Potentiometric titration detection method for silver element in antibacterial medical titanium-based silver alloy

Abstract

The invention discloses a potentiometric titration detection method for a silver element in an antibacterial medical titanium-based silver alloy, which comprises the following steps: dissolving a titanium-based silver alloy sample by hydrofluoric acid and nitric acid, adding hydrochloric acid to convert silver ions into silver chloride precipitates, adding a saturated boric acid solution to complex fluorine ions in the solution, and carrying out tilting filtration on supernatant by using medium-speed filter paper to obtain the silver element in the antibacterial medical titanium-based silver alloy. After washing for multiple times, filtering and collecting precipitates, dissolving the precipitates by dropwise adding ammonia water for multiple times, titrating with a potassium iodide standard titration solution by taking a silver-potassium iodide silver electrode as an indicator electrode and a saturated calomel electrode as a reference electrode in an ammoniacal medium, and indicating an end point by adopting a potentiometric method. According to the method, the to-be-detected element silver is separated by adopting a dissolution-precipitation-separation method, the saturated boric acid is added to avoid corrosion of fluorine ions in the solution to glassware and electrodes, and the method is reliable, high in precision and accuracy and suitable for accurate detection of the silver element in the common antibacterial medical titanium-based silver alloy in the field of biological medicine.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical element detection, and in particular relates to a potentiometric titration detection method for silver elements in an antibacterial medical titanium-based silver alloy. Background Art

[0002] Commercially pure titanium and titanium alloys have been one of the most commonly used materials in biomedical applications due to their excellent mechanical friction properties, corrosion resistance, biocompatibility, and light weight. By giving titanium alloys certain antibacterial properties to prevent the invasion and adhesion of free bacteria to avoid infection, adding antibacterial metal silver to make titanium alloys have antibacterial properties is currently a hot topic in the research of medical titanium alloys. Studies have shown that both Ti2Ag particles and silver ions have sterilization capabilities, but the former is more effective. When the silver content is controlled at 1% to 15%, it can prevent silver from causing serious effects on bone cell activity while producing a significant killing effect on Streptococcus mutans and inhibiting the formation of bacterial biofilms.

[0003] At present, the detection methods of chemical composition in titanium and titanium alloys include national standard GB / T 4698 series "Chemical Analysis Methods for Sponge Titanium, Titanium and Titanium Alloys (28 parts in total)"; industry standard YS / T 1262-2018 "Chemical Analysis Methods for Sponge Titanium, Titanium and Titanium Alloys - Determination of Multi-element Content - Inductively Coupled Plasma Atomic Emission Spectrometer", YS / T 892-2013 "Chemical Analysis Methods for High Purity Titanium - Determination of Trace Impurity Elements - Inductively Coupled Plasma Mass Spectrometry"; HB7716 series standard "Spectral Analysis Methods for Chemical Composition of Titanium Alloys"; foreign analysis standards ASTM E2371-21a "Standard Test Methods for Analysis of Titanium and Titanium Alloys by Direct Current Plasma and Inductively Coupled Plasma Emission Spectrometry (Based on Performance Test)", ASTM E2994-21 "Standard Test Methods for Analysis of Titanium and Titanium Alloys by Spark Atomic Emission Spectrometry and Glow Discharge Atomic Emission Spectrometry (Performance-Based Method)", etc. However, the above titanium and titanium alloy detection method specifications do not include silver.

[0004] Titanium alloy is an important structural metal and is widely used in many fields such as aerospace, shipbuilding, transportation, weapons, medical treatment, daily necessities, etc. Titanium does not react with nitric acid, dilute sulfuric acid and alkali, but is soluble in concentrated sulfuric acid, hydrofluoric acid and aqua regia. The most common method to dissolve titanium and titanium alloys is to use dilute hydrofluoric acid aqueous solution to react with titanium to generate complex ions and hydrogen.

[0005] Methods for detecting silver elements in metal materials include flame atomic absorption spectrometry, X-ray fluorescence spectrometry, inductively coupled plasma atomic emission spectrometry, titration, etc. The first three methods are suitable for the detection of trace silver components. When the silver component content is high, potentiometric titration is often used for detection. This method is based on the use of a sudden jump in the potential of the indicator electrode to indicate the titration end point. The silver electrode is used as the indicator electrode, and its potential changes with the change of the Ag+ concentration in the solution. During the titration process, as the titrant is continuously added, the potential E of the indicator electrode continues to change, and a sudden jump occurs at the titration end point.

[0006] The current research difficulty of the potentiometric titration detection method for silver element in titanium-based silver alloy is how to completely dissolve the sample, separate the titanium matrix from the silver element, and finally obtain an analytical solution containing only silver ions that is suitable for titration conditions. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a potentiometric titration detection method for silver in antibacterial medical titanium-based silver alloy in view of the deficiencies of the above-mentioned prior art. The method uses a dissolution-precipitation-separation method to separate the matrix element titanium and the element silver to be detected in the titanium-silver alloy, and adds saturated boric acid to prevent the corrosion of fluoride ions in the solution to glassware and electrodes, then uses ammonia water to dissolve the precipitate, uses potassium iodide as a titration solution, and uses a potentiometric titration method to detect the silver content. The determination method is reliable, with high precision and accuracy, filling the gap that there is no detection basis for silver in titanium-based alloys at present.

[0008] In order to solve the above technical problems, the technical scheme adopted by the present invention is: a potentiometric titration detection method for silver element in antibacterial medical titanium-based silver alloy, characterized in that the method adopts hydrofluoric acid and nitric acid to dissolve the titanium-based silver alloy sample, then adds hydrochloric acid to convert silver ions into silver chloride precipitates, then adds saturated boric acid solution to complex fluoride ions in the solution, and uses medium-speed filter paper to decant the upper clear liquid, and after multiple washings, filters and collects the precipitate, dissolves the precipitate by dripping ammonia water in batches, and in an ammonia medium, uses a silver-potassium iodide silver electrode as an indicator electrode, a saturated calomel electrode as a reference electrode, and uses a potassium iodide standard titration solution for titration, and adopts a potentiometric method to indicate the end point.

[0009] The above-mentioned potentiometric titration detection method for silver element in an antibacterial medical titanium-based silver alloy is characterized in that the method comprises the following steps:

[0010] Step 1: Sample preparation: Cut the titanium-based silver alloy sample into pieces no larger than 5 mm, and then weigh the pieces as the sample to an accuracy of 0.0001 g;

[0011] Step 2, reagent or material preparation: prepare hydrofluoric acid, nitric acid, hydrochloric acid, saturated boric acid solution, ammonia water, potassium iodide standard titration solution, and silver standard solution;

[0012] Step 3: Preparation of analytical solution:

[0013] Step 301, placing the sample weighed in step 1 in a 150mL polytetrafluoroethylene beaker and adding water, adding 2mL of hydrofluoric acid in portions and heating at low temperature to dissolve the sample, after the sample is completely dissolved, adding 1mL of nitric acid dropwise and continuing to heat until the solution is clear, removing, cooling to room temperature, blowing off water, adding 5mL of hydrochloric acid, continuing to heat, removing, cooling to room temperature in the dark, and obtaining a sample solution; the hydrochloric acid is (1+4) hydrochloric acid, which is prepared by mixing 1 volume of concentrated hydrochloric acid with a mass concentration of 37% with 4 volumes of water;

[0014] Step 302, add 40 mL of saturated boric acid solution to the sample solution obtained in step 301, gently shake the beaker, and place it away from light;

[0015] Step 303, filtering the sample solution after being placed in the dark in step 302 using medium-speed filter paper, decanting the supernatant, first washing the precipitate in the polytetrafluoroethylene beaker and the medium-speed filter paper with dilute hydrochloric acid, then washing the precipitate in the medium-speed filter paper with pure water, retaining the neutral filter paper and the precipitate, and discarding the filtrate; the dilute hydrochloric acid is (1+100) dilute hydrochloric acid, which is prepared by mixing 1 volume of concentrated hydrochloric acid with a mass concentration of 37% with 100 volumes of water;

[0016] Step 304, using 8 mL to 15 mL of ammonia water to dissolve the precipitate retained on the medium-speed filter paper in step 303 into the original tetrafluoroethylene beaker, washing the medium-speed filter paper with water five times, shaking the original tetrafluoroethylene beaker, and after the precipitate is completely dissolved, adding water along the wall of the beaker to 50 mL to obtain an analytical test solution;

[0017] Step 4, determination of analytical solution: using an automatic potentiometric titrator, using a silver-potassium iodide silver electrode as an indicator electrode, and a saturated calomel electrode as a reference electrode, using a potassium iodide standard titration solution to titrate the analytical solution obtained in step 304, and using the potential difference to indicate the titration endpoint;

[0018] The calibration process of the potassium iodide standard titration solution is as follows: three portions of the silver standard solution are transferred and placed in 150 mL polytetrafluoroethylene beakers respectively, and steamed on an electric furnace at low temperature until nearly dry, and then cooled and blown to a volume of 30 mL, and 5 mL of hydrochloric acid is added, and the solution is heated continuously until the supernatant is clear and separated from the precipitate, and the solution is removed, cooled to room temperature in a dark place, and then 40 mL of saturated boric acid solution is added, and the beaker is gently shaken and placed in a dark place for 15 minutes; the solution is filtered using medium-speed filter paper, and the upper clear liquid is decanted, and the precipitate in the polytetrafluoroethylene beaker and the medium-speed filter paper is washed with dilute hydrochloric acid for more than five times, and then the precipitate in the medium-speed filter paper is washed with pure water for seven to eight times, and the neutral filter paper and the precipitate are retained, and the filtrate is discarded; 8 mL to 1 The precipitate retained on the medium-speed filter paper is dissolved in the original tetrafluoroethylene beaker several times with 5mL of ammonia water, the medium-speed filter paper is rinsed with water five times, the original tetrafluoroethylene beaker is shaken, and after the precipitate is completely dissolved, water is added along the wall of the beaker to 50mL, and an automatic potentiometric titrator is used to titrate until the potential jump is maximum, which is the end point. The extreme value of the volume of the potassium iodide standard titration solution consumed by the parallel calibration of three silver standard solutions should not exceed 0.1mL, and the average value is taken; the hydrochloric acid is (1+4) hydrochloric acid, which is prepared by mixing 1 volume of concentrated hydrochloric acid with a mass concentration of 37% with 4 volumes of water; the dilute hydrochloric acid is (1+100) dilute hydrochloric acid, which is prepared by mixing 1 volume of concentrated hydrochloric acid with a mass concentration of 37% with 100 volumes of water;

[0019] The actual concentration of the potassium iodide standard titration solution is expressed as f, and f is calculated according to formula (1), and the calculation result is retained to five decimal places:

[0020]

[0021] In formula (1), f is the actual concentration of potassium iodide standard titration solution, that is, the mass of silver equivalent to unit volume of potassium iodide standard titration solution, in g / mL, V2 is the volume of each portion of silver standard solution transferred, in mL, c is the concentration of silver standard solution, in g / mL, V1 is the average volume of potassium iodide standard titration solution consumed in titration, in mL;

[0022] Step 5: Calculate the silver content in titanium-based silver alloy: Ag According to formula (2), we can calculate ω Ag , and the calculation result is retained to two decimal places:

[0023]

[0024] In formula (2), ω Ag is the mass content of silver element in the sample, in %, V3 is the volume of potassium iodide standard titration solution consumed by titrating the analysis test solution in step 4, in mL, and m is the mass of the sample in step 1, in g.

[0025] The above-mentioned potentiometric titration detection method for silver element in an antibacterial medical titanium-based silver alloy is characterized in that the boric acid in the hydrofluoric acid, nitric acid, hydrochloric acid, boric acid saturated solution, ammonia water, and potassium iodide in the potassium iodide standard titration solution in step 2 are all of high-grade purity, and the solution preparation uses laboratory first-grade water. The specific preparation process is:

[0026] Boric acid saturated solution: Take 50g of boric acid and place it in a 500mL beaker, add 400mL of water, heat and stir thoroughly to dissolve it, remove it, cool it to room temperature, and the supernatant obtained is the boric acid saturated solution;

[0027] Potassium iodide standard titration solution: weigh 4.85g potassium iodide and place it in a 500mL beaker, add 200mL water and stir thoroughly to dissolve it, transfer to a 1000mL volumetric flask, dilute to the scale with water, mix well, and obtain a 0.03mol / L potassium iodide standard titration solution;

[0028] Silver standard solution: Weigh 2.000g of metallic silver with a mass fraction of not less than 99.99%, weigh to an accuracy of 0.01mg, place in a 150mL beaker, add 20mL of nitric acid, cover with a watch glass, heat until completely dissolved, continue heating for 10min, remove nitrogen oxides, remove, cool to room temperature, transfer to a 1000mL brown volumetric flask with water, dilute to the scale with water, mix well, and obtain a silver standard solution. This silver standard solution contains 2.00mg of silver per 1mL. Store away from light.

[0029] The above-mentioned potentiometric titration detection method for silver element in an antibacterial medical titanium-based silver alloy is characterized in that water is blown to a volume of 30 mL in step 301. The present invention increases the solubility of silver fluoride by blowing water to increase the amount of solvent, so that silver ions and fluoride ions can be easily dissociated in water, and silver chloride can be stably combined after the introduction of chloride ions.

[0030] The above-mentioned potentiometric titration detection method for silver element in an antibacterial medical titanium-based silver alloy is characterized in that, after adding hydrochloric acid in step 301, heating is continued until the supernatant is clear and separated from the precipitate. The present invention controls the degree of heating to fully remove nitrogen oxides and ensure that all silver ions in the sample solution exist in the form of silver chloride. At the same time, it should be kept away from light during storage to prevent the decomposition of the precipitate.

[0031] The above-mentioned potentiometric titration detection method for silver element in antibacterial medical titanium-based silver alloy is characterized in that in step 302, after adding the saturated boric acid solution, it is placed away from light for 15 minutes to fully complex with fluoride ions in the sample solution to prevent fluoride ions from corroding glassware and glass electrodes used subsequently.

[0032] The above-mentioned potentiometric titration detection method for silver element in an antibacterial medical titanium-based silver alloy is characterized in that in step 303, dilute hydrochloric acid is used to wash the precipitate in the polytetrafluoroethylene beaker and the medium-speed filter paper for more than five times, and then the precipitate in the medium-speed filter paper is washed with pure water for seven to eight times. By washing the precipitate with dilute hydrochloric acid for more than five times, it is ensured that the silver ions in the sample solution are completely converted into silver chloride, and by washing the precipitate with pure water for seven to eight times, the acid residue in the precipitate is removed, and the next step of dissolving the precipitate is better performed.

[0033] The above-mentioned potentiometric titration detection method for silver element in antibacterial medical titanium-based silver alloy is characterized in that ammonia water is used to dissolve the precipitate multiple times in step 304. The present invention utilizes the solubility of ammonia water in silver chloride precipitate to convert all silver elements into silver ions in the test solution again, obtain an analysis test solution, and perform the next step of analysis.

[0034] The above-mentioned potentiometric titration detection method for silver element in antibacterial medical titanium-based silver alloy is characterized in that the extreme difference of the volume of the three silver standard solutions in step 4 does not exceed 0.1 mL, and the calibration process of the potassium iodide standard titration solution using the silver standard solution is completely consistent with the process of titrating the analytical test solution using the potassium iodide standard titration solution.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] 1. The present invention adopts a dissolution-precipitation-separation method to separate the matrix element titanium and the test element silver in the titanium-silver alloy, and adds saturated boric acid to prevent the corrosion of fluoride ions in the solution to glassware and electrodes, then uses ammonia water to dissolve the precipitate, uses potassium iodide as a titration solution, and uses a potentiometric titration method to detect the silver content. The determination method is reliable, with high precision and accuracy, filling the gap that there is no detection basis for the silver element in the titanium-based alloy at present.

[0037] 2. The present invention ingeniously utilizes the complexing property of silver chloride to separate silver ions from matrix elements and coexisting elements, and adds a saturated boric acid solution before filtering to neutralize the hydrofluoric acid introduced when dissolving the sample, thereby preventing the fluoride ions from corroding the glassware and glass electrodes used subsequently.

[0038] 3. The present invention utilizes the solubility of ammonia water to silver chloride to convert the silver element into silver ions in the test solution again, thereby using a silver-potassium iodide silver electrode as an indicator electrode, a saturated calomel electrode as a reference electrode, and a potassium iodide standard titration solution for titration. The potentiometric method automatically indicates the end point, thereby achieving accurate determination of the silver element.

[0039] 4. The present invention innovatively proposes a potentiometric titration method for detecting silver in antibacterial medical titanium-based silver alloys. Currently, no detection method specification or literature has reported this method. The method has high precision and accuracy, and the silver content can be determined in the range of 1% to 20%. This method is particularly suitable for the accurate detection of silver in antibacterial medical titanium-based silver alloys commonly used in the biomedical field.

[0040] The technical solution of the present invention is further described in detail below through embodiments. DETAILED DESCRIPTION

[0041] The titanium-based silver alloy sample in Example 1 of the present invention is a Ti10Ag sample produced by Western Titanium Co., Ltd. and is tested using a Metrohm 905 Titrando automatic potentiometric titrator with a potentiometer accuracy of 1 mV, a liquid addition rate of 5 mL / min, a stirring rate of 5, a volume of 3 mL added after reaching the equivalence point, a stop at equivalence point 1, an equivalence point recognition standard of 5, and a maximum equivalence point recognition.

[0042] Example 1

[0043] In this embodiment, hydrofluoric acid and nitric acid are used to dissolve the titanium-based silver alloy sample, and then hydrochloric acid is added to convert silver ions into silver chloride precipitates, and then a saturated boric acid solution is added to complex the fluoride ions in the solution, and the supernatant is decanted using medium-speed filter paper, and the precipitate is collected by filtering after multiple washings, and the precipitate is dissolved by dripping ammonia water in portions, and in an ammonia medium, a silver-potassium iodide silver electrode is used as an indicator electrode, and a saturated calomel electrode is used as a reference electrode, and a potassium iodide standard titration solution is used for titration, and the end point is indicated by a potentiometric method;

[0044] The method comprises the following steps:

[0045] Step 1: Sample preparation: Cut the titanium-based silver alloy sample into pieces no larger than 5 mm, and then weigh 0.2502 g of the pieces as the sample;

[0046] Step 2, reagent or material preparation: prepare hydrofluoric acid, nitric acid, hydrochloric acid, saturated boric acid solution, ammonia water, potassium iodide standard titration solution, and silver standard solution; the boric acid in the hydrofluoric acid, nitric acid, hydrochloric acid, saturated boric acid solution, ammonia water, and potassium iodide in the standard titration solution of potassium iodide are all of high-grade purity, and the solutions are prepared using laboratory first-grade water that complies with GB / T 6682-2008 "Specifications and Test Methods for Water Use in Analytical Laboratories". The specific preparation process is as follows:

[0047] Boric acid saturated solution: Take 50g of boric acid and place it in a 500mL beaker, add 400mL of water, heat and stir thoroughly to dissolve it, remove it, cool it to room temperature, and the supernatant obtained is the boric acid saturated solution;

[0048] Potassium iodide standard titration solution: weigh 4.85g potassium iodide and place it in a 500mL beaker, add 200mL water and stir thoroughly to dissolve it, transfer to a 1000mL volumetric flask, dilute to the scale with water, mix well, and obtain a 0.03mol / L potassium iodide standard titration solution;

[0049] Silver standard solution: weigh 2.000g of metallic silver with a mass fraction of not less than 99.99%, weigh to the nearest 0.01mg, place in a 150mL beaker, add 20mL of nitric acid, cover with a watch glass, heat until completely dissolved, continue heating for 10min, remove nitrogen oxides, remove, cool to room temperature, transfer to a 1000mL brown volumetric flask with water, dilute to scale with water, mix well, and obtain a silver standard solution. This silver standard solution contains 2.00mg of silver per 1mL, and is stored away from light;

[0050] Step 3: Preparation of analytical solution:

[0051] Step 301, placing the sample weighed in step 1 in a 150mL polytetrafluoroethylene beaker and adding 10mL of water, adding 2mL of hydrofluoric acid in portions and heating at low temperature to dissolve the sample, after the sample is completely dissolved, adding 1mL of nitric acid dropwise and continuing to heat until the solution is clear, removing, cooling to room temperature, blowing water to a volume of 30mL, adding 5mL of hydrochloric acid, continuing to heat until the supernatant is clear and separated from the precipitate, removing, cooling to room temperature in the dark, and obtaining a sample solution; the hydrochloric acid is (1+4) hydrochloric acid, which is prepared by mixing 1 volume of concentrated hydrochloric acid with a mass concentration of 37% with 4 volumes of water;

[0052] Step 302, add 40 mL of saturated boric acid solution to the sample solution obtained in step 301, gently shake the beaker, and place it away from light for 15 minutes;

[0053] Step 303, filtering the sample solution after being placed in the dark in step 302 using medium-speed filter paper, decanting the upper clear liquid, first washing the precipitate in the polytetrafluoroethylene beaker and the medium-speed filter paper with dilute hydrochloric acid for more than five times, then washing the precipitate in the medium-speed filter paper with pure water for seven to eight times, retaining the neutral filter paper and the precipitate, and discarding the filtrate; the dilute hydrochloric acid is (1+100) dilute hydrochloric acid, which is prepared by mixing 1 volume of concentrated hydrochloric acid with a mass concentration of 37% with 100 volumes of water;

[0054] Step 304, using 12 mL of ammonia water to dissolve the precipitate retained on the medium-speed filter paper in step 303 into the original tetrafluoroethylene beaker five times, washing the medium-speed filter paper with water five times, shaking the original tetrafluoroethylene beaker, and after the precipitate is completely dissolved, adding water along the wall of the beaker to 50 mL to obtain an analytical test solution;

[0055] Step 4, determination of analytical solution: using an automatic potentiometric titrator, using a silver-potassium iodide silver electrode as an indicator electrode, and a saturated calomel electrode as a reference electrode, using a potassium iodide standard titration solution to titrate the analytical solution obtained in step 304, and using the potential difference to indicate the titration endpoint;

[0056] The calibration process of the potassium iodide standard titration solution is as follows: accurately transfer three portions of 20.00 mL of the silver standard solution, the extreme difference of the volume of the three portions of the silver standard solution does not exceed 0.1 mL, place them in 150 mL polytetrafluoroethylene beakers respectively, steam them on an electric furnace at low temperature until they are nearly dry, blow water to a volume of 30 mL after cooling, add 5 mL of hydrochloric acid, continue to heat until the supernatant is clear and separated from the precipitate, remove it, cool it to room temperature in a dark place, then add 40 mL of saturated boric acid solution, shake the beaker gently, and place it in a dark place for 15 minutes; filter it with medium-speed filter paper, decant the upper clear liquid, first wash the polytetrafluoroethylene beaker and the precipitate in the medium-speed filter paper with dilute hydrochloric acid for more than five times, then wash the precipitate in the medium-speed filter paper with pure water for seven to eight times, retain the neutral filter paper and the precipitate, and discard the filtrate; use 1 The precipitate retained on the medium-speed filter paper is dissolved in the original tetrafluoroethylene beaker several times with 2mL of ammonia water, the medium-speed filter paper is rinsed with water five times, the original tetrafluoroethylene beaker is shaken, and after the precipitate is completely dissolved, water is added along the wall of the beaker to 50mL, and an automatic potentiometric titrator is used to titrate until the potential jump is maximum, which is the end point. The volumes of potassium iodide standard titration solutions consumed in parallel calibration of three silver standard solutions are 18.6254mL, 18.5779mL, and 18.7143mL, respectively, and the average value is 18.6392mL; the hydrochloric acid is (1+4) hydrochloric acid, which is prepared by mixing 1 volume of concentrated hydrochloric acid with a mass concentration of 37% with 4 volumes of water; the dilute hydrochloric acid is (1+100) dilute hydrochloric acid, which is prepared by mixing 1 volume of concentrated hydrochloric acid with a mass concentration of 37% with 100 volumes of water;

[0057] The actual concentration of the potassium iodide standard titration solution is expressed as f, and f is calculated according to formula (1), and the calculation result is retained to five decimal places:

[0058]

[0059] In formula (1), f is the actual concentration of potassium iodide standard titration solution, that is, the mass of silver equivalent to unit volume of potassium iodide standard titration solution, in g / mL, V2 is the volume of each portion of silver standard solution transferred, in mL, c is the concentration of silver standard solution, in g / mL, V1 is the average volume of potassium iodide standard titration solution consumed in titration, in mL;

[0060] After calculation, the actual concentration of the potassium iodide standard titration solution in this embodiment is 0.002146 g / mL;

[0061] Step 5: Calculate the silver content in titanium-based silver alloy: Ag According to formula (2), we can calculate ω Ag , and the calculation result is retained to two decimal places:

[0062]

[0063] In formula (2), ω Ag is the mass content of silver element in the sample, in %, V3 is the volume of potassium iodide standard titration solution consumed by titrating the analysis solution in step 4, in mL, and m is the mass of the sample in step 1, in g;

[0064] According to calculation, the silver content in the titanium-based silver alloy in this embodiment is 10.04%.

[0065] The precision and accuracy of the determination method of this embodiment were tested:

[0066] (1) Precision: Under the determination conditions of this embodiment, precision tests were performed on titanium-based silver alloy samples with different silver contents. Since it is difficult to find multiple samples with different silver contents, the present invention adopts a method of adding a certain volume of silver standard solution to the weighed Ti2Ag sample to synthesize a simulated sample for the test. The simulated sample preparation scheme is shown in Table 1 below. The Ti10Ag sample and simulated sample 1 and simulated sample 2 were independently measured 7 times according to the method of this embodiment, and the RSD of the results was calculated. The precision test results are shown in Table 2.

[0067] Table 1

[0068] Sample name Preparation plan Ti10Ag sample / Simulation Sample 1 0.25g sample + 6.25mL silver standard solution (2.00mg / mL) Simulation Sample 2 0.25g sample + 12.50mL silver standard solution (2.00mg / mL)

[0069] Table 2

[0070]

[0071] (2) Accuracy: The accuracy of the determination method was investigated by calculating the spike recovery rate. The results are shown in Table 3.

[0072] Table 3

[0073] Sample name Before spike / % Added amount / % After spike / % Ag recovery rate / % Simulation Sample 1 10.03 5.00 14.95 98.4 Simulation Sample 2 10.03 10.00 19.99 99.6

[0074] From the results in Tables 2 and 3, it can be seen that the determination method of this embodiment has high precision and accuracy.

[0075] Similarly, the determination process of this embodiment is applicable to the determination of silver element in titanium-based silver alloys with a silver content of 1% to 20%.

[0076] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A potentiometric titration method for detecting silver in antibacterial medical titanium-based silver alloy, characterized in that: The method adopts hydrofluoric acid and nitric acid to dissolve the titanium-based silver alloy sample, then adds hydrochloric acid to convert silver ions into silver chloride precipitates, then adds saturated boric acid solution to complex fluoride ions in the solution, and uses medium-speed filter paper to decant the upper clear liquid, collects the precipitate by filtering after multiple washings, dissolves the precipitate by dripping ammonia water in batches, and uses a silver-potassium iodide silver electrode as an indicator electrode and a saturated calomel electrode as a reference electrode in an ammonia medium, and titrates with a potassium iodide standard titration solution, and uses a potentiometric method to indicate the end point.

2. The potentiometric titration detection method for silver element in an antibacterial medical titanium-based silver alloy according to claim 1, characterized in that: The method comprises the following steps: Step 1: Sample preparation: Cut the titanium-based silver alloy sample into pieces no larger than 5 mm, and then weigh the pieces as the sample to an accuracy of 0.0001 g; Step 2, reagent or material preparation: prepare hydrofluoric acid, nitric acid, hydrochloric acid, saturated boric acid solution, ammonia water, potassium iodide standard titration solution, and silver standard solution; Step 3: Preparation of analytical solution: Step 301, placing the sample weighed in step 1 in a 150mL polytetrafluoroethylene beaker and adding water, adding 2mL of hydrofluoric acid in portions and heating at low temperature to dissolve the sample, after the sample is completely dissolved, adding 1mL of nitric acid dropwise and continuing to heat until the solution is clear, removing, cooling to room temperature, blowing off water, adding 5mL of hydrochloric acid, continuing to heat, removing, cooling to room temperature in the dark, and obtaining a sample solution; the hydrochloric acid is (1+4) hydrochloric acid, which is prepared by mixing 1 volume of concentrated hydrochloric acid with a mass concentration of 37% with 4 volumes of water; Step 302, add 40 mL of saturated boric acid solution to the sample solution obtained in step 301, gently shake the beaker, and place it away from light; Step 303, filtering the sample solution after being placed in the dark in step 302 using medium-speed filter paper, decanting the supernatant, first washing the precipitate in the polytetrafluoroethylene beaker and the medium-speed filter paper with dilute hydrochloric acid, then washing the precipitate in the medium-speed filter paper with pure water, retaining the neutral filter paper and the precipitate, and discarding the filtrate; the dilute hydrochloric acid is (1+100) dilute hydrochloric acid, which is prepared by mixing 1 volume of concentrated hydrochloric acid with a mass concentration of 37% with 100 volumes of water; Step 304, using 8 mL to 15 mL of ammonia water to dissolve the precipitate retained on the medium-speed filter paper in step 303 into the original tetrafluoroethylene beaker, washing the medium-speed filter paper with water five times, shaking the original tetrafluoroethylene beaker, and after the precipitate is completely dissolved, adding water along the wall of the beaker to 50 mL to obtain an analytical test solution; Step 4, determination of analytical solution: using an automatic potentiometric titrator, using a silver-potassium iodide silver electrode as an indicator electrode, and a saturated calomel electrode as a reference electrode, using a potassium iodide standard titration solution to titrate the analytical solution obtained in step 304, and using the potential difference to indicate the titration endpoint; The calibration process of the potassium iodide standard titration solution is as follows: three portions of the silver standard solution are transferred and placed in 150 mL polytetrafluoroethylene beakers respectively, and steamed on an electric furnace at low temperature until nearly dry, and then cooled and blown to a volume of 30 mL, and 5 mL of hydrochloric acid is added, and the solution is heated continuously until the supernatant is clear and separated from the precipitate, and the solution is removed, cooled to room temperature in a dark place, and then 40 mL of saturated boric acid solution is added, and the beaker is gently shaken and placed in a dark place for 15 minutes; the solution is filtered using medium-speed filter paper, and the upper clear liquid is decanted, and the precipitate in the polytetrafluoroethylene beaker and the medium-speed filter paper is washed with dilute hydrochloric acid for more than five times, and then the precipitate in the medium-speed filter paper is washed with pure water for seven to eight times, and the neutral filter paper and the precipitate are retained, and the filtrate is discarded; 8 mL to 1 The precipitate retained on the medium-speed filter paper is dissolved in the original tetrafluoroethylene beaker several times with 5mL of ammonia water, the medium-speed filter paper is rinsed with water five times, the original tetrafluoroethylene beaker is shaken, and after the precipitate is completely dissolved, water is added along the wall of the beaker to 50mL, and an automatic potentiometric titrator is used to titrate until the potential jump is maximum, which is the end point. The extreme value of the volume of the potassium iodide standard titration solution consumed by the parallel calibration of three silver standard solutions should not exceed 0.1mL, and the average value is taken; the hydrochloric acid is (1+4) hydrochloric acid, which is prepared by mixing 1 volume of concentrated hydrochloric acid with a mass concentration of 37% with 4 volumes of water; the dilute hydrochloric acid is (1+100) dilute hydrochloric acid, which is prepared by mixing 1 volume of concentrated hydrochloric acid with a mass concentration of 37% with 100 volumes of water; The actual concentration of the potassium iodide standard titration solution is expressed as f, and f is calculated according to formula (1), and the calculation result is retained to five decimal places: In formula (1), f is the actual concentration of potassium iodide standard titration solution, that is, the mass of silver equivalent to unit volume of potassium iodide standard titration solution, in g / mL, V2 is the volume of each portion of silver standard solution transferred, in mL, c is the concentration of silver standard solution, in g / mL, V1 is the average volume of potassium iodide standard titration solution consumed in titration, in mL; Step 5: Calculate the silver content in titanium-based silver alloy: Ag According to formula (2), we can calculate ω Ag , and the calculation result is retained to two decimal places: In formula (2), ω Ag is the mass content of silver element in the sample, in %, V3 is the volume of potassium iodide standard titration solution consumed by titrating the analysis test solution in step 4, in mL, and m is the mass of the sample in step 1, in g.

3. The potentiometric titration detection method for silver element in an antibacterial medical titanium-based silver alloy according to claim 1, characterized in that: The hydrofluoric acid, nitric acid, hydrochloric acid, boric acid in the saturated solution, ammonia water, and potassium iodide in the potassium iodide standard titration solution described in step 2 are all of high-grade purity, and the solutions are prepared using laboratory first-grade water. The specific preparation process is as follows: Boric acid saturated solution: Take 50g of boric acid and place it in a 500mL beaker, add 400mL of water, heat and stir thoroughly to dissolve it, remove it, cool it to room temperature, and the supernatant obtained is the boric acid saturated solution; Potassium iodide standard titration solution: weigh 4.85g potassium iodide and place it in a 500mL beaker, add 200mL water and stir thoroughly to dissolve it, transfer to a 1000mL volumetric flask, dilute to the scale with water, mix well, and obtain a 0.03mol / L potassium iodide standard titration solution; Silver standard solution: Weigh 2.000g of metallic silver with a mass fraction of not less than 99.99%, weigh to an accuracy of 0.01mg, place in a 150mL beaker, add 20mL of nitric acid, cover with a watch glass, heat until completely dissolved, continue heating for 10min, remove nitrogen oxides, remove, cool to room temperature, transfer to a 1000mL brown volumetric flask with water, dilute to the scale with water, mix well, and obtain a silver standard solution. This silver standard solution contains 2.00mg of silver per 1mL. Store away from light.

4. The potentiometric titration detection method for silver element in an antibacterial medical titanium-based silver alloy according to claim 1, characterized in that: In step 301, water is blown off to a volume of 30 mL.

5. The potentiometric titration detection method for silver element in an antibacterial medical titanium-based silver alloy according to claim 1, characterized in that: After adding hydrochloric acid in step 301, heating is continued until the supernatant is clear and separated from the precipitate.

6. The potentiometric titration detection method for silver element in an antibacterial medical titanium-based silver alloy according to claim 1, characterized in that: In step 302, after adding the saturated boric acid solution, the mixture is placed away from light for 15 minutes.

7. The potentiometric titration detection method for silver element in an antibacterial medical titanium-based silver alloy according to claim 1, characterized in that: In step 303, the polytetrafluoroethylene beaker and the precipitate in the medium-speed filter paper are washed with dilute hydrochloric acid for more than five times, and then the precipitate in the medium-speed filter paper is washed with pure water for seven to eight times.

8. The potentiometric titration detection method for silver element in an antibacterial medical titanium-based silver alloy according to claim 1, characterized in that: In step 304, ammonia water is used to dissolve the precipitate multiple times.

9. The potentiometric titration detection method for silver element in an antibacterial medical titanium-based silver alloy according to claim 1, characterized in that: The extreme difference of the volumes of the three silver standard solutions in step 4 does not exceed 0.1 mL, and the calibration process of the potassium iodide standard titration solution using the silver standard solution is completely consistent with the process of titrating the analytical test solution using the potassium iodide standard titration solution.

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