Titration-based analytical method for measuring Au in Au-sulfite treated solution

Abstract

The disclosed subject relates to techniques for a titration-based analytical method for measuring the concentration of gold (Au) in an Au-treated solution. Exemplary methods may include the addition of complexing agents and / or pH adjusters to achieve sharp inflection points in the titration curve.

Description

[Technical Field]

[0001] The disclosed subject matter relates to analytical chemistry, and more specifically, to a titration-based analytical method for measuring Au in Au-treated solutions. [Background technology]

[0002] Various methods can be used to analyze gold and its concentration in a solution. One method has been applied to treatment solutions. Treatment solutions containing gold during the formation of soluble sulfite complexes can avoid the more dangerous gold cyanide complexes. Gold sulfite baths can provide improved ductility and uniform electrodeposition, good alloy deposition, and resistance to impurities.

[0003] To quantify the concentration of gold in solution, analytical techniques have been used, including atomic absorption spectroscopy (AAS), inductively coupled plasma (ICP) and polarography, as well as XRF and spectroscopy after reaction with selective reagents. Unfortunately, each of these methods can suffer from drawbacks such as the use of open flames, complex measuring equipment, and / or toxic reagents. These methods may also have the disadvantage of being difficult to automate and can produce inaccurate results. Furthermore, the use of toxic reagents may make these methods unsuitable for use in the cleanroom environment of semiconductor manufacturing plants. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] U.S. Patent Application Publication No. 2019 / 0345626 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] As a result, there is a need for a simple and reliable method for analyzing the concentration of gold in gold-sulfite electroplating solutions that can be easily automated and does not require the use of toxic reagents or complex measuring equipment. [Means for solving the problem]

[0006] To address the issues of inaccuracy and toxicity in measurement, the disclosed subject provides a simple and reliable analytical method for the quantitative measurement of gold (Au) concentration in an Au-sulfite electrodeposition solution.

[0007] Disclosed is a titration-based analytical method for determining the concentration of gold (Au) in an Au-sulfite treatment solution. An exemplary method includes adding a complexing agent of a predetermined concentration to the treatment solution, adding an Au-sulfite solution to the treatment solution, adding a metal salt of a predetermined concentration to the treatment solution, and determining the concentration of Au by measuring the endpoint of a back titration. The complexing agent reacts with gold in the first reaction, and the metal salt reacts with the remaining complexing agent in the second reaction.

[0008] In one embodiment, the first product of the first reaction has a greater stability constant than Au-sulfite.

[0009] In one embodiment, the second product of the second reaction has a smaller stability constant than the first product of the first reaction.

[0010] In one embodiment, the first reaction generates a first precipitate product, and the second reaction generates a second precipitate product.

[0011] In one embodiment, the processing solution is an electrodeposition solution.

[0012] In one embodiment, the treatment solution contains a plating metal selected from nickel, cobalt, iron, and combinations thereof.

[0013] In one embodiment, the complexing agent is selected from thiourea, EDTA, thiosulfate, nitrilotriacetic acid, iminodiacetic acid, polyaspartic acid, S,S-ethylenediamine-N,N-diacetic acid, methylglycine diacetic acid, L-glutamic acid, N,N-diacetic acid, their salts, and combinations thereof.

[0014] In one embodiment, the method further includes adding a pH adjusting reagent to the treatment solution.

[0015] In one embodiment, the method further includes adding a pH adjusting reagent to the treatment solution before adding the Au-sulfite solution.

[0016] In one embodiment, the pH adjusting reagent lowers the pH value of the treatment solution.

[0017] In one embodiment, the pH adjusting reagent is selected from nitric acid, hydrochloric acid, sulfuric acid, and combinations thereof.

[0018] In one embodiment, the metal salt is selected from Ag, Cu, Fe, Al, and combinations thereof.

[0019] In one embodiment, the back titration includes quantifying the Au concentration based on the difference in the amount at the end point from the blank analysis and the end point of the sample analysis.

[0020] In one embodiment, the method further includes tracking the titration using an Ag-billet electrode.

[0021] Here, reference will be made in detail to various exemplary embodiments of the disclosed subject matter, which are shown in the accompanying drawings. The accompanying drawings, in which like reference numerals refer to identical or functionally similar elements throughout all the separate figures, serve to further illustrate the various embodiments and to explain all the principles and advantages in accordance with the disclosed subject matter.

Brief Description of the Drawings

[0022] [Figure 1]This figure provides images showing the expected and measured Au concentrations in embodiments of the disclosed subject matter. [Figure 2A] In embodiments of the disclosed subject matter, the figure provides titration results at different expected concentrations with respect to the potentiometer titration volume. [Figure 2B] In embodiments of the disclosed subject matter, the figure provides titration results at different expected concentrations with respect to gradient versus titration volume. [Figure 3] This figure provides the results of titration data points at expected concentrations in embodiments of the disclosed subject matter. [Figure 4A] In embodiments of the disclosed subject matter, this figure provides the results of titrations with three complexing agents in terms of potentiometer titration volume. [Figure 4B] In embodiments of the disclosed subject matter, this figure provides the results of titrations with three complexing agents in terms of gradient versus titration volume. [Modes for carrying out the invention]

[0023] Please understand that both the above summary and the following detailed explanation are illustrative and intended to provide further explanation of the disclosed subject matter.

[0024] The disclosed subject provides a method using titration to measure the amount of Au in a solution containing an Au sample. Such a method can be applied to Au solutions for different purposes, such as analyzing, monitoring, measuring, or quantifying the Au concentration in an Au solution.

[0025] To make it easier to understand, rather than as a limitation, the detailed description of the subject matter currently disclosed is divided into the following sub-sections. I. Definition II. Titration Method

[0026] I. Definition Terms used herein generally have their ordinary meanings in the art within the context of this disclosure and in the specific context in which each term is used. Some terms are discussed below or elsewhere in this specification to provide practitioners with further guidance by describing the compositions and methods of the disclosed subject matter and their preparation and use.

[0027] For the purposes of interpreting this specification, the following definitions shall apply, and whenever appropriate, a singular term shall also include a plural form, and vice versa.

[0028] As used herein, the terms “about” or “approximately” mean within an acceptable margin of error for a particular value quantified by those skilled in the art, and this will depend in part on how the value is measured or quantified, i.e., the limitations of the measuring system. For example, “about” may mean within three standard deviations or more, depending on the practice in the art. Alternatively, “about” may mean a range of up to 20%, up to 10%, up to 5%, and up to 1% of a given value. Alternatively, for example, for a biological system or biological process, the term “about” may mean within an order of magnitude, up to five times, and up to two times the magnitude of the value.

[0029] As used herein, the term "high level" refers to a concentration in the range of grams per liter (g / L) when used in the context of the concentration of metal ions in a solution.

[0030] As used herein, the term "low level" refers to a concentration in the range of parts per million (ppm) when used in relation to the concentration of metal ions in a solution.

[0031] As used herein, the term “trace” refers to concentrations below 1000 ppm. In some embodiments, the trace level refers to a concentration range from 0.1 ppm to 1000 ppm.

[0032] The ranges provided herein are understood to be abbreviated representations of all values ​​within a range. For example, the range from 1 to 50 is understood to include not only any number, combination of numbers, or subrange from the group consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50, but also all of the integers and their intermediate decimal values, such as 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, and 1.9. The ranges disclosed herein, for example, “between about X and about Y,” include not only the range limits about X and about Y but also X and Y, unless otherwise specified. For subranges, “nested subranges” extending from either endpoint of the range are particularly intended. For example, nested subranges of the exemplary range 1 to 50 may include 1 to 10, 1 to 20, 1 to 30, and 1 to 40 in one direction, or 50 to 40, 50 to 30, 50 to 20, and 50 to 10 in the other direction.

[0033] As used herein, the term “predetermined concentration” refers to a known, target, standard, or optimal concentration of a component in a solution.

[0034] As used herein, the terms “selective” or “selectively” refer to, for example, the specific monitoring, measurement, or quantification of the properties of a particular or specific component. For example, selective measurement of an ion refers to the measurement of one specific or predetermined target ion from among several ions present in a solution.

[0035] As used herein, the terms “accurate” or “precisely” refer to, for example, a measured or quantitative value that is relatively close to or near a current or true value, a standard or known measured or quantitative value. In some embodiments, the accuracy error of the measured or quantitative value is less than ±5%, with a standard deviation of less than 0.02 and / or a residual standard deviation (RSD) of less than 4%.

[0036] As used herein, the terms “about” or “approximately” mean within an acceptable margin of error for a particular value quantified by those skilled in the art, and that will depend in part on how the value is measured or quantified, i.e., the limitations of the measuring system. For example, “about” may mean a range of up to 20%, up to 10%, up to 5%, and / or up to 1% of a given value.

[0037] As used herein, the term “processing solution” refers to a chemical solution used to analyze the concentration of a substance in a solution by reacting the substance with a known amount of a standard solution. Processing solutions are used in several industries, including electroplating / electroless plating, metallurgy, chemical, pharmaceutical, and other industries, where the measurement, monitoring, and control of samples are required.

[0038] As used herein, the term “stability constant,” also known as the formation constant K, refers to the degree of strength of the interaction between two or more chemical species, such as a metal ion and a ligand. The term “stability constant” quantitatively describes the equilibrium constant of a complex formation reaction in solution, which refers to the stability of the resulting complex. The larger the stability constant, the more stable the complex becomes, and the greater / stronger the tendency of the reactants to form the complex.

[0039] As used herein, the term “complexing agent” refers to a substance that forms a complex with a metal ion, for example, to control the concentration of a metal ion in a solution for titration purposes. The use of complexing agents can play several important roles in titration chemistry. For example, the addition of a complexing agent may shift the equilibrium toward the formation of a metal-ligand complex, thereby facilitating the measurement of the concentration of the metal ion. Some complexing agents may include, but are not limited to, EDTA, cyanides, dithizones, thioureas, thiosulfates, and NTAs.

[0040] As used herein, the term “Ag-billet electrode” refers to a type of electrode used in electrochemistry to measure the concentration of a particular ion in a solution. It may include a silver rod partially immersed in the solution being analyzed. When a potential is applied to the Ag-billet electrode, silver ions are released into the solution and react with other ions in the solution to generate an electric current. By measuring the current and / or potential, the concentration of the ion being measured can be quantified.

[0041] As used herein, the term “back titration,” also known as reverse titration, refers to a type of titration method used to quantify or measure the amount of a substance present in a sample. It may be used when direct titration is impossible due to the characteristics of the sample or the nature of the reaction being investigated.

[0042] As used herein, the term “blank analysis” is also known as “blank titration” and refers to a controlled titration process performed when no sample (the substance being analyzed) is present, in order to correct for impurities or contaminants in the titrator or solvent used during titration. Blank analysis can be performed without adding a sample, using the same volumes of solvent and titrator as would be used in the actual titration. The endpoint of the blank analysis is determined using the same method as for the actual quantification (e.g., using an indicator or an instrument such as a potentiometer or pH meter). The amount of titrator used in the blank analysis (also known as a blank bend) is then subtracted from the amount of titrator used in the actual titration to quantify the amount of titrator needed to neutralize the sample in the sample and to correct for any impurities or contaminants that may have affected the titration. The use of blank analysis may be important to ensure that the titrator and solvent do not contain interfering substances that could affect the accuracy of the titration.

[0043] As used herein, the term “sample analysis” is also known as sample titration and refers to a controlled titration process performed in the presence of a sample (the substance being analyzed) to determine the endpoint of the titrant in a solution containing the sample, the controlled titration process being used to quantify the sample concentration by comparing it to the endpoint of the titrant in a solution during a blank titration.

[0044] As used herein, the term “titrate” refers to a standard solution containing a reagent of known concentration that chemically reacts with a “reactant” or “unknown species,” thereby quantifying the concentration of the standard solution in the sample solution. “Titration” is an analytical procedure involving repeated addition of a known amount of titrate solution to an analytical solution (including the sample solution), with simultaneous monitoring of the concentration of an indicator species involved in, or indirectly affected by, the reaction between the titrate and the reactant.

[0045] As used herein, the term “equivalence point” refers to the point in a titration where the reaction between the titrant and the reactant is complete, and corresponds to the stoichiometric equilibrium between the number of moles of the titrant and the number of moles of the reactant with respect to the formation of a compound or complex.

[0046] As used herein, the term “titration endpoint” refers to the relatively rapid change in the concentration of the indicator species when additional titrant is added to the analyte after the equivalence point has been reached. The concentration of the unknown species in the sample solution can be calculated from the amount of titrant solution added to the analyte at the equivalence point (approximately equal to the endpoint). “Back titration” involves the standard addition (to the analyte) of the back titrant that reacts with the unknown species. The excess back titrant is added to the analyte and then reacted with the titrant in the titration to return to the equivalence point.

[0047] As used herein, the term “titration curve” refers to a graph of the concentration of the titration indicator in the analyte, or a parameter proportional to this concentration, as a function of the amount of titrant solution added to the analyte. It may be more convenient to use a concentration parameter proportional to the concentration of the indicator, especially when the indicator is involved in a complexing reaction with competing complexing agents. The titration endpoint can be determined from curve features corresponding to rapid changes in the indicator concentration, such as a curve knee point or inflection point. Detection of the titration endpoint can be smoothed by differentiating the titration curve, thereby converting the inflection point into a peak. Titration data may be processed as a titration curve or graph; however, such data may be presented in tables and used directly, for example, by a computer, and the term “titration curve” includes presented data.

[0048] The disclosed subject matter method can be applied to various types of solutions, including electroplating solutions. In some embodiments, the treatment solution may contain Au-sulfite. Those skilled in the art will understand that there is a wide variety of Au-sulfites or forms of Au, and that the compounds thereof are suitable for use herein. In some embodiments, the treatment solution may contain Au-sulfite.

[0049] II. Titration Method The disclosed subject provides techniques for the analysis and measurement of Au in Au-sulfite treatment solutions, such as electrodeposition solutions. In some embodiments, the techniques of the disclosed subject can provide a safe and non-toxic method with accurate, rapid, and efficient measurement results for the analysis of Au concentration in treatment solutions containing Au-sulfite. In some embodiments, the methods of the disclosed subject can assist in the process control of Au in metal alloy plating baths.

[0050] Such methods utilize non-toxic reagents or much simpler titration methods using complex analytical instruments. Furthermore, such methods can be automated more quickly, at lower cost, and more easily in the cleanroom environments of manufacturing industries, such as the semiconductor industry.

[0051] The methods of the disclosed subject matter can be incorporated into existing methods as an extension of their applications, including for the quantification, monitoring, and / or analysis of Au(I) concentration in Au-sulfite electrodeposition solutions. Furthermore, such methods of the disclosed subject matter can be applied to novel chemical monitoring and / or measurement systems for the analysis of Au(I) concentration in Au-sulfite electrodeposition solutions.

[0052] In an exemplary method, a titration-based analytical method for measuring gold (Au) in an Au-sulfite treatment solution may be carried out as follows: A complexing agent of a predetermined concentration is added to the treatment solution. The Au-sulfite solution is added to the treatment solution, followed by the addition of a metal salt of a predetermined concentration. The concentration of Au is quantified by measuring the endpoint of the back titration. In such a method, the complexing agent reacts with the metal salt in the first reaction, and the metal salt reacts with the remaining complexing agent in the second reaction.

[0053] In the first reaction of the titration-based analytical method for the measurement of Au-Au-sulfite, the Au-sulfite compound decomposes after the addition of the complexing agent, which results in a greater stability constant (e.g., its K ≥ 10) in the treated solution. 23 In the much larger amount of Au-sulfites, K is about 10 10 This can be achieved by forming a new Au complex (Au(I)-X, where X is the ligand for the complexing agent) having the following properties. In a selective implementation, substantially all of the Au can be precipitated from the treatment solution as a precipitating agent.

[0054] After all Au(I) has been substantially removed from the treatment solution, a second complex may be formed via a second reaction between the excess / remaining complexing agent and the metal salt, and the second reaction results in a lower stability constant, for example, a stability constant of 10. 10 ≤K ≤ 10 23 This can be achieved by maintaining the second complex (MX, where M is a metal element and X is the ligand of the complexing agent). Thus, the second complex can be completely precipitated during the second reaction. The endpoint of the titration can be measured at the stopping point of the second reaction between the remaining complexing agent and the metal salt. In combination with back titration, the titration volume / concentration of the first reaction can be quantified based on the difference between the titration volume / concentration of the back titration and the titration volume / concentration of the second reaction.

[0055] A predetermined concentration of complexing agent X may be added to form a new Au complex. As embodied herein, the first reaction can be represented by the following chemical formula. [W]Au-sulfite+[S1]X- ->Au y1 -X x1 (1) y1 and x1 are the standard stoichiometric ratios of Au-sulfite and complexing agent X, respectively, and W and S1 are the respective amounts of the reactants in the first reaction.

[0056] Metal salt (Me + A metal element is added to the treatment solution as a titration of a predetermined concentration, and the metal salt (Me +) at least a portion of, and the precipitating agent (X remaining in the processing solution that did not react with Au(I) - ) can cause a reaction between substantially all of. As embodied herein, the second reaction can be represented by the following equation. [T2]Me + +[S2]X - ->Me y2 -X x2 (2) However, y2 and x2 are the respective stoichiometric ratios of the metal salt and the complexing agent X, and T2 and S2 are the respective amounts of the reactants in the second reaction. Notably, T2 can be readily determined by the end point of (2) via titration, and S2 can be calculated via the stoichiometric ratio.

[0057] The end point of the back titration can be measured using the same metal salt (Me + ) as the titrant. In the blank analysis, the reaction can be represented by the following equation. [T]Me + +[S]X - ->Me y2 -X x2 (3) However, T and S are the respective amounts of the reactants in the blank analysis without the sample solution. Notably, T can be readily determined by the end point of (3) via titration, and S is a predetermined value.

[0058] (2) The titration amount associated with the end point can be subtracted from the back titration amount associated with the end point of (3). To obtain the difference, the amount of the complexing agent that reacts with Au in (1) can be calculated, and as a result, based on the standard stoichiometric ratio between the reactants in the equation, the concentration of Au(I) in the Au-sulfite processing solution can be quantified.

[0059] As embodied herein, the Au concentration can be calculated as follows. S=T*y2 / x2 (4) S2=T2*y2 / x2 (5) S1=S-S2 (6) W=S1*x1 / y1 (7) concentration Au =W / V (8) Note: V is the specified amount of sample solution to be added to the processing solution.

[0060] In some embodiments, the back titration may include a blank analysis and a sample analysis. In some embodiments, the sample titration may include adding Au-sulfite as a sample solution to the treatment solution. The back titration may quantify the Au concentration based on the difference in volume between the endpoint from the blank titration and the endpoint from the sample titration. In some embodiments, the method may include tracking the titration by using an Ag-billet electrode.

[0061] In some embodiments, the Au-sulfite can react with a complexing agent, and the metal salt can react with the remaining complexing agent. The complexing agent in the treatment solution is typically commonly used as a metal chelating agent to bind the metal ions to be analyzed or measured. In some embodiments, both the first reaction between the Au-sulfite and the complexing agent and the second reaction between the metal salt and the remaining complexing agent can produce a precipitate for quantifying the titration endpoint.

[0062] To obtain the expected results from the titration described above, the selection of complexing agents and metal salts is sometimes desirable to generate precipitates in the solution. Generally, in solution, the larger the stability constant K of a compound, the greater the tendency for the compound to form (e.g., precipitate in the solution). Therefore, the disclosed subject provides a complexing agent that can enable the formation of a product (Au-X) having a K greater than that of Au-sulfite in the first reaction. Furthermore, in the second reaction, the formation of a product (Me-X) having a K greater than that of Au-sulfite but smaller than that of Au-X. This enables an analytical method based on titration of Au to an Au-sulfite treated solution.

[0063] In some embodiments, the complexing agent may be one or more of the following: thiourea, EDTA, thiosulfates, nitrilotriacetic acid, iminodisuccinic acid, polyaspartic acid, S,S-ethylenediamine-N,N'-disuccinic acid, methylglycinediacetic acid, L-glutamic acid, N,N-diacetic acid, salts thereof, and combinations thereof. Those skilled in the art will readily understand that the complexing agent may include standard derivatives of the above selection, such as chelating agents, chelating agents, or complexers.

[0064] In one embodiment, the treatment solution is an electrodeposition solution. In another embodiment, the treatment solution contains a plating metal selected from nickel, cobalt, iron, aluminum, and combinations thereof.

[0065] In one embodiment, the method further includes adding a pH adjusting reagent to the treatment solution. The Au-sulfite complex is alkaline pH (K, about 10 10 It is normally stable in solution. When the pH decreases, the complex can be effectively decomposed, and Au(I) can be converted to Au(III) and / or metallic Au. Such a method can decompose this complex, and by adding pH adjusting reagents, a new Au complex (K, ≥ 10) can be added to an acidic pH solution. 23 This pH adjustment reagent can form a sharp inflection point that is effective for accurate quantification during titration.

[0066] In one embodiment, the addition of a pH-adjusting reagent to the treatment solution is performed selectively, for example, before or after adding the Au-sulfite solution, because the pH adjustment does not substantially affect the formation of Au(I)-X or the reaction between Au and the complexing agent. In another embodiment, the pH-adjusting reagent lowers the pH value of the treatment solution.

[0067] In one embodiment, the pH adjusting reagent is selected from nitric acid, hydrochloric acid, and combinations thereof.

[0068] In one embodiment, the metal salt is selected from Ag, Cu, iron, Al, and combinations thereof.

[0069] In one embodiment, the treatment solution is an electrodeposition solution. In another embodiment, the method may include adding a pH adjusting reagent to the treatment solution.

[0070] In one embodiment, the pH adjusting reagent lowers the pH value of the treatment solution.

[0071] Furthermore, the methods provided by the disclosed subject matter are not limited to analyzing, controlling, and adjusting the Au concentration in Au-sulfite treatment solutions, but may be applied to several other expandable applications, including these.

[0072] On the other hand, those skilled in the art will understand that, provided the above-mentioned stability constant criteria are met, the methods of the disclosed subject matter may be applied to similar or equivalent sample solutions containing, but not limited to, Au-sulfides, Au-sulfates, and Au-thiosulfates. example

[0073] The disclosed subject matter will be better understood by reference to the following examples. The following examples are merely illustrative of the subject matter currently disclosed and should not be considered in any way as limiting the scope of the subject matter. The examples utilize the following reagents and analyzers.

[0074] Reagents: Nitric acid, thiourea, EDTA, thiosulfate, silver nitrate, and Au-sulfite electrodeposition solution.

[0075] Analyzers: ECI Qualilab EZ (for feasibility study), CI Qualifill Libra (for final development), and Ag-billet electrodes.

[0076] In the following embodiments, these relevant measurement terms relating to the accuracy for evaluating the method may be understood and characterized as follows. Accuracy (%) = [(Measured mean) - (Expected value) / (Expected value)] * 100 (9) Relative Standard Deviation (RSD) (%) = (Standard Deviation * 100) / (Measured Mean) (10) [Examples]

[0077] Au concentration determination The disclosed subject matter method provides for measuring the concentration of Au in a pH-adjusted Au-sulfite electrodeposition solution. The Au concentration in such a solution (M, g / l, expected target 0.50, low 0.25, high 1.00) can be quantified as follows:

[0078] Process I Blank Analysis:

[0079] 1) Deionized water is added to the reaction vessel (approximately 50-100 ml).

[0080] 2) Reagent 1 (complexing agent, thiourea) is added to the reaction vessel (approximately 2-5 ml depending on the sample concentration).

[0081] 3) The resulting mixture is titrated with a metal salt (silver nitrate).

[0082] 3) Reagent 2 (nitric acid) is added to the reaction vessel (approximately 5-10 ml depending on the sample concentration).

[0083] 4) The resulting mixture is titrated with a metal salt.

[0084] 5) The endpoint is automatically detected via potentiometric titration, selectively using either a "constant potential" setting or an "inflection point" algorithm.

[0085] 6) Blank bends are recorded in relation to the volume at the endpoint.

[0086] 7) The titration is automatically stopped based on the "stop point" algorithm.

[0087] 8) The reaction vessel and electrodes were cleaned using a washing solution (nitric acid) and deionized water.

[0088] Process II: Sample Analysis:

[0089] 1) Deionized water is added to the reaction vessel (approximately 50-100 ml).

[0090] 2) Reagent 1 (thiourea) is added to the reaction vessel (approximately 2-5 ml depending on the sample concentration).

[0091] 3) Reagent 2 (nitric acid) is added to the reaction vessel (approximately 5-10 ml depending on the sample concentration).

[0092] 4) The sample solution (Au-sulfite) is added to the reaction vessel (approximately 2-6 ml depending on the sample concentration).

[0093] 5) The resulting mixture is titrated with silver nitrate, a metal salt.

[0094] 6) The endpoint is automatically detected by either the "constant potential" setting or the "inflection point" algorithm, and the titration volume in the second reaction is recorded.

[0095] 7) The sample bend is calculated by subtracting the endpoint volume from the blank bend.

[0096] 8) The sample concentration is automatically calculated based on the bend, sample volume, and titration concentration.

[0097] 9) The titration is automatically stopped based on the "stop point" algorithm.

[0098] 10) The reaction vessel and electrodes were cleaned using a washing solution (nitric acid) and deionized water.

[0099] Table 1 summarizes the results of Au concentration measurements based on online prototype suitability data (ECI Qualifill Libra). The calculated results for Au concentration demonstrate the accuracy and precision of the methods in the currently disclosed examples. [Table 1]

[0100] In relation to Table 1, Figure 1 substantially illustrates the accuracy and precision of the exemplary method in this embodiment. The measurement method is substantially linear as shown in Figure 1, and it has been demonstrated that the values ​​measured in the embodiment increase in proportion to the expected change in the Au concentration in the solution.

[0101] Table 2 shows the potential curve and gradient curve for titration (using AgNO3 as the titrant) in this example. [Table 2]

[0102] In relation to Table 2, Figures 2A-2B show the potential and gradient curves of the titrations described herein. The endpoint for back titration is clearly visible as a good, sharp inflection point in the curve. Notably, in the gradient curve Figure 2B, the inflection point and peak point for the Au concentration in solution are shown with high accuracy and precision. The Au concentration in the Au-sulfite solution was calculated from the amounts of sample and complexing agent in the first reaction through the standard stoichiometric ratio in the first reaction. The amount of complexing agent in the first reaction was previously calculated by measuring the amount of titrant in the second reaction (associated with the endpoint of sample analysis) and the amount of titrant in the blank analysis. The calculation can be performed by referring to the formulas described above.

[0103] As shown in Figures 2A-2B, the endpoint of the second reaction is determined by a constant potential setting or inflection point algorithm associated with a fixed point or inflection point on the curve. Once the endpoint is determined, the measured value for Au concentration is calculated using the above formula based on predetermined and standard parameters. [Examples]

[0104] Long-term effectiveness verification for Au concentration measurement In this specification, to perform the measurement, an Au-sulfite solution with an expected Au concentration of 0.50 g / l is used in the measurement method. Following the same procedures and parameters as in the above examples, 92 data points were measured to examine the accuracy and precision of the measurement in the currently disclosed method.

[0105] Table 3 lists the data points related to the Au concentration in this embodiment. [Table 3]

[0106] Figure 3 shows the distribution of data points for Au concentration. All data points in this embodiment were distributed within a narrow range, approximately 0.499 to 0.550, with an accuracy of 4.35%, a standard deviation of 0.01 (StDev), and an RSD of 2.15%.d. [Examples]

[0107] Comparison of different complexing agents In this embodiment, different complexing agents were used in the method for determining the concentration of Au in solution. As described above, complexing agents with a large stability constant K have a greater tendency to form complexes with Au ions in solution, for example, to produce a stable product as a precipitate. In other words, with an ideal complexing agent, Au-sulfite (K, 10 10 This makes it possible to produce a complex compound (Au-X) with a substantially larger stability constant K than ).

[0108] On the other hand, the metal complex (Me-X) produced in the second reaction (sample titration) ideally has a higher K than Au-sulfite. Table 4 lists the K values ​​of different complexes Au-X and Ag-X associated with three different complexing agents in solution. Notably, although cyanide can act as a complexing agent to form a complex with Au in Au-sulfite solution, it can cause considerable toxicity problems in the process. Furthermore, cyanide does not effectively form a complex with Ag in the second reaction, according to the K values ​​on Table 4. [Table 4]

[0109] In this specification, measurements are performed using different complexing agents, thiourea, thiosulfate, and EDTA, using the same steps and parameters as in the examples described above. Table 5 lists the measurement results for data points regarding titration volume, potential, and gradient for three different complexing agents used in the Au concentration analysis method. [Table 5]

[0110] In relation to the data values ​​in Table 5, Figures 4A-4B show the potential curves and gradient curves during titration. In these titration curves, the titration volume (AgNO3 as the titrant) is on the horizontal axis. When EDTA is used as a complexing agent, the potential curve gradually becomes a flat line, and the equivalence point becomes virtually indistinguishable. Therefore, EDTA is not an effective complexing agent for measuring Au concentration.

[0111] In comparison with EDTA, thiourea or thiosulfate is more appropriately used as a complexing agent. As shown in Figures 4A-4B, the equivalence point of the titration curve is clearly discernible, and as shown in Figure 4B, the gradient curve exhibits a sharp inflection. Notably, when thiourea is used as a complexing agent for measuring Au concentration, the gradient curve is steep, as shown in Figure 4B, and is almost a vertical line around the equivalence point.

[0112] This is because the stability constant K of the product (Au-thiourea) in solution is up to 10 28 This is because it rapidly changes the K value in the solution. In solution, the sudden transition from the weaker compound to the stronger compound (Au-thiourea, which has a larger stability constant K) occurred around the equivalence point.

[0113] Various modifications and changes to the embodiments described will be apparent to those skilled in the art in terms of teaching in this specification. Therefore, the disclosures herein are intended to be illustrative rather than limiting the scope of the disclosed subject matter. Furthermore, the principles of the disclosed subject matter can be implemented in various configurations and are not intended to be limited in any way to the specific embodiments presented herein.

[0114] In addition to the various embodiments described and claimed, the disclosed subject matter further covers other embodiments having other combinations of the features disclosed and claimed herein. Thus, specific features presented herein can be combined with each other in other ways within the scope of the disclosed subject matter, such that the disclosed subject matter includes any preferred combination of the features disclosed herein. The prior descriptions of specific embodiments of the disclosed subject matter have been presented for illustrative and explanatory purposes only. They are neither exhaustive nor limit the disclosed subject matter to those disclosed embodiments.

[0115] Various patents and patent applications are described herein, their contents incorporated herein by reference in their entirety.

Claims

1. A titration-based analytical method for measuring gold (Au) in an Au-sulfite-treated solution, a. Adding a complexing agent having a predetermined concentration to the aforementioned treatment solution, b. Adding Au-sulfite solution to the aforementioned treatment solution, c. Adding a metal salt having a predetermined concentration to the treatment solution, d. Quantifying the concentration of Au by measuring the endpoint of the back titration. Includes, An analytical method characterized in that, in a first reaction, the complexing agent reacts with the complexing agent, and in a second reaction, the metal salt reacts with the remaining complexing agent.

2. A method according to claim 1, characterized in that the first product of the first reaction has a stability constant greater than that of Au-sulfite.

3. A method according to claim 1, characterized in that the second product of the second reaction has a smaller stability constant than the first product of the first reaction.

4. A method according to claim 1, characterized in that the first reaction generates a first precipitate product and the second reaction generates a second precipitate product.

5. A method according to claim 1, characterized in that the processing solution is an electrodeposition solution.

6. A method according to claim 1, characterized in that the treatment solution comprises a plating metal selected from the group consisting of nickel, cobalt, iron, and combinations thereof.

7. A method according to claim 1, characterized in that the complexing agent is selected from the group consisting of thiourea, EDTA, thiosulfate, nitrilotriacetic acid, iminodisuccinic acid, polyaspartic acid, S,S-ethylenediamine-N,N-disuccinic acid, methylglycinediacetic acid, L-glutamic acid, N,N-diacetic acid, salts thereof, and combinations thereof.

8. A method according to claim 1, further comprising adding a pH adjusting reagent to the treatment solution.

9. A method according to claim 1, further comprising adding a pH adjusting reagent to the treatment solution before adding the Au-sulfite solution.

10. A method according to claim 8, characterized in that the pH adjusting reagent lowers the pH value of the treatment solution.

11. A method according to claim 8, characterized in that the pH adjusting reagent is selected from the group consisting of nitric acid, hydrochloric acid, sulfuric acid, and combinations thereof.

12. A method according to claim 1, characterized in that the metal salt is selected from the group consisting of Ag, Cu, Fe, Al, and combinations thereof.

13. A method according to claim 1, characterized in that the back titration includes quantifying the Au concentration based on the difference between the endpoint volume from a blank analysis and the endpoint volume from a sample analysis.

14. A method according to claim 1, further comprising tracking the titration using an Ag-billet electrode.

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