Detection chip and method for detecting hexavalent chromium

Abstract

The application relates to the technical field of water quality detection, and discloses a detection chip and a detection method of hexavalent chromium. The detection chip comprises a base plate and a cover plate, the cover plate is used for covering the upper surface of the base plate, the base plate comprises a sample adding groove, a reaction area and a detection area which are sequentially communicated through connecting channels, a sample inlet and an air outlet are arranged on the cover plate, the sample inlet is correspondingly arranged with the sample adding groove, and a freeze-dried reagent for detecting hexavalent chromium is arranged in the reaction area; wherein the freeze-dried reagent contains a chromogenic agent, a buffer, a masking agent, a solubilizer and an excipient, the chromogenic agent is diphenyl carbonyl dihydrazine, the buffer is at least one of phosphoric acid, sulfamic acid and salicylic acid, and the solubilizer is at least one of ethanol, acetamide and sodium chloride. The technical scheme can improve the dissolution speed of the reagent, shorten the reaction time, improve the repeatability and uniformity of the detection, and is simple to operate by prepositioning the reagent in the chip.

Description

Technical Field

[0001] This invention relates to the field of water quality testing technology, specifically to a detection chip and a method for detecting hexavalent chromium. Background Technology

[0002] Hexavalent chromium is one of the important indicators for water pollution detection. Its main sources are industries such as smelting, printing and dyeing, leather making and chromium ore processing. It is easily absorbed by the human body, has high toxicity and has carcinogenic and teratogenic effects.

[0003] Common methods for detecting hexavalent chromium in water include atomic absorption spectrometry, inductively coupled plasma atomic absorption spectrometry, fluorescence spectrometry, and spectrophotometry. Among these, spectrophotometry is simple to operate, inexpensive, and portable. The existing spectrophotometric method for diphenylcarbazide involves reacting hexavalent chromium with diphenylcarbazide under acidic conditions to form a purple-red complex, and then detecting the absorbance at a wavelength of 540 nm. Patent application CN104001562B discloses a rapid method for detecting hexavalent chromium ions in wastewater. While this method is simple and easy to operate, diphenylcarbazide has poor water solubility, often requiring acetone for dissolution, which results in a long dissolution time. Acetone is highly toxic and easily causes environmental pollution, and it decomposes easily in light, resulting in a short shelf life. Patent application CN101900670A discloses a reagent for spectrophotometric determination of hexavalent chromium. Although this invention avoids the use of high-concentration acetone, which is harmful to humans and pollutes the environment, by using anhydrous ethanol to dissolve diphenylcarbazide. However, the pH is adjusted using strong acids such as concentrated sulfuric acid, which are highly corrosive. The strong oxidizing acid interferes with the measurement results, and the colorimetric solution has poor stability, making it unsuitable for on-site testing.

[0004] Therefore, there is an urgent need to develop a detection chip and a detection method for hexavalent chromium that can effectively improve the dissolution rate of reagents, shorten reaction time, and improve the repeatability and uniformity of detection. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems existing in the detection of hexavalent chromium in water, such as poor reaction stability due to the strong oxidizing property of concentrated sulfuric acid, low solubility of diphenylcarbazide in acetone, long overall reaction time, and poor repeatability and uniformity. This invention provides a detection chip and a method for detecting hexavalent chromium. By preparing the detection reagent into lyophilized reagent balls, this technical solution effectively improves the reagent dissolution rate, shortens the reaction time, and enhances the repeatability and uniformity of the detection. Furthermore, by pre-loading the reagent into the chip, additional mixing operations are eliminated, facilitating efficient detection of hexavalent chromium.

[0006] To achieve the above objectives, a first aspect of the present invention provides a detection chip, comprising a substrate and a cover plate, the cover plate being used to cover the upper surface of the substrate. The substrate includes a sample loading tank, a reaction zone, and a detection zone sequentially connected by a connecting channel. The cover plate is provided with a sample inlet and a gas outlet, the sample inlet being correspondingly disposed to the sample loading tank. The reaction zone is provided with a lyophilized reagent for detecting hexavalent chromium. The lyophilized reagent contains a colorimetric agent, a buffer, a masking agent, a cosolvent, and an excipient. The colorimetric agent is diphenylcarbazide, the buffer is at least one selected from phosphoric acid, aminosulfonic acid, and salicylic acid, and the cosolvent is at least one selected from ethanol, acetamide, and sodium chloride.

[0007] Preferably, the mass ratio of the color developer, the buffer, the masking agent, the cosolvent, and the excipient is 1:(6-15):(4-9):(6-12):(7-15).

[0008] Preferably, the total mass ratio of the color developer, the buffer, the masking agent, the cosolvent, and the excipient to the mass of the lyophilized reagent is 2-10%.

[0009] Preferably, the masking agent is at least one of sodium thiosulfate, sodium citrate, and ascorbic acid.

[0010] Preferably, the excipient is at least one of mannitol, trehalose, and sorbitol.

[0011] Preferably, the lyophilized reagent is in the form of spherical particles.

[0012] A second aspect of the present invention provides a method for detecting hexavalent chromium, which is implemented in the above-mentioned detection chip. The method includes: adding a water sample to be tested into a sample loading tank through a sample inlet, then allowing it to flow into a reaction zone to react with a lyophilized reagent therein, and the resulting mixture flowing into a detection zone. Then, the absorbance of the mixture in the detection zone is detected using a spectrophotometer, and the concentration of hexavalent chromium in the water sample to be tested is determined based on the detected absorbance data.

[0013] Preferably, the lyophilized reagent for detecting hexavalent chromium is prepared according to the following steps:

[0014] The spherical droplets of the hexavalent chromium detection reagent were pre-frozen and then freeze-dried under vacuum.

[0015] Preferably, the process of preparing and pre-freezing the spherical droplets of the hexavalent chromium detection reagent includes: dissolving the colorimetric agent and co-solvent in water, then adding a buffer, masking agent and excipient, and then using an automatic liquid nitrogen dispensing system to drop the resulting mixed solution into liquid nitrogen for pre-freezing and solidification to form small spheres of 0.8-3 mm.

[0016] Preferably, the vacuum freeze-drying conditions include: a vacuum degree of 1-100 Pa, a temperature of -60°C to -80°C, and a time of 8-24 h.

[0017] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in:

[0018] (1) The detection chip described in this invention integrates functions such as pretreatment, mixing, and reaction, simplifying the operation process; it also reduces the amount of reagents used, produces very little waste liquid, requires no special treatment, and is both environmentally friendly and cost-effective.

[0019] (2) The freeze-dried reagent described in this invention has good water resolubility, fast reaction rate, and uniform mixing; moreover, it uses aminosulfonic acid instead of strong acids such as concentrated sulfuric acid and nitric acid, which has less corrosiveness and increases stability; at the same time, sodium chloride is chosen as the cosolvent instead of acetone, which is non-toxic, avoids decomposition in light, and has a longer shelf life.

[0020] (3) The lyophilized reagent described in this invention is an all-solid reagent, which avoids factors such as instability of liquid solutions, is easy to carry, and is suitable for on-site testing; moreover, the lyophilized reagent is pre-loaded in the chip, so there is no need to prepare the reagent, only to add water sample, and the operation of adding water sample is simple and does not require professional personnel.

[0021] The detection chip and hexavalent chromium detection method described in this invention are applicable to the food, medical, chemical, and environmental fields, and are especially suitable for water quality detection in scenarios such as industrial wastewater, rivers and lakes, and aquaculture. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the detection chip described in this invention;

[0023] Figure 2 This is a top view of the detection chip described in this invention.

[0024] Figure 3 This is a standard curve diagram of the detection chip described in this invention.

[0025] Explanation of reference numerals in the attached figures

[0026] 1. Substrate; 2. Cover plate; 11. Reaction zone; 12. Detection zone; 13. Sample loading tank; 14. First channel; 15. Second channel; 16. Third channel; 21. Sample inlet; 22. Gas outlet. Detailed Implementation

[0027] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0028] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0029] like Figure 1 and Figure 2 As shown, where Figure 2 This is a top view schematic diagram of the detection chip of the present invention. The detection chip of the present invention includes a substrate 1 and a cover plate 2. The cover plate 2 is used to cover the upper surface of the substrate 1. The substrate 1 includes a sample loading tank 13, a reaction zone 11 and a detection zone 12 connected in sequence by a connecting channel. The cover plate 2 is provided with a sample inlet 21 and a gas outlet 22. The sample inlet 21 is correspondingly arranged with the sample loading tank 13. The reaction zone 11 is provided with a lyophilized reagent for detecting hexavalent chromium. The lyophilized reagent contains a colorimetric agent, a buffer, a masking agent, a cosolvent and an excipient. The colorimetric agent is diphenylcarbazide, the buffer is at least one of phosphoric acid, aminosulfonic acid and salicylic acid, and the cosolvent is at least one of ethanol, acetamide and sodium chloride.

[0030] The detection chip according to this invention reduces reagent usage, generates minimal waste liquid, requires no special treatment, and is both environmentally friendly and cost-effective. Furthermore, the lyophilized reagent is pre-immobilized in the chip, eliminating the need for reagent preparation; only the water sample needs to be added, requiring no professional personnel and simplifying operation. The lyophilized reagent exhibits good water resolubility, rapid reaction rate, and uniform mixing. It also contains sulfamic acid, thus reducing corrosiveness and increasing stability. Simultaneously, the co-solvent is non-toxic sodium chloride, preventing light-induced decomposition and extending shelf life.

[0031] In the detection chip of the present invention, the mass ratio of the chromogenic agent, the buffer, the masking agent, the cosolvent, and the excipient can be 1:(6-15):(4-9):(6-12):(7-15). To improve the water resolubility and stability of the lyophilized reagent, the preferred mass ratio of the chromogenic agent, the buffer, the masking agent, the cosolvent, and the excipient is 1:(7.5-10):(4.2-7.4):(7.5-9.1):(9-10.5), specifically, for example, 1:10:4.2:8:10.2, 1:9.1:5.5:7.5:10.3, 1:8.2:7.4:7.8:9, or 1:7.5:5.3:9.1:10.5.

[0032] In the detection chip of the present invention, the total mass ratio of the color developer, the buffer, the masking agent, the cosolvent, and the excipient to the mass of the lyophilized reagent can be 2-10%, preferably 2-5%.

[0033] In the detection chip described in this invention, the buffer can maintain a stable pH value in the reaction system, ensure the reaction rate of hexavalent chromium and lyophilized reagents, reduce interference from other metal ions, and thus improve the stability of the detection. To improve the dissolution rate of the reagents and shorten the reaction time, thereby improving the repeatability and uniformity of the detection, the buffer is preferably aminosulfonic acid.

[0034] In the detection chip described in this invention, the co-solvent provides a medium for the reaction, increases the solubility of diphenylcarbazide, promotes the reaction, and improves the accuracy and stability of the reaction. To ensure the stability of hexavalent chromium while inhibiting the conversion of chromium in different valence states, the co-solvent is preferably sodium chloride.

[0035] In the detection chip of this invention, the masking agent can form a stable complex with interfering substances, thereby preventing the interfering substances from reacting with hexavalent chromium and improving the accuracy of detection. The masking agent can be at least one of sodium thiosulfate, sodium citrate, and ascorbic acid. To reduce the influence of interfering substances on the detection results and thus improve the accuracy of detection, the masking agent is preferably ascorbic acid.

[0036] In the detection chip of the present invention, the excipient can maintain the morphological characteristics and stability of the lyophilized reagent. The excipient can be at least one selected from mannitol, trehalose, and sorbitol. For the morphological stability of the lyophilized reagent, mannitol is preferred as the excipient.

[0037] In the detection chip described in this invention, the lyophilized reagent can be spherical particles. The lyophilized reagent is an all-solid reagent, avoiding the instability of liquid solutions, making it easy to carry and suitable for on-site testing. It also reduces reagent usage, produces minimal waste liquid, requires no special treatment, and is environmentally friendly while lowering costs. To ensure the reaction rate, the diameter of the lyophilized reagent is preferably 1-3 mm.

[0038] In some embodiments, the detection chip of the present invention can be made of a polymer material, specifically, for example, methyl methacrylate (PMMA), polycarbonate (PC), cycloolefin copolymer (COC), or polystyrene (PS), preferably polycarbonate (PC). The polymer material has excellent transparency and high surface hardness.

[0039] In some embodiments, the detection chip of the present invention has a single-channel or multi-channel structure. The connection channels include a first channel 14, a second channel 15, and a third channel 16. The first channel 14 connects the sample loading chamber 13 and the reaction zone 11. The second channel 15 connects the reaction zone 11 and the detection zone 12. The third channel 16 connects the detection zone 12 and the gas outlet 22.

[0040] In the detection chip of the present invention, the thickness of the substrate 1 can be 4-6 mm, preferably 4.5-5.5 mm. The thickness of the cover plate 2 can be 1-3 mm, preferably 1-2 mm. The cover plate 2 is used to cover the upper surface of the substrate 1 by encapsulation. The encapsulation method includes thermoforming bonding, surface modification bonding, or adhesive bonding, preferably thermoforming bonding.

[0041] In the detection chip of the present invention, the water sample to be tested and the lyophilized reagent react in the reaction zone 11. The reaction zone 11 is cylindrical in shape. The volume of the reaction zone 11 can be 200-500 μL, preferably 200-250 μL.

[0042] In the detection chip of the present invention, a color-stable analyte is generated in the detection region 12. The analyte is a purplish-red compound. The detection region 12 is cylindrical in shape. The volume of the detection region 12 can be 220-700 μL, preferably 250-450 μL.

[0043] In the detection chip of the present invention, the sample inlet 21 is used to add the liquid to be tested, and the air outlet 22 is used to release the pressure inside the detection chip. Both the sample inlet 21 and the air outlet 22 are cylindrical.

[0044] In some embodiments, the detection chip of the present invention includes a substrate 1 with a thickness of 4-6 mm and a cover plate 2 with a thickness of 1-3 mm. The cover plate 2 is used to cover the upper surface of the substrate 1. The substrate 1 includes a sample loading groove 13, a reaction zone 11 with a volume of 200-500 μL, and a detection zone 12 with a volume of 220-700 μL, which are sequentially connected by connecting channels. The cover plate 2 is provided with a sample inlet 21 and a gas outlet 22. The sample inlet 21 is correspondingly arranged with the sample loading groove 13. The reaction zone 11 is provided with 3-8 lyophilized reagents with a diameter of 1-3 mm for detecting hexavalent chromium. The connecting channels include a first channel 14, a second channel 15, and a third channel 16. The first channel 14 is used to connect the sample loading groove 13 and the reaction zone 11, and the second channel 15 is used to connect the reaction zone 11 and the detection zone 16. Zone 12, the third channel 16 is used to connect the detection zone 12 and the air outlet 22; wherein, the lyophilized reagent contains a colorimetric agent, a buffer, a masking agent, a cosolvent, and an excipient, the mass ratio of the colorimetric agent, the buffer, the masking agent, the cosolvent, and the excipient is 1:(6-15):(4-9):(6-12):(7-15), the total mass of the colorimetric agent, the buffer, the masking agent, the cosolvent, and the excipient accounts for 2-10% of the mass of the lyophilized reagent, the colorimetric agent is diphenylcarbazide, the buffer is at least one of phosphoric acid, aminosulfonic acid, and salicylic acid, the cosolvent is at least one of ethanol, acetamide, and sodium chloride, the masking agent is at least one of sodium thiosulfate, sodium citrate, and ascorbic acid, and the excipient is at least one of mannitol, trehalose, and sorbitol.

[0045] The present invention also provides a method for detecting hexavalent chromium, which is implemented in the above-mentioned detection chip. The method includes: adding the water sample to be tested into the sample tank 13 through the sample inlet 21, then flowing into the reaction zone 11 to react with the lyophilized reagent therein, and the resulting mixture flowing into the detection zone 12. Then, the absorbance of the mixture in the detection zone 12 is detected using a spectrophotometer, and the concentration of hexavalent chromium in the water sample to be tested is determined based on the detected absorbance data.

[0046] In the method described in this invention, the water sample to be tested is added to the inlet 21 via a pipette or a syringe pump. The injection rate of the water sample to be tested can be 0.2-1.5 mL / min.

[0047] The method described in this invention may further include preparing the lyophilized reagent for detecting hexavalent chromium according to the following steps: pre-freezing and vacuum lyophilizing spherical droplets of the hexavalent chromium detection reagent sequentially.

[0048] In the method described in this invention, the preparation and pre-freezing process of the spherical droplets of the hexavalent chromium detection reagent includes: dissolving the chromogenic agent and co-solvent in water, then adding a buffer, masking agent, and excipient; and then pre-freezing and solidifying the resulting mixed solution into liquid nitrogen using an automated liquid nitrogen dispensing system to form 0.8-3 mm spheres. To control the uniformity of the lyophilized reagent and ensure its volume is suitable for the detection chip, the dispensing volume of the automated liquid nitrogen dispensing system is preferably 0.5-30 μL. To improve the accuracy and stability of the detection, the ratio of the amount of the water sample to be tested to the amount of the lyophilized reagent is preferably 90-210 μL:1. The ratio of the volume of the reaction zone 11 to the amount of the lyophilized reagent can be 30-100 μL:1.

[0049] In the method described in this invention, the method may further include: uniformly mixing the color developer and the co-solvent by grinding; and uniformly mixing the buffer, the masking agent, and the excipient by grinding. The grinding may be performed in a mortar.

[0050] In the method described in this invention, the vacuum freeze-drying conditions include: a vacuum degree of 1-100 Pa, preferably 1-50 Pa; a temperature of -60°C to -80°C, preferably -70°C to -80°C; and a time of 8-24 h, preferably 12-14 h. The process of pre-freezing and vacuum freeze-drying spherical droplets of hexavalent chromium detection reagent can include: sequentially discharging the droplets into liquid nitrogen for freeze-drying to form small spheres, and then placing the resulting spheres in a freeze dryer for vacuum drying.

[0051] In the method described in this invention, the method may further include: injecting several hexavalent chromium standard solutions of varying concentrations into the detection chip to obtain absorbance; fitting a standard curve with the concentration y of the hexavalent chromium standard solution as the ordinate and the absorbance x as the abscissa; and determining the concentration of hexavalent chromium in the water sample to be tested based on the standard curve and the absorbance of the tested water sample.

[0052] In some embodiments, the method for detecting hexavalent chromium according to the present invention, implemented in the aforementioned detection chip, includes the following steps: The preparation and pre-freezing of spherical droplets of the hexavalent chromium detection reagent comprises: dissolving a colorimetric agent and a co-solvent in water, then adding a buffer, a masking agent, and an excipient; then, using an automated liquid nitrogen dispensing system, dropping the resulting mixed solution into liquid nitrogen for pre-freezing and solidification to form 0.8-3 mm microspheres. The obtained microspheres are then freeze-dried for 8-24 hours under a vacuum of 1-100 Pa and a temperature of -70°C to -90°C to obtain a freeze-dried reagent. The water sample to be tested is added to the sample loading tank 13 through the injection port 21 at an injection rate of 0.2-1.5 mL / min. Then it flows into the reaction zone 11 and reacts with the lyophilized reagent therein. The resulting mixture flows into the detection zone 12. The absorbance of the mixture in the detection zone 12 is then detected using a spectrophotometer. Several hexavalent chromium standard solutions of varying concentrations are injected into the detection chip to obtain the absorbance. A standard curve is obtained by fitting the concentration y of the hexavalent chromium standard solution as the ordinate and the absorbance x as the abscissa. The concentration of hexavalent chromium in the water sample to be tested is determined based on the standard curve and the absorbance of the detected water sample.

[0053] The following examples further illustrate the detection chip and hexavalent chromium detection method of the present invention. These examples are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following examples.

[0054] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available.

[0055] Example 1

[0056] (1) Weigh diphenylcarbazide, aminosulfonic acid, ascorbic acid, sodium chloride and mannitol in a mass ratio of 1:10:4.2:8:10.2. First, mix diphenylcarbazide and sodium chloride and dissolve them in water. Then mix the remaining reagents and grind them in a mortar. Next, dissolve them in water (the mass ratio of the total mass of diphenylcarbazide, aminosulfonic acid, ascorbic acid, sodium chloride and mannitol to the mass of water is 5:100) to obtain a mixed solution.

[0057] (2) The obtained mixed solution was added to the liquid nitrogen automatic dispensing system (purchased from Guangzhou Feisheng Precision Equipment Co., Ltd.), and the dispensing volume was adjusted to 4.5 μL. The liquid droplets were discharged drop by drop into the liquid nitrogen to solidify and form small balls. Then the small balls were placed in a freeze dryer and freeze-dried for 14 h under the conditions of vacuum degree of 10 Pa and temperature of -80℃ to obtain freeze-dried balls S1 with a diameter of 2 mm.

[0058] Example 2

[0059] (1) Weigh diphenylcarbazide, aminosulfonic acid, ascorbic acid, sodium chloride and mannitol in a mass ratio of 1:9.1:5.5:7.5:10.3. First, mix diphenylcarbazide and sodium chloride and dissolve in water. Then mix the remaining reagents and grind them in a mortar. Next, dissolve them in water (the mass ratio of the total mass of diphenylcarbazide, aminosulfonic acid, ascorbic acid, sodium chloride and mannitol to the mass of water is 5:100) to obtain a mixed solution.

[0060] (2) The obtained mixed solution was added to the liquid nitrogen automatic dispensing system (purchased from Guangzhou Feisheng Precision Equipment Co., Ltd.), and the dispensing volume was adjusted to 4.5 μL. The liquid droplets were discharged drop by drop into the liquid nitrogen to solidify and form small balls. Then the small balls were placed in a freeze dryer and freeze-dried for 12 h under the conditions of vacuum degree of 5 Pa and temperature of -75℃ to obtain freeze-dried balls S2 with a diameter of 2 mm.

[0061] Example 3

[0062] (1) Weigh diphenylcarbazide, aminosulfonic acid, ascorbic acid, sodium chloride and mannitol in a mass ratio of 1:8.2:7.4:7.8:9. First, mix diphenylcarbazide and sodium chloride and dissolve in water. Then mix the remaining reagents and grind them in a mortar. Next, dissolve them in water (the mass ratio of the total mass of diphenylcarbazide, aminosulfonic acid, ascorbic acid, sodium chloride and mannitol to the mass of water is 5:100) to obtain a mixed solution.

[0063] (2) The obtained mixed solution was added to the liquid nitrogen automatic dispensing system (purchased from Guangzhou Feisheng Precision Equipment Co., Ltd.), and the dispensing volume was adjusted to 4.5 μL. The liquid droplets were discharged drop by drop into the liquid nitrogen to solidify and form small balls. Then the small balls were placed in a freeze dryer and freeze-dried for 14 h under the conditions of vacuum degree of 15 Pa and temperature of -85℃ to obtain freeze-dried balls S3 with a diameter of 2 mm.

[0064] Example 4

[0065] The method of Example 1 was followed, except that the weight ratio of diphenylcarbazide, aminosulfonic acid, ascorbic acid, sodium chloride and mannitol was 1:7.5:5.3:9.1:10.5, to obtain freeze-dried spheres S4 with a diameter of 2 mm.

[0066] Comparative Example 1

[0067] The method was implemented according to Example 1, except that the weight ratio of diphenylcarbazide, aminosulfonic acid, ascorbic acid, sodium chloride and mannitol was 1:12:6:8.3:6.

[0068] In this comparative example, the lyophilized reagent had a collapsed morphology after freeze-drying due to the low amount of excipient (mannitol), and could not form lyophilized spheres.

[0069] Comparative Example 2

[0070] The method of Example 1 was followed, except that the weight ratio of diphenylcarbazide, aminosulfonic acid, ascorbic acid, sodium chloride and mannitol was 1:5:7.5:9.8:10, to obtain freeze-dried pellets A1.

[0071] Comparative Example 3

[0072] In this comparative example, the reagent is not prepared as a lyophilized product; instead, the raw materials are directly mixed to form a mixture. The specific steps are as follows:

[0073] Diphenylcarbazide, aminosulfonic acid, ascorbic acid, sodium chloride and mannitol were mixed in a weight ratio of 1:7.5:5.3:9.1:10.5 to obtain mixture A2.

[0074] Example 5

[0075] The detection chip in this embodiment includes a substrate 1 (made of polycarbonate) with a thickness of 5 mm and a cover plate 2 (made of polycarbonate) with a thickness of 1.5 mm. The cover plate 2 is used to encapsulate the upper surface of the substrate 1 by thermoforming. The substrate 1 includes a sample loading groove 13, a reaction zone 11 with a volume of 220 μL, and a detection zone 12 with a volume of 300 μL, which are connected sequentially by connecting channels. The cover plate 2 is provided with a sample inlet 21 and a gas outlet 22, with the sample inlet 21 corresponding to the sample loading groove 13. The connection channels include a first channel 14, a second channel 15, and a third channel 16. The first channel 14 is used to connect the sample loading tank 13 and the reaction zone 11. The second channel 15 is used to connect the reaction zone 11 and the detection zone 12. The third channel 16 is used to connect the detection zone 12 and the gas outlet 22. The reaction zone 11, the detection zone 12, and the sample loading tank 13 are cylindrical. The width and depth of the first channel 14, the second channel 15, and the third channel 16 are all 1 mm. The reaction zone 11 contains 5 freeze-dried bulbs S1.

[0076] Example 6

[0077] The method was implemented according to Example 5, except that 5 freeze-dried balls S2 were packed in the reaction zone 11.

[0078] Example 7

[0079] The method was implemented according to Example 5, except that 5 freeze-dried balls S3 were packed in the reaction zone 11.

[0080] Example 8

[0081] The method was implemented according to Example 5, except that 5 freeze-dried balls S4 were packed in the reaction zone 11.

[0082] Example 9

[0083] The method was implemented according to Example 5, except that the reaction zone 11 contained 6 freeze-dried balls S1.

[0084] Example 10

[0085] The method was implemented according to Example 5, except that the reaction zone 11 contained 3 freeze-dried balls S1.

[0086] Comparative Example 4

[0087] The method was implemented according to Example 5, except that 5 freeze-dried balls A1 were placed in the reaction zone 11.

[0088] Comparative Example 5

[0089] The method was carried out according to Example 5, except that 10 mg of mixture A2 was contained in reaction zone 11.

[0090] Test Example 1

[0091] The detection chips described in Examples 5-10 and Comparative Examples 4-5 were subjected to the following tests:

[0092] A 1 mg / L hexavalent chromium standard solution was injected into the detection chip at a rate of 0.25 mL / min using a pipette. The volume of the injected hexavalent chromium standard solution was 0.6 mL, and the absorbance measured at a detection wavelength of 540 nm was recorded. The results are shown in Table 1.

[0093] Table 1

[0094] Example number absorbance Example 5 0.260 Example 6 0.249 Example 7 0.237 Example 8 0.226 Example 9 0.250 Example 10 0.214 Comparative Example 4 0.161 Comparative Example 5 0.208

[0095] As can be seen from the results in Table 1, the embodiment using the lyophilized reagent described in this invention can detect the concentration of hexavalent chromium in water samples.

[0096] Test Example 2

[0097] A 2 mg / L hexavalent chromium standard solution was injected into six detection chips described in Example 9 at a rate of 0.25 mL / min using a pipette. The volume of hexavalent chromium standard solution injected into each chip was 0.6 mL. The absorbance measured at a detection wavelength of 530 nm was recorded. The detected absorbances were 0.452, 0.459, 0.467, 0.476, 0.474, and 0.453, respectively, with an average value of 0.463 and a relative standard deviation of 2.25%.

[0098] The results above show that the lyophilized reagent and detection chip described in this invention have good repeatability.

[0099] Test Example 3

[0100] (1) Prepare hexavalent chromium standard solutions with concentrations of 0.02 mg / L, 0.04 mg / L, 0.1 mg / L, 0.2 mg / L, 0.4 mg / L, 1 mg / L, 1.6 mg / L, and 3 mg / L. Prepare six detection chips as described in Example 5. Then, inject the above standard solutions into the six detection chips as described in Example 5 at a rate of 0.25 mL / min for detection. The volume of the injected hexavalent chromium standard solution is 0.6 mL. Obtain absorbance data. Plot a standard curve with the concentration y of the hexavalent chromium standard solution as the ordinate and the absorbance x as the abscissa, as shown below. Figure 3 As shown, the fitted linear equation is y = 14.3315x - 0.0256, R0 2 =0.9995;

[0101] (2) Prepare solutions with hexavalent chromium concentrations of 0.5 mg / L, 1.2 mg / L and 2.0 mg / L as test solutions. Prepare three detection chips as described in Example 5. Then inject the above standard solutions into the three detection chips as described in Example 5 at a rate of 0.25 mL / min for detection. The volume of the injected hexavalent chromium standard solution is 0.6 mL. Obtain absorbance data. Then substitute the absorbance data into the relationship obtained in step (1) for calculation to obtain the measured concentration.

[0102] The results obtained in step (2) were compared with the theoretical values ​​of the test liquid, and the results are shown in Table 2.

[0103] Table 2

[0104] Theoretical value (mg / L) Measuring absorbance Detected value (mg / L) error 0.5 0.115 0.47 6.0％ 1.2 0.302 1.26 4.7％ 2.0 0.478 2.05 2.5％

[0105] As can be seen from the results in Table 2, the embodiment using the lyophilized reagent and detection chip described in this invention can accurately measure the concentration of hexavalent chromium in water samples of different concentrations.

[0106] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A detection chip, characterized in that, The detection chip includes a substrate (1) and a cover plate (2). The cover plate (2) is used to cover the upper surface of the substrate (1). The substrate (1) includes a sample loading groove (13), a reaction zone (11) and a detection zone (12) connected in sequence by a connecting channel. The cover plate (2) is provided with a sample inlet (21) and an air outlet (22). The sample inlet (21) is correspondingly provided with the sample loading groove (13). The reaction zone (11) is provided with a lyophilized reagent for detecting hexavalent chromium. The lyophilization reagent contains a color developer, a buffer, a masking agent, a cosolvent, and an excipient. The color developer is diphenylcarbazide, the buffer is at least one of phosphoric acid, aminosulfonic acid, and salicylic acid, and the cosolvent is at least one of ethanol, acetamide, and sodium chloride.

2. The detection chip according to claim 1, characterized in that, The mass ratio of the color developer, the buffer, the masking agent, the cosolvent, and the excipient is 1:(6-15):(4-9):(6-12):(7-15).

3. The detection chip according to claim 1 or 2, characterized in that, The total mass ratio of the color developer, the buffer, the masking agent, the cosolvent, and the excipient to the mass of the lyophilized reagent is 2-10%.

4. The detection chip according to any one of claims 1-3, characterized in that, The masking agent is at least one of sodium thiosulfate, sodium citrate, and ascorbic acid.

5. The detection chip according to any one of claims 1-4, characterized in that, The excipient is at least one of mannitol, trehalose, and sorbitol.

6. The detection chip according to any one of claims 1-5, characterized in that, The lyophilized reagent is in the form of spherical particles.

7. A method for detecting hexavalent chromium, characterized in that, The method is implemented in the detection chip according to any one of claims 1-6. The method includes: adding the water sample to be tested into the sample loading tank (13) through the sample inlet (21), then flowing into the reaction zone (11) to react with the lyophilized reagent therein, and the mixture obtained after the reaction flowing into the detection zone (12), then using a spectrophotometer to detect the absorbance of the mixture in the detection zone (12), and determining the concentration of hexavalent chromium in the water sample to be tested based on the detected absorbance data.

8. The method according to claim 7, characterized in that, It also includes the preparation of the lyophilized reagent for detecting hexavalent chromium according to the following steps: The spherical droplets of the hexavalent chromium detection reagent were pre-frozen and then freeze-dried under vacuum.

9. The method according to claim 8, characterized in that, The process of preparing and pre-freezing the spherical droplets of the hexavalent chromium detection reagent includes: dissolving the colorimetric agent and co-solvent in water, then adding a buffer, masking agent and excipient, and then using an automatic liquid nitrogen dispensing system to drop the resulting mixed solution into liquid nitrogen for pre-freezing and solidification to form small spheres of 0.8-3 mm.

10. The method according to claim 8 or 9, characterized in that, The vacuum freeze-drying conditions include: a vacuum degree of 1-100 Pa, a temperature of -60℃ to -80℃, and a time of 8-24 h.

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