 was repeated with the following differences: at sampling point W as shown in FIG. 401000mL of the fiber is taken to be pulped, poured into a clean tray, kept with the liquid level flat and placed in a 100 ℃ oven to be dried to constant weight, and a sample C is obtained. Weighing 0.5g (accurate to 0.01g) of sample C strips (about 0.5cm multiplied by 2.5cm) baked at 105 ℃ for 2h, putting the strips into a 150mL beaker, adding 4.5mL of 0.5mol/L hydrochloric acid solution, stirring the mixture sufficiently by a glass rod until fibers are dispersed and no bubbles overflow, adding 95.5mL of pure water, filtering the mixture by qualitative filter paper after sufficient mixing, adding 3g of activated carbon particles with the particle size of 400 meshes into the filtrate, shaking the mixture for 15min for decolorization, filtering the mixture by the qualitative filter paper, and collecting the filtrate as a sample C solution for later use.
2. Results and discussion
2.1 optimization of pipelines and analysis conditions
In order to adapt to the increased concentration range of the standard working solution, an online sample solution dilution channel is added, fig. 1 shows the flow path design of the prior continuous flow analyzer, and the flow path design of the invention is shown in fig. 2.
After the pipeline is improved, the response peak can not reach the reaction platform after 45 seconds of sample introduction, so the sample introduction time is prolonged to 90 seconds, the sample introduction/cleaning time ratio is 1: 1, the detection speed is 20 samples/h, and the response peak can basically reach the reaction platform. See table 1 for details.
TABLE 1 Effect of injection/purge time on Peak shape
2.2 optimum concentration Range of Standard solution
Aiming at the condition that the sample easily exceeds the highest concentration of the standard working solution when the calcium carbonate content is low, the concentration range of the standard working solution is improved: preparing and calibrating HCl standard stock solution with concentration of 0.5mol/L, transferring 1.0, 2.0, 3.0, 4.0 and 5.0mL of the standard stock solution, and fixing the volume to 100mL to obtain the corresponding CaCO3Standard working solution with contents of 25.00mg, 50.00mg, 75.00mg, 100.00mg and 125.00mg respectively;
through the improvement, the linear correlation coefficient can reach r through experimental verification2>0.999。
When the standard working solution is used as a sample for verification, the concentration points of 25.00mg, 50.00mg, 75.00mg, 100.00mg and 125.00mg are basically consistent with the concentration of the marked line, and the ratio of the difference between the concentration points and the concentration of the marked line is basically lower than 2%.
TABLE 2 difference between the measured concentration of the standard working solution and the concentration of the marked line
2.3 Effect of activated carbon on assay results
2.3.1 orthogonal Experimental protocol
Weighing 0.5g (accurate to 0.01g) of sample A thin strip (about 0.5cm multiplied by 2.5cm) baked at 105 ℃ for 2h, putting the sample A thin strip into a 150mL beaker, adding 4.5mL of 0.5mol/L hydrochloric acid solution, fully stirring by a glass rod until the fibers are dispersed and no bubbles overflow, adding 95.5mL of pure water, fully mixing, filtering by qualitative filter paper, treating the filtrate according to the scheme in Table 3, filtering by qualitative filter paper, and collecting the filtrate for later use, thereby obtaining the test solution. The absorbance of the sample solution was measured at a wavelength of 420nm using a spectrophotometer.
And comparing the influences of 3 factors and 4 levels of the particle size of the activated carbon, the using amount of the activated carbon and the treatment time of the activated carbon on the detection result. 3 factor 4 level, the minimum number of experiments is (4-1) × 3+1 ═ 10, an orthogonal table arrangement experiment with the processing combination number slightly more than 10 is selected from a 4n factor orthogonal table, and accordingly an L16(43 × 26) orthogonal table header is selected, wherein A, B, C factors are respectively placed in columns 1, 2 and 3.
Particle size of activated carbon: 6-8 meshes, 40-60 meshes, 200 meshes and 400 meshes
The dosage of the activated carbon is as follows: 2.3, 4, 5g
Activated carbon treatment time: 10. 15, 20 and 25min
2.3.2 influence of active carbon use conditions on detection results of paper-making reconstituted tobacco
TABLE 3 visual analysis of the results of the orthogonal test for activated carbon use conditions for sample A
Note: reconstituted tobacco as sample A WAObtaining a finished product; the test data are the mean of three replicates.
As shown in Table 3, the average of the results of the four level experiments for each factor was compared
The smaller the average value, the optimal experimental conditions for this level of the factor are indicated. Accordingly, the optimum levels of the particle size of the activated carbon, the amount of the activated carbon and the treatment time of the activated carbon are four levels, two levels and two levels, namely the particle size of the activated carbon, the amount of the activated carbon and the treatment time of the activated carbon are 400 meshes, 3g and 15min respectively.
The influence degree of each factor on the experimental result can be seen from the range of each factor, and the larger the range is, the larger the influence of the factor on the experimental result is. According to the results, the influence degrees of the three factors on the experimental results are ranked as follows: the particle size of the activated carbon is larger than the treatment time of the activated carbon and the dosage of the activated carbon, and the influence of the particle size of the activated carbon on the result is far larger than other two factors.
According to the found optimal conditions, namely the particle size of the activated carbon is 400 meshes, two verification tests are carried out, wherein the test conditions are as follows: the method comprises the steps of preparing activated carbon with the particle size of 400 meshes, using amount of the activated carbon of 5g and treating the activated carbon for 15 min; the particle size of the activated carbon is 400 meshes, the dosage of the activated carbon is 2g, and the treatment time of the activated carbon is 25 min. The results were 0.07% (average of 0.06%, 0.08% of the two results) and 0.06% (average of 0.06%, 0.07% of the two results), respectively, and as compared with the results in Table 3, the optimum condition was satisfactory.
In conclusion, the influence degree of the factors on the detection result and the experiment cost are comprehensively considered, and the optimal conditions for using the activated carbon when the content of the calcium carbonate in the paper-making reconstituted tobacco is determined are as follows: the grain size of the activated carbon is 400 meshes, the dosage of the activated carbon is 3g, and the treatment time of the activated carbon is 15 min.
2.4 methodological considerations
2.4.1 Standard Curve and detection Limit
The series of standard working solutions of 1.5 was measured with the instrument configuration defined in 1.4, with a linear correlation coefficient r2>0.99 is used as a criterion to determine the highest CaCO corresponding to the linear response of the liquid to be detected3The content is 125mg, and the standard working curve equation obtained in the content range is as follows: 5.0583x-0.0826, correlation coefficient r21. As shown in fig. 3. The lowest concentration standard solution was measured 10 times continuously, and the standard deviation of the measured value was 0.063mg, the detection limit of the method was 0.189mg with 3SD, and the quantification limit was 0.63mg with 10 SD.
2.4.2 repeatability
The finished paper A, the filler finished pulp B and the fiber pulping C3 samples are continuously detected for 6 times respectively, and the results are shown in Table 4. The variation coefficient ranges from 0.57 to 1.24 percent, and the variation coefficients are all less than 5 percent, which shows that the method has high precision.
TABLE 4 repeatability
This data is the mean of six replicates
2.4.3 recovery
Adding a certain amount of calcium carbonate into a sample with known content (shown in table 5), drying at 110-120 ℃ for 1.5-2 h, and cooling in a sulfuric acid dryer, and measuring the content of the calcium carbonate. The average recovery rate of 3 samples is 98.3-100.1%, which shows that the method has good accuracy and reliable detection result.
TABLE 5 recovery
Each data is the average of 3 consecutive determinations
3. Conclusion
The method can simultaneously meet the requirements of determining various samples such as paper-making reconstituted tobacco fiber pulping, filler finished product pulp, paper forming and the like. The method is simple, convenient, rapid and accurate to operate, and is very suitable for measuring mass samples.
Claims (2)
1. A continuous flow method for determining the content of calcium carbonate in paper-making reconstituted tobacco comprises the following steps:
(1) taking 0.5g of a sample to be detected, placing the sample at 105 ℃ for drying for 2h, transferring the sample into a 150mL beaker, adding 4.5mL of hydrochloric acid solution with the concentration of 0.5mol/L, stirring the mixture by using a glass rod until fibers are dispersed and no bubbles overflow, adding 95.5mL of pure water, fully mixing the mixture, filtering the mixture by using qualitative filter paper, adding 3g of activated carbon particles with the particle size of 400 meshes into the filtrate, oscillating the mixture for 15 minutes for decolorization, and filtering the mixture by using the qualitative filter paper to obtain a sample solution for later use;
(2) analyzing the sample solution with a continuous flow analyzer to obtain residual H+Corresponding calcium carbonate instrumental observations:
concentration of reagent: potassium iodate solution: 5g/L, potassium iodide solution: 50 g/L;
a flow path is provided: mixing the sample solution with dilution water through a 5-turn mixing ring, then mixing with a potassium iodate reagent through the 5-turn mixing ring, and then entering the upper layer of a dialyzer; the lower layer of the dialyzer is a potassium iodate reagent, and the mixed solution obtained by dialysis and the potassium iodide reagent undergo a color reaction and then enter a continuous flow analyzer after passing through 10 circles of mixing rings; the sample solution is pumped by a black/black pump tube at the flow rate of 0.32 mL/min; an ash/ash pump pipe for dilution water is used, and the flow rate is 1.02 mL/min; a purple/purple pump tube is used for a potassium iodate reagent, and the flow rate is 2.50 mL/min; the potassium iodide reagent is pumped by an orange/white pump tube at the flow rate of 0.23 mL/min; an orange/orange pump tube is used for secondary sample introduction, and the flow rate is 0.42 mL/min;
detecting wavelength by the analyzer: 420 nm; detecting speed: 20 samples/h; sample introduction/cleaning time ratio: 1: 1; sample introduction time is 90 s; baseline correction: opening; carrying out factor passing: 1.06 percent;
(3) drawing a standard working curve: preparing and calibrating HCl standard stock solution with concentration of 0.5mol/L, transferring 1.0, 2.0, 3.0, 4.0 and 5.0mL of the standard stock solution, and diluting to 100mL to obtain corresponding CaCO3Standard working solution with contents of 25.00mg, 50.00mg, 75.00mg, 100.00mg and 125.00mg respectively;
analyzing the standard working solution by the same method as the step (2), drawing a standard working curve, setting the linear regression equation y to 5.0583x-0.0826 and obtaining the correlation coefficient r2＝1；
(4) And (4) calculating a result: the residual H in the sample solution+Substituting the observed value of the corresponding calcium carbonate instrument into the formula (1) for calculation to obtain the calcium carbonate content in the sample;
in the formula:
CaCO3-the content of calcium carbonate in the sample in mass percent (%);
50-mass of calcium carbonate consumed by the reaction per millimole of hydrochloric acid in milligrams per millimole (mg/mmol);
C1the exact concentration of 0.5mol/L HCl standard solution in moles per liter (mol/L);
V1-the volume of 0.5mol/L HCl standard solution added in milliliters (mL);
C2residual H in the sample solution+Corresponding calcium carbonate instrumental observations in milligrams (mg);
g-sample mass in milligrams (mg);
the average value of two parallel measurements is used as the final measurement result, the accuracy is 0.1%, and the difference between the absolute values of the two parallel measurements should not exceed 0.4%.
2. The method for measuring according to claim 1, wherein: the sample to be detected is as follows: cutting the reconstituted tobacco into strips as samples to be detected; or 1000mL of fiber pulping or filler finished product pulp is placed in a clean tray, the liquid level is kept flat, and the fiber pulping or filler finished product pulp is dried to constant weight at 100 ℃ and is used as a sample to be detected for later use.
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