Colorimetric determination method and device for plumbum limit in electronic cigarette liquid based on color space processing

Abstract

Disclosed is a colorimetric determination method for plumbum (Pb) limit in electronic cigarette liquid based on color space processing. By digesting tobacco materials into a solution to be tested, a color value of the solution to be tested is obtained by photographing, and a color difference from a standard solution is calculated. By comparing the color difference, it can be effectively determined Whether the Pb content in the solution to be tested exceeds the limit requirements. The method is simple in operation, has low requirements for equipment and reagents, and can be used to measure the Pb content in tobacco products objectively and efficiently. A colorimetric determination device for Pb limit in electronic cigarette liquid based on color space processing is further provided, which is novel in structure and convenient to operate, and can quickly and conveniently realize the colorimetric determination method.

Description

TECHNICAL FIELD The present invention relates to the technical eld of heavy metal detection, and more particularly to a colorimetric determination method and device for plumbum (Pb) limit in electronic cigarette liquid based on color space processing. BACKGROUND Pb is a harmful component of tobacco in the Hoffman list, the elements may exist in tobacco, tobacco products and new tobacco products. Pb can cause protein irreversible deformation, loss of physiological activity, some have a certain carcinogenicity, and some will accumulate in the human body, causing long-term hazards. The new tobacco products, including electronic cigarette and heating non-combustion cigarette, have attracted the attention of tobacco products smokers all over the world. However, due to the imperfect laws or relevant management systems on new tobacco products in various countries, there is a lack of effective supervision on impurities and harmful substances including heavy metals, carbonyl compounds, and solvent residues, etc. At present, the People's Republic of China issued and implemented the national standard "GB 41700-2022 E-cigarette" in 2022. This standard strictly stipulates the electronic cigarette, which is a new tobacco product. There are clear requirements for the content of heavy metal--heavy metal (calculated as Pb): S 10 mg / Kg. The electronic aerosol is strictly tested according to the national standard" GB 5009.74 National Standard for Food SafetyLimit Test of Heavy Metals in Food Additives", thereby ensuring that the limits of heavy metals in electronic aerosol meet the requirements of this standard. After the preliminary exploration, the new tobacco products are detected according to the detection standard method, it is found that the components of different new tobacco products are complex and difcult to be digested, and the pretreatment time is long. The test results are determined subjectively by human, only qualitative results can be obtained (colorimetric with standard color tube, determine whether the content exceeds the standard value or not), and specic content of heavy metals cannot be obtained. As the result output of the detection method, the color space can be used to replace the human eye contrast for more in-depth content analysis. The color space is a mathematical model that denes a set of rules and coordinate systems that are used to describe and quantify the manner of color representation. The model species how each color point in the visible spectrum is represented by a set of values. As a representation of color standardization, it is ensured that color data can be accurately transferred and reproduced between various devices. The huesaturationbrightness (HSB) color model includes three color parameters: saturation (S), brightness (B) and hue (H), which is closest to the color change seen by human eyes. Therefore, a colorimetric determination method for Pb limit in new tobacco products based on HSB color model is provided. Microwave digestion is used to improve the digestion efciency of new tobacco products and reduce the pretreatment time. The objective qualitative evaluation and quantitative analysis can be achieved by using the method of color contrast calculation after objective image processing instead of subjective colorimetry. SUMMARY An object of the present invention is to provide a colorimetric determination method for Pb limit in electronic cigarette liquid based on color space processing, which can extract and digitize the color information in a color reaction between Pb and hydrogen sulde (H28), and determine and calculate the Pb limit, with the features of objectivity, saving, safety, semiquantitative and high efciency. Another object of the present invention is to provide a colorimetric determination device for Pb limit in electronic cigarette liquid based on color space processing, which can be applied to the above-mentioned colorimetric determination method to realize efcient and convenient detection operation. Examples of the present invention are implemented as follows. A colorimetric determination method for Pb limit in electronic cigarette liquid based on color space processing includes the following steps: Sl, conguring ve Pb standard solutions with different concentrations in colorimetric tubes, the Pb standard solutions being obtained by diluting a Pb standard mother solution; S2, adding a saturated H28 solution to the Pb standard solutions for reaction, and standing for 510 min; S3, photographing the Pb standard solutions with different concentrations after the reaction in a pure color background; S4, collecting H, S and B values of not less than 200X30 pixel points in a bottom area of the colorimetric tube in each picture under a HSB color space mode, and taking averages of all the H, S and B values obtained from each picture to obtain color values , and of each the Pb standard solution; S5, calculating a color comprehensive characterization value of each of the Pb standard solutions by the following formula, 1 1 =§><(100% )xzx 2 ><sin( ) where a value of is l5, corresponding to ve Pb standard solutions with different concentrations, and R is a hue corresponding to the pure color background; S6, carrying out curve tting with the comprehensive characterization value as an ordinate and a concentration as an abscissa to obtain a semi-quantitative calculation equation of Pb concentration; and S7, measuring and calculating a comprehensive characterization value of a solution to be tested by the method of S2S5, substituting into the semiquantitative calculation equation, and calculating a Pb concentration in the solution to be tested. A colorimetric determination device for Pb limit in electronic cigarette liquid based on color space processing includes a box body. The box body includes a bottom plate, a back plate and a top plate, and the back plate is arranged on one side in a length direction of the bottom plate; a bottom of the top plate is arranged with a standard light source, and the back plate is arranged with a colorimetric background plate of a pure color; the bottom plate is arranged with a colorimetric tube rack for placing colorimetric tubes, a bottom of the colorimetric tube rack is slidably connected to the bottom plate via a sliding rail, and the sliding rail is arranged along the length direction of the bottom plate; the colorimetric tube rack has a plurality of rst placement holes, and the plurality of rst placement holes are disposed along the length direction of the bottom plate; and a camera support for placing a camera is arranged on a side of the colorimetric tube rack away from the back plate. The examples of the present invention have the following advantageous effects. The examples of the present invention provide a colorimetric determination method for Pb limit in electronic cigarette liquid based on color space processing, by digesting a tobacco material to prepare a solution to be tested, a color value of the solution to be tested is obtained by photographing, and the color difference from a standard solution is calculated. Through the comparison of color difference, whether the Pb content in the solution to be tested exceeds the limit requirement can be effectively determined. The method is simple in operation, and has low requirements for equipment and reagents, and can be used to measure the Pb content in tobacco products objectively and efciently. The present invention also provides a colorimetric determination device for Pb limit in electronic cigarette liquid based on color space processing, which is novel in structure and convenient to operate, and can quickly and conveniently realize the colorimetric determination method. BRIEF DESCRIPTION OF THE DRAWINGS In order to explain the technical solutions of the examples of the present invention more clearly, and a brief description will be given below with reference to the accompanying drawings which are used in the examples. It is to be understood that the following drawings illustrate only some examples of the present invention and are not to be considered as limiting the scope, and other relevant drawings can be obtained according to these drawings without creative work for those ordinary skilled in the art. FIG. 1 is a cone model of semiquantitative analysis provided by the present invention; FIG. 2 is a schematic diagram of a semi-quantitative analysis method provided by the present invention; FIG. 3 is a tted curve of color integration characterization values and concentration provided in Example 1 of the present invention; FIG. 4 is a linear tted curve of hue and concentration provided by Example 1 of the present invention; FIG. 5 is a linear tted curve of saturation and concentration provided by Example 1 of the present invention; FIG. 6 is a linear tted curve of brightness and concentration provided by Example l of the present invention; FIG. 7 is a schematic diagram of a colorimetric determination device provided by Example 4 of the present invention; FIG. 8 is a schematic diagram of a colorimetric background plate of the colorimetric determination device provided by Example 4 of the present invention; FIG. 9 is a top view of a colorimetric tube rack of the colorimetric determination device provided by Example 4 of the present invention; FIG. 10 is a top view of a sample turntable of the colorimetric determination device provided by Example 4 of the present invention; and FIG. 11 is a schematic diagram of the colorimetric determination device provided by Example 4 of the present invention in a state in which a reagent is added. Reference numerals and denotations thereof: 1, box body; ll, top plate; l2, back plate; 13, bottom plate; 2, standard light source; 3, colorimetric background plate; 31, roller; 32, white background plate; 33, black background plate; 34, blue background plate; 3-5, handle; 3-6, magnetic strip; 4, colorimetric tube rack; 4-1, sliding rail; 5, sample tube rack; 5-1, sample turntable; 5-2, sample tray; 5-3, track; 5-4, rotating motor; 5-5, Vshaped connecting rod; and 6, camera support. DETAILED DESCRIPTION In order that the objects, technical solutions and advantages of the examples of the present invention will become more apparent, a more complete description of the examples of the present invention will be rendered by reference to the following description. In case the specic conditions are not specied in the examples, the conventional conditions or the conditions suggested by the manufacturer shall be followed. The reagents or instruments used are not specied by the manufacturer, and all are conventional products which can be obtained through commercial purchase. A colorimetric determination method for Pb limit in electronic cigarette liquid based on color space processing according to an example of the present invention will now be described in detail. An example of the present invention provides a colorimetric determination method for Pb limit in electronic cigarette liquid based on color space processing, including the following steps. In 81, ve Pb standard solutions with different concentrations were congured in colorimetric tubes, and the Pb standard solutions were obtained by diluting a Pb standard mother solution. In S2, saturated H28 solutions were added to the Pb standard solutions for reaction and stand for 5-10 min. In 83, the Pb standard solutions with different concentrations after the reaction were photographed in a pure color background. In 84, H, S and B values of not less than 200><30 pixel points in a bottom area of the colorimetric tube in each picture were collected under a HSB color space mode, and all the H, S and B values obtained from each picture are averaged respectively to obtain color values Hi, Si and Bi of each Pb standard solution. In 85, a color comprehensive characterization value of each Pb standard solution was calculated by the following formula, 1 1 =§><(100% )xzx 2 ><sin( ) where the value of is 15, corresponding to ve Pb standard solutions with different concentrations, and R is a hue corresponding to the pure color background. In 86, curve tting was carried out with the comprehensive characterization value as an ordinate and the concentration as an abscissa, and a semi-quantitative calculation equation of Pb concentration is obtained. In 87, a comprehensive characterization value of a solution to be tested was measured and calculated by the method of 8285, and substituted into the semiquantitative calculation equation to calculate the Pb concentration in the solution to be tested. This method uses the HSB color space as the basis of semi-quantitative model, and the HSB color space is an inverted cone, as shown in FIG. 1. In FIG. 1, S and B are two color components perpendicular to each other, and S, a decrease value of brightness (lOO%-B), a background-subtracted hue value (R-H), and a volume of a rectangular tetrahedron enclosed are taken as a characterization value MV indicating the depth of color, the height of the tetrahedron is the decrease value of brightness (100%B), a base area of the tetrahedron is the backgroundsubtracted hue value (RH), which is an included angle, and 8 is an isosceles triangle of sides. The Rvalue depends on the color of the background, for a white background the R-value is 130°, and for a black background the R-value is 120°. Further, the preparation method of solutions to be tested are as follows. 1-4 g of electronic cigarette liquid to be tested was weighted, the electronic cigarette liquid was mixed with the digestive reagent, and predigested at 100150°C for 12 h; the mixture was digested in a microwave digesting instrument for 520 min to obtain a digestive sample; and the digestive reagent includes concentrated nitric acid and hydrogen peroxide, and a volumetomass ratio of digestive reagent and the electronic cigarette liquid is 5-15 mL / g. The digestive sample was added into a colorimetric tube, diluted to constant volume, phenolphthalein was added, the pH is adjusted with ammonia water until the pink color fades, and an acetate buffer solution was added to obtain the solution to be tested. Alternatively, the concentration of concentrated nitric acid is 65% and the concentration of hydrogen peroxide is 30%. When pre-digestion was carried out, only concentrated nitric acid was used, and 3-8 mL of concentrated nitric acid was added to each gram of the electronic cigarette liquid according to the mass of the tobacco products to be tested. In the microwave digestion, a mixed solution of concentrated nitric acid and hydrogen peroxide was used, and 25 mL of concentrated nitric acid and l3mL of hydrogen peroxide are added to each gram of the electronic cigarette liquid according to the mass of the electronic cigarette liquid. Alternatively, the concentration of the Pb standard solution is 2-20 mg / kg. In the linear tting, ve Pb standard solutions with concentrations of 2 mg / kg, 5 mg / kg, 10 mg / kg, 15 mg / kg and 20 mg / kg can be selected for testing. The results of determination in the above concentration range are better. Further, the preparation method of the Pb standard solution are as follows. The Pb standard mother solution was added into the colorimetric tube, diluted to constant volume, and phenolphthalein and acetate buffer solution were added to obtain the Pb standard solution. Alternatively, the conditions for photographing the reacted Pb standard solution, the solution to be tested and the control solution are as follows. Light source parameters: standard light source with color temperature of 5300-5 800 K and illuminance of 18002200; and camera parameters: aperture 5.0; international organization for standardization (ISO) 1250; shutter l / 250 second; and color temperature of 5500 K. Further, examples of the present invention provide a colorimetric determination method, further including the following steps. The Pb standard mother solution with the same dosage as the Pb standard solution and the digestive reagent with the same dosage as the solution to be tested are added into the colorimetric tube, diluted to constant volume, phenolphthalein is added, the pH is adjusted with ammonia water until the pink color fades, and acetate buffer solution is added to obtain a control solution. The color values HA, SA and BA of Pb standard solution are respectively determined according to the method of 82-84, the color values of the solution to be tested are HB, SB and BB, and the color values of the control solution are Hc, Sc and Bc. A color difference AEl between the Pb standard solution and the solution to be tested is calculated by using the color values thereof, and a color difference AEZ between the Pb standard solution and the control solution is calculated by using the color values thereof; and by comparing AEl and AEZ and combining with the difference of color values, whether the Pb content of the solution to be tested exceeds the limit requirements is qualitatively analyzed. Further, the basis of the qualitative analysis is as follows: when AEl AEZ, the Pb content of the solution to be tested is equal to the limit requirement; when AEl > AEZ, and AHÉO O A820 0 AB<0, and the Pb content of the solution to be tested is lower than the limit requirement; when AE1> AEZ, and AHBO ASSO O AB >0, and the Pb content of the solution to be tested is higher than the limit requirement; and where AH, AS and AB are the differences of H, S and B values of the two solutions in the HSB color space, respectively. Specically, when using the above analysis basis or calculating AEl, AH, AS and AB are the difference values of H, S and B values of the solution to be tested and the Pb standard solution. However, in the calculation of AEZ, the corresponding AH, AS and AB are the difference values of H, S and B values of the control solution and the Pb standard solution. Further, the average value of each pixel point is calculated using the following formula, where is a hue value of each pixel point, is a saturation value of each pixel point, is the brightness of each pixel point, and is a total number of pixel points. Further, the color difference is calculated by the following formula, |A | _ Iïl A >< A A A = / (2>2 + (_)2 + (_)2 , and are weight coefcients of H, S and B values, respectively. Altematively, , and are obtained by a linear tting, and specic operations are as follows: ve Pb standard solutions with different concentrations are prepared, and the H, S and B values are determined; a linear curve of H value was obtained by linear tting between (180H) and concentration C using the least square method, and a slope of the curve was ; a linear curve of S value was obtained by linear tting between 8 value and concentration C using least square method, and a slope of the curve was ; and a linear curve of B value was obtained by linear tting between (lOO-B) and concentration C using least square method, and a slope of the curve was . Further, examples of the present invention thher provide a colorimetric determination device for Pb limit in electronic cigarette liquid based on color space processing includes a box body. The box body includes a bottom plate, a back plate and a top plate, and the back plate is arranged on one side in a length direction of the bottom plate; a bottom of the top plate is arranged with a standard light source, and the back plate is arranged with a colorimetric background plate of a pure color; the bottom plate is arranged with a colorimetric tube rack for placing colorimetric tubes, a bottom of the l ] colorimetric tube rack is slidably connected to the bottom plate via a sliding rail, and the sliding rail is arranged along the length direction of the bottom plate; the colorimetric tube rack has a plurality of rst placement holes, and the plurality of rst placement holes are disposed along the length direction of the bottom plate; and a camera support for placing a camera is arranged on a side of the colorimetric tube rack away from the back plate. Further, the bottom of the colorimetric tube rack is slidably connected to the bottom plate via a sliding rail, the sliding rail is arranged along the length of the bottom plate. Further, the bottom plate is further arranged with a sample turntable, the sample turntable is arranged with a plurality of second placement holes for placing sample tubes, the plurality of second placement holes are disposed along a circumference of the sample turntable, and the sample tumtable is connected to a rotating shaft of a rotating motor via a track. Further, the colorimetric background plate has a white background plate, a black background plate, and a blue background plate arranged in a stack, tops of the white background plate, the black background plate, and the blue background plate are independently arranged with rollers and can be rolled up independently of each other; and magnetic strips are arranged at bottoms for magnetically connecting to the bottom plate. The features and properties of the present invention are described in further detail below with reference to examples. The reagents involved in the examples include: nitric acid (65% HNO3), hydrogen peroxide (30% H202), hydrochloric acid (36% HCl), ammonia (25% HN3'H2O), phenolphthalein (C2OH14O4), ammonium acetate (C2H7NO2), hydrogen sulde (H28), Pb standard stock solution (1 mg / mL), and hydrouoric acid (40% HF). The conguration method for each solution used is as follows: 18% hydrochloric acid solution: 50 mL of hydrochloric acid was taken, and diluted with water to 100 ml; 2.5% ammonia solution: 10 ml of ammonia water was taken, and diluted with water to 100 ml; l2 1% phenolphthalein solution: 1.0 g of phenolphthalein was dissolved in 100 mL of ethanol solution; acetate buffer solution: 30 g of ammonium acetate was weighed and dissolved in 30 mL of water, 55 mL of 18% hydrochloric acid solution was added, the pH was adjusted to 3.5 with 2.5% ammonia solution, and diluted with water to 100 mL; saturated hydrogen sulde solution: hydrogen sulde gas was introduced into the water at a ow rate of 50 mL / min for l h; and Pb standard mother solution: 1 mL of Pb standard solution (1 mg / mL) was taken, and diluted with water to 100 ml. Example 1 The example provides a colorimetric determination method for Pb limit in electronic cigarette liquid based on color space processing, including the following steps. In 81-1, 0.2 mL, 0.5 mL, 1.0 mL, 1.5 mL and 2.0 mL were respectively sucked from the Pb standard mother solution into a 50 mL Nessler tube (labeled as AlA5 in sequence), water was added to 25 mL, 1 drop of 1% phenolphthalein was added, and 5 mL acetate buffer solution was added. The limit concentration C of AlA5 colorimetric tube is equivalent to the limit of heavy metals of 2 mg / kg (A1), 5 mg / kg (A2), 10 mg / kg (A3), 15 mg / kg (A4) and 20 mg / kg (A5). In 81-2, 10 mL of saturated hydrogen sulde solution was added to each of Al-A5 colorimetric tubes, water was added to 50 mL, and stood for 5 min. In 81-3, under the standard light source conditions of color temperature of 5300 K5800 K and illuminance of 2000i200, photos were taken under white and black backgrounds (camera parameters: aperture 5.0; ISO 1250; shutter 1 / 250 second; and color temperature 5500 K). If precipitation occurred, it was allowed to stand for 2 h until clear. In 814, a picture of AlA5 colorimetric tubes under white background were taken, under the HSB color space mode (H is hue, S is saturation and B is brightness), the values of H, S and B at the bottom area of each tube with no less than 200><30 pixels were collected, and the average value of each color component of the obtained pixels was taken. The test results are shown in Table 1. Table 1. Color parameters of colorimetric tubes Al-A5 ----- ___- ___um ___- _ In Sl-5, the data in Table 1 were used to calculate the color comprehensive characterization value MV at each concentration through the calculation formula of color comprehensive characterization value MV. The results are shown in Table 2. Table 2. Color comprehensive characterization values MV for colorimetric tubes A1A5 ----- Color comprehensive 8.627 33.24 57.7 207.2 522 characterization value MV 302 572 4375 594 .3136 Curve tting (as shown in FIG. 3) was carried out with the comprehensive characterization value MV as an ordinate and the concentration C as an abscissa, and a semi-quantitative calculation equation of Pb concentration is obtained. MV= 0.1l8c3l.6111c2+11.498c5.9635 (R2=0.9992). The equation is a simple cubic equation, R2 reaches 0.9992, and the test accuracy is high. In 816, the linear curve of H value was obtained by linear tting between (180H) and concentration C using the least square method, and the slope of the curve was = 2.6417; the linear curve of S value (as shown in FIG. 5) was obtained by linear tting between S values and concentration C using least square method, and the slope of the curve was = 0.439; and the linear curve of B value (as shown in FIG. 6) was obtained by linear tting between (100-B) and concentration C using least square method, and the slope of the curve was = 0.6604. It can be seen that H value is negatively correlated with the concentration C, 8 value is positively correlated with the concentration C, and B value is negatively correlated with the concentration C. In 81-7, The , and were substituted into the color difference calculation formula, |A | _ Iïl A >< A A A = / (2>2 + (_)2 + (_)2 Example 2 The example provides a colorimetric determination method for Pb limit in electronic cigarette liquid based on color space processing, including the following steps: In 821, 1.00 g of electronic cigarette liquid was weighted into a Teon digestion tank, 5 mL of 65% nitric acid was added, and predigested in a heating jacket at 120°C for 2 h. In 822, 3 mL of 65% nitric acid and 2 mL of 30% hydrogen peroxide are continuously added in the digestion tank, and the solution is sealed and placed into the microwave digestion instrument. The digestion of electronic cigarette liquid shall be carried out according to the following temperature rise programs. Table 3. Microwave digestion reference conditions Steps Hold time / min time / min temperature / °C ---- In 823, the digestion tank was cooled to room temperature, transferred to a 10 mL volumetric ask, and diluted with water to 100 ml. In S2-4, a blank was prepared according to the above steps without the addition of the electronic cigarette liquid. In S2-5, all the samples digested in 82-3 were added into the colorimetric tube, water was added to 25 mL, 1 drop of 1% phenolphthalein was added, pH was adjusted with 2.5% ammonia water until the pink color fades, and 5mL of acetate buffer solution was added to obtain the solution to be tested (labeled as tube B). In 826, 1.0 mL was sucked from the Pb standard mother solution into the colorimetric tube, all the reagent blank digested in 82-4 was added into the colorimetric tube, 1 drop of 1% phenolphthalein was added, the pH was adjusted with 2.5% ammonia water until the pink color fades, and 5 mL of acetate buffer solution was add to obtain the control solution (labeled as C tube). In 827, The B tube and the C tube were treated according to 812 to 814 in Example 1 to obtain the color values HB, SB and BB of the solution to be tested and Hc, Sc and Bc of the control solution, respectively. In SZ8, the color values HB, SB and BB of the solution to be tested were used to calculate the color comprehensive characterization value thereof according to the following formula: 1 1 =§><(100% )Xîx 2 ><sin( ) , the Pb concentration in the solution to be tested was calculated by the semiquantitative calculation equation of 815 in Example 1. In 829, the color difference AEl between the Pb standard solution and the solution to be tested was calculated by using the color difference calculation formula in Sl7 of Example 1, and the color difference AEZ between the Pb standard solution and the control solution was calculated by using the color value of the Pb standard solution and the control solution. By comparing AEl and AE2 and combining with the difference of color values, whether the Pb content of the solution to be tested exceeds the limit requirements is qualitatively analyzed. Example 3 About 1 g of three different electronic cigarette liquids (samples 1-3) were weighed, digested by the method of Example 2, the HB, 813 and BB values were determined, and qualitative and semiquantitative tests were carried out. At the same time, the Pb concentration of tobacco products to be tested was measured by inductively coupled plasma mass spectrometry, and the accuracy of the two methods was compared. The measurement results are shown in Table 4 and Table 5. Table 4. Qualitative test results of tobacco products to be tested Sample Sa tubeA Sample 1 Sample 2 Sample 3 mple (standard tube C value) .- ____l- n__n-um A 11 H A l 2 S A 6.162 3.304 9.112 El A 0.757 0.757 0.757 E2 Below the Below the Below the onclusi limit limit limit on Table 5. Semi-quantitative testing result of tobacco products to be tested _ ___ ___- Calculated concentration 6.23 6.579 4.55 (mg / kg) Test concentration 5.97 6.62 4.42 (mg / kg) 4.37% -0.61% 2.90% (%) ___- The calculated concentrations in the table are the concentration data calculated by the semi-quantitative calculation equation of 81-6 in Example 1, the detected concentrations are the concentration data detected by inductively coupled plasma mass spectrometry, and the error rate is calculated by the following formula. Error rate=(calculated concentrationdetected concentration) / detected concentration>< 100% As can be seen from Table 4 and Table 5, when the detection method provided in the example of the present invention performs qualitative detection, the qualitative conclusions obtained are consistent with the quantitative detection results in Table 5, indicating that the qualitative detection method has reliability. In addition, from the semi-quantitative detection results in Table 5, the calculated concentration of each sample is substantially equivalent to that detected by inductively coupled plasma mass spectrometry, and the error rate is maintained at 5% or less, indicating that the monitoring method provided by the example of the present invention has high accuracy in semi-quantitative detection. Example 4 The present example provides a colorimetric determination device for Pb limit in electronic cigarette liquid based on color space processing, including a box body 1. The box body includes a bottom plate 13, a back plate 12 and a top plate ll, and the back plate 12 is arranged on one side of a length direction of the bottom plate 13. The box body 1 is made of metal, indicating that it is painted white. A bottom of the top plate l-1 is arranged with a standard light source 2, the standard light source 2 includes ve lamp tubes, and the light source parameters thereof are: color temperature: 5300 K-5800 K, illuminance: 2000i200. Before the test, the standard light source 2 is turned on to test the illumination uniformity. An upper surface of the bottom plate 13 is divided into 20 areas, and each area is tested once. The test conditions are as follows: the illumination of each area is 2000i200, the tested illumination uniformity of each area is 2 0.8, and the test can be carried out. Illumination uniformity = minimum illumination value + average illumination value. The back plate 1-2 is arranged with a colorimetric background plate 3 of a pure color. The colorimetric background plate 3 has a white background plate 3-2, a black background plate 3-3 and a blue background plate 3-4 arranged in a stack, and tops of the white background plate 3-2, the black background plate 3-3 and the blue background plate 3-4 are independently arranged with rollers 31 which can be rolled up independently of each other; and magnetic strips 36 are arranged at bottoms for magnetically connecting to the bottom plate 13. The area on that right side of the white background plate 32, the black background plate 33, and the blue background plate 34 decrease in order. When not in use, each background plate is taken up by the top roller 3-1. When in use, corresponding handles 3-5 are pulled to unfold the background plates and secured by the bottom magnetic strips 3-6. The bottom plate l3 is arranged with a colorimetric tube rack 4 for placing colorimetric tubes, the colorimetric tube rack 4 has a plurality of rst placement holes, and the plurality of rst placement holes are disposed along the length direction of the bottom plate 1-3. Alternatively, the rst placement holes are arranged in six, which are respectively used for placing ve Pb standard solution with different concentrations and the control solution. A bottom of the colorimetric tube rack 4 is slidably connected to the bottom plate l3 via a sliding rail 4l, and the sliding rail is arranged along the length direction of the bottom plate 13. When the reagent is added, the colorimetric tube rack can be pulled out to the left; when comparing colors, the colorimetric tube rack is returned to the right to home position. The bottom plate 1-3 is further arranged with a sample tube rack 5 for placing sample tubes, the sample tube rack 5 is arranged with a sample tumtable 5-1, the sample turntable 5-1 is arranged with a plurality of second placement holes for placing the sample tubes, the plurality of second placement holes are disposed along a circumference of the sample turntable 51, and the sample turntable 51 is connected to a rotary shaft of a rotating motor 54 via a track 53. A sample tray 52 arranged concentrically is arranged below the sample turntable 51, and the sample tray 52 is connected to a central position of the sample turntable 5-1 through a connecting shaft, and the sample tray 5-2 can support the bottom of the sample tube. At least one of the plurality of second placement holes is collinear with the plurality of rst placement holes, and the color comparison can be carried out by rotating the corresponding sample to this position. The sample tube rack 5 further includes a vertical rod rotatably connected to the bottom plate 13, the rotating motor 54 is arranged at a top of the vertical rod, and the sample tray 52 is xedly connected to the vertical rod via a Vshaped connecting rod 55. A side of the colorimetric tube rack 5 remote from the back plate 12 is arranged with a camera support 6 for placing a camera. The camera is detachably connected to the camera support 6, and a corresponding camera can be arranged according to requirements in actual use. There is no need to x the camera support 6 and the bottom plate 1-3, and the position of the camera support 6 can be easily adjusted at any time. The using methods of colorimetric determination device are as follows. 1) During detection, the colorimetric tube rack 4 is pulled out from the box body 1 to the left, and six colorimetric tubes are put in, standard solutions and control solutions with ve concentrations are added respectively, after pH is adjusted and chromogenic reagents are added, the reagent addition of standard samples is completed, and the colorimetric tube rack 4 is returned to the original position. 2) The vertical rod is rotated to turn the sample turntable 51 out of the box body 1 to the right, a plurality of colorimetric tubes are placed in the sample turntable 51, different processed samples are added, pH is adjusted and chromogenic reagents are added to complete the reagent addition of the samples to be tested, and after the addition is completed, the vertical rod is rotated to reset the sample turntable 5-1. 3) The sample turntable 5-1 is rotated, and the colorimetric tube of the sample to be tested rotates to a position collinear with the colorimetric tubes of multiple standard solutions. The standard light source 2 is turned on, the colorimetric background plates 3 with different colors are pulled down, and the standard solution, the control solution and the solution to be tested are respectively photographed by the camera, thereby realizing image color information collection with different backgrounds. In summary, the examples of the present invention provide a colorimetric determination method for Pb limit in electronic cigarette liquid based on color space processing, by digesting the tobacco material to prepare the solution to be tested, the color value of the solution to be tested is obtained by photographing, and the color difference from the standard solution is calculated. Through the comparison of color difference, whether the Pb content in the solution to be tested exceeds the limit requirement can be effectively determined. The method is simple in operation, and has low requirements for equipment and reagents, and can be used to measure the Pb content in tobacco products objectively and efciently. The present invention also provides a colorimetric determination device for Pb limit in electronic cigarette liquid based on color space processing, which is novel in structure and convenient to operate, and can quickly and conveniently realize the colorimetric determination method. The above is only the preferred example of the present invention, and is not used to limit the present invention, and for those skilled in the art, the present invention may have various modications and changes. Any modications, equivalent replacements, and improvements made within the spirit and principle of the present invention are included in protection scope of the present invention.

Claims

1. Colorimetric determination method for plumbum (Pb) limit in electronic cigarette liquid based on color space processing, consisting of: Sl, configuring five Pb standard solutions with different concentrations in colorimetric tubes, and obtaining the Pb standard solutions that are obtained by diluting a Pb standard mother solution; S2, adding a saturated hydrogen sulfide solution (HzS) to the Pb- standard solutions for reaction, and let stand for 5-10 minutes; 83, take photographs of the Pb standard solutions with different concentrations after the reaction in a pure color background; S4, collecting hue (H), saturation (S), and lightness (B) values from ten least 200><30 pixel points in a bottom area of the colorimetric tube in each photo under a hue, saturation, lightness (HSB) color space mode, and respectively taking an average of all H, S and B values obtained from each photograph to obtain color values H i, S i and B i of each Pb standard solution; S5, calculating a color extended characteristic value characteristic value M Vi of each of the Pb standard solutions by the following formula, MVi =ä>< (100%B,-) x%xsä > <sin(rhi) where the a-value of i is 15, corresponding to five Pb- respectively standard solutions of different concentrations, and R is a shade corresponding to the pure color background; S6, performing curve fitting with the extended characterization value M Vi as ordinate and the a concentration C i as abscissa to a semi-quantitative calculation to obtain a comparison of Pb concentration; and S7, measuring and calculating an extended characteristic value M VB of the test solution by the method of S2S5, substituting M VB in the semiquantitative calculation equation and calculating the a Pb concentration in the solution to be tested.

2. Colorimetric determination method according to claim 1, comprising a preparation method for a solution to be tested includes the steps of: mixing the electronic cigarette liquid to be tested with a digestive reagent, and pre-digesting a mixture at 100-150°C for 1-2 hours; digesting the mixture in a microwave digestion device for 5-20 minutes to to obtain a digestive sample, the digestive reagent consisting of concentrated nitric acid and hydrogen peroxide, and a volume-to-mass ratio of the digestive reagent until the electronic cigarette liquid is 5-15 ml / g; and Add the digestive sample to the colorimetric tube, followed by dilution to a constant volume; and add phenolphthalein, adjust the pH with ammonia water until the pink color fades and add an acetate buffer solution to test the to obtain a solution.

3. Colorimetric determination method according to claim 2, in which a concentration of the Pb standard solution is 2-20 mg / kg; and the Pb standard mother solution is added to the colorimetric tube, and after dilution to a constant volume phenolphthalein and the acetate buffer solution were added to make the Pb standard solution. to acquire.

4. Colorimetric determination method according to requirement 1, specifying the conditions for the photograph the Pb standard solution or the solution to be tested after the reaction as follows are: Light source parameters: standard light source with a color temperature of 5300-5800 K and a illuminance of 1800-2200; and Camera parameters: aperture 5.0; International Organization for Standardization (ISO) 1250; shutter 1 / 250 second; and a color temperature of 5500 K.

5. Colorimetric determination method according to claim 4, further comprising the following steps: adding the Pb standard mother solution in the same amount as that of the Pb standard solution and the digestive reagent in the same amount as that of the test solution in the colorimetric tube, after dilution to a constant volume, the adding phenolphthalein, adjusting the pH with ammonia water until it turns pink fades and adding the acetate buffer solution to make a control solution to acquire; determining the color values HA, SA and BA of the Pb standard solution according to the method of S2-S4, where the color values of the solution to be tested are HB, SB and 133 and the colour values of the control solution Hc, Sc and Bc; and calculate a color difference AEI between the Pb standard solution and the solution to be tested using their color values, and calculate a color difference AE2 between the Pb standard solution and the control solution using their colour values; and by comparing and combining AE2 and AE2 with the difference in color values, qualitatively analyze whether the Pb content of the solution to be tested meets the limit values exceeds.

6. Colorimetric determination method according to claim 5, in which the color difference is calculated using the following formula, AE : (& M+A3|y . (M,. . (ä,. kB ks kn where kH, kS and kB are weight coefficients of H, S and B values, respectively.

7. Colorimetric determination device for Pb limit in electronic cigarette liquid based on color space processing, consisting of a box body, in which the box body comprises a base plate, a back plate and a top plate, and the back plate on one side of a lengthwise direction of the base plate is arranged; a bottom of the top plate is fitted with a standard light source, and the back plate is fitted with a colorimetric background plate of a pure color; the base plate is arranged with a colorimetric tube rack for placing colorimetric tubes, it has colorimetric tube rack a majority of initial placement holes, and the majority of first placement holes are placed along the length of the base plate; and a camera support for placing a camera is arranged on one side of the colorimetric tube rack from the back plate.

8. A colorimetric determination device according to claim 7, wherein the bottom of the colorimetric tube rack which is slidably connected to the base plate and the sliding rail is fitted along the length of the base plate.

9. Colorimetric determination device according to claim 8, wherein the base plate is further equipped with a sample tube rack, the sample tube rack consists of a sample turntable, the sample turntable is equipped with a number of second placement holes for placing sample tubes, the number of second placement holes are in a circumferential direction of the sample turntable and the sample turntable is connected via a track connected to a rotating shaft of a rotating engine.

10. A colorimetric determination apparatus according to claim 9, wherein the colorimetric background plate a white background plate, a black background plate and a blue one background plate has which are arranged in a stack, with the tops of the white background plate, the black background plate and the blue background plate are arranged independently of each other with roles and can act independently of each other are rolled up; and magnetic strips are arranged at the bottoms to to be magnetically connected to the base plate. 1 / 6 FIG.1