Method for detecting sulfate ions in water body based on smart phone

Abstract

The invention discloses a method for detecting sulfate ions in a water body based on a smart phone, and belongs to the technical field of sulfate ion detection. According to the portable detection equipment based on the smart phone, laser emitted by a laser pen is divided into two beams through a beam splitter, then a to-be-detected liquid and a reference solution are compared, the smart phone is used for shooting and identifying RGB values, so that the L ratio of the to-be-detected liquid to the reference solution is obtained, the linear relation between sulfate ions with different concentrations and the L ratio is constructed, and the content of sulfate ions in the to-be-detected liquid and the content of sulfate ions in the to-be-detected liquid are calculated. Compared with the traditional turbidimeter detection, the high-sensitivity detection on the sulfate radical is realized, the sensitivity is higher, and the field detection on the water sample to be detected is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of sulfate ion detection in water, and in particular to a method for detecting sulfate ions in water based on a smart phone. Background Art

[0002] Sulfate ions are common anions in water. Due to their great impact on human health, the detection of sulfate ions in water has never stopped and is constantly developing. At present, the methods and technologies for detecting sulfate ions include capillary electrophoresis, ion chromatography, surface enhanced Raman method, ion selective electrode and high performance liquid chromatography.

[0003] Capillary electrophoresis has the advantages of simple instrumentation, fast analysis speed and less sample required. In addition, it is miniaturized and portable, so it is widely used in the fields of food analysis and environmental testing. However, this method often has the problems of low sensitivity and poor reproducibility in practical applications. Surface-enhanced Raman method is a promising technology for rapid and sensitive detection of chemicals. It has the characteristics of non-destructive detection, low sample requirements, high sensitivity, and can realize in situ and in vitro analysis. Raman spectroscopy causes characteristic Raman emission due to changes in the frequency or wavelength of the incident light caused by changes in molecular polarization. This emission provides the molecular identity or fingerprint information of the molecular structure and intermolecular interaction of the compound, making its detection quite sensitive and selective. However, this method usually requires professional personnel to operate, and requires more complex pretreatment of the sample to be tested and preparation of nano-substrates for enhancing spectral signals. High-performance liquid chromatography has the advantages of high sensitivity, high selectivity and automated operation, but the supporting equipment of this method is usually expensive and the equipment maintenance cost is high, which makes its detection cost high. In addition, the detection time is longer than other equipment.

[0004] Although there are many methods for detecting sulfate ions and the determination is accurate, most sensors or precision instruments involved can only be used in laboratory environments with relatively harsh conditions, and there is a lack of methods for rapid on-site detection. Although gravimetric methods, titration methods, and turbidimetric methods do not require large-scale detection equipment and have the potential for on-site detection, they are usually cumbersome and time-consuming, and have many influencing factors, resulting in poor practicality. Summary of the invention

[0005] In order to solve the technical problem of difficulty in on-site detection of sulfate ions in the prior art, the present invention provides a method for detecting sulfate ions in water based on a smart phone. The present invention uses a liquid to be tested and a reference solution as a comparison, and uses a smart phone to shoot and identify RGB values, thereby obtaining the ratio of the brightness value L of the liquid to be tested and the reference solution, constructing a linear relationship between the ratio of sulfate ions of different concentrations and L, and realizing rapid and accurate detection of sulfate ions in water.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] On the one hand, the present invention provides a portable detection device based on a smart phone, including a beam splitter, a reflector, a cuvette, a laser pen fixing tube and a detection box;

[0008] The detection box is provided with a partition plate for dividing the detection box into a light mirror area and a sample area; the partition plate is provided with light-transmitting holes, and the light-transmitting holes include a first light-transmitting hole and a second light-transmitting hole;

[0009] The optical mirror area is used to place the beam splitter and the reflector; the sample area is used to place a cuvette, and the cuvette includes a first cuvette and a second cuvette;

[0010] In the optical mirror area, an incident hole is provided on the side wall of the detection box, the laser pen fixing tube is used to fix the laser pen on the side wall of the detection box, the laser emitted by the laser pen is irradiated onto the beam splitter through the incident hole, and the beam splitter is used to split the laser into two beams of laser light with the same power and parallel to each other; one beam of laser light is irradiated onto the first cuvette through the first light-transmitting hole, and the other beam of laser light is irradiated onto the reflector, and is reflected by the reflector and then irradiated onto the second cuvette through the second light-transmitting hole.

[0011] Preferably, a support frame is provided below the laser pen fixing tube for supporting the laser pen fixing tube;

[0012] The bottom of the detection box is provided with two sample slots, namely a first sample slot and a second sample slot. The first sample slot is used to fix the first cuvette, and the second sample slot is used to fix the second cuvette.

[0013] As an embodiment of the present invention, the portable detection device further includes a cover, a conical cylinder cover, a hollow cylinder, a smart phone fixing slot, and a mobile phone camera shooting hole;

[0014] The cover is installed at one end of the top of the detection box, so that the optical microscope area becomes a dark room; the conical tube cover is installed at the other end of the top of the detection box, so that the sample area becomes a dark room;

[0015] The top of the conical cylinder cover is fixedly connected to the hollow cylinder, the top of the hollow cylinder is fixed with the smartphone fixing groove, a mobile phone camera shooting hole is arranged at the connection position between the smartphone fixing groove and the hollow cylinder, and a smartphone can be used to take photos of the sample area through the mobile phone camera shooting hole.

[0016] The bottom of the detection box is provided with two positioning posts, namely a first positioning post and a second positioning post, and the top of the positioning post is provided with a thread;

[0017] The beam splitter is fixed by a beam splitter optical adjustment frame, and the reflector is fixed by a reflector optical adjustment frame. Internal threads are arranged at the bottom of the beam splitter optical adjustment frame and the reflector optical adjustment frame. The beam splitter optical adjustment frame and the reflector optical adjustment frame are respectively fixed on the first positioning column and the second positioning column.

[0018] As another embodiment of the present invention, the optical mirror area is provided with a light source reflector, and the laser emitted by the laser pen is irradiated to the light source reflector through the incident hole, and the light is reflected to the beam splitter by the light source reflector;

[0019] The portable detection device also includes a cover disposed on the top of the detection box, so that the detection box forms a dark room;

[0020] The cover corresponds to the middle position between the first cuvette and the second cuvette, and is provided with a shooting hole for a mobile phone camera;

[0021] Three positioning posts are fixed on the bottom of the detection box, namely the first positioning post, the second positioning post and the third positioning post, and threads are provided on the tops of the positioning posts; the beam splitter is fixed by the beam splitter optical adjustment frame, the reflector is fixed by the reflector optical adjustment frame, and the light source reflector is fixed by the light source reflector frame, and the bottoms of the beam splitter optical adjustment frame, the reflector optical adjustment frame and the light source reflector frame are all provided with internal threads, which cooperate with the threads on the tops of the positioning posts, and the beam splitter optical adjustment frame, the reflector optical adjustment frame and the light source reflector frame are respectively fixed on the first positioning post, the second positioning post and the third positioning post.

[0022] On the other hand, the present invention also provides a method for detecting sulfate ions in water based on a smart phone, comprising:

[0023] Step 1: Prepare sulfate ion and barium ion standard solutions;

[0024] Step 2: Mix the sulfate ion standard solution and the barium ion standard solution evenly as the sample solution, then add it to the portable detection device, use the barium ion solution of the corresponding concentration as a reference, turn on the laser pen of the portable detection device, and then use a smartphone to take relevant photos;

[0025] Step 3: Cut out the effective area of ​​the photograph, and obtain the R, G, and B values ​​of the corresponding areas of the sample solution and the reference solution respectively, and then calculate the brightness value according to formula (I), and then calculate L 样品 With L 参比 The ratio of (L ratio);

[0026] (I);

[0027] L is 0-1, L=1 is white, L=0 is black;

[0028] Step 4: Take photos of the mixed solutions of sulfate standard solution and barium ion standard solution with different concentrations in sequence, intercept the effective areas of each to identify the corresponding R, G, and B values, calculate the L ratio in each picture, and establish a standard working curve with sulfate ion concentration as the horizontal axis and L ratio as the horizontal axis;

[0029] Step 5: After the water sample to be tested is pretreated, the corresponding L ratio is determined by analogy with the above steps S2-S3, and the sulfate ion concentration of the water sample to be tested is converted in combination with the standard working curve.

[0030] Furthermore, the step 1 is specifically as follows:

[0031] (11) Accurately weigh 1.479 g of anhydrous sodium sulfate, add ultrapure water to dissolve, and dilute to volume with a 1000 mL volumetric flask to obtain a 1000 mg / L sulfate ion standard solution. Dilute the standard solution with ultrapure water to obtain standard working solutions with concentrations of 800, 500, 200, 100, 80, 60, 40, 20, 10, 5, 1, 0.5, 0.2, 0.1 and 0.05 mg / L, respectively; store the above solutions at room temperature in a sealed container away from light.

[0032] (12) Accurately weigh 1.78 g of barium chloride dihydrate, add ultrapure water to dissolve, and dilute to volume with a 100-mL volumetric flask to obtain a 10 g / L barium ion standard solution; dilute the standard solution with ultrapure water stepwise to a 5 g / L standard working solution; store the above solution in a sealed container at room temperature away from light.

[0033] Furthermore, the step 2 is specifically as follows:

[0034] Add 2mL of sulfate ion standard solution to a 5mL centrifuge tube, then add 1mL of barium ion standard solution, mix well, add to the portable detection device, use 1mL of barium ion standard solution and 2mL of water mixed solution as a reference, turn on the laser pen of the device, and then take pictures. Repeat 3 times for each group.

[0035] Preferably, in step 3, the wavelength of the laser emitted by the laser pen is 500-550nm.

[0036] Furthermore, in step 4, the image is processed using Matlab software; the effective area is the area occupied by the solution in the entire cuvette.

[0037] Preferably, a water sample to be tested is collected, filtered through a 0.45 μm pore size filter syringe, and then excess HCl is added to remove excess carbonate ions in the water, so that the pH of the mixed solution is below 4.

[0038] The present invention uses the detection box as the device shell, which not only fixes the position of each device, but also creates a dark environment for detection to avoid interference from the external environment.

[0039] The present invention uses a commercially available laser pen as a light source. For example, a commercially available laser pen can emit a light beam with a wavelength of 532 nm. After passing through a plurality of optical lenses, the light beam is divided into two parallel beams that are both perpendicular to the light beams irradiated by the laser pen before the optical lenses are illuminated, and then irradiated into the corresponding cuvette through the light transmission hole. The principle is as follows: Figure 1 The device has simple internal components and does not require any complicated operations, so anyone can assemble it.

[0040] The invention is based on the fact that precipitation will be generated after sulfate radical solution and barium ions are mixed, and then the light scattering principle is used to process the photographed pictures and the light scattering evaluation is performed on the pictures by using the brightness value.

[0041] RGB color space is a common color numerical method. The combination of the three primary colors R, G, and B in RGB can represent all color changes in the color domain. When the color change occurs from dark to light in the same color, the RGB model is used as a quantization model. The above RGB model decomposes the color into basic components but cannot fully explain the color perception process. The color domain is a two-dimensional color space concept, mainly composed of hue and saturation (HS), but there is no concept of brightness. Therefore, brightness (B) is proposed, and the color domain is extended from two dimensions to a complete three-dimensional space. The HSB space (also known as HSV) is proposed, which can more intuitively reflect human perception. The specific value of HSB can be converted through RGB values. For the calculation of lightness value (L), different brightness is perceived according to the different sensitivity of humans to the three colors of red, green, and blue, that is, psychological brightness, usually in the ratio of red: green: blue = 1: 1.5: 0.6. Considering that the human eye's perception of brightness is not proportional to power, but a power function relationship, this function exponent is the Gamma value. Gamma correction and conversion to psychological brightness are used to obtain the lightness value calculation.

[0042]

[0043] In addition, the experiment found that the more turbid the solution is, the higher the overall brightness of the solution will be after laser irradiation. Because the turbidity is different, the intensity of scattered light generated when the laser passes through them is also different, making them appear different in brightness. Therefore, when the scattering method of the device is tested, the value of the brightness value L is used to evaluate the intensity of the scattered light. When measuring sulfate ions, barium ions can be added to produce precipitation. Different amounts of precipitation are produced according to different sulfate ion concentrations. The solution turbidity is different, and the concentration of sulfate ions can be measured by the change in brightness value.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] The present invention is based on the fact that precipitation will be produced after the sulfate solution is mixed with barium ions. In the experiment, it is found that the more turbid the solution is, the higher the overall brightness of the solution will be after laser irradiation. After laser irradiation, the sample and the reference solution are photographed, and then the ratio of the brightness value of the sample and the reference solution is calculated, thereby obtaining a linear relationship between the ratio of sulfate ions of different concentrations to the brightness value. The water sample to be tested is tested by the portable device of the present invention, and the sulfate ion concentration of the water sample can be quickly and accurately determined. The present invention reduces the demand for actual water sample detection conditions, takes the actual water sample to be tested as the analysis basis, realizes the sulfate ion determination of the actual water sample, and conducts on-site detection, which is convenient and fast. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a schematic diagram of a portable detection device based on a smart phone according to Embodiment 1 of the present invention;

[0047] Figure 2 The portable detection device based on a smart phone in Example 1 of the present invention is a stereoscopic Figure 1 ;

[0048] Figure 3 The present invention is based on the stereoscopic portable detection device of the smart phone in Example 1 Figure 2 ;

[0049] Figure 4 The portable detection device based on a smart phone detects the interior of the three-dimensional Figure 1 ;

[0050] Figure 5 The portable detection device based on a smart phone detects the interior of the three-dimensional Figure 2 ;

[0051] Figure 6 The portable detection device based on a smart phone detects the interior of the three-dimensional Figure 3 ;

[0052] Figure 7 The portable detection device based on a smart phone detects the interior of the three-dimensional Figure 4 ;

[0053] Among them, 1 is a beam splitter, 2 is a reflector, 3 is a cuvette, 3-1 is a first cuvette, 3-2 is a second cuvette, 4 is a cover, 5 is a hollow cylinder, 6 is a conical cylinder cover, 7 is a smart phone fixing slot, 8 is a mobile phone camera shooting hole, 9 is a laser pen fixing cylinder, 10 is a detection box, 11 is a partition, 12 is a light-transmitting hole, 12-1 is a first light-transmitting hole, 12-2 is a second light-transmitting hole; 13 is an incident hole, 14 is a laser pen, 15 is a support frame, 16 is a positioning column, 16-1 is a first positioning column, 16-2 is a second positioning column, 17 is a sample slot, 17-1 is a first sample slot, 17-2 is a second sample slot, 18 is a beam splitter optical adjustment frame, 19 is a reflector optical adjustment frame;

[0054] Figure 8 This is a front view of a portable detection device based on a smart phone according to Embodiment 2 of the present invention;

[0055] Fig. 9 The present invention is a three-dimensional portable detection device based on a smart phone in Example 2 Figure 1 ;

[0056] Fig.10 A top view of the interior of the detection box of the portable detection device based on a smart phone in Example 2 of the present invention Figure 1 ;

[0057] Fig.11 The internal stereoscopic image of the detection box of the portable detection device based on a smart phone in Example 2 of the present invention Figure 1 ;

[0058] Fig.12 A top view of the interior of the detection box of the portable detection device based on a smart phone in Example 2 of the present invention Figure 2 ;

[0059] Fig.13 The internal stereoscopic image of the detection box of the portable detection device based on a smart phone in Example 2 of the present invention Figure 2 ;

[0060] Among them, 1' beam splitter, 2' reflector, 3' cuvette, 3-1' first cuvette, 3-2' second cuvette, 4' cover, 8' mobile phone camera shooting hole, 9' laser pen fixing tube, 10' detection box, 11' partition, 12' light transmission hole, 12-1' first light transmission hole, 12-2' second light transmission hole; 13' incident hole, 14' laser pen, 15' support frame, 16' positioning column, 16-1' first positioning column, 16-2' second positioning column, 16-3' third positioning column, 17' sample slot, 17-1' first sample slot, 17-2' second sample slot, 18' beam splitter optical adjustment frame, 19' reflector optical adjustment frame, 20' light source reflector, 21' light source reflector frame;

[0061] Fig.14This is a picture of the sample area taken in step 2 of Example 3 of the present invention, with the reference on the right and the sample on the left;

[0062] Fig.15 The standard working curve diagram of sulfate ion concentration and L ratio in Example 3;

[0063] Fig.16 These are photos taken after the laser of the device in Example 2 passed through solutions of different turbidities (the turbidities of the solutions from left to right are 1 NTU, 5 NTU, 10 NTU, 20 NTU, 40 NTU, and 80 NTU);

[0064] Fig.17 This is a time stability test of the device in Example 2;

[0065] Fig.18 (a) The linear relationship diagram of the standard turbidity solution measured by the turbidity meter; (b) The linear relationship diagram of the standard turbidity solution measured by the SPSD in Example 2 of the present invention; (c) The linear relationship diagram of the SPSD and the turbidity meter measurement results in Example 2 of the present invention;

[0066] Fig.19 (a) The turbidity diagram of water samples measured by turbidity meter and SPSD, where the data on the left are the results of turbidity meter measurement and the data on the right are the results of SPSD measurement; (b) The comparison diagram of the ratio results of turbidity of water samples measured by turbidity meter and SPSD;

[0067] Fig. 20 (a) The effect of different region selection on the ratio signal of different sulfate concentrations; (b) The actual location of different regions;

[0068] Fig.21 A linear relationship is established for (a) different concentrations of sulfate ions and R ratios; (b) different concentrations of sulfate ions and G ratios; (c) different concentrations of sulfate ions and B ratios; (d) different concentrations of sulfate ions and L ratios;

[0069] Fig. 22 The figure shows the effect of different concentrations of barium ions on the ratio signal intensity, where the left side shows the data with added sulfate ions, and the right side shows the data without added sulfate ions;

[0070] Fig.23 This is a picture showing the selectivity and anti-interference of the SPSD in detecting sulfate ions according to Example 2 of the present invention. DETAILED DESCRIPTION

[0071] In order to make the technical problems to be solved, technical solutions and advantages of the present invention more clear, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0072] In the present invention, the materials and reagents used can be obtained from commercial sources unless otherwise specified. The optical lenses in the portable detection device based on a smart phone in the present invention are shown in Table 1 below.

[0073] Table 1

[0074]

[0075] The present invention provides a method for detecting sulfate ions in water based on a smart phone, and specific embodiments are as follows.

[0076] Example 1

[0077] A smartphone-based portable detection device (SPSD), such as Figure 1-7 , including a beam splitter 1, a reflector 2, a cuvette 3, a cover 4, a hollow cylinder 5, a conical cylinder cover 6, a smart phone fixing slot 7, a mobile phone camera shooting hole 8, a laser pen fixing cylinder 9 and a detection box 10;

[0078] The detection box 10 is provided with a partition 11 for dividing the detection box 10 into a light mirror area and a sample area; the partition 11 is provided with light-transmitting holes 12, and the light-transmitting holes 12 include a first light-transmitting hole 12-1 and a second light-transmitting hole 12-2;

[0079] The optical mirror area is used to place the beam splitter 1 and the reflector 2, and the cover 4 is used to make the optical mirror area a dark room; the sample area is used to place the cuvette 3, and the conical tube cover 6 is used to make the sample area a dark room, and the cuvette 3 includes a first cuvette 3-1 and a second cuvette 3-2;

[0080] In the optical mirror area, an incident hole 13 is provided on the side wall of the detection box 10, and the laser pen fixing tube 9 is used to fix the laser pen 14 on the side wall of the detection box 10. The laser emitted by the laser pen 14 is irradiated onto the beam splitter 1 through the incident hole 13. The beam splitter 1 is used to split the laser into two laser beams with little difference in power and perpendicular to each other; one of the laser beams is irradiated onto the first cuvette 3-1 through the first light-transmitting hole 12-1, and the other laser beam is irradiated onto the reflector 2, and is reflected by the reflector 2 and then irradiated onto the second cuvette 3-2 through the second light-transmitting hole 12-2;

[0081] The top of the conical cylinder cover 6 is fixedly connected to the hollow cylinder 5. A smartphone fixing groove 7 is fixed on the top of the hollow cylinder 5 for fixing the smartphone. The smartphone fixing groove 7 has a hole at the connection position with the hollow cylinder 5, which is a mobile phone camera shooting hole 8. The smartphone can be used to take photos of the sample area through the mobile phone camera shooting hole 8.

[0082] The detection box of the present invention is a dark box, the position of the light source is fixed by a laser pen fixing tube, and then a beam splitter and a reflector are arranged to split the laser into two beams with similar power, and the two beams are respectively irradiated into the sample cuvette and the reference cuvette, so that the two emit fluorescence synchronously, and then the two are photographed on the same photo by a mobile phone, which is convenient for subsequent analysis. The internal components of the device of the present invention are simple, without any complicated operations, and easy to assemble.

[0083] Preferably, two positioning posts 16 are fixed to the bottom of the detection box 10, namely the first positioning post 16-1 and the second positioning post 16-2, and the top of the positioning post 16 is provided with a thread; the beam splitter 1 is fixed by the beam splitter optical adjustment frame 18, and the reflector 2 is fixed by the reflector optical adjustment frame 19, and the bottom of the beam splitter optical adjustment frame 18 and the reflector optical adjustment frame 19 are both provided with internal threads, which cooperate with the top threads of the positioning posts 16, and the beam splitter optical adjustment frame 18 and the reflector optical adjustment frame 19 are respectively fixed on the first positioning post 16-1 and the second positioning post 16-2; it is convenient to determine the fixed position of the optical lens during on-site installation. After the beam splitter and the reflector are installed, the focal position height of the lens is consistent with the incident height of the laser pen, thereby ensuring the accuracy of the test results.

[0084] Two sample slots 17 are provided at the bottom of the detection box 10, namely a first sample slot 17-1 and a second sample slot 17-2. The first sample slot 17-1 is used to fix the first cuvette 3-1, and the second sample slot 17-2 is used to fix the second cuvette 3-2; it is convenient to fix the position of the cuvette, and the liquid height in the cuvette 3 is higher than the position height of the light-transmitting hole 12, so as to ensure the accuracy of the test results.

[0085] Preferably, a support frame 15 is provided below the laser pen fixing tube 9 for supporting the laser pen fixing tube 14 ; during use, the laser pen 14 is inserted into the laser pen fixing tube 9 , and the laser emitted by the laser pen 14 will pass through the incident hole 13 to irradiate the beam splitter.

[0086] Furthermore, the smartphone fixing groove 7 is used to fix the smartphone. For different smartphones, a smartphone fixing groove 7 matching them can be prepared in advance; a smartphone fixing groove 7 with adjustable size can also be prepared by simple components such as springs to make it suitable for all smartphones.

[0087] Example 2

[0088] A smartphone-based portable detection device (SPSD), such as Figure 8-13 , including a light source reflector 20', a beam splitter 1', a reflector 2', a cuvette 3', a cover 4', a laser pen fixing tube 9' and a detection box 10';

[0089] The detection box 10' is provided with a partition 11' for dividing the detection box 10' into a light mirror area and a sample area; the partition 11' is provided with light-transmitting holes 12', and the light-transmitting holes 12' include a first light-transmitting hole 12-1' and a second light-transmitting hole 12-2';

[0090] The light mirror area is provided with a light source reflector 20', a beam splitter 1' and a reflector 2' in sequence along the light direction, and the sample area is used to place a cuvette 3', and the cuvette 3' includes a first cuvette 3-1' and a second cuvette 3-2';

[0091] In the optical mirror area, an incident hole 13' is provided on the side wall of the detection box 10', and the laser pen fixing tube 9' is used to fix the laser pen 14' on the side wall of the detection box 10'. The laser emitted by the laser pen 14' is irradiated to the light source reflector 20' through the incident hole 13', and the light is reflected to the beam splitter 1 through the light source reflector 20'. The beam splitter 1' is used to split the laser into two laser beams with little difference in power and perpendicular to each other; one of the laser beams is irradiated to the first cuvette 3-1' through the first light-transmitting hole 12-1', and the other laser beam is irradiated to the reflector 2', and after being reflected by the reflector 2', it is irradiated to the second cuvette 3-2' through the second light-transmitting hole 12-2';

[0092] A cover 4' is provided on the top of the detection box 10', which is used to form a darkroom in the detection box 10'. A mobile phone camera shooting hole 8' is provided at the middle position of the cover 4' corresponding to the first cuvette 3-1' and the second cuvette 3-2'. A smart phone is placed on the cover, and the mobile phone camera is aligned with the mobile phone camera shooting hole 8' to take a picture of the sample area cuvette. The internal components of the device of the present invention are simple, without any complicated operations, and easy to assemble.

[0093] Preferably, three positioning posts 16' are fixed at the bottom of the detection box 10', namely a first positioning post 16-1', a second positioning post 16-2' and a third positioning post 16-3', and threads are provided on the top of the positioning post 16'; the beam splitter 1' is fixed by a beam splitter optical adjustment frame 18', the reflector 2' is fixed by a reflector optical adjustment frame 19', the light source reflector 20' is fixed by a light source reflector frame 21', the beam splitter optical adjustment frame 18', the reflector optical adjustment frame 19', the light source reflector 20' is fixed by a light source reflector frame 21', The bottom of the source reflector frame 21' is provided with internal threads, which cooperate with the top threads of the positioning column 16', and the beam splitter optical adjustment frame 18', the reflector optical adjustment frame 19', and the light source reflector frame 21' are respectively fixed on the first positioning column 16-1', the second positioning column 16-2' and the third positioning column 16-3'; it is convenient to determine the fixed position of the optical lens during on-site installation. After the beam splitter and the reflector are installed, the focal position height of the lens is consistent with the incident height of the laser pen, thereby ensuring the accuracy of the test results.

[0094] Two sample slots 17' are provided at the bottom of the detection box 10', namely a first sample slot 17-1' and a second sample slot 17-2'. The first sample slot 17-1' is used to fix the first cuvette 3-1', and the second sample slot 17-2' is used to fix the second cuvette 3-2'; it is convenient to fix the position of the cuvette, and the liquid height in the cuvette 3' is higher than the position height of the light-transmitting hole 12', so as to ensure the accuracy of the test results.

[0095] Preferably, a support frame 15' is provided below the laser pen fixing tube 9' for supporting the laser pen fixing tube 14'; during use, the laser pen 14' is inserted into the laser pen fixing tube 9', and the laser emitted by the laser pen 14' will pass through the incident hole 13' and irradiate the light source reflector 20'.

[0096] The portable detection device in this embodiment has a simple structure, can realize on-site rapid detection of sulfate ions, and has high detection accuracy.

[0097] Example 3

[0098] A method for detecting sulfate ions in water based on a smartphone, comprising:

[0099] Step 1: Accurately weigh 1.479 g of anhydrous sodium sulfate, add ultrapure water to dissolve, and use a 1000 mL volumetric flask to dilute to obtain a 1000 mg / L sulfate ion standard solution. Dilute the standard solution with ultrapure water to a standard working solution with concentrations of 800, 500, 200, 100, 80, 60, 40, 20, 10, 5, 1, 0.5, 0.2, 0.1 and 0.05 mg / L, respectively. Store the above solutions at room temperature in a sealed container away from light.

[0100] Accurately weigh 1.78 g of barium chloride dihydrate, add ultrapure water to dissolve, and use a 100 mL volumetric flask to dilute to obtain a 10 g / L barium ion standard solution. Dilute the standard solution with ultrapure water step by step to a 5 g / L standard working solution. Store the above solution at room temperature in a sealed container away from light;

[0101] Step 2: Add 2 mL of 1 mg / L sulfate ion solution to a 5 mL centrifuge tube, then add 1 mL of 5 g / L barium ion solution, mix well, pour into a cuvette, and place it on the left side of the sample area of ​​the device in Example 2. Place a reference solution on the right side of the sample area: 1 mL of 5 g / L barium ion + 2 mL of water and mix well; then turn on the laser pen of the portable detection device, and then use a smart phone to take relevant photos, see Fig.14 , 3 times per set;

[0102] Step 3: Cut out the effective area of ​​the photo, and then save the cut effective area image to the specified folder. Use Matlab software to write the following program:

[0103] =mread('file location\image name.jpg','jpg');

[0104] RGB_mean=mean(mean());

[0105] R_mean=RGB_mean(:,:,1);

[0106] G_mean=RGB_mean(:,:,2);

[0107] B_mean=RGB_mean(:,:,3);

[0108] By running the above program, the R, G, and B values ​​of each valid area image are calculated, that is, the process of converting optical signals into electrical signals and finally into digital signals is completed. The results are shown in Table 2;

[0109] Then calculate the brightness value according to formula (I) and take the average of 3 measurements. The results are shown in Table 2-3;

[0110] (I)

[0111] Then calculate L 样品 With L 参比 The ratio of (L ratio);

[0112] Step 4: According to steps 2 and 3, take photos of the mixed solution containing sulfate standard solution of different concentrations (2, 4, 8, 10, 15, 20, 40, 60, 100 mg / L) and barium ion standard solution in turn, and provide photos of the mixed solution of 0 mg / L and barium ion standard solution. Cut out the corresponding R, G, B values ​​of each effective area to identify, and calculate the L ratio in each picture. The results are shown in Table 2-3.

[0113] The standard working curve was established with sulfate ion concentration as the horizontal axis and L ratio as the vertical axis. Fig.15 .

[0114] Table 2

[0115]

[0116] Depend on Figure 2 It can be seen that the fitting curve equation of sulfate concentration and ratio signal is: , R²=0.9964, with good linear correlation, indicating that this method is feasible for detecting the sulfate ion concentration in the solution.

[0117] Step 5: Collect surface water samples, filter through a 0.45 μm pore size filter syringe to remove most impurities, add excess HCl to remove excess carbonate ions in the water, then add NaOH and use a pH meter to adjust the pH of the water sample to neutral. Take 2 mL of the pretreated water sample and add 1 mL of a 5 g / L barium ion solution. Mix thoroughly, and then determine the corresponding The value is 14.3314. Substituting it into the above standard working curve, the sulfate ion concentration of the water sample to be tested is calculated to be 74.25 mg / L.

[0118] To further illustrate the beneficial effects of the method of the present invention, the inventors also conducted the following experiments.

[0119] 1. Stability evaluation

[0120] Use a laser pen to illuminate the standard turbidity solutions of 1NTU, 5NTU, 10NTU, 20NTU, 40NTU, and 80NTU, and take photos. Fig.16 ; It is found that due to different turbidity, the intensity of scattered light generated when the laser passes through them is also different, making the brightness they show different. Therefore, when testing the scattering method of the device, the value of the brightness value L can be used to evaluate the intensity of the scattered light.

[0121] To verify whether the scattering detection of the device in Example 2 is stable, a 10 NTU standard turbidity solution is placed on the left side, and ultrapure water is placed on the right side as a reference. After turning on the laser pen switch, use a smartphone to directly take photos of the sample pool at 0, 1, 2, 3, 4, 5, 7, 9, 11, 13, 15, and 20 minutes, and measure three times for each group. Then process the image to obtain Fig.17 The image brightness L ratio on both sides of the sample cell changes with time. It can be found that despite the fluctuation of laser power, the results measured by the ratio method are stable and do not fluctuate significantly.

[0122] 2. Feasibility evaluation

[0123] In order to evaluate the scattering detection performance of the detection device of Example 2, the existing turbidity meter and the device of Example 2 were used to detect the turbidity of the same standard turbidity liquid and the same actual water sample, and the measurement results were compared. The prepared standard turbidity liquids: 200NTU, 100NTU, 80NTU, 40NTU, 20NTU, 10NTU, 5NTU, 1NTU, 0.5NTU, 0.2NTU, 0.1NTU, 0.05NTU were measured by the turbidity meter and the device of Example 2, respectively. When the device of Example 2 was measured, ultrapure water was placed on the right side as a reference, and standard liquids of different turbidities were placed on the left side in sequence. Each group was measured three times, as shown in FIG. Fig.18. It can be found Fig.18 The result of the turbidity meter in (a) measuring the standard turbidity solution is accurate, with R²=0.9990. Although it cannot be measured at 0.05 NTU, the turbidity meter measurement result can still be used as a standard to evaluate the measurement performance of the device in Example 2. Fig.18 (b) is the result of measuring the standard turbidity solution by the equipment in Example 2. It can be found that when the turbidity of the solution exceeds 60NTU, the measurement of the equipment in Example 2 reaches the limit value. If the turbidity of the solution continues to increase, the measurement result will no longer increase and tend to be flat. However, accurate results can still be measured at 0.05NTU, which is also the limit value that the turbidity meter cannot measure. Therefore, the turbidity range of 0.05-60NTU is selected to make a linear standard curve with the same brightness ratio value, and its R²=0.9723. Fig.18 In (c), the turbidity meter measurement results in the range of 0.1-60NTU are linearly fitted with the measurement results of the device in Example 2, and its R²=0.9846. It can be seen that although the device in Example 1 cannot achieve the accuracy of the standard turbidity meter, its minimum measurement limit is lower than that of the turbidity meter, and the measurement accuracy can still meet the actual measurement requirements.

[0124] Water samples were collected from rivers in and around the school and from other places. A total of 19 water samples were collected and their turbidity was measured using a turbidity meter and the device in Example 2. The water samples were fully shaken and mixed before measurement, and each water sample was measured three times. Fig.18 (b) The final result of linear fitting curve conversion. Fig.18 (b) The method of converting the final turbidity using the linear fitting curve is recorded as the SPSD measurement result, such as Fig.19 (a). The ratio of the results of the two tests on the same water sample is calculated, as Fig.19 As shown in (b), it can be found that the ratio of the turbidity result of the water sample measured by the equipment in Example 2 to the result measured by the turbidity meter is controlled within 0.9284-1.090, which is close to 1.000, indicating that the difference between the two measurement results is small, confirming that the result of measuring water turbidity with the assistance of the portable detection device with the help of the smartphone is reliable. Fig.18 (c) A linear curve is established between the equipment in Example 2 and the turbidity meter measurement results, and its R²=0.9846, which also proves that the results of measuring water turbidity by the equipment in Example 2 are reliable.

[0125] 3. Selection of effective area

[0126] Since the determination of sulfate ions is obtained indirectly by photographing the cuvette of the device in Example 2 with a smartphone, the selection of the effective area is crucial. Fig. 20As shown in (b), the captured image is divided into three effective areas for evaluation: the light column area (the light column area formed by the laser beam irradiating through the solution in the cuvette), the peripheral area (the solution area in the cuvette except the light column area), and the entire area (the sum of the light column area and the peripheral area, that is, the area of ​​the solution in the entire cuvette in the photo). 1 mL of 100 mg / L barium ions was added to 2 mL of sulfate ions with concentrations of 0, 1, 5, 10, 20, 40, and 60 mg / L, and after mixing evenly, the device in Example 2 was used for photographing and measuring, wherein the reference was 3 mL of ultrapure water. Fig. 20 As shown in (a), the three regions all have a tendency of increasing ratio signals with the increase of sulfate concentration, but the ratio signals of the light column region and the peripheral region increase slowly, and begin to change slowly and stabilize after reaching 40 mg / L. This is because the light column region is formed by direct laser irradiation, and its color is darker and brighter, so that the RGB value of its region is always maintained at a high level (R, G, B values ​​are maintained above 220). Continuing to increase the sulfate concentration will make the RGB value eventually reach the maximum value and no longer change. The change in the peripheral region is caused by the turbidity of the solution causing light scattering, which is theoretically more suitable for the selection of the region for determining sulfate. However, the peripheral region alone is used because the method generates less precipitation and the turbidity change is also small. The peripheral region is distributed more widely and the area directly irradiated by the laser is removed, so the change in sulfate concentration does not significantly affect the brightness change of the peripheral region, and the sensitivity to the change in sulfate concentration is much lower than that of other regions. In summary, all the areas that take into account the light column region and the peripheral region are selected as the effective areas selected for subsequent determination.

[0127] 4. Selection of RGB channels

[0128] After taking 2 mL of sulfate ion solutions with concentrations of 100, 60, 40, 20, 10, 5 and 1 mg / L, 1 mL of 5000 mg / L barium ion solution was added and ultrasonically mixed to be evenly tested. On the left side of the device in Example 2, 1 mL of 5g / L barium ions + 2 mL of water was placed and mixed evenly. As a reference, the above mixed solutions of different concentrations were placed on the right side in turn, and each group was photographed three times with a smartphone. Through data processing of the captured images, the data are shown in Table 3. Then construct the ratio of sulfate ions to R at different concentrations ( )、G ratio( )、B ratio( )、L ratio( ), such as Fig.21 shown.

[0129] Table 3

[0130]

[0131] Then, the linear relationship between different concentrations of sulfate ions and R ratio (average value), G ratio (average value), B ratio (average value), and L ratio (average value) was constructed, such as Fig.21 As shown. It can be found that the slope of the linear fitting curve of a single channel in RGB is significantly lower than that of the L channel fitting curve, indicating that the change of sulfate ions will be more significant when the linear curve is fitted using the L channel. And the linear fitting R² of the L channel is also better than that of any channel in RGB. This is because the change of L is jointly affected by the three channels of R, G, and B, and the change of brightness is not comprehensive when using any channel in RGB to evaluate. In summary, the L channel is selected as the best channel for SPSD detection of sulfate ions.

[0132] 5. Selection of barium chloride concentration

[0133] Barium sulfate is a white precipitate with stable properties and is almost insoluble in water. It is a common insoluble precipitate. The solubility product of barium sulfate is the product of the concentrations of barium ions and sulfate ions in the solution when the precipitation dissolution equilibrium is reached under certain conditions. It is usually expressed as K. sp When the product of the sulfate ion concentration and the barium ion concentration in the solution (denoted as Q) is greater than K sp When the solution is in an unsaturated state, a precipitate will be precipitated. Otherwise, the solution will not precipitate. Therefore, in order to detect sulfate ions at a lower concentration in the solution and precipitate, it is necessary to add excess barium ions to meet the precipitation conditions, that is, In this experiment, 1 mL of barium ions with concentrations of 10000, 5000, 1000, 500 and 100 mg / L were added to 2 mL of ultrapure water and 5 mg / L of sulfate solution, and the mixture was thoroughly mixed before determination. Fig. 22 As shown in the figure, in the experimental group without sulfate, the ratio signal remained stable and did not change significantly regardless of the change in barium ion concentration; while in the experimental group with sulfate, the ratio signal increased slightly as the barium ion concentration increased, but when the barium ion concentration exceeded 5000 mg / L, the ratio signal decreased slightly, and the overall change was not obvious. This is because the sulfate ion concentration in the solution is constant. As the barium ion concentration increases, the precipitation dissolution equilibrium in the solution will move toward the precipitation direction, and precipitation will continue to be produced until a new equilibrium is formed. It will also be more "sensitive" to the sulfate ions in the solution, but when the barium ion concentration exceeds 5000 mg / L, it may reach a saturated state, and the sensitivity to sulfate will no longer increase, but tend to be flat. Considering the above, a barium ion concentration of 5000 mg / L was selected for subsequent experiments.

[0134] 6. Evaluation of selectivity and anti-interference

[0135] In order to better detect sulfate ions in actual water samples, this experiment selected common anions in water samples, including: F - , Cl - Br - ,I,CO3 2- 、HCO3 - 、NO3 - 、NO2 - ,Ac - As the interfering ion, the selectivity and anti-interference experiment of sulfate ion was carried out. Prepare other anions with a concentration of 1mM, sulfate ions with a concentration of 10mg / L (about 100μM), and barium ions with a concentration of 5g / L; take 1mL of the interfering ion with a concentration of 1mM and add 1mL of sulfate ions with a concentration of 100μM in turn, add 1mL of barium ions with a concentration of 5g / L in turn after mixing, and measure after mixing; set the blank group to only add the same volume of ultrapure water and the same volume of sulfate ions. In addition, pretreatment with HCl and pH adjustment is required before measurement.

[0136] like Fig.23 As shown, although the concentration of other interfering ions is 10 times that of sulfate ions, the ratio of other interfering ions is close to that of the blank group, that is, since their solutions do not produce precipitation to make the solution turbid, the scattering they show is almost the same as that of ultrapure water. And when each anion group after adding sulfate ions, its ratio increases significantly, and it can be found that the change of ratio is caused by the addition of sulfate ions in comparison with the blank group. In summary, for common ions in water bodies, it can be seen that the detection of sulfate ions using the device of Example 2 using sulfate and barium ions to produce precipitation has good selectivity and interference resistance.

[0137] The above experiments have verified that the portable detection device based on a smart phone of the present invention can realize high-precision detection of sulfate ions in water, which is convenient and fast.

[0138] 7. Accuracy evaluation

[0139] In order to verify that the sulfate determination method established above is applicable to the determination in actual water samples, water samples from different regions were collected for testing. The sulfate ion content of the collected water samples was first determined by this method, and then determined by ion chromatography. The results of this method and ion chromatography (IC) were compared to evaluate the reliability of this method in determining actual water samples. The results are shown in Table 4.

[0140] Table 4

[0141]

[0142] As shown in Table 4, the method of the present invention is relatively accurate in determining sulfate ions in actual water samples, and its error is less than 3% compared with the results determined by a precise ion chromatograph, which proves that the method of the present invention has high accuracy and can be used for on-site detection.

[0143] In summary, the present invention is based on the principle that the intensity of scattered light generated when a light beam enters a sample is proportional to the turbidity in the sample within a certain concentration range. Excess barium ions are added to the water sample to be tested in an acidic environment, and precipitate is generated specifically with sulfate ions in the water sample, thereby achieving rapid detection of sulfate ions in the water sample.

[0144] The above is a preferred embodiment of the present invention. For ordinary technicians in this technical field, making several improvements and modifications without departing from the principles of the present invention should also be regarded as within the protection scope of the present invention.

Claims

1. A method for detecting sulfate ions in water based on a smart phone, characterized in that: include: Step 1: Prepare sulfate ion and barium ion standard solutions; Step 2: Mix the sulfate ion standard solution and the barium ion standard solution evenly as the sample solution, then add it to the portable detection device, use the barium ion solution of the corresponding concentration as the reference, turn on the laser pen of the portable detection device, and then use a smartphone to take pictures of the sample solution and the reference solution; Step 3: Cut out the effective area of ​​the photograph, and obtain the R, G, and B values ​​of the corresponding areas of the sample solution and the reference solution respectively, and then calculate the brightness value according to formula (I), and then calculate L 样品 With L 参比 The effective area is the area occupied by the solution in the entire cuvette of the photographed image; （I）； Step 4: Take photos of the mixed solutions of sulfate standard solution and barium ion standard solution with different concentrations in sequence, intercept the effective areas of each to identify the corresponding R, G, and B values, calculate the L ratio in each picture, and establish a standard working curve with sulfate ion concentration as the horizontal coordinate and L ratio as the vertical coordinate; Step 5: After pre-treating the water sample to be tested, determine the L ratio of the water sample to be tested based on the above steps 2-3 and convert it into the sulfate ion concentration of the water sample to be tested in combination with the standard working curve.

2. The detection method according to claim 1, characterized in that: The step 1 specifically comprises: (11) accurately weighing 1.479 g of anhydrous sodium sulfate, adding ultrapure water to dissolve, and using a 1000 mL volumetric flask to dilute to obtain a 1000 mg / L sulfate ion standard solution; diluting the standard solution with ultrapure water step by step to obtain standard working solutions with concentrations of 1-100 mg / L; and storing the above solution in a sealed container at room temperature away from light; (12) Accurately weigh 1.78 g of barium chloride dihydrate, add ultrapure water to dissolve, and dilute to volume with a 100-mL volumetric flask to obtain a 10 g / L barium ion standard solution; dilute the standard solution with ultrapure water stepwise to a 5 g / L standard working solution; store the above solution in a sealed container at room temperature away from light.

3. The detection method according to claim 2, characterized in that: The step 2 is specifically as follows: 2 mL of sulfate ion standard solution is added to a 5 mL centrifuge tube, and then 1 mL of barium ion standard solution is added. After mixing evenly, the mixture is added to a portable detection device, and a mixed solution of 1 mL of barium ion standard solution and 2 mL of water is used as a reference. The laser pen of the device is turned on, and then photos are taken. Each group is repeated 3 times.

4. The detection method according to claim 1, characterized in that: In step 3, the wavelength of the laser emitted by the laser pen is 500-550nm; In the steps 3-4, the image is processed by Matlab software to obtain R, G, and B values.

5. The detection method according to claim 1, characterized in that: In step 5, a water sample to be tested is collected, filtered through a 0.45 μm pore size filter syringe, and then excess HCl is added to remove excess carbonate ions in the water, so that the pH of the mixed solution is below 4.

6. The detection method according to claim 1, characterized in that: In step 2, the portable detection device includes a beam splitter, a reflector, a cuvette, a laser pen fixing tube, a detection box and a laser pen; The detection box is provided with a partition plate for dividing the detection box into a light mirror area and a sample area; the partition plate is provided with light-transmitting holes, and the light-transmitting holes include a first light-transmitting hole and a second light-transmitting hole; The optical mirror area is used to place the beam splitter and the reflector; the sample area is used to place a cuvette, and the cuvette includes a first cuvette and a second cuvette; In the optical mirror area, an incident hole is provided on the side wall of the detection box, the laser pen fixing tube is used to fix the laser pen on the side wall of the detection box, the laser emitted by the laser pen is irradiated onto the beam splitter through the incident hole, and the beam splitter is used to split the laser into two beams of laser light with the same power and parallel to each other; one beam of laser light is irradiated onto the first cuvette through the first light-transmitting hole, and the other beam of laser light is irradiated onto the reflector, and is reflected by the reflector and then irradiated onto the second cuvette through the second light-transmitting hole.

7. The detection method according to claim 6, characterized in that: A support frame is provided below the laser pen fixing tube for supporting the laser pen fixing tube; The bottom of the detection box is provided with two sample slots, namely a first sample slot and a second sample slot. The first sample slot is used to fix the first cuvette, and the second sample slot is used to fix the second cuvette.

8. The detection method according to claim 7, characterized in that: The portable detection device also includes a cover, a conical cylinder cover, a hollow cylinder, a smart phone fixing slot, and a mobile phone camera shooting hole; The cover is installed at one end of the top of the detection box, so that the optical microscope area becomes a dark room; the conical tube cover is installed at the other end of the top of the detection box, so that the sample area becomes a dark room; The top of the conical cylinder cover is fixedly connected to the hollow cylinder, the top of the hollow cylinder is fixed with the smartphone fixing groove, a mobile phone camera shooting hole is arranged at the connection position between the smartphone fixing groove and the hollow cylinder, and a smartphone can be used to take photos of the sample area through the mobile phone camera shooting hole.

9. The detection method according to claim 8, characterized in that: The bottom of the detection box is provided with two positioning posts, namely a first positioning post and a second positioning post, and the top of the positioning post is provided with a thread; The beam splitter is fixed by a beam splitter optical adjustment frame, and the reflector is fixed by a reflector optical adjustment frame. Internal threads are arranged at the bottom of the beam splitter optical adjustment frame and the reflector optical adjustment frame. The beam splitter optical adjustment frame and the reflector optical adjustment frame are respectively fixed on the first positioning column and the second positioning column.

10. The detection method according to claim 7, characterized in that: The light mirror area is provided with a light source reflector, and the laser emitted by the laser pen is irradiated to the light source reflector through the incident hole, and the light is reflected to the beam splitter by the light source reflector; The portable detection device also includes a cover disposed on the top of the detection box, so that the detection box forms a dark room; The cover corresponds to the middle position between the first cuvette and the second cuvette, and is provided with a shooting hole for a mobile phone camera; Three positioning posts are fixed on the bottom of the detection box, namely the first positioning post, the second positioning post and the third positioning post, and threads are provided on the tops of the positioning posts; the beam splitter is fixed by the beam splitter optical adjustment frame, the reflector is fixed by the reflector optical adjustment frame, and the light source reflector is fixed by the light source reflector frame, and the bottoms of the beam splitter optical adjustment frame, the reflector optical adjustment frame and the light source reflector frame are all provided with internal threads, which cooperate with the threads on the tops of the positioning posts, and the beam splitter optical adjustment frame, the reflector optical adjustment frame and the light source reflector frame are respectively fixed on the first positioning post, the second positioning post and the third positioning post.

Images