CN111257494B - Method for detecting cyanide content in gold product by electroforming process through headspace gas chromatography - Google Patents
Method for detecting cyanide content in gold product by electroforming process through headspace gas chromatography Download PDFInfo
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Abstract
The invention belongs to the technical field of gold product detection, and particularly discloses a method for determining cyanide content in an electroformed gold product by using a gas chromatography technology, which comprises the following steps: 1) weighing an electroformed gold product as a test sample, and dissolving the test sample by adopting a mixed reagent of hydrogen peroxide, sodium chloride and oxalic acid; 2) distilling out hydrogen cyanide by using disodium ethylene diamine tetraacetate, tartaric acid and trichloroacetic acid under a boiling condition, and absorbing by using a sodium hydroxide solution to obtain a cyanide aqueous solution to be detected. 3) The headspace sample injection bottle contains phosphoric acid and chloramine T, 10mL of sample is added, the concentration of cyanide is determined by adopting the headspace gas chromatography technology, and the determination of the content of cyanide in the solution to be detected is calculated by calibrating a working curve. The method can accurately measure the cyanide content in the gold product in the electroforming process, fills the technical blank that the cyanide of the product cannot be measured, and has the advantages of convenient and quick detection process, accurate detection result and good consistency.
Description
Technical Field
The invention belongs to the technical field of gold product detection, and particularly relates to a method for measuring cyanide (in terms of cyanide ions) content in gold products in an electroforming process, in particular to a method for detecting cyanide content in gold products in the electroforming process by adopting a headspace gas chromatography technology.
Background
Along with the development of social economy, the demand of people for consumption of precious metal ornaments is continuously increased, the traditional gold ornaments are easy to deform when being worn due to the fact that the traditional gold ornaments are soft, the hardness of the products is improved by means of increasing the thickness and the like in production and processing, and the wearing is very heavy. The current mainstream precious metal ornaments require both beauty and comfort. In recent years, a gold product, namely an electroforming process gold product, is produced at the same time. The electroforming gold ornament has the advantages that the hardness is harder than that of the traditional gold under the condition of thinner thickness, the difficult problem that the gold lacks firmness and stereoscopic impression is effectively solved through integrated forming, the purity can reach the purity of common pure gold, the gold has the toughness of K gold, and the gold has stronger plasticity, so that the shape is more vivid and lively, various hollow shapes can be made according to the requirements, the styles are more exquisite and various, and the gold ornament is popular with consumers once being produced, so that the gold ornament quickly occupies the market.
The production process of gold product by electroforming process is different from traditional gold product, and said product is made up by using cyanide or other compound to prepare electrolyte, under the condition of electrifying the gold ion can be reduced into gold, and the electrolytic time can be prolonged so as to form the electroformed gold product. Different processing enterprises respectively own unique production process and formula, more than 70% of the production enterprises in the market still use cyanide as a raw material for preparing the electrolyte, the product has high risk of cyanide, and no related product standard limits the product. At present, the detection of the products is mainly carried out according to the standard of the traditional gold products, and the key safety and health indexes of the products are not reflected, so that the market of the novel electroforming process gold ornaments is disordered. The most important point is that the production technology of gold products by electroforming process takes cyanide electrolyte as the main material, cyanide as a highly toxic substance has definite limit value and is strictly controlled in other related products, however, the products are not provided with corresponding detection methods, so that the products sold in the current market are clearly shown as cyanide-free products, the standard service limit value requirements of the related products seriously disturb the normal market order, and consumers cannot obtain the real information of the products.
The data retrieval finds that no relevant cyanide detection method exists for the products, and the detection of cyanides in other products, namely food and wastewater can be measured through simple sample treatment. Therefore, whether the cyanide existing in the gold product in the electroforming process can be effectively extracted and separated is critical. In addition, cyanide has poor stability, for example, the cyanide is easily damaged under the conditions of strong oxidant and strong acid, and the dissolution of gold usually needs to be completed under the condition of aqua regia; in addition, the gold element in the gold product has the capability of chelating cyanide ion (binding constant 1 x 10) 45 ) The detection method is very strong, and a large amount of gold existing in the sample in the processing process seriously influences the detection result, so that a large amount of innovative research works are carried out, the extraction and separation of cyanide of gold products are realized, a method suitable for measuring the content of cyanide by using the ion chromatography technology of the gold products is explored, and the blank of detection of the cyanide of the electroformed gold products is filled.
Therefore, an efficient and accurate method for measuring the cyanide content in gold products produced by the electroforming process is established, the blank of measuring the cyanide content in gold ornaments is filled, the development of the method provides a basis for increasingly increasing the detection of the safety performance of gold ornaments produced by the electroforming process, better guarantees the personal health and safety of people, provides a detection basis and technical support for government supervision and control, and promotes the healthy development of precious metal jewelry industry.
Disclosure of Invention
In order to solve the technical problems in the prior art, the invention aims to provide a method for accurately detecting the cyanide content in a gold product in an electroforming process.
In order to achieve the technical purpose, the invention adopts the following technical scheme: a method for detecting cyanide content in gold products of an electroforming process by using top air chromatography comprises the following steps:
step one, an electroforming process gold product dissolving procedure: weighing and crushing gold products subjected to electroforming process to serve as test samples, and dissolving the test samples by adopting a mixed aqueous solution reagent consisting of hydrogen peroxide, sodium chloride and oxalic acid to obtain a cyanide aqueous solution;
crushing 0.05-0.5g of sample, adding the crushed sample into a beaker, adding 5-100mL of water and 1-50mL of hydrogen peroxide solution into the beaker, adding 17-20 g of sodium chloride, adding 1-6 g of oxalic acid, heating at 60-90 ℃ for reaction, taking out the sample after the sample is completely dissolved, cooling the beaker, and extracting and separating cyanide in the sample; a blank solution was prepared following the same procedure.
Step two, the extraction and separation process of cyanide: adding tartaric acid, disodium ethylene diamine tetraacetate and trichloroacetic acid solution into the cyanide aqueous solution obtained in the second step, heating and distilling to obtain hydrogen cyanide, and absorbing by using sodium hydroxide solution to obtain cyanide absorption solution;
the method specifically comprises the following steps: transferring the sample solution obtained in the step one into a round bottom flask, adding 0.2-5 g of trichloroacetic acid, 1-10 g of tartaric acid and 1-50 g of disodium ethylene diamine tetraacetate into the flask, distilling at 100 ℃, absorbing distillate by using 5-60 g/L of sodium hydroxide aqueous solution under a sealed condition to obtain cyanide absorption liquid, adjusting the pH value of the solution to 12.0-12.8 by using dilute phosphoric acid solution and sodium hydroxide solution, and fixing the volume to 50mL by using water.
Step three, a cyanide detection procedure: and testing the content of cyanide ions in the solution in the second step by adopting a headspace gas chromatography technology.
Specifically, in the third step, the content of cyanide ions in the solution in the third step is tested by adopting a headspace gas chromatography electronic capture detection technology, wherein a headspace mixed solution is prepared: 10mL of sample is added into a headspace bottle, 20-100 mu L of phosphoric acid analytical pure solution and 0.01-0.2 mL of 20g/L chloramine T solution are added into the headspace bottle, the mass fraction of phosphoric acid in the mixed solution in the headspace bottle is 0.1-0.5%, and the concentration of chloramine T is 0.1-0.5 g/L.
The content calculation formula of cyanide ions is as follows:
the content of cyanide ions is calculated according to the formula (1):
in the formula:
x-the content of cyanide ions in the sample in milligrams per kilogram (. mu.g/g);
c-cyanide ion concentration in the sample solution for measurement (calculated from the regression equation) in units of microgram per liter (. mu.g/L);
c 0 concentration of cyanide ions in reagent blank (calculated from regression equation) in units of micrograms per liter (μ g/L);
V 1 -determining the total volume of the sample solution in milliliters (mL);
f-constant volume sample solution of disodium ethylenediaminetetraacetate liquid Total (V) and sampling headspace bottle solution (V) 1 ) The volume ratio of (A) to (B);
m-mass of the sample in grams (g).
The detection limit calculation formula of the method is as the following formula (2):
L CN ＝K*3*δ…………………………(2)
L CN : indicating the detection limit of cyanide ions;
δ: representing the standard deviation of 5 measurements of cyanide ions in a blank test solution of 0.2g of non-cyanide technical gold product;
k: representing a confidence factor, taking 3 in the method;
the detection limit of cyanide ions was 0.3. mu.g/g.
Preferably, in the step one, the sample for measuring cyanide content of gold product in electroforming process is prepared by weighing 0.2g of crushed gold sample, adding 40mL of water, adding 10mL (mass fraction of 30%) of hydrogen peroxide solution, adding 18g of sodium chloride and 2g of oxalic acid, heating at 80 ℃ for 30 minutes, stopping reaction until the sample is completely dissolved, and cooling at room temperature to obtain sample solution. A blank solution was prepared according to the same procedure.
Preferably, in the second step, the cyanide separation and extraction step: transferring the sample solution obtained in the step one into a round bottom flask, adding 2g of trichloroacetic acid, 8g of tartaric acid and 15g of ethylene diamine tetraacetic acid, refluxing at 100 ℃, absorbing the distillation fraction by using 40mL of 30g/L sodium hydroxide aqueous solution under a sealed condition to obtain cyanide absorption liquid, adjusting the pH value of the solution to be 12.0-12.8 by using dilute phosphoric acid solution and sodium hydroxide solution, and fixing the volume to 50mL by using water.
Preferably, in the third step, the content of cyanide ions in the solution in the third step is tested by adopting a headspace gas chromatography electronic capture detection technology, wherein a headspace mixed solution is prepared: phosphoric acid mass fraction 0.2%, chloramine T concentration 0.2g/L and 10mL of sample solution. Gas chromatography test conditions: the chromatographic column is a WAX capillary column, and the thickness of the chromatographic column is 30m multiplied by 0.25mm (inner diameter) multiplied by 0.25 mu m (film thickness); the temperature of the chromatographic column is kept for 5min at 40-80 ℃, and is increased to 200 ℃ at the speed of 40 ℃/min and kept for 2 min; carrier gas 99.999% nitrogen; the temperature of a sample inlet is 200 ℃; the temperature of the electron capture detector is 260 ℃; the split ratio is 5: 1; the column flow rate was 2.0 mL/min.
The invention provides a method for measuring cyanide in gold products by electroforming process, which comprises the steps of firstly dissolving a sample to be measured, then separating and extracting to obtain a cyanide solution, and accurately measuring the content by adopting a headspace gas chromatography electronic capturing technology.
Compared with the prior art, the method has at least the following beneficial effects:
1) the key steps of dissolving the gold product in the electroforming process, extracting and separating cyanide and detecting the headspace gas chromatography are firstly constructed, so that the method for detecting the cyanide in the gold product in the electroforming process by using the gas chromatography is formed;
2) in the process of dissolving gold products in the electroforming process, the mixed reagent consisting of hydrogen peroxide, sodium chloride and oxalic acid is used for dissolving the sample, so that the detection amount of cyanide is increased;
3) when the cyanide is extracted and separated, mixed solution of tartaric acid, disodium ethylene diamine tetraacetate and trichloroacetic acid is used as an extracting agent; trichloroacetic acid and tartaric acid can provide obvious acidity and have weaker volatility, disodium ethylenediaminetetraacetate is chelated with gold to replace cyanide ions, no acidic volatile matter is distilled out, and evaporated cyanide gas is effectively absorbed in time;
4) when the method is used for detecting cyanide by adopting headspace gas chromatography, the headspace mixed solution is optimized, and when the mass fraction of phosphoric acid in the mixed solution is controlled to be 0.1-0.5% and the concentration of chloramine T is controlled to be 0.1-0.5 g/L, complete derivation of cyanide ions can be ensured, and the detection amount is increased;
5) the invention adopts headspace gas chromatography electronic capture detection technology to accurately measure the cyanide content in the electroformed gold product, and fills the blank of cyanide measurement in the electroformed gold product. The method provides more effective sharps for government market supervision, promotes the long-term development of market health, and provides important technical support for determination of harm factors of electroformed gold products.
Drawings
Fig. 1 is a calibration work graph of the headspace gas chromatography electron capture detection technology constructed in the present invention for measuring cyanide content (Y-0.01282X + 0.01016).
The specific implementation mode is as follows:
a method for detecting cyanide content in gold products of an electroforming process by headspace gas chromatography comprises the following steps:
in the preferred step one, the sample for determining the cyanide content of the gold product in the electroforming process is prepared by weighing 0.2g of crushed gold sample, adding 40mL of water, adding 10mL (30% by mass) of hydrogen peroxide solution, adding 18g of sodium chloride and 2g of oxalic acid, heating at 80 ℃ for 30 minutes, stopping reaction after the sample is completely dissolved, and cooling at room temperature to obtain a sample solution. A blank solution was prepared following the same procedure.
In the second preferred step, the cyanide separation and extraction step: transferring the sample solution in the step one into a round bottom flask, adding 2g of trichloroacetic acid, 8g of tartaric acid and 15g of ethylene diamine tetraacetic acid, refluxing at 100 ℃, absorbing the distillation fraction with 40mL of 30g/L sodium hydroxide aqueous solution under a sealed condition to obtain cyanide absorption liquid, adjusting the pH value of the solution to 12.0-12.8 by using dilute phosphoric acid solution and sodium hydroxide solution, and fixing the volume to 50mL by using water.
In the preferable third step, the cyanide ion content in the solution in the third step is tested by adopting a headspace gas chromatography electronic capture detection technology, wherein a headspace mixed solution is prepared: phosphoric acid mass fraction 0.2%, chloramine T concentration 0.2g/L and 10mL of sample solution. Gas chromatography test conditions: the chromatographic column is WAX capillary column, and is 30m × 0.25mm (inner diameter) × 0.25 μm (film thickness); the temperature of the chromatographic column is kept for 5min at 40-80 ℃, and is increased to 200 ℃ at the speed of 40 ℃/min and is kept for 2 min; 99.999 percent of nitrogen; the temperature of a sample inlet is 200 ℃; the temperature of the electron capture detector is 260 ℃; the split ratio is 5: 1; the column flow rate was 2.0 mL/min.
Calculating and disclosing the content of cyanide ions:
the content of cyanide ions is calculated according to formula (1):
in the formula:
x-the content of cyanide ions in the sample in milligrams per kilogram (. mu.g/g);
c-the concentration of cyanide ions in the sample solution for measurement (calculated from the regression equation) in units of microgram per liter (. mu.g/L);
c 0 concentration of cyanide ions in reagent blank (calculated from regression equation) in units of micrograms per liter (μ g/L);
V 1 -determining the total volume of the sample solution in milliliters (mL);
f-Total volume (V) of edetate disodium solution dissolved in constant volume sample and sampling headspace bottle solution (V) 1 ) The volume ratio of (a);
m-mass of the sample in grams (g).
The detection limit calculation formula of the method is as the following formula (2):
L CN ＝K*3*δ……………………………(2)
L CN : indicating the detection limit of cyanide ions;
δ: the standard deviation of 5 measurements of cyanide ions in 0.2g of blank test solution of the cyanide-free technical gold product is weighed;
k: representing a confidence factor, and taking 3 in the method;
the detection limit of cyanide ions was 0.3. mu.g/g.
EXAMPLE 1 Effect of different dissolution reagents on the detection of cyanide content in electroformed gold products
Selection 6Two of the electroforming process gold product samples are cyanide-free electroforming processes (No. 1 and No. 2), and 4 of the electroforming processes are cyanide electroforming processes (No. 3, No. 4, No. 5 and No. 6). The pure solution for hydrogen peroxide analysis is a 30 wt% hydrogen peroxide solution which is commercially available. Standard electrode potential due to gold element
The voltage of the crystal is 1.498V,
1.692V, the ionic oxidability of the gold is very strong, and the reducibility of the gold atom is very weak, so that the gold atom is difficult to oxidize; the method therefore requires first selecting a suitable reagent to reduce its redox potential, increase the reducibility of the gold atom, and the presence and concentration of chloride ions to be increased to effectively reduce its oxidation, for example:
the standard electrode potential is 1.002V, and the electrode potential is lower as the concentration of chloride ions increases, at which time the gold atoms are more easily oxidized. Secondly, a proper oxidant is selected, the principle of the oxidant selection is firstly to oxidize gold atoms, secondly to reduce the damage to cyanide ions, because the cyanide ions have certain reducibility,
the standard electrode potential is 1.763V, so that H can be reduced 2 O 2 The oxidizing property of the aqueous solution is reduced, and in addition, under the alkaline condition,
the standard electrode potential is 0.867V, gold atoms are difficult to oxidize, and the oxidation property of the gold atoms is obviously enhanced under the strong acid condition, so that the gold atoms are required to be adjusted to obtain proper oxidation property under the weak acid condition, the gold atoms can be dissolved, and the damage to cyanide ions can be reduced; the chelating ability of the cyanide ions and the gold ions is very strong (the binding constant is 10) 45 ) The chelated gold cyanide has strong stability and can reduce the oxidizing agentDamage to it.
Weighing 0.2g of sample, crushing, selecting 5 different reagents to dissolve the sample according to the step one, and analyzing a pure solution by using 1-SJ-1#:50mL of hydrogen peroxide; 50mL of hydrogen peroxide solution and a solution prepared by 2g of oxalic acid are analyzed in 1-SJ-2 #; 50mL of hydrogen peroxide solution, 18g of sodium chloride and 2g of oxalic acid are used for analyzing a pure solution in 1-SJ-3 #; 1-SJ-4# 50mL of water, 18g of sodium chloride and 2g of oxalic acid; 30mL of hydrogen peroxide and 20mL of hydrochloric acid are analyzed and purified in the model 1-SJ-5; 30mL of hydrogen peroxide analytically pure, 20mL of hydrochloric acid analytically pure and 2g of oxalic acid prepared mixed solution are used as 1-SJ-6 #; 30mL of hydrogen peroxide analytically pure, 20mL of phosphoric acid analytically pure and 2g of oxalic acid prepared mixed solution are used as 1-SJ-7 #; 50mL of mixed reagent (10 mL of pure hydrogen peroxide, 40mL of water, 18g of sodium chloride and 2g of oxalic acid) is subjected to No. 1-SJ-8, and the content of cyanide (calculated as cyanide ions) is measured under the conditions preferred in the second step and the third step, and the result is shown in Table 1.
TABLE 1 cyanide content in selected electroformed gold products treated with different reagents
The results in Table 1 show that cyanide was not detected in the 1-SJ-1# sample treated with strong oxidizing agent, four cyanide samples, and 1-SJ-2# increased the acidity over 1-SJ-1# but gold preparations prepared by the cyanide process were also free of cyanide; 1-SJ-3# is added with a mixed reagent prepared by an acidic chemical reagent and sodium chloride under the condition of a strong oxidant, and a large amount of cyanide ions are detected in four cyanide samples; 1-SJ-4# under the condition that the acid chemical reagent and sodium chloride are the same, no oxidant exists, and no cyanide ions are detected in four cyanide process gold products; 1-SJ-5# has increased acidity compared with 1-SJ-6# sample treatment conditions, has slight reduction in the amount of cyanide ions detected, and the amount of cyanide ions detected changes less because the increased oxalic acid has less influence on acidity compared with hydrochloric acid; no cyanide ion is detected in 1-SJ-7# under the acid condition and the reinforcing agent condition, and a test sample is not dissolved; the detected cyanide content of samples treated by the reagent No. 1-SJ-8 is more than 10 mug/g and is obviously higher than the detected cyanide ion content of the reagent No. 1-SJ-5, and a part of cyanide ions are damaged in the dissolving process in the presence of strong acid and strong oxidation probably. The results show that cyanide is detected in gold products with cyanide processes of 1-SJ-3#, 1-SJ-5#, 1-SJ-6#, and 1-SJ-8#, and under an acidic condition, a reinforcer obviously damages cyanide ions or loses cyanide ions in the sample dissolving process; 1-SJ-1#, 1-SJ-2#, 1-SJ-4#, and 1-SJ-7# have no reaction.
EXAMPLE 2 Effect of different extraction reagents on the detection of cyanide content in electroformed gold products
The cyanide separation extraction test was carried out using six samples selected in example 1, and 0.2g of the sample was weighed and pulverized, and the samples (1-SJ-8#) were dissolved in this order according to the preferable conditions of step one to obtain an aqueous sample solution.
The aqueous sample solution was transferred to a round bottom flask and 6 different extraction reagents, 3-SJ-1 #: 15mL of hydrochloric acid; 3-SJ-2 #: 15mL of phosphoric acid; 3-SJ-3 #: 15g of trichloroacetic acid; 3-SJ-4 #: 15g of tartaric acid; 3-SJ-5 #: 15mL of hydrochloric acid and 15g of ethylene diamine tetraacetic acid; 3-SJ-6 #: 2g of trichloroacetic acid and 15g of ethylene diamine tetraacetic acid; 3-SJ-7 #: tartaric acid 8g and ethylene diamine tetraacetic acid 15 g; 3-SJ-8 #: refluxing 2g of trichloroacetic acid, 8g of tartaric acid and 15g of disodium ethylenediamine tetraacetate respectively at 100 ℃, absorbing the distillation fraction by 40mL of 30g/L sodium hydroxide aqueous solution under a closed condition to obtain cyanide absorption liquid, and fixing the volume to 50mL by 20g/L sodium hydroxide solution; and step three, under the preferred conditions, measuring the content of cyanide (calculated by cyanide ions), and the result is shown in table 2.
TABLE 2 content of cyanide in electroformed gold products under different extraction reagent conditions
The result shows that the eight reagents can extract cyanide ions existing in the sample, the cyanide detection value is low by independently using hydrochloric acid, phosphoric acid, trichloroacetic acid and tartaric acid as extraction reagents, the phosphoric acid is the lowest and possibly causes a certain oxidation property of the phosphoric acid, the cyanide ions are greatly destroyed under the high-temperature condition, in addition, a large amount of gold ions are combined with the cyanide ions in the sample, and the cyanide ions cannot be replaced by the change of an independent acidic system. Under the condition of adding excessive disodium ethylene diamine tetraacetate, the detection value of cyanide ions is obviously improved by combining the change of acidic conditions, the concentration of the hydrochloric acid solution is higher, so that a large amount of hydrochloric acid is distilled off under the strong acidic conditions to enter an absorption solution, the distilled hydrogen cyanide cannot be absorbed and lost obviously in time, and in addition, a large amount of chloride ions have great influence on the test result of the step three, so the detected cyanide ions are lower. Trichloroacetic acid and tartaric acid can provide obvious acidity and have weak volatility, disodium ethylene diamine tetraacetate is chelated with gold to replace cyanide ions, no acidic volatile is distilled out, and the evaporated cyanide gas is effectively absorbed in time.
Example 3
The six samples selected in example 1 were used for research experiments, 0.2g of the sample was weighed and crushed, the samples were dissolved and cyanide was separated and extracted in sequence according to the preferred conditions of step one and step two (1-SJ-8# and 2-SJ-8#) to obtain cyanide absorption solution, the separated cyanide absorption solution was made to be 50mL in volume, and 10mL was taken and added to different headspace gas chromatography headspace solutions.
Investigating the influence of different headspace gas chromatography headspace solutions on the detection of the cyanide content in the electroformed gold product:
the different headspace gas chromatography headspace solutions were as follows, 3-SHY-1 #: 40 μ L phosphoric acid was analytically pure; 3-SHY-2 #: 0.1mL of a 20g/L solution of chloramine T; 3-SHY-3 #: 20 μ L of phosphoric acid analytically pure and 0.1mL of a 20g/L solution of chloramine T; 3-SHY-4 #: 40 μ L of phosphoric acid analytically pure and 0.05mL of a 20g/L solution of chloramine T; 3-SHY-5 #: 80 μ L of phosphoric acid analytically pure and 0.1mL of a 20g/L solution of chloramine T; 3-SHY-6 #: 40 μ L of phosphoric acid analytically pure and 0.3mL of a 20g/L solution of chloramine T; 3-SHY-7 #: 40 μ L of phosphoric acid was analyzed neat and 0.1mL of a 20g/L solution of chloramine T.
Gas chromatography test conditions: the chromatographic column is a WAX capillary column, and the thickness of the chromatographic column is 30m multiplied by 0.25mm (inner diameter) multiplied by 0.25 mu m (film thickness); the temperature of the chromatographic column is kept for 5min at 40-80 ℃, and is increased to 200 ℃ at the speed of 40 ℃/min and is kept for 2 min; carrier gas 99.999% nitrogen; the temperature of a sample inlet is 200 ℃; the temperature of the electron capture detector is 260 ℃; the split ratio is 5: 1; the column flow rate was 2.0mL/min, and the cyanide content (in terms of cyanide ion) was measured under the above conditions, and the results are shown in Table 3.
TABLE 3 content of cyanide in electroformed gold products under different headspace test solutions
The results show that no cyanide is detected after five different headspace liquids, namely 3-HSY-1# and 3-HSY-2# react with the sample, because the acidic condition and chloramine T solution can not react independently of cyanide ions in the sample to generate volatile derivatives; cyanide is detected after other five different headspace test solutions react with the sample, and the measurement result shows that the reduction of acidity and the reduction of chloramine T concentration can not lead cyanide ions existing in the sample to be completely derived, so the detection amount is obviously reduced; the increase of acidity and the increase of concentration of chloramine T have no obvious influence on the detection of cyanide, the detection amount of the cyanide with the increase of related acidity is slightly reduced, and the possible reasons are that phosphoric acid has certain oxidizability and partial hydrogen cyanide is easy to form under the strong acid condition to have certain influence on the result.
Example 4
And constructing a calibration working curve under the preferred conditions of the third step, wherein the standard sample is 1000mg/L of a commercially available sodium cyanide standard solution, is diluted to 10mg/L by using a 0.1% NaOH solution, and is prepared into working solutions with the concentrations of 0 mu g/L, 1 mu g/L, 2 mu g/L, 10 mu g/L, 50 mu g/L and 100 mu g/L by using water. 10.0mL of the above 6 groups of cyanide ion working solutions are accurately transferred into 6 headspace bottles respectively, 0.1mL of phosphoric acid analytical pure solution is added, after vortex mixing, 0.1mL of chloramine T solution (20g/L) is added, and then the bottles are immediately capped, sealed and vortex mixed to be tested. Testing cyanides in 6 groups of samples to be tested by adopting headspace gas chromatography (HS-GC-ECD) under the three preferred conditions, constructing a calibration working curve by adopting an external standard method and using the calibration working curve for quantitative analysis of the samples to be tested, wherein the standard curve is shown in figure 1.
Claims (4)
1. A method for detecting cyanide content in gold products of an electroforming process by headspace gas chromatography comprises the following steps:
step one, an electroforming process gold product dissolving procedure: weighing and crushing an electroforming process gold product, taking the gold product as a test sample, and dissolving the test sample by adopting a mixed aqueous solution reagent consisting of hydrogen peroxide, sodium chloride and oxalic acid to obtain a cyanide aqueous solution;
step two, the extraction and separation process of cyanide: adding tartaric acid, disodium ethylene diamine tetraacetate and trichloroacetic acid solution into the cyanide aqueous solution obtained in the step two, heating and distilling to obtain hydrogen cyanide, and absorbing by using sodium hydroxide solution to obtain cyanide absorption solution;
step three, a cyanide detection procedure: testing the content of cyanide ions in the solution in the step two by adopting a headspace gas chromatography technology;
the content of cyanide ions is calculated according to the formula (1):
in the formula:
x is the cyanide ion content in the sample in milligrams per kilogram;
c, the concentration of cyanide ions in the sample solution for determination is microgram per liter;
c 0 -the concentration of cyanide ions in the reagent blank in micrograms per litre;
V 1 -determining the total volume of the sample solution in milliliters;
f-constant volume sample solution of disodium edetate solution general V and sampling headspace bottle solution V 1 The volume ratio of (a);
m is the mass of the sample, in grams;
the first step is that the concrete steps of the sample dissolving treatment are as follows: crushing 0.05-0.5g of sample, adding the crushed sample into a beaker, adding 5-100mL of water and 1-50mL of hydrogen peroxide solution into the beaker, adding 17-20 g of sodium chloride, adding 1-6 g of oxalic acid, carrying out heating reaction at 60-90 ℃, taking out the beaker after the sample is completely dissolved, and cooling the beaker to separate cyanide after extraction; preparing a blank solution according to the same steps;
in the second step, the cyanide separation and extraction step is as follows: transferring the sample solution obtained in the first step into a round-bottom flask, adding 0.2-5 g of trichloroacetic acid, 1-10 g of tartaric acid and 1-50 g of disodium ethylene diamine tetraacetate into the flask, distilling at 100 ℃, absorbing distillate by using 5-60 g/L of sodium hydroxide aqueous solution under a closed condition to obtain cyanide absorption solution, adjusting the pH value of the solution to 12.0-12.8 by using dilute phosphoric acid solution and sodium hydroxide solution, and fixing the volume to 50mL by using water;
in the third step, testing the content of cyanide ions in the solution in the third step by adopting a headspace gas chromatography electronic capture detection technology, wherein a headspace mixed solution is prepared: adding 10mL of sample into a headspace bottle, adding 20-100 mu L of phosphoric acid analytical pure solution and 0.01-0.2 mL of 20g/L chloramine T solution, wherein the mass fraction of phosphoric acid in the mixed solution in the headspace bottle is 0.1-0.5%, and the concentration of chloramine T is 0.1-0.5 g/L;
gas chromatography test conditions: the chromatographic column is a WAX capillary column, and the thickness of the chromatographic column is 30m multiplied by 0.25mm (inner diameter) multiplied by 0.25 mu m (film thickness); the temperature of the chromatographic column is kept for 5min at 40-80 ℃, and is increased to 200 ℃ at the speed of 40 ℃/min and kept for 2 min; carrier gas 99.999% nitrogen; the temperature of a sample inlet is 200 ℃; the temperature of the electron capture detector is 260 ℃; the split ratio is 5: 1; the column flow rate was 2.0 mL/min.
2. The method of claim 1, wherein: weighing 0.2g of crushed gold sample, adding 40mL of water, adding 10mL of hydrogen peroxide solution with the mass fraction of 30%, adding 18g of sodium chloride and 2g of oxalic acid, heating at 80 ℃ for 30 minutes, stopping reaction when the sample is completely dissolved, and cooling at room temperature to obtain a sample solution; a blank solution was prepared following the same procedure.
3. The method of claim 1, wherein:
in the second step, the cyanide separation and extraction step: and (3) transferring the sample solution obtained in the step one into a round-bottom flask, adding 2g of trichloroacetic acid, 8g of tartaric acid and 15g of ethylene diamine tetraacetic acid, refluxing at 100 ℃, absorbing the distillation fraction with 40mL of 30g/L sodium hydroxide aqueous solution under a sealed condition to obtain cyanide absorption liquid, adjusting the pH value of the solution to be 12.0-12.8 by using dilute phosphoric acid solution and sodium hydroxide solution, and fixing the volume to be 50mL by using water.
4. The method of claim 1, wherein: in the third step, the cyanide ion content in the solution in the third step is tested by adopting a headspace gas chromatography electronic capture detection technology, wherein a headspace mixed solution is prepared: the phosphoric acid mass fraction was 0.2%, and the chloramine T concentration was 0.2 g/L.
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