Method for determining quality and content of plastic package gold product

Abstract

The invention relates to the technical field of chemical detection, in particular to a method for determining the quality and content of a plastic-packaged gold product, which comprises the following steps: S1, putting the plastic-packaged gold product to be detected into DMF (Dimethyl Formamide), heating to 150 DEG C or above, heating for 10-15 minutes, taking out, and tearing off the plastic package on the surface to obtain a colloid-containing gold product; s2, the colloid-containing gold product is subjected to oxidation soot blowing treatment so as to remove a colloid part on the surface, and a treated gold product is obtained; and S3, the mass of gold in the treated gold product is weighed, and the gold content in the treated gold product is detected through a fire assaying method. According to the method, through combined application of DMF primary treatment, composite sol agent pretreatment, multi-stage oxidation soot blowing and a fire assaying method, various types of plastic packaging materials and colloids can be effectively removed, meanwhile, the gold product is protected to the maximum extent, and the quality of the plastic packaging gold product and the efficiency and precision of content determination are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical detection, and in particular to a method for determining the quality and content of plastic-sealed gold products. Background Art

[0002] Gold products, such as gold foil and commemorative banknotes, are often sealed in a plastic film after being subjected to high-temperature treatment using a laminator. This process creates a tight seal, preventing the infiltration of dust and other substances and protecting them from the external environment, making it highly effective in protecting precious metals. However, this also presents another problem: if the seal remains intact, it cannot be easily removed, making it extremely difficult to remove. In actual testing, there is no specialized tool or method for handling these samples.

[0003] When testing gold foil products with surface coatings, gold content and quality are key concerns for manufacturers and consumers. Currently, the industry mostly uses strong acids or bases to soften the colloid, or employs a fire-burning method. Using strong acids and bases to remove the glue requires the coated gold foil to be completely immersed in the strong acid or base solution. This can cause impurity metal elements such as iron, zinc, aluminum, and copper in the gold layer to react with the acid or base, destroying the impurity content of the gold layer and resulting in inaccurate gold content testing. Using a fire-burning method, if the gold foil is very thin, there is a risk of melting the foil, or the coated colloid may not be completely burned, making it impossible to obtain a complete gold layer for subsequent quality and gold content measurement. Furthermore, the fire-burning method involves burning the polymer coating, which is not environmentally friendly and has numerous drawbacks.

[0004] The existing patent CN201610332962.6 discloses a method for rapidly determining the gold content and gold mass of surface-coated gold sheets. The surface-coated gold sheets are pre-treated with a sol agent for stripping, and then the gold content is detected using X-ray fluorescence spectroscopy. The sol step for pre-stripping only reacts with the colloid on the membrane and has no reaction to the gold layer. It can not only quickly and conveniently separate the membrane from the gold layer, but also maintain the integrity of the gold layer to a large extent. The stripped gold sheets can be conveniently subjected to X-ray fluorescence spectroscopy to accurately measure the gold mass. In the above technical solution, the surface-coated gold sheet is treated mainly by sol treatment, and then the coating layer is peeled off after re-cleaning. The following problems still exist: First, a single or simple combination of organic solvents is used as a sol agent for demolding, and the sol effect is limited, and it cannot effectively process all types of plastic packaging materials, especially for plastic packaging materials with complex structures or difficult to process. The effect is poor; second, after the sol treatment, the coating layer is directly peeled off by re-cleaning, and there may be colloid residues on the surface of the gold sheet, thereby affecting the detection results; in addition, the sol treatment time in this method is 1-2 hours, and the long processing time will significantly reduce the efficiency of sample processing. When a large number of samples need to be analyzed, this will greatly prolong the entire detection process and reduce the efficiency of quality inspection work. Summary of the Invention

[0005] In view of this, the present invention proposes a method for determining the quality and content of plastic-sealed gold products to solve the problem in existing plastic-sealed gold product testing that the surface plastic film and colloid are not completely removed, remaining on the surface of the gold products, thereby affecting the accuracy of the quality and content detection of plastic-sealed gold products.

[0006] The technical solution of the present invention is achieved as follows: The present invention provides a method for determining the quality and content of plastic-sealed gold products, comprising the following steps: S1. Place the plastic-sealed gold product to be tested in DMF, heat to above 150°C, heat for 10-15 minutes, take it out, and tear off the plastic seal on the surface to obtain the colloidal gold product; S2, performing an oxidation ash blowing treatment on the colloidal gold product to remove the colloidal portion on the surface, thereby obtaining a treated gold product; S3. Weigh the mass of gold in the treated gold product and detect the gold content in the treated gold product using a fire assay method.

[0007] In this method, high-temperature treatment with DMF (above 150°C) effectively removes the plastic layer, making it suitable for various types of plastic-encapsulated materials. Secondly, a combination of composite sol pretreatment and oxidized ash blowing thoroughly removes surface colloids, ensuring sample purity. Fire assaying is used for precise determination, which may be more suitable for the determination of high-purity gold than X-ray fluorescence spectrometry. Through high-temperature treatment with DMF, composite sol pretreatment, and oxidized ash blowing, impurities are removed while the metal itself is retained to the greatest extent possible, minimizing sample loss. By combining efficient stripping, thorough impurity removal, and precise measurement techniques, a comprehensive, accurate, and highly applicable method for determining the quality and content of plastic-encapsulated gold products is provided, capable of meeting the measurement requirements of various types of plastic-encapsulated gold products.

[0008] Based on the above technical solution, preferably, step S1 specifically includes: cutting off the edges of the plastic-sealed gold product to be tested to expose the plastic-sealed main body, then cutting it into multiple sections and placing it in DMF, heating it to above 150°C until it is slightly boiling, and then continuing to heat it for 10-15 minutes until the plastic film and the colloid part soften, taking it out, tearing off the surface plastic seal, and obtaining the colloid-containing gold product.

[0009] Specifically, by cutting the plastic-encapsulated gold product to be tested into multiple sections, the surface area can be increased, allowing DMF to more fully contact the plastic material and accelerate the dissolution process. As a solvent, DMF has a strong dissolving ability, especially for polymer materials. By raising the temperature to above 150°C, until it slightly boils, DMF's high boiling point is utilized, further enhancing its dissolving power at high temperatures, allowing it to soften and dissolve the plastic layer more quickly and effectively. Compared to traditional single-solvent treatments at room temperature, this method is more efficient and can handle various types of plastic materials, including some difficult-to-remove plastic layers. Furthermore, because DMF has little effect on metallic gold, it can maximize the protection of the gold product itself, minimize sample loss, and lay the foundation for subsequent deep cleaning and precise measurement, thereby improving the efficiency and accuracy of the entire measurement process.

[0010] On the basis of the above technical solution, preferably, in step S2, before subjecting the colloidal gold product to the oxidation ash blowing treatment, the method further includes: placing the colloidal gold product in a composite sol for pretreatment.

[0011] On the basis of the above technical solution, preferably, the pretreatment includes: placing the colloidal gold product into a composite sol, ultrasonically stirring at room temperature for 10-15 minutes, taking out the gold product, washing it with anhydrous ethanol and deionized water in sequence, and vacuum drying it to obtain the pretreated gold product.

[0012] A composite sol is used for pretreatment before the oxidation ash blowing process to further remove residual plastic packaging materials and colloids. The strong dissolving ability and versatility of the composite sol are utilized to soften and dissolve the residues under relatively mild conditions (55-65°C). This pretreatment can remove stubborn residues that may still exist after the DMF high-temperature treatment, which can reduce the burden of the oxidation ash blowing process and improve its efficiency. It may also reduce the potential impact of high-temperature treatment on the gold products themselves.

[0013] Based on the above technical solution, preferably, the composite sol agent comprises the following components in parts by mass: 60-80 parts of mixed solvent, 4-6 parts of polyethylene glycol monolaurate, 2-4 parts of copper chloride, 1-1.5 parts of ascorbic acid, 1-2 parts of polyvinyl alcohol, and 2-4 parts of citric acid.

[0014] On the basis of the above technical solution, preferably, the mixed solvent comprises the following components in parts by mass: 40-50 parts of DMF, 10-13 parts of acetone, 8-12 parts of γ-butyrolactone, and 2-5 parts of toluene.

[0015] Based on the above technical solution, preferably, the preparation method of the composite sol comprises: stirring and mixing DMF, acetone and γ-butyrolactone uniformly, then adding toluene, polyethylene glycol monolaurate, copper chloride, ascorbic acid, polyvinyl alcohol and citric acid in sequence, and continuously stirring at room temperature for 30-60 minutes to obtain the composite sol.

[0016] Specifically, DMF in the composite sol can effectively soften and dissolve various plastic packaging materials and is the core component of the entire solvent system; acetone has good permeability and rapid volatilization characteristics, which can accelerate the dissolution process and improve the fluidity of the solution; γ-butyrolactone can enhance the stability and durability of the solution, and also has good dissolving ability; toluene, as a non-polar solvent, is suitable for dissolving certain hydrophobic plastics and colloids, making up for the shortcomings of other polar solvents; polyethylene glycol monolaurate can significantly reduce the surface tension of the solution, promote full contact between the solvent and the plastic packaging material, and improve the dissolution efficiency; copper chloride and ascorbic acid form a controllable redox system, creating a mild and continuous redox environment, which helps to destroy certain chemical bonds in the plastic packaging material and colloid, and accelerate their decomposition process; polyvinyl alcohol can form a protective film during the dissolution process to prevent excessive corrosion of the surface of gold products, and also helps to stabilize the entire solution system; citric acid may act as a chelating agent, helping to remove oxides or other impurities on the metal surface and improve the cleaning effect. The synergistic effect between the above components enables the composite sol agent to efficiently soften and remove various types of plastic sealing materials and colloids, while maximally protecting the gold products themselves.

[0017] Based on the above technical solution, preferably, the oxidation ash blowing includes: placing the pretreated gold product in a muffle furnace, heating it to 275-325°C, maintaining it for 5-10 min, then heating it to 475-525°C, maintaining it for 5-10 min, and finally heating it to 550-650°C, maintaining it for 5-10 min.

[0018] Specifically, the process is maintained at 275-325°C for 5-10 minutes. This lower temperature allows for the initial oxidation and decomposition of residual organic matter while preventing over-oxidation of the metal. Subsequently, the temperature is raised to 475-525°C and maintained for 5-10 minutes. This intermediate temperature range further oxidizes and removes more stubborn organic residues while also initiating the decomposition of some complex inorganic compounds. Finally, the high-temperature stage, maintained at 550-650°C for 5-10 minutes, thoroughly oxidizes and removes nearly all impurities, including some difficult-to-remove metal oxides. This entire process utilizes the varying thermal behavior of materials at different temperatures. By gradually increasing the temperature and precisely controlling the time, it ensures the complete removal of impurities while maximizing the protection of the gold itself. This process not only effectively removes trace impurities that may remain after pretreatment with the composite sol, but also removes the oxide layer on the gold surface, resulting in a high-purity gold sample and providing a reliable basis for subsequent content determination.

[0019] Based on the above technical solution, preferably, the fire assay method includes: mixing the treated gold product with silver particles, then wrapping it with lead foil, and blowing oxidized ash for 15-25 minutes; smashing and annealing, and then rolling it into a thin sheet with a thickness of 0.15-0.20 mm, and performing gold separation treatment on the thin sheet.

[0020] On the basis of the above technical solution, preferably, the mass ratio of the gold product, silver particles and lead foil after the treatment is 1:2.1-2.5:4, and the temperature of the oxidation ash blowing is 900-950°C.

[0021] Based on the above technical solution, preferably, the gold separation treatment includes: placing the thin slice in a nitric acid solution, heating it to 90-95°C, separating the gold for 25-35 minutes, washing and drying; placing the thin slice in a nitric acid solution, heating it to 100-120°C, separating the gold for 25-35 minutes, washing and drying, weighing and calculating to obtain the gold content of the plastic-sealed gold product.

[0022] Specifically, the fire assay method is used to detect the gold content of gold products. The high-temperature molten metallic lead has a great ability to capture gold, silver and precious metals, and can completely dissolve the gold and silver exposed in the molten state in the lead. The metallic lead and the slag have different specific gravities. The lead in the melt sinks to form lead buckles, and the slag floats on it, thereby achieving the separation of the lead buckles and the slag. With the help of the different solubility of gold and silver in nitric acid, gold and silver are separated. The silver forms silver nitrate and enters the solution, and the remaining gold is weighed and its content is calculated.

[0023] The method for determining the quality and content of plastic-sealed gold products of the present invention has the following beneficial effects compared with the prior art: (1) The DMF preliminary treatment is carried out at high temperature, which can effectively soften and dissolve most of the plastic sealing materials, so that the surface plastic sealing can be easily removed; the composite sol agent pretreatment is carried out under relatively mild conditions, and its multi-component system is used to further soften and dissolve the plastic sealing materials and colloids remaining after the DMF treatment. The multi-stage oxidation ash blowing treatment uses a temperature gradient to gradually oxidize and remove impurities that cannot be completely removed in the first two steps, including some difficult-to-remove inorganic compounds and metal oxides; through the combined application of DMF preliminary treatment, composite sol agent pretreatment, multi-stage oxidation ash blowing and fire assay, comprehensive cleaning and accurate determination of plastic-sealed gold products are achieved. Compared with the existing technology, the sol treatment time is greatly shortened, and at the same time, various types of plastic sealing materials and colloids can be effectively removed, thereby maximizing the protection of the gold products themselves and significantly improving the efficiency and accuracy of the quality and content determination of plastic-sealed gold products; (2) The composite sol agent contains a mixed solvent, a surfactant, a redox system, a protective agent and a chelating agent. The multiple components work synergistically. Under relatively mild conditions (55-65°C), combined with ultrasonic stirring, this pretreatment step can soften and dissolve stubborn residues, creating better conditions for subsequent oxidation ash blowing treatment, and improving the accuracy of the measurement results; the multi-stage oxidation ash blowing treatment achieves deep cleaning and purification of the pretreated gold products through temperature gradient control, from initial oxidation and decomposition of organic matter to complete removal of stubborn impurities. This progressive temperature control can not only effectively remove various types of impurities, including complex inorganic compounds and metal oxides, but also protect the gold itself from excessive oxidation to the maximum extent, so as to obtain high-purity gold samples and further improve the accuracy and credibility of the measurement results. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 This is a flow chart of the method for determining the quality and content of plastic-sealed gold products of the present invention. DETAILED DESCRIPTION

[0026] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0027] Example 1 This embodiment provides a method for determining the quality and content of plastic-sealed gold products. Figure 1 As shown, the specific steps include: S1. Trim the edges of a 1g sample to expose the main plastic seal. Add 100 mL of N,N-dimethylformamide (DMF) to a beaker. Cut the sample into multiple sections according to the liquid level in the beaker. Place the sections into the beaker, immersing the sample in the DMF. Cover with a watch glass and heat on a hot plate, maintaining a temperature above 150°C until slightly boiling. Hold for 12 minutes, until the plastic seal and the colloid have softened. Remove the sample and remove the plastic seal to obtain the colloid-containing gold product. S2. 45 g of DMF, 12 g of acetone, and 10 g of γ-butyrolactone were stirred and mixed uniformly, and then 3 g of toluene, 5 g of polyethylene glycol monolaurate, 3 g of copper chloride, 1.2 g of ascorbic acid, 1.5 g of polyvinyl alcohol, and 3 g of citric acid were added in sequence, and the mixture was stirred at room temperature for 45 min to obtain a composite sol; 1 g of the colloidal gold product was placed in 10 g of the composite sol, and ultrasonically stirred at room temperature for 12 min. The gold product was taken out, and washed with anhydrous ethanol and deionized water in sequence, and vacuum-dried to obtain a pretreated gold product; Select a porcelain crucible (30 mL) of appropriate specifications, place the pretreated gold product in it, blow off the oxidation ash to remove the surface colloid, place it in a muffle furnace, open the furnace door, and heat it to 300°C for 8 minutes, then to 500°C for 8 minutes, and finally to 600°C for 8 minutes. Remove the treated gold product, cool it to room temperature, and weigh the net weight of the gold. S3. Weigh 1g of treated gold product, add 2.3g of high-purity silver particles, place in 4g of lead foil, wrap, and place in an ash-blowing furnace. Oxidize and ash-blow for 20 minutes, then air-cool. After slicing and annealing, roll into a sheet approximately 0.18mm thick. After annealing, roll into a cylindrical shape and place in a gold-separating basket. Place in 93°C nitric acid (1+1) to separate the gold for 30 minutes, wash three times, then place in 110°C nitric acid (2+1) to separate the gold again for 30 minutes, wash three times, dry and cool, and weigh and calculate the gold content of the gold roll.

[0028] Example 2 This embodiment provides a method for determining the quality and content of a plastic-sealed gold product, which specifically includes the following steps: S1. Trim the edges of a 1g sample to expose the main plastic seal. Add 100 mL of N,N-dimethylformamide (DMF) to a beaker. Cut the sample into multiple sections according to the liquid level in the beaker. Place the sections into the beaker, immersing the sample in the DMF. Cover with a watch glass and heat on a hot plate, maintaining a temperature above 150°C until slightly boiling. Hold for 10 minutes, until the plastic seal and the colloid have softened. Remove the sample and remove the plastic seal to obtain the colloid-containing gold product. S2. 40 g of DMF, 10 g of acetone, and 8 g of γ-butyrolactone were stirred and mixed uniformly, and then 2 g of toluene, 4 g of polyethylene glycol monolaurate, 2 g of copper chloride, 1 g of ascorbic acid, 1 g of polyvinyl alcohol, and 2 g of citric acid were added in sequence, and the mixture was stirred at room temperature for 30 min to obtain a composite sol; 1 g of the colloidal gold product was placed in 10 g of the composite sol, and ultrasonically stirred at room temperature for 10 min. The gold product was taken out, and washed with anhydrous ethanol and deionized water in sequence, and vacuum-dried to obtain a pretreated gold product; Select a porcelain crucible (30 mL) of appropriate specifications, place the pretreated gold product in it, blow off the oxidation ash to remove the surface colloid, place it in a muffle furnace, open the furnace door, and heat it to 275°C, hold it for 10 minutes, then to 475°C, hold it for 10 minutes, and finally to 550°C, hold it for 10 minutes. Remove the treated gold product, cool it to room temperature, and weigh the net weight of the gold. S3. Weigh 1g of treated gold product, add 2.1g of high-purity silver particles, put it in 4g of lead foil, wrap it and put it in an ash blowing furnace, oxidize the ash blowing for 15 minutes, and air cool it down. After smashing and annealing, grind it into a thin sheet with a thickness of about 0.15 mm. After annealing, roll it into a cylindrical shape and put it into a gold separation basket. Put it into 90℃ nitric acid (1+1) to separate the gold for 35 minutes, wash it 3 times, then put it into 100℃ nitric acid (2+1), separate the gold for a second time for 35 minutes, wash it 3 times, dry and cool it, weigh and calculate the gold content of the gold roll. Example 3 This embodiment provides a method for determining the quality and content of a plastic-sealed gold product, which specifically includes the following steps: S1. Trim the edges of a 1g sample to expose the main plastic seal. Add 100mL of N,N-dimethylformamide (DMF) to a beaker. Cut the sample into multiple sections according to the liquid level in the beaker. Place the sections into the beaker, immersing the sample in the DMF. Cover with a watch glass and heat on a hot plate, maintaining a temperature above 150°C until slightly boiling. Hold for 15 minutes, until the plastic seal and the colloid have softened. Remove the sample and remove the plastic seal to obtain the colloid-containing gold product. S2. 50 g of DMF, 13 g of acetone, and 12 g of γ-butyrolactone were stirred and mixed uniformly, and then 5 g of toluene, 6 g of polyethylene glycol monolaurate, 4 g of copper chloride, 1.5 g of ascorbic acid, 2 g of polyvinyl alcohol, and 4 g of citric acid were added in sequence, and the mixture was stirred at room temperature for 60 min to obtain a composite sol; 1 g of the colloidal gold product was placed in 10 g of the composite sol, and ultrasonically stirred at room temperature for 15 min. The gold product was taken out, and washed with anhydrous ethanol and deionized water in sequence, and vacuum-dried to obtain a pretreated gold product; Select a porcelain crucible (30 mL) of appropriate specifications, place the pretreated gold product in it, blow off the oxidation ash to remove the surface colloid, place it in a muffle furnace, open the furnace door, and heat it to 325°C for 5 minutes, then to 525°C for 5 minutes, and finally to 650°C for 5 minutes. Remove the treated gold product, cool it to room temperature, and weigh the net weight of the gold. S3. Weigh 1g of treated gold product, add 2.5g of high-purity silver particles, put it in 4g of lead foil, wrap it and put it in the ash blowing furnace, oxidize the ash blowing for 25 minutes, and air cool it down. After smashing and annealing, grind it into a thin sheet with a thickness of about 0.20 mm. After annealing, roll it into a cylindrical shape and put it into a gold separation basket. Put it into 95℃ nitric acid (1+1) to separate the gold for 25 minutes, wash it 3 times, then put it into 120℃ nitric acid (2+1), separate the gold for a second time for 25 minutes, wash it 3 times, dry and cool it, weigh and calculate the gold content of the gold roll. Example 4 This embodiment provides a method for determining the quality and content of a plastic-sealed gold product, which specifically includes the following steps: S1. Trim the edges of a 1g sample to expose the main plastic seal. Add 100mL of N,N-dimethylformamide (DMF) to a beaker. Cut the sample into multiple sections according to the liquid level in the beaker. Place the sample into the beaker, immersing it in the DMF. Cover with a watch glass and heat on a hot plate, maintaining a temperature above 150°C until slightly boiling. Hold for 13 minutes, until the plastic seal and the colloid have softened. Remove the sample and remove the plastic seal to obtain the colloid-containing gold product. S2. 48 g of DMF, 11 g of acetone, and 9 g of γ-butyrolactone were stirred and mixed uniformly, and then 4 g of toluene, 4.5 g of polyethylene glycol monolaurate, 2.5 g of copper chloride, 1.3 g of ascorbic acid, 1.8 g of polyvinyl alcohol, and 2.5 g of citric acid were added in sequence, and the mixture was stirred at room temperature for 40 min to obtain a composite sol; 1 g of the colloidal gold product was placed in 10 g of the composite sol, and ultrasonically stirred at room temperature for 13 min. The gold product was removed, and washed with anhydrous ethanol and deionized water in sequence, and vacuum-dried to obtain a pretreated gold product; Select a porcelain crucible (30 mL) of appropriate specifications, place the pretreated gold product in it, blow off the oxidation ash to remove the surface colloid, place it in a muffle furnace, open the furnace door, and heat it to 310°C for 6 minutes, then to 510°C for 7 minutes, and finally to 620°C for 6 minutes. Remove the treated gold product, cool it to room temperature, and weigh the net weight of the gold. S3. Weigh 1g of treated gold product, add 2.2g of high-purity silver particles, place in 4g of lead foil, wrap, and place in an ash-blowing furnace. Oxidize and ash-blow for 18 minutes, then air-cool. After slicing and annealing, roll into a sheet approximately 0.16mm thick. After annealing, roll into a cylindrical shape and place in a gold-separating basket. Place in 92°C nitric acid (1+1) to separate the gold for 32 minutes, wash three times, then place in 115°C nitric acid (2+1) to separate the gold again for 28 minutes, wash three times, dry and cool, and weigh and calculate the gold content of the gold roll.

[0029] Comparative Example 1 This comparative example provides a method for determining the quality and content of plastic-sealed gold products, which specifically includes the following steps: S1. Trim the edges of a 1g sample to expose the main plastic seal. Add 100mL of N,N-dimethylformamide (DMF) to a beaker. Cut the sample into multiple sections according to the liquid level in the beaker. Place the sections into the beaker, immersing the sample in the DMF. Cover with a watch glass and heat on a hot plate, maintaining a temperature above 150°C until slightly boiling. Hold for 12 minutes, until the plastic seal and the colloid are softened. Remove the sample and remove the plastic seal to obtain the colloid-containing gold product. S2. Stir and mix 45 g of DMF and 12 g of acetone to obtain a mixed sol; place 1 g of the colloidal gold product into 10 g of the mixed sol, and ultrasonically stir at room temperature for 12 min. Remove the gold product, wash it with anhydrous ethanol and deionized water in sequence, and vacuum dry it to obtain a pretreated gold product; Select a porcelain crucible (30 mL) of appropriate specifications, place the pretreated gold product in it, blow off the oxidation ash to remove the surface colloid, place it in a muffle furnace, open the furnace door, and heat it to 300°C for 8 minutes, then to 500°C for 8 minutes, and finally to 600°C for 8 minutes. Remove the treated gold product, cool it to room temperature, and weigh the net weight of the gold. S3. Weigh 1g of treated gold product, add 2.3g of high-purity silver particles, place in 4g of lead foil, wrap, and place in an ash-blowing furnace. Oxidize and ash-blow for 20 minutes, then air-cool. After slicing and annealing, roll into a sheet approximately 0.18mm thick. After annealing, roll into a cylindrical shape and place in a gold-separating basket. Place in 93°C nitric acid (1+1) to separate the gold for 30 minutes, wash three times, then place in 110°C nitric acid (2+1) to separate the gold again for 30 minutes, wash three times, dry and cool, and weigh and calculate the gold content of the gold roll.

[0030] Comparative Example 2 This comparative example provides a method for determining the quality and content of plastic-sealed gold products, which specifically includes the following steps: S1. Trim the edges of a 1g sample to expose the main plastic seal. Add 100mL of N,N-dimethylformamide (DMF) to a beaker. Cut the sample into multiple sections according to the liquid level in the beaker. Place the sample into the beaker, immersing it in the DMF. Cover with a watch glass and heat on a hot plate, maintaining a temperature above 150°C until slightly boiling. Hold for 12 minutes, until the plastic seal and the colloid are softened. Remove the sample and remove the plastic seal to obtain the colloid-containing gold product. S2. 45 g of DMF, 12 g of acetone, and 10 g of γ-butyrolactone were stirred and mixed uniformly, and then 3 g of toluene, 5 g of polyethylene glycol monolaurate, 3 g of copper chloride, 1.2 g of ascorbic acid, 1.5 g of polyvinyl alcohol, and 3 g of citric acid were added in sequence, and the mixture was stirred at room temperature for 45 min to obtain a composite sol; 1 g of the colloidal gold product was placed in 10 g of the composite sol, and ultrasonically stirred at room temperature for 12 min. The gold product was taken out, and washed with anhydrous ethanol and deionized water in sequence, and vacuum-dried to obtain a pretreated gold product; S3. Weigh 1g of pretreated gold product, add 2.3g of high-purity silver particles, place in 4g of lead foil, wrap, and place in an ash-blowing furnace. Oxidize and ash-blow for 20 minutes, then air-cool. After slicing and annealing, roll into a sheet approximately 0.18mm thick. After annealing, roll into a cylindrical shape and place in a gold-separating basket. Place in 93°C nitric acid (1+1) to separate the gold for 30 minutes, wash three times, then place in 110°C nitric acid (2+1) to separate the gold again for 30 minutes, wash three times, dry and cool, and weigh and calculate the gold content of the gold roll.

[0031] The effect of this embodiment is further explained below in conjunction with the test results.

[0032] The quality and content of the plastic-sealed gold products of the Examples and Comparative Examples were tested before plastic sealing (i.e., before the gold products were plastic-sealed) and after sol-treatment (i.e., after the plastic-sealed gold products were subjected to sol-treatment to remove the plastic film and colloid material). The sol-treatment time (including the time to remove the plastic film and surface colloid) was also calculated. The results are shown in Table 1.

[0033] Table 1 Quality and content of gold products As shown in Table 1, after the sol-gel stripping treatment of the present invention, the gold mass and content of the gold products were not significantly different from those before plastic packaging, fully meeting the testing requirements. In addition, compared with the prior art, the preparation method provided by the present invention can control the sol-gel treatment time to less than 1 hour, thereby shortening the sol-gel treatment time while ensuring that the gold mass and content of the gold products after sol-gel treatment are not significantly different from those before plastic packaging.

[0034] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for determining the quality and content of plastic-sealed gold products, characterized by: The following steps are involved: S1. Place the plastic-sealed gold product to be tested in DMF, heat it to above 150°C, heat it for 10-15 minutes, remove it, and tear off the plastic seal on the surface to obtain the colloidal gold product; S2, performing an oxidation ash blowing treatment on the colloidal gold product to remove the colloidal portion on the surface, thereby obtaining a treated gold product; S3. Weigh the mass of gold in the treated gold product and detect the gold content in the treated gold product using a fire assay method.

2. The method for determining the quality and content of a plastic-sealed gold product according to claim 1, wherein: In step S2, before the ash blowing treatment of the colloidal gold product, the process further includes: placing the colloidal gold product in a composite sol for pretreatment.

3. The method for determining the quality and content of a plastic-sealed gold product according to claim 2, wherein: The composite sol comprises the following components by mass: 60-80 parts of a mixed solvent, 4-6 parts of polyethylene glycol monolaurate, 2-4 parts of copper chloride, 1-1.5 parts of ascorbic acid, 1-2 parts of polyvinyl alcohol, and 2-4 parts of citric acid.

4. The method for determining the quality and content of a plastic-sealed gold product according to claim 3, wherein: The mixed solvent comprises the following components in parts by mass: 40-50 parts of DMF, 10-13 parts of acetone, 8-12 parts of gamma-butyrolactone, and 2-5 parts of toluene.

5. The method for determining the quality and content of a plastic-sealed gold product according to claim 4, wherein: The preparation method of the composite sol comprises: stirring and mixing DMF, acetone and gamma-butyrolactone uniformly, then sequentially adding toluene, polyethylene glycol monolaurate, copper chloride, ascorbic acid, polyvinyl alcohol and citric acid, and continuously stirring at room temperature for 30-60 minutes to obtain the composite sol.

6. A method for determining the quality and content of a plastic-sealed gold product according to claim 2, characterized in that: The pretreatment comprises: placing the colloidal gold product into a composite sol, ultrasonically stirring at room temperature for 10-15 minutes, taking out the gold product, washing it with anhydrous ethanol and deionized water in sequence, and vacuum drying it to obtain the pretreated gold product.

7. A method for determining the quality and content of a plastic-sealed gold product according to claim 6, characterized in that: The oxidation ash blowing comprises: placing the pretreated gold product into a muffle furnace, heating it to 275-325° C., maintaining it for 5-10 minutes, then heating it to 475-525° C., maintaining it for 5-10 minutes, and finally heating it to 550-650° C., maintaining it for 5-10 minutes.

8. The method for determining the quality and content of a plastic-sealed gold product according to claim 1, wherein: The fire assay method comprises: mixing the treated gold product with silver particles, then wrapping it with lead foil, and blowing oxidized ash for 15-25 minutes; smashing and annealing the gold product, and then rolling the gold product into thin slices with a thickness of 0.15-0.20 mm, and performing gold separation on the thin slices.

9. A method for determining the quality and content of a plastic-sealed gold product according to claim 8, characterized in that: The mass ratio of the gold product, silver particles and lead foil after the treatment is 1:2.1-2.5:4, and the temperature of the oxidation ash blowing is 900-950°C.

10. A method for determining the quality and content of a plastic-sealed gold product according to claim 8, characterized in that: The gold separation treatment includes: placing the thin slice in a nitric acid solution, heating it to 90-95° C., separating the gold for 25-35 minutes, washing and drying; placing the thin slice in a nitric acid solution, heating it to 100-120° C., separating the gold for 25-35 minutes, washing and drying, weighing and calculating to obtain the gold content of the plastic-sealed gold product.

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