Method for determining tin and its inorganic compounds in the air of the workplace

Abstract

The application discloses a method for determining tin and inorganic compounds thereof in workplace air. The method comprises the following steps: firstly, using a microporous filter membrane to sample the workplace air; then, using a disposable PP polypropylene digestion tube, a digestion solution and a graphite digestion instrument to digest the microporous filter membrane after sampling; taking down the cooled microporous filter membrane and quantitatively placing it into a test tube by using a hydrochloric acid solution; adjusting the Ph value by using a sodium hydroxide solution and setting the volume to 25.0 mL; preparing a tin standard solution series and drawing a fluorescence intensity-tin content curve by using an atomic fluorescence spectrometer; analyzing the sample by using the atomic fluorescence spectrometer; the sample fluorescence intensity is proportional to the tin content; and obtaining the corresponding tin content from the fluorescence intensity of the sample according to the drawn fluorescence intensity-tin content curve. The method realizes the analysis and determination of trace, ultratrace tin and inorganic compounds thereof, reduces the instability of blank filter membranes caused by external interference, avoids the phenomenon that the blank filter membrane concentration is opposite to the sample concentration, and improves the determination precision.

Description

Technical Field

[0001] This invention relates to the field of chemical detection technology, and in particular to a method for determining tin and its inorganic compounds in workplace air. Background Technology

[0002] Tin is a low-melting-point metal. In nature, tin rarely exists in a free state, so pure metallic tin is rare. The most important tin ore is cassiterite, chemically composed of tin dioxide, which is currently the main raw material for tin smelting. In addition, tin can combine with various minerals to form symbiotic tin deposits. Currently, about 18 tin minerals have been discovered. Tin's main industrial use is as electronic solder in the semiconductor industry. Driven by the photovoltaic industry, tin, as a green material, has huge potential applications in the chemical industry, such as PVC flame retardants and zinc stannate, which are large-scale replacements for PVC as green materials. In the field of heat stabilizers, methyl tin mercaptan is a non-toxic and environmentally friendly PVC heat stabilizer, and zinc stannate, as a new type of safe and non-toxic flame retardant, is an environmentally friendly alternative to antimony trioxide. Furthermore, trace amounts of tin have various physiological functions, especially in anti-tumor effects. In the human thymus, it can produce anti-tumor tin compounds that inhibit the formation of cancer cells. In addition, tin promotes the synthesis of proteins and nucleic acids, which is beneficial to the body's growth and development; it also forms a variety of enzymes and participates in the biological reaction of flavin enzymes, which can enhance the stability of the internal environment. Most tin and its inorganic compounds are low-toxicity or slightly toxic, while organic compounds are moderately to highly toxic. However, exposure to high concentrations of dust particles can cause changes in lung X-rays, and long-term exposure may lead to metal pneumoconiosis; some hydrocarbon tin compounds can cause cerebral leukodystrophy, manifested as severe headaches and visual impairment, and in severe cases, death. Therefore, tin dioxide (calculated as Sn), dibutyltin dilaurate, trimethyltin chloride, triethyltin chloride, and bis(thioglycolic acid) dioctyltin have all been included in "GBZ2.1-2019 Occupational Exposure Limits for Hazardous Factors in the Workplace Part 1: Chemical Hazardous Factors".

[0003] Currently, most domestic methods for determining tin and its inorganic compounds in workplace air are based on "Determination of Toxic Substances in Workplace Air - Part 26: Tin and its Inorganic Compounds" (GBZ / T 300.26-2017), which includes two detection methods: "Acid Digestion-Flame Atomic Absorption Spectrometry of Tin and its Inorganic Compounds" and "Dry Ashing of Tin Dioxide-Quercusin Spectrophotometry".

[0004] The main principle of the "Acid Digestion-Flame Atomic Absorption Spectrometry for Tin and its Inorganic Compounds" method is as follows: aerosol tin and its inorganic compounds in the air are collected using a microporous membrane. After acid digestion, the absorbance is measured at a wavelength of 224.6 nm using an acetylene-air flame atomic absorption spectrophotometer for quantification. The pretreatment process is as follows: the sampled microporous membrane is placed in a beaker, and 4 mL of digestion solution (1 volume of nitric acid mixed with 9 volumes of hydrochloric acid) is added. A watch glass is placed on top, and digestion is carried out at approximately 130℃ on a temperature-controlled heater until the digestion solution volume is approximately 0.5 mL. After cooling, the solution is quantitatively transferred to a stoppered graduated test tube using hydrochloric acid solution and brought to a final volume of 10.0 mL. The sample is then analyzed using atomic absorption spectrometry. The detection limit of this method is 0.5 μg / mL, and the lower limit of quantitation is 1.6 μg / mL. Based on a 75 L air sample, the lowest detectable concentration is 0.07 mg / mL. 3 The minimum quantitative concentration is 0.2 mg / m³. 3 When the tin concentration in the sample solution is 40 μg / mL, 500 μg / mL Ni 2＋ Fe 3＋ Zn 2＋ Pb 2＋ 100 μg / mL Na ＋ Al 3＋ Mn 2＋ As 3＋ Cr 6＋ Ca 2 ＋ 50 μg / mL Cd 2＋ Cu 2＋ It does not interfere with the measurement.

[0005] The main principle of the "dry ashing-quercetin spectrophotometric method for tin dioxide" is as follows: Tin dioxide in the air is collected using a microporous membrane. After ashing, tin ions react with quercetin in an acidic solution in the presence of thiourea to form a yellow complex. The absorbance is measured at 440 nm using a spectrophotometer for quantification. The limit of quantification for this method is 0.8 μg / mL, and the quantitative range is 0.8 μg / mL to 20 μg / mL. Based on a 75 L air sample, the lowest quantification concentration is 0.11 mg / mL. 3 This method requires melting with sodium hydroxide, which is cumbersome and has poor precision.

[0006] In actual production, there are still many aspects of the acid digestion-flame atomic absorption spectrometry technique for tin and its inorganic compounds according to GBZ / T 300.26-2017 that warrant further discussion. Firstly, there is the issue of method sensitivity. The concentration of tin and its inorganic compounds in workplaces varies greatly. In some precision processes, the tin content is extremely low, often only 0.001-0.1 μg / mL after membrane digestion. The sensitivity of the acetylene-air flame atomic absorption spectrophotometry method is only 0.5 μg / mL, which is insufficient to guarantee the accuracy of trace tin determination. Secondly, there is the issue of sample pretreatment. The method involves placing the membrane in a beaker, adding 4 mL of digestion solution, covering it with a watch glass, and digesting it at approximately 130℃ on a temperature-controlled heater. However, the concentration of tin and its inorganic compounds on the blank membrane is very low, and impurities are easily introduced into the beaker, causing instability in the blank membrane measurement and severely affecting the detection accuracy. Summary of the Invention

[0007] The technical problem to be solved by this invention is to provide a method for determining tin and its inorganic compounds in workplace air. This method overcomes the defects of traditional detection methods, adopts a highly sensitive analytical method, and realizes the analysis and determination of trace and ultra-trace tin and its inorganic compounds. This ensures that the detection results of occupational hazard factors of tin and its inorganic compounds in precision tin processing are accurate and reliable, reduces the instability of blank filter membrane caused by external interference, avoids the phenomenon of inversion between blank filter membrane solubility and sample solubility, and improves the accuracy of determination.

[0008] To solve the above-mentioned technical problems, the method for determining tin and its inorganic compounds in workplace air according to the present invention includes the following steps:

[0009] Step 1: Use a microporous filter membrane to sample the workplace air. After sampling, fold the microporous filter membrane twice with the dust-collecting side facing inward, put it in a clean plastic bag or paper bag, and place it in a clean container for transportation and storage. Air samples can be stored for a long time at room temperature and blank tests can be performed simultaneously.

[0010] Step 2: After sampling, the microporous filter membrane is placed in a disposable PP polypropylene digestion tube, 4 mL of digestion solution is added, the digestion tube is loosely capped, and digested at 130℃ on a graphite digester until about 0.5 mL is obtained; after cooling, it is quantitatively transferred into a stoppered graduated test tube with 10% (v / v) hydrochloric acid solution, the pH value is adjusted to 4-5 with sodium hydroxide solution, and the volume is brought to 25.0 mL.

[0011] Step 3: Prepare a series of standard tin solubility solutions and analyze them with an atomic fluorescence spectrometer to plot a standard curve of fluorescence intensity versus tin content;

[0012] Step 4: The sample is analyzed using an atomic fluorescence spectrometer. After the sample is digested by acid heating, tin is oxidized to tetravalent tin. Under the action of sodium borohydride, tin hydride is generated. Tin hydride is carried into the atomizer by the carrier gas for atomization. Under the irradiation of a specially made hollow tin cathode lamp, the ground state tin atoms are excited to a high energy state. When deactivated and returned to the ground state, they emit fluorescence of a characteristic wavelength. The fluorescence intensity is proportional to the tin content.

[0013] Step 5: Based on the plotted fluorescence intensity-tin content standard curve, obtain the corresponding tin content from the fluorescence intensity of the sample.

[0014] Furthermore, in step one, the sampling of workplace air using a microporous filter membrane includes either a short-time sampling mode or a long-time sampling mode. In the short-time sampling mode, a sampling clip with a microporous filter membrane is installed at the sampling point, and an air sample is collected for 15 minutes at a flow rate of 5 L / min. In the long-time sampling mode, a sampling clip with a microporous filter membrane is installed at the sampling point, and an air sample is collected for 2 to 8 hours at a flow rate of 1 L / min.

[0015] Furthermore, in step one, blank samples for sample blank testing are collected simultaneously at the sampling point. The sampling clip containing the microporous filter membrane is opened, the filter membrane is immediately removed, and placed in a clean plastic or paper bag. Then, it is transported, stored, and measured together with the sample. Each batch of samples should have no less than two blank samples.

[0016] Furthermore, in step three, the preparation of the tin standard solubility series solution involves gradually diluting the tin standard stock solution into a series of standard solutions with a concentration of 0.1 ug / mL, while maintaining the solubility in the medium as 2% H2SO4 (V / V).

[0017] Furthermore, in step four, the carrier gas used in the atomic fluorescence spectrometer is a 1.5% H2SO4 (V / V) solution. This solution is prepared by measuring 15 mL of concentrated sulfuric acid, slowly adding it to deionized water while stirring, and then cooling it to a final volume of 1000 mL.

[0018] Furthermore, in step four, the reducing agent used in the atomic fluorescence spectrometer is 2% KBH4 (W / V) + 0.5% NaOH (W / V). To prepare this reducing agent, first dissolve 2g of NaOH in 200mL of deionized water, add 8g of KBH4, and then dilute with deionized water to 400mL and shake well.

[0019] Furthermore, in step four, the analytical parameters of the atomic fluorescence spectrophotometer are set as follows: negative high voltage 300V, total lamp current 90mA, atomizer height 8mm, carrier gas 300mL / min, and shielding gas 900mL / min.

[0020] Further, the tin content of the sample in step five is calculated as follows:

[0021] Convert the sampling volume to a standard sampling volume:

[0022] (1)

[0023] In the formula: V0 is the standard sampling volume, V is the sampling volume, t is the temperature at the sampling point, and P is the atmospheric pressure at the sampling point.

[0024] Calculate the concentration of tin in the air using formula (2):

[0025] (2)

[0026] In the formula: C is the concentration of tin in the workplace air, 25 is the volume of the sample solution, and C0 is the measured concentration of tin in the sample solution.

[0027] Since the method for determining tin and its inorganic compounds in workplace air of this invention adopts the above-mentioned technical solution, the method first uses a microporous filter membrane to sample workplace air. After sampling, the microporous filter membrane is digested using a disposable PP polypropylene digestion tube, digestion solution, and graphite digestion instrument. After cooling, hydrochloric acid solution is quantitatively added to the test tube, the pH value is adjusted to 4-5 with sodium hydroxide solution, and the volume is adjusted to 25.0 mL. A series of tin standard solubility solutions are prepared, and the fluorescence intensity-tin content curve is plotted by atomic fluorescence spectrometry. The sample is analyzed by atomic fluorescence spectrometry. The fluorescence intensity of the sample is directly proportional to the tin content. According to the plotted fluorescence intensity-tin content curve, the corresponding tin content is obtained from the fluorescence intensity of the sample. This method overcomes the shortcomings of traditional detection methods and adopts a highly sensitive analytical approach to achieve the analysis and determination of trace and ultra-trace tin and its inorganic compounds. It ensures the accuracy and reliability of the detection results of occupational hazard factors of tin and its inorganic compounds in precision tin processing, reduces the instability of blank filter membranes caused by external interference, avoids the phenomenon of inversion between the solubility of blank filter membranes and sample solubility, and improves the accuracy of determination. Detailed Implementation

[0028] The method for determining tin and its inorganic compounds in workplace air according to the present invention includes the following steps:

[0029] Step 1: Use a microporous filter membrane to sample the workplace air. After sampling, fold the microporous filter membrane twice with the dust-collecting side facing inward, put it in a clean plastic bag or paper bag, and place it in a clean container for transportation and storage. Air samples can be stored for a long time at room temperature and blank tests can be performed simultaneously.

[0030] Step 2: After sampling, the microporous membrane is placed in a disposable PP polypropylene digestion tube, 4 mL of digestion solution is added, the tube is loosely capped, and digested at 130℃ on a graphite digester until approximately 0.5 mL is obtained. After cooling, the solution is quantitatively transferred into a stoppered graduated test tube using 10% (v / v) hydrochloric acid solution. The pH value is adjusted to 4-5 with sodium hydroxide solution, and the volume is brought to 25.0 mL. The digestion solution is 1 volume of nitric acid (… r 20 = 1.42 g / mL) and 9 volumes of hydrochloric acid ( r Mix (20 = 1.18 g / mL);

[0031] Step 3: Prepare a series of standard tin solutions and analyze them with an atomic fluorescence spectrometer to plot a standard curve of fluorescence intensity versus tin content;

[0032] Step 4: The sample is analyzed using an atomic fluorescence spectrometer. After the sample is digested by acid heating, tin is oxidized to tetravalent tin. Under the action of sodium borohydride, tin hydride is generated. Tin hydride is carried into the atomizer by the carrier gas for atomization. Under the irradiation of a specially made hollow tin cathode lamp, the ground state tin atoms are excited to a high energy state. When deactivated and returned to the ground state, they emit fluorescence of a characteristic wavelength. The fluorescence intensity is proportional to the tin content.

[0033] Step 5: Based on the plotted fluorescence intensity-tin content standard curve, obtain the corresponding tin content from the fluorescence intensity of the sample.

[0034] Preferably, step one involves sampling workplace air using a microporous filter membrane, which can be either a short-time sampling mode or a long-time sampling mode. In the short-time sampling mode, a sampling clip with a microporous filter membrane is installed at the sampling point, and an air sample is collected for 15 minutes at a flow rate of 5 L / min. In the long-time sampling mode, a sampling clip with a microporous filter membrane is installed at the sampling point, and an air sample is collected for 2 to 8 hours at a flow rate of 1 L / min.

[0035] Preferably, in step one, blank samples for sample blank testing are collected at the sampling point simultaneously. The sampling clip containing the microporous filter membrane is opened, the filter membrane is immediately removed, and placed in a clean plastic bag or paper bag. Then, it is transported, stored, and measured together with the sample. Each batch of samples shall have no less than two blank samples.

[0036] Preferably, in step three, the preparation of the tin standard solubility series solutions involves progressively diluting the tin standard stock solution to a concentration of 0.1 μg / mL, while maintaining a solubility of 2% H₂SO₄ (V / V) medium. Specifically, 20 mL of concentrated sulfuric acid is slowly added to deionized water while stirring, and after cooling, the volume is adjusted to 1000 mL, which is then used as the diluent for the 0.1 μg / mL tin standard series solutions.

[0037] Preferably, the carrier gas used in the atomic fluorescence spectrometer in step four is a 1.5% H2SO4 (V / V) solution. This solution is prepared by measuring 15 mL of concentrated sulfuric acid, slowly adding it to deionized water while stirring, and then cooling it to a final volume of 1000 mL.

[0038] Preferably, the reducing agent used in the atomic fluorescence spectrometer in step four is 2% KBH4 (W / V) + 0.5% NaOH (W / V). The reducing agent is prepared by first dissolving 2g of NaOH in 200mL of deionized water, adding 8g of KBH4, and then diluting it with deionized water to 400mL and shaking well.

[0039] Preferably, in step four, the analytical parameters of the atomic fluorescence spectrophotometer are set as follows: negative high voltage 300V, total lamp current 90mA, atomizer height 8mm, carrier gas 300mL / min, and shielding gas 900mL / min.

[0040] Preferably, the tin content calculation of the sample in step five is as follows:

[0041] Convert the sampling volume to a standard sampling volume:

[0042] (1)

[0043] In the formula: V0 is the standard sampling volume, V is the sampling volume, t is the temperature at the sampling point, and P is the atmospheric pressure at the sampling point.

[0044] Calculate the concentration of tin in the air using formula (2):

[0045] (2)

[0046] In the formula: C is the concentration of tin in the workplace air, 25 is the volume of the sample solution, and C0 is the measured concentration of tin in the sample solution.

[0047] This method was used to sample and analyze tin and its inorganic compounds in the workplace air of a factory. The method detection limit, precision, accuracy, and linear range of tin were tested. The method detection limit was found to be 0.067 μg / L, and the relative standard deviation remained within 5%. The recoveries of the spiked filter membrane samples were consistently between 90.4% and 103%, and the method maintained good linearity, demonstrating its promising practical application. Specific experimental data are as follows:

[0048] Standard curve of the method

[0049] Tin standard solutions of 0 μg / L, 1.0 μg / L, 2.0 μg / L, 4.0 μg / L, 8.0 μg / L, and 10.0 μg / L were prepared and analyzed. The fluorescence intensity was directly proportional to the tin content. The correlation coefficient r = 0.9993, the intercept a = -8.878, and the slope b = 101.180, maintaining a good linear relationship, which fully meets the concentration range requirements for the determination of tin and its inorganic compounds in workplace air.

[0050] Method detection limit

[0051]

[0052] Method precision

[0053]

[0054] Spiked recovery rate

[0055]

[0056] Traditional acetylene-air flame atomic absorption spectrophotometry (AAS-A) analysis of tin, which uses beakers and hot plates for pretreatment, suffers from the introduction of new impurities and uneven heating, leading to instability in blank filter membrane analysis. For trace and ultra-trace tin analysis, the concentration of tin in the blank sample often exceeds that in the analytical sample, resulting in low sensitivity and significant chemical interference. Furthermore, AAS-A has a detection limit of only 0.5 μg / mL, which is insufficient to meet the requirements of trace and ultra-trace tin analysis in some precision manufacturing workshops. This method utilizes disposable PP polypropylene digestion tubes and a graphite digester for sample pretreatment, reducing the introduction of impurities and improving sample stability.

[0057] This method employs a highly sensitive analytical approach to analyze trace and ultra-trace tin and its inorganic compounds, ensuring accurate and reliable detection results of occupational hazard factors related to tin and its inorganic compounds in precision tin processing. Pretreatment using disposable PP polypropylene digestion tubes and a graphite digester reduces the instability of the blank filter membrane caused by external interference, avoiding the inversion of the solubility of the blank filter membrane with that of the sample.

[0058] This method fully utilizes the low detection limit and high sensitivity of atomic fluorescence spectrometry to analyze the content of tin and its inorganic compounds in the workplace. The detection limit for tin by atomic fluorescence spectrometry is 0.067 μg / L, far exceeding the 0.5 μg / ml detection limit recommended by atomic absorption spectrometry in GBZ / T300.26-2017, which can fully meet the requirements for trace and ultra-trace tin analysis. At the same time, atomic fluorescence spectrometry has the advantages of less interference, high method sensitivity and safety, and the method precision and accuracy results are ideal, which can fully meet the requirements for trace, especially ultra-trace, tin analysis in workshop air and meet the needs of precise occupational health management.

Claims

1. A method for determining tin and its inorganic compounds in workplace air, characterized in that... This method includes the following steps: Step 1: Use a microporous filter membrane to sample the workplace air. After sampling, fold the microporous filter membrane twice with the dust-collecting side facing inward, put it in a clean plastic bag or paper bag, and place it in a clean container for transportation and storage. Air samples can be stored at room temperature and blank tests can be performed simultaneously. Step 2: After sampling, the microporous filter membrane is placed in a disposable PP polypropylene digestion tube, 4 mL of digestion solution is added, the digestion tube is loosely capped, and digested at 130℃ on a graphite digester until about 0.5 mL is obtained; after cooling, it is quantitatively transferred into a stoppered graduated test tube with 10% (v / v) hydrochloric acid solution, the pH value is adjusted to 4-5 with sodium hydroxide solution, and the volume is brought to 25.0 mL. Step 3: Prepare a series of tin standard solubility solutions and plot the fluorescence intensity-tin content standard curve using an atomic fluorescence spectrophotometer. The preparation of the tin standard solubility series solutions involves gradually diluting the tin standard stock solution to a concentration of 0.1 ug / mL, while maintaining the solubility medium as 2% H2SO4 (V / V). Step 4: The sample is analyzed using an atomic fluorescence spectrometer. After acid heating digestion, tin is oxidized to tetravalent tin. Under the action of sodium borohydride, tin hydrides are generated. These tin hydrides are carried by a current carrier into the atomizer for atomization. Under irradiation by a tin hollow cathode lamp, the ground-state tin atoms are excited to a high-energy state. Upon deactivation and return to the ground state, they emit fluorescence of a characteristic wavelength, the intensity of which is proportional to the tin content. The current carrier used in the atomic fluorescence spectrometer is 1.5%. The H2SO4 (V / V) solution was prepared by measuring 15 mL of concentrated sulfuric acid, slowly adding it to deionized water while stirring, and then cooling and bringing the volume to 1000 mL. The reducing agent used in the atomic fluorescence spectrometer was 2% KBH4 (W / V) + 0.5% NaOH (W / V). The reducing agent was prepared by dissolving 2 g of NaOH in 200 mL of deionized water, adding 8 g of KBH4, dissolving it, and then diluting it with deionized water to 400 mL and shaking well. Step 5: Based on the plotted fluorescence intensity-tin content standard curve, obtain the corresponding tin content from the fluorescence intensity of the sample.

2. The method for determining tin and its inorganic compounds in workplace air according to claim 1, characterized in that: Step one involves sampling workplace air using a microporous filter membrane, including either a short-time sampling mode or a long-time sampling mode. In the short-time sampling mode, a sampling clip with a microporous filter membrane is installed at the sampling point, and air samples are collected for 15 minutes at a flow rate of 5 L / min. In the long-time sampling mode, a sampling clip with a microporous filter membrane is installed at the sampling point, and air samples are collected for 2 to 8 hours at a flow rate of 1 L / min.

3. The method for determining tin and its inorganic compounds in workplace air according to claim 1, characterized in that: In step one, blank samples for blank testing are collected at the sampling point. The sampling clip containing the microporous filter membrane is opened, the filter membrane is immediately removed and placed in a clean plastic or paper bag. Then, it is transported, stored and measured together with the sample. Each batch of samples should have no less than two blank samples.

4. The method for determining tin and its inorganic compounds in workplace air according to claim 1, characterized in that: In step four, the analytical parameters of the atomic fluorescence spectrophotometer are set as follows: negative high voltage 300V, total lamp current 90mA, atomizer height 8mm, carrier gas flow rate 300mL / min, and shielding gas flow rate 900mL / min.

5. The method for determining tin and its inorganic compounds in workplace air according to claim 1, characterized in that: Calculation of tin content in the sample during step five: Convert the sampling volume to the standard sampling volume: （1） In the formula: V0 is the standard sampling volume, V is the sampling volume, t is the temperature at the sampling point, and P is the atmospheric pressure at the sampling point. Calculate the concentration of tin in the air using formula (2): （2） In the formula: C is the concentration of tin in the workplace air, 25 is the volume of the sample solution, and C0 is the measured concentration of tin in the sample solution.

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