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CN-122016680-A - Method for determining iodine in regional geochemical survey sample

CN122016680ACN 122016680 ACN122016680 ACN 122016680ACN-122016680-A

Abstract

The invention provides a method for measuring iodine in a regional geochemical survey sample, and belongs to the technical field of measuring methods. The invention adopts spectrophotometry to measure the iodine content in the sample. Firstly, mixing a sample with Ai Sika mixed flux, heating, melting, extracting in water bath, and then fixing the volume. Taking supernatant, sequentially adding sodium carbonate, acetic acid, tetrakaline and chloramine T solution for color development, and measuring absorbance at 600nm wavelength and a cuvette of 1cm or 3 cm. And drawing a standard curve through an iodine standard solution, and calculating the iodine content of the sample according to the absorbance after blank deduction. The method has low detection limit, high accuracy and good precision. The method is easy to operate, low in cost, better than the existing national standard in efficiency, suitable for analysis and test of mass geochemical sample iodine, and has wide application prospect.

Inventors

  • YANG XIAOYAN
  • Liang Ruixuan
  • Du Yupin
  • DONG WEI
  • CHEN FUQIANG
  • CHEN HUILIAN
  • YANG HUIWEI
  • HE GUANGTAO
  • Li Ruineng
  • ZHONG SHENGHUI

Assignees

  • 广东省地质实验测试中心(广东省矿产应用研究所)

Dates

Publication Date
20260512
Application Date
20260128

Claims (9)

  1. 1. A method for determining iodine in a regional geochemical survey sample, comprising the steps of, S1, sample preparation, namely crushing and sieving a sample, and then drying; S2, sample pretreatment, namely uniformly mixing and stirring a sample and Ai Sika mixed fluxes, putting the mixture into a container, then covering a layer of Ai Sika mixed fluxes, heating and calcining in a temperature programming mode, cooling after calcining, transferring the fused block into the container by hot water, carrying out water bath in boiling water, cooling to a fixed volume to scale, standing for clarification, and obtaining a sample liquid; the Ai Sika mixed flux is prepared by mixing sodium carbonate and zinc oxide in a mass ratio of 3:2; S3, preparing blank samples, namely preparing at least two blank samples for standby by using an S2 sample pretreatment mode; S4, measuring a sample, namely adding water into supernatant in the sample liquid to obtain a constant volume solution, sequentially and quantitatively adding a sodium carbonate solution and an acetic acid solution to make the supernatant uniform, adding a 4,4' -tetramethyl diaminodiphenyl methane solution to make the supernatant uniform, adding a chloramine T solution to make the solution uniform, transferring the solution into a cuvette, taking the water as a reference solution at the wavelength of 600nm of a spectrophotometer, measuring absorbance, simultaneously carrying out the same operation on a blank experiment liquid, and recording blank absorbance; S5, measuring a curve, namely respectively taking iodine standard solutions with different concentrations, measuring the maximum absorbance value and drawing an absorbance-iodine content standard curve in the same step as the measurement of the sample in the step S4; S6, calculating the iodine content, namely subtracting the absorbance of the sample after blank absorbance, and calculating the iodine content of the sample according to an absorbance-iodine content standard curve; The iodine content formula is: wherein: A Sample of -uncorrected sample to determine absorbance; a Blank space -average value of absorbance of blank; a-slope of absorbance-iodine content standard curve; b-intercept of absorbance-iodine content standard curve; s-dilution factor; m-the mass of the sample in grams (g).
  2. 2. The method for determining iodine in a regional geochemical survey sample according to claim 1, wherein in the preparation of the S1 sample, the particle size of the sample is less than 74 μm and the sample is dried for 2 hours at 105±5°.
  3. 3. The method for determining iodine in a regional geochemical survey sample according to claim 1, wherein in the step S2 of the pretreatment of the sample, ai Sika mixed flux is used in an amount of three times the mass of the sample when the sample is mixed with Ai Sika mixed flux, and Ai Sika mixed flux is used in an amount of three times the mass of the sample when the mixed flux is covered with Ai Sika.
  4. 4. The method for determining iodine in a regional geochemical survey sample according to claim 1, wherein in the S2 sample pretreatment, the specific method for programming the temperature is: A stage of raising the room temperature to 400 ℃ and keeping for 30min; And in the two stages, the temperature is increased to 700 ℃ at 400 ℃ and the temperature is kept for 60 minutes.
  5. 5. The method for determining iodine in a regional geochemical survey sample of claim 1 wherein the S2 sample pretreatment is performed in a boiling water bath for 60 minutes.
  6. 6. The method for geochemical investigation of iodine in a measurement zone according to claim 1, wherein in the measurement of the sample in step S4, a sodium carbonate solution, an acetic acid solution, a 4,4' -tetramethyl diaminodiphenyl methane solution, and a chloramine T solution are sequentially and quantitatively added.
  7. 7. The method for geochemical investigation of iodine in a measurement zone according to claim 1, wherein in the measurement of the S4 sample, the measurement of absorbance after adding 4,4' -tetramethyl diaminodiphenylmethane solution is completed within 60min, and the ambient temperature at the time of measurement is between 18 and 23 ℃.
  8. 8. The method for determining iodine in a regional geochemical investigation sample according to claim 1, wherein the concentration of 4,4' -tetramethyl diaminodiphenyl methane is 0.1 g/L, the concentration of sodium carbonate solution is 36 g/L, the concentration of acetic acid solution is 8% (v/v), and the concentration of chloramine-T solution is 1.0 g/L.
  9. 9. The method for geochemical investigation of iodine in a measurement area according to claim 1, wherein when the iodine content in the sample is less than or equal to 1.0 mg/kg, 2.0mL of supernatant is separated, 1cm cuvette is used for colorimetric, or 1.0mL of supernatant is separated, and 3cm cuvette is used for colorimetric in the measurement of the sample in step S4; When the iodine content in the sample is more than 1.0 mg/kg, 1.0mL of supernatant is separated, and a cuvette with the size of 1cm is used for colorimetric; the total volume of the constant volume solution was 10.0mL.

Description

Method for determining iodine in regional geochemical survey sample Technical Field The invention belongs to the technical field of measurement methods, and particularly relates to a method for measuring iodine in a regional geochemical survey sample. Background The iodine determination method is various, and trace iodine in the current regional geochemical investigation sample mainly adopts ion chromatography, inductively coupled plasma mass spectrometry (ICP-MS) and catalytic spectrophotometry. The ion chromatography generally needs to be matched with an ampere detector, so that the investment of whole equipment is higher, the detection limit of the method is relatively higher, few reports are made in recent years, the sensitivity of the ICP-MS method is excellent, the detection limit can be as low as 0.00Xmg/kg, the linear range is wide, the method is widely applied to the detection fields of soil, food, environment, agriculture and the like, but the detection cost of the method is higher, the resin treatment and exchange steps are longer, the instrument has stronger memory effect, the classical spectrophotometry is low in cost consumption, the equipment is economical and easy to popularize, the method is still widely applied, but the traditional spectrophotometry of the Fe 3+-CNS--NO2- catalysis system has more interference factors, the stability is poor, the operation period is long, the detection limit of the practical method is larger than 1.0mg/kg, the content of a sample of <1.0mg/kg cannot be accurately measured, and the detection requirement of the geochemical survey specification (1:250000) of multiple target areas (DZ/T0258-2014) cannot be met. The research adopts an optimized chloramine T-four-base catalytic photometry, and provides a method which has the advantages of low cost, high accuracy, good precision and low detection limit and is suitable for batch detection of regional geochemical samples. Disclosure of Invention The invention provides a method for determining iodine in a regional geochemical survey sample, which comprises the following steps, S1, sample preparation, namely crushing and sieving a sample, and then drying; S2, sample pretreatment, namely uniformly mixing and stirring a sample and Ai Sika mixed fluxes, putting the mixture into a container, then covering a layer of Ai Sika mixed fluxes, heating and calcining in a temperature programming mode, cooling after calcining, transferring the fused block into the container by hot water, carrying out water bath in boiling water, cooling to a fixed volume to scale, standing for clarification, and obtaining a sample liquid; the Ai Sika mixed flux is prepared by mixing sodium carbonate and zinc oxide in a mass ratio of 3:2; S3, preparing blank samples, namely preparing at least two blank samples for standby by using an S2 sample pretreatment mode; S4, measuring a sample, namely adding water into supernatant in the sample liquid to obtain a constant volume solution, sequentially and quantitatively adding a sodium carbonate solution and an acetic acid solution to make the supernatant uniform, adding a 4,4' -tetramethyl diaminodiphenyl methane solution to make the supernatant uniform, adding a chloramine T solution to make the solution uniform, transferring the solution into a cuvette, taking the water as a reference solution at the wavelength of 600nm of a spectrophotometer, measuring absorbance, simultaneously carrying out the same operation on a blank experiment liquid, and recording blank absorbance; S5, measuring a curve, namely respectively taking iodine standard solutions with different concentrations, measuring the maximum absorbance value and drawing an absorbance-iodine content standard curve in the same step as the measurement of the sample in the step S4; S6, calculating the iodine content, namely subtracting the absorbance of the sample after blank absorbance, and calculating the iodine content of the sample according to an absorbance-iodine content standard curve; The iodine content formula is: wherein: A Sample of -uncorrected sample to determine absorbance; a Blank space -average value of absorbance of blank; a-slope of absorbance-iodine content standard curve; b-intercept of absorbance-iodine content standard curve; s-dilution factor; m-the mass of the sample in grams (g). Preferably, in the preparation of the S1 sample, the particle size of the sample is less than 74 μm, and the sample is dried for 2 hours under the condition of 105+/-5 ℃ C. Preferably, in the step S2 of sample pretreatment, the amount of Ai Sika mixed flux is three times the mass of the sample when the sample is mixed with Ai Sika mixed fluxes, and the amount of Ai Sika mixed flux is three times the mass of the sample when the mixed fluxes are covered with Ai Sika. Preferably, in the S2 sample pretreatment, the specific method for temperature programming is as follows: A stage of raising the room temperature to 400 ℃ and keeping for 30min; And i