Method for determining arsenic in pyrite

Is the content high? For low concentrations, use a hydride generator and atomic absorption spectroscopy. What is the substance you are testing?

Atomic absorption equipment is expensive to acquire, and the limited-testing method involves highly toxic hazardous substances; it is recommended to outsource such tasks to external agencies if they are not part of regular testing procedures.

Raw materials need to be tested upon arrival at the warehouse; so what are some good methods for conducting these tests?

Pyrite ore? If it is the ore in its original state, a test report showing the content of relevant elements should be requested at the time of purchase. Laboratories that undergo qualification assessment should generally have the appropriate experimental equipment, and the atomic absorption spectrometer is the most commonly used device for detecting trace elements. If not, it is very expensive to send items that are regularly tested outside for inspection; you can calculate the costs to see whether it is indeed necessary to purchase a machine. You can do without a graphite furnace, which can save a lot of costs. I have analyzed the arsenic content in pyrite on two occasions; the hydride generation method works well for this purpose, and the levels of arsenic are quite low – around 0.001 percent. If you need it, I can help you look up the original records

The process isn’t complicated, right? Are there any other methods?

There is a national standard, GBT 7686-2008 \"General Methods for the Determination of Arsenic Content in Chemical Products\", which uses spectrophotometry; this standard can be used as a reference. The detection limit for arsenic is 1–20 ug. The standards should be easy to find; if you can’t locate them, feel free to contact me.

Determination of Arsenic (Gu Cai’s Method for Arsenic Determination) I. Objectives and Requirements: 1. Master the principle and procedures of Gu Cai’s method for determining arsenic content. II. Principle: After digestion of the sample, potassium iodide and stannous chloride are used to reduce arsenic in its higher valence states to arsenic in its trivalent state; thereafter, hydrogen gas generated by zinc particles and acid reacts with this arsenic to form arsine. This arsine then reacts with mercuric bromide test strips to produce yellow to orange-colored spots, which are used for quantitative analysis. III. Reagents and Instruments: 1. 5% ethanol solution of mercuric bromide 2. Mercuric bromide test strips: Cut filter paper into circles with a diameter of 2 cm, and soak them in the ethanol solution of mercuric bromide. Remove it before use, let it dry naturally, and then set it aside for later use. 3. 40% acidic stannous chloride solution: Weigh 20 grams of stannous chloride (SnCl2·2H2O), dissolve it in 12.5 milliliters of concentrated hydrochloric acid, and dilute with water to 50 milliliters. Add 2 more tin particles to the solution. 4. 10% lead acetate solution. 5. Lead acetate cotton: Immerse the absorbent cotton in a 10% lead acetate solution, remove it after 1 hour, loosen it, dry it in an oven at 100°C, then take it out and store it in a glass bottle with the lid sealed tight for future use. 6. Lead acetate test strip: Soak ordinary filter paper in a 10% lead acetate solution, remove it after 1 hour, let it dry naturally, cut it into strips (8×5 cm), and store them in a bottle for later use. 7. Arsenic-free zinc fine particles. 8. Concentrated hydrochloric acid. 9. 20% potassium iodide solution. 10. 10% magnesium nitrate solution. 11. Magnesium oxide ； 12. Arsenic standard solution: Accurately weigh 0.1320 grams of arsenic trioxide, which has been dried in a sulfuric acid desiccator or dried at 100°C for 2 hours, and dissolve it in 10 milliliters of 1N sodium hydroxide solution. Add 10 milliliters of 1N sulfuric acid solution to this mixture, then carefully transfer the solution into a 1000-milliliter volumetric flask and dilute to the mark with water. This solution contains 0.1 milligrams of arsenic per milliliter. When in use, this solution can be diluted to contain 1 or 10 mg of arsenic per milliliter. 13. 1N sodium hydroxide: Measure 52 milliliters of a saturated sodium hydroxide solution and add it to 1000 milliliters of carbon dioxide-free water, then mix well. 14. 1N sulfuric acid solution. IV. Operating procedure: 1. Sample preparation: Accurately weigh 10 grams of the sample, place it in a porcelain crucible, add 2 grams of magnesium oxide powder and 10 milliliters of 10% magnesium nitrate solution, then evaporate it to dryness in a water bath. After being carbonized at low temperature, it is transferred to a furnace at 550°C for ashing until it turns into white ashes. Once cooled, 10 milliliters of concentrated hydrochloric acid is added to dissolve the residue; then the mixture is transferred to a 100-milliliter volumetric flask with water and diluted to the mark, after which it is shaken well. 2. Sample analysis: Accurately pipette 20 milliliters of the sample solution and transfer it into the arsenic spot assay device. Place them in Erlenmeyer flasks, and add 0.0, 1.0, 2.0, 3.0, 4.0, and 5.0 milliliters of the standard solution containing 1 mg of arsenic per milliliter, respectively. Add 5 ml of 20% potassium iodide solution to each bottle. 2 ml of a 40% stannous chloride solution was added to the sample solution, followed by the addition of 13 ml of concentrated hydrochloric acid. To each standard solution, 15 ml of concentrated hydrochloric acid was added, and water was added to each to bring the total volume to 45 ml. After 10 minutes of placement. Add 5 grams of zinc granules and quickly fill the arsenic testing tube that already contains mercuric bromide test strips, lead acetate cotton, and filter paper. Place in the dark at 25-30°C for 45 minutes. Remove the mercuric bromide test strip, visually compare the sample with the standard color patches, and determine the arsenic content in the sample solution. Calculation: Arsenic (mg/kg) = C/W × 100. C: the standard amount of arsenic in mg; W: the weight of the sample solution used in the measurement in grams. Note: (1) The amount of sample solution taken can be determined based on the arsenic content in the sample, as long as the final total volume is 45 milliliters. (2) The amount of arsenic equivalent to the color spot in the sample should be deducted by the amount of arsenic equivalent to the color spot in the blank solution. (3) The reagent blank is only allowed to show a very faint pale yellow color (it generally should not exhibit any arsenic spots). If arsenic appears as a color in the blank, the cause should be identified. (4) The reagents require high purity; they must be arsenic-free zinc granules and grade-one hydrochloric acid. (5) When filling the lead acetate cotton, it should not be too tight or too soft; the degree of tightness should be appropriate. (6) When adding zinc granules, after each addition, immediately cover it with a pre-prepared lead acetate cotton wad and the glass tube of the mercury bromide test strip. (7) If the sample contains antimony, antimony spots similar to arsenic spots can also be formed. Antimony dissolves in 80% ethanol, whereas arsenic spots do not. Experiment (II): DDC-Ag colorimetric method. I. Principle: After the sample is digested, potassium iodide and stannous chloride are used to reduce arsenic in its higher valence states to arsenic in its trivalent state. Hydrogen generated from zinc particles and acid then reacts with arsenic to form arsine. This arsine is absorbed by a silver salt solution, resulting in the formation of a red colloidal substance; the amount of this substance is determined by comparison with a standard series. II. Reagents and Instruments 1. Absorption of arsenic: Weigh 0.25 grams of DDC-Ag and 0.25 grams of quinine (C20H24O2N2), dissolve them in 100 milliliters of chloroform, let the mixture stand overnight, and filter if necessary. The clarified absorbent solution should be stored in a brown bottle. Treatment of quinine: Generally, quinine exists in salt form, such as quinine sulfate. Dissolve it in boiling water, add 1N sodium hydroxide solution to make the solution alkaline, at which point a large amount of quinine precipitates. Filter; the chloride residue is washed several times with water, then dissolved in chloroform. This chloroform solution is placed in a separatory funnel, and the water layer is washed until it becomes neutral. The chloroform layer is dried over anhydrous sodium sulfate, after which the chloroform is evaporated. The remaining chloroform solution is also placed in a separatory funnel, and the water layer is washed again until it becomes neutral. After the chloroform layer was dried over anhydrous sodium sulfate, the chloroform was evaporated, and the residue was treated with a small amount of acetone to yield quinine powder. The purpose of adding quinine to the arsenic absorption solution is to make the solution alkaline, thereby accelerating the stable formation of colloidal silver. Others such as pyridine also have chromophoric effects. 2. The preparation of other reagents is the same as that in the Gu-Cai arsenic test method. 3. Spectrophotometer ； III. Procedure: 1. Sample preparation: Follow the sample preparation method for the Gu Cai arsenic spot test. Add 10 milliliters of water and 10 milliliters of 1:1 H2SO4 solution to the resulting ash to dissolve the residue, then filter it into a 100-milliliter volumetric flask and dilute to the mark with water. 2. Sample analysis: Take an appropriate amount of the sample solution (depending on the arsenic content in the sample) and place it in an Erlenmeyer flask. Additionally, 0.0, 1.0, 2.0, 3.0, 4.0, and 5.0 milliliters of the standard solution, in which each milliliter corresponds to 1 microgram of arsenic, were accurately taken and placed in Erlenmeyer flasks respectively. To the Erlenmeyer flasks containing the sample solution or standard solution, 60 milliliters of water was added each, along with 15 milliliters of 1:1 H2SO4 solution, 5 milliliters of 15% potassium iodide solution, and 2 milliliters of 40% stannous chloride solution. After mixing well, the mixture was allowed to stand for 10 minutes. Then, 6 grams of zinc granules were added, and the rubber stopper equipped with a glass tube was immediately sealed. The tip of the outlet tube was dipped into a colorimetric test tube that already contained 5 milliliters of absorbing solution. The reaction proceeded at room temperature (around 25°C) for 40 minutes. Remove the absorption tubes and use chloroform to bring the volume of the absorbent solution in each tube to 5 milliliters. The optical density was determined using a spectrophotometer at a wavelength of 500 nm. A standard curve is drawn based on the optical density readings from the standard tubes. Based on the optical density measured for the sample solution, the corresponding arsenic content is determined from the standard curve. Calculation: Arsenic (mg/kg) = C/W × 1000, where C is the standard amount of arsenic in mg ； W: Weight (g) of the sample solution used for determination. Note: (1) The reaction absorption for arsenic should be carried out at around 25°C as much as possible. When measuring in hot weather, the absorption tube should be placed in ice water to prevent the absorption solution from evaporating. (2) When using arsenic-free zinc granules, it is best to add two larger zinc granules, with the rest remaining as fine zinc granules. If all fine zinc particles are used, the reaction is too intense.

For high concentrations, the potassic bromate titration method can be used, while for low concentrations, the copper reagent silver photometry method is applicable; both require inexpensive reagents and equipment. The expensive one is just the photometer, over 3,000. The rest are just bottles and jars.

What is the determination method for potassium bromate volumetry?

What is a good method for determining the arsenic content in oil during the arsenic removal process from naphtha?

General test methods for the salt industry – Determination of arsenic ions GB/T 13025-94 2 Referenced standards: GB 6682 Specifications for laboratory water; GB 9721 General rules for molecular absorption spectrophotometry (ultraviolet and visible light region); JJG 694 Atomic absorption spectrophotometers 3 Method 1: Atomic absorption spectrophotometry 3. Principle: In an acidic solution, arsenic reacts with sodium borohydride to form arsine trihydrate, which is then determined using atomic absorption spectrophotometry. 3.2 Instruments: Atomic absorption spectrophotometer that meets the requirements of JJG6 94, equipped with a hydride generator attachment and a recorder, as well as Eppendorf micropipettes. Instrument parameters selected: wavelength 193.7 nm, spectral bandwidth. .7 nm; T-shaped quartz cell with an optical path length of 15 cm. The cleaning gas is nitrogen, with a flow rate of 100 mL/min. The quartz cell can be heated to 900°C either by flame or by electric heating. 3.3 Reagents and solutions: The water used in this method must meet the requirements for grade 1 water as specified in GB6652; the reagents employed are of analytical grade and high purity. 3.3 Arsenic standard solution: A 1M solution containing 100 pg of As is prepared by weighing 0.1320 g of arsenic trioxide, to an accuracy of 0.1 mg, and placing it in a 100 mL beaker. 5.0 mL of 100 g/L sodium hydroxide solution is added until dissolution occurs; thereafter, the mixture is neutralized using 10% sulfuric acid, with phenolphthalein as an indicator. The solution is then transferred to a 100 mL volumetric flask, filled to the mark with water, and mixed thoroughly for use. 13.2 Arsenic standard working solution: 1 mL of this solution contains 1.00 pg of As. Transfer 100 μL of the arsenic standard solution into a 100 mL volumetric flask, add water to the mark, and mix well. 3. 3.3 Hydrochloric acid (GB 622); 1+1 solution. 13.4 Potassium iodide-thiosulfate reduction solution: Weigh 2.0 g of potassium iodide (GB1 272) and 0.20 g of thiosulfate (HG3-979) in a 50 mL beaker, add 10 mL of water, heat gently to dissolve them; prepare this solution just before use. 3.3.5 Sodium borohydride solution: 10 g/L solution – Weigh 1.00 g of sodium borohydride (NaBH4), dissolve it in 100 mL of 0.001 M sodium hydroxide solution; prepare it just before use. **The Technical Supervision Bureau approved it on 1994-07-06 and implemented it on 1995-02-01 in accordance with Gs/T 13025.13-94, Section 3.4: Analysis Procedures; 3.4.1 Standard Curve: Take a 25 mL colorimetric tube, add 2.0 mL of hydrochloric acid (1+1) solution and 0.5 mL of potassium iodide-thiosulfate reduction solution to it, then fill the tube to 25 mL with water and mix well. Four 3.0 ml portions of this solution were taken and placed in a hydride generator; 0, 20, 40, and 60 pL of arsenic standard working solution were added sequentially using micropipettes, and the absorbance of each sample was measured. These values were then plotted against the corresponding arsenic concentrations. 3.4.2 Sample determination: Weigh 20.00 g of the sample, dissolve it in water, transfer it to a 100 mL volumetric flask, add water to the mark, and mix well. Transfer 10.0 mL of the solution into a 25 mL colorimetric tube, add 2.0 mL of hydrochloric acid (1+1) solution, mix well, seal the tube, and heat it in an 80–90°C water bath for 30 minutes, then add . 0.5 mL of potassium iodide-pyridine sulfide reduction solution is then placed in a boiling water bath for 5 minutes; after removal and cooling, water is added to bring the volume to 25 mL, and the mixture is shaken well. 3 mL of this solution is taken and placed in a hydride generator, sodium borohydride solution is added, the absorbance is measured, and the arsenic content is determined by referring to a standard curve, from which the arsenic content in the sample is calculated. 3.5 In the formula, the result is given as m(As)/10-s = pxV Chonghan. …⋯ ⋯ . . .。 II. ·..·..。 II. II(1):.(A,)/10-0— Total As content, pg/g; p— Measured total As amount, pg/mL; V— Volume of the sample solution used in the measurement, mL. — To determine the quality of the sampled material; Method 4: Arsenic spot method. Principle: In an acidic solution, potassium iodide and stannous chloride are used to reduce arsenic in its pentavalent state to arsenic in its trivalent state. Zinc granules are then added to the acid, which generates atomic hydrogen that further reduces arsenic trivalent to arsine. When hydrogen arsenide gas reacts with mercuric azide reagent, brownish-yellow arsenic spots (mercury arsenide compounds) are formed, which are used for the visual colorimetric determination of arsenic. 4.2 Instruments and Equipment 4.2.1 General laboratory instruments. 4.2.2 Arsenic detection device, as shown in Figure 1. Equipment for preparing baths: 1 – conical flask; 2 – rubber stopper; 3 – glass tube for arsenic measurement; 4 – glass cap at the tube opening. GB/T 13025.13–94 4.2.2.1 Conical flask: volume of 100 ml. 4.2.2.2 Glass tube for arsenic measurement: total length of 180 mm, thicker at the top and thinner at the bottom. The inner diameter at a distance of 130 mm from the tube opening is approximately 6.5 mm; it gradually narrows from there, with the inner diameter at the end being 1–3 mm. There is a hole with a diameter of 2 mm located about 1 cm from the end. The narrower part of the tube fits tightly into the rubber stopper, so that the lower portion extends just below the rubber stopper, right above the hole. The thicker upper part is filled with lead acetate cotton, measuring 50–60 mm in height. The upper end of the glass tube has a smoothed surface, with a hook on each of the lower sides for securing the glass cap. 4.2-2.3 Glass cap: the bottom is flattened, with a meniscus-shaped groove on the top; there is a hole in the center that connects to the glass tube, with a diameter of 6.5 mm. When in use, place the glass cap over the opening of the glass tube so that the circular holes align with each other; insert a mercuric azide test strip between them, and secure the glass cap to the glass tube using an rubber band or some other suitable method. 4.3 Reagents and Materials Unless otherwise specified for the reagents used in this method, analytical grade reagents shall be employed; the laboratory water should meet the specifications for grade 3 water as defined in GB6682. 4.3.1 Hydrochloric acid (GB 622): (1+1) solution. 4.3.2 Potassium iodide (GB 1272): 150 g/L solution (prepare fresh before use). 4.3.3 Stannous chloride (GB 638): 50 g/L solution (prepare fresh before use). Weigh 2.5 g of stannous chloride, dissolve it in 50 mL of hydrochloric acid (1+1) solution, heat to ensure complete dissolution, and then cool it for later use. 4.3.4 Lead acetate-treated cotton: Take the degreased cotton, moisten it with a solution of lead acetate (100 g/L), remove excess solution, loosen the cotton, dry it at a temperature below 100°C, and store it in a sealed container. 4.3.5 Arsenic-free zinc granules (GB 2304): Select zinc granules with a diameter of about 2 mm. 4-3.6 Arsenic standard solution: 1 mL of the solution contains. For 0.100 mg of As, 0.132 g of arsenic trioxide dried in a sulfuric acid desiccator was dissolved in 10 mL of sodium hydroxide solution (40 g/L). Water was added to bring the volume to 500 mL, after which 10 mL of sulfuric acid with c (1/2H,SO4) = 1 mol/L was added. The mixture was then transferred to a 1,000 mL volumetric flask, diluted to the mark with water, and mixed thoroughly. 4.3.7 Arsenic standard working solution: 1 mL of this solution contains 1.00 mg of As. 1.00 mL of the arsenic standard solution is taken and placed in a 100 mL volumetric flask, then diluted with water to the mark and mixed thoroughly. 4.3.8 Mercuric azide test strip: Weigh 1.25 g of mercuric azide and dissolve it in 25 mL of ethanol. Place filter paper sheets cut into circles with a diameter of 2 cm into this solution and soak them for more than 1 hour. After that, remove them and let them dry in a dark place, storing them in a sealed brown bottle. 4.4 Analysis procedure: Weigh 5 g of the sample, to an accuracy of 0.01 g, and place it in a conical flask. Add water up to 25 mL, then add 15 mL of hydrochloric acid solution, 5 mL of potassium iodide solution, and 1 mL of stannous dichloride solution. Stir well and allow the mixture to stand for 10 minutes. Add 3 g of zinc granules, immediately insert the arsenic testing tube pre-filled with lead acetate-soaked cotton and mercuric iodide test strips, and leave it at room temperature for 40–60 minutes. Then remove the sample and the mercuric iodide test strips used as controls, and compare them with the standard arsenic spots. The standard involves taking 2.50 ml; the arsenic standard working solution is placed in a conical flask. The subsequent steps are carried out in the same manner as for the sample, and a reagent blank test is also performed simultaneously. 4.5 Presentation of results: If the yellow color shown on the mercuric azide test strip for the sample is lower than or equal to the brownish-yellow color on the mercuric azide test strip of the arsenic standard working solution, it is considered qualified; otherwise, it is considered unqualified. 5 Third Method: Silver Salt Method (Silver Diethyldithiocarbamate Method) 5 Principle: In an acidic solution, arsenic in the +5 valence state is reduced to arsenic in the +3 valence state using potassium iodide and stannous chloride. The reaction of zinc granules with acid produces atomic hydrogen, which further reduces arsenic(III) to arsine. Hydrogen arsenide gas is absorbed by a silver diethyldithiocarbamate solution to form a red complex, which is determined by spectrophotometry. 5.2 Instruments and Equipment 5.2.1 General laboratory instruments. Gs/T 13025.13-94 5.2.2 Spectrophotometer: Complies with the requirements of GB 9721. 5.2.3 Arsenic detection device, as shown in Figure 2. Figure 2: 1 – 100 mL conical flask; 2 – gas delivery tube; 3 – lead acetate wad; 4–5 – centrifuge tubes with 5 mL markings. 5.2.3 Flanged conical flask: volume of 100 mL, standard mouth No. 19. 5.2.3. 2 Vent pipe: When the standard port No. 19 at the pipe opening is fitted tightly with a ground conical flask, there should be no air leakage. The diameter of the other end of the tube is 1.0 m mo 5.2.3.3 Absorption tube: 5 mL centrifuge tubes are used as absorption tubes. 5.3 Reagents and Solutions 5.3., same as the arsenic spot method 4.3.1 4.3.7. 5.3.2 Silver diethyldithiocarbamate-triethanolamine-trichloromethane solution: Weigh . .2 g of silver diethyldithiocarbamate, dissolved in a small amount of trichloromethane, to which 3 mL of triethanolamine was added; the mixture was then diluted to 100 mL with trichloromethane, left to stand overnight, filtered, and stored in a brown bottle. 5.4 Analysis procedure: Weigh 5 g of the sample, to an accurate weight. 0.01 g was placed in a 100 mL ground-mouth conical flask, and water was added to bring the volume to 25 mL. Then, 0.00, 2.00, 4.00, 6.00, and 8.00 mL of arsenic standard solutions (corresponding to 0.00, 2.00, 4.00, 6.00, and 8.00 ppb of arsenic) were taken and placed in separate 100 mL ground-mouth conical flasks, with water added to reach 25 mL in each. To each of the sample solution, reagent blank, and arsenic standard solutions, 15 mL of hydrochloric acid, 5 mL of potassium iodide solution, and 1 mL of stannous chloride solution were added, mixed well, and allowed to stand for 15 minutes. 3 g of arsenic-free zinc granules were added to each sample. Immediately, a gas delivery tube filled with lead acetate-soaked cotton was inserted, with its tip submerged below the liquid level in the absorption tube containing 5.00 mL of the silver salt solution. The reaction was carried out at room temperature for 30–50 minutes (the reaction time should be reduced if the room temperature is high, and increased if it is low). After that, the absorption tube was removed, and trichloromethane was added to bring the volume back to 5.00 mL. Using a 1 cm absorption cell, the absorbance is measured at a wavelength of 520 nm, with the reagent blank as a reference. A standard working curve is prepared by plotting the amount of arsenic standard against the corresponding absorbance values; the amount of arsenic in the sample solution is then determined by looking up the absorbance value on this standard curve, from which the result is calculated. 5.5 Calculate 66 cs/T 13025.13–94 m(A s)/1. Scene 1 ······ ····· ····· ······ ····· ····· ···⋯ ⋯(2) Where: . — The arsenic content in the sample solution is determined from the standard curve. pH; m— mass of the sample, 9. Additional notes: This standard was proposed by the Ministry of Light Industry of the People’s Republic of China. It is under the jurisdiction of the National Standardization Center for Sea and Lake Salts and the National Standardization Center for Well and Mine Salts. Method 1 of this standard was drafted by the National Standardization Center for Sea and Lake Salts, while Methods 2 and 3 were drafted by the National Standardization Center for Well and Mineral Salts. The main drafters of Method 1 in this standard are Li Bingquan and Li Menghua. The main drafters of Method 2 and Method 3 are Zhang Nengjun and Shen Min.

Thank you to the friend above; we are also using this method at the moment, but the reproducibility of the analysis is not very good – there are significant issues with the instrument

It is relatively easy to measure using atomic fluorescence. The sample is digested with HNO3+KClO3; Vc and thiourea are used to pre-reduce pentavalent arsenic to trivalent form while masking other interferences. During measurement, potassium borohydride acts as a reducing agent to convert trivalent arsenic into arsine, and non-dispersive atomic fluorescence spectroscopy is employed for detection, allowing measurements in the range of 0.0000x–0.x%

We use the arsenic spot method, which can only provide an approximate range; for example, less than a certain number of PPM

Could you explain the atomic fluorescence analysis method in more detail? We are also working on arsenic analysis right now, and it’s quite challenging!

It can also be determined by back-titration of potassium dichromate with ammonium ferrous sulfate; the endpoint is satisfactory, and it’s a direct volumetric method that’s quite simple to use, :)

Dear sailors upstairs, in what area do you carry out arsenic analysis? We want to conduct an analysis of arsenic in naphtha! Some methods are for the analysis and determination of arsenic in foods! Are they not different?

What we do is conduct tests on food industry salts

For UG grade samples, atomic fluorescence spectroscopy can be used; it’s quite simple. For levels of 0.0x to x%, ICP-AES can be employed as well, and that’s also simple