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CN-121878080-B - Method for measuring DMPP content in compound fertilizer

CN121878080BCN 121878080 BCN121878080 BCN 121878080BCN-121878080-B

Abstract

The invention discloses a method for measuring DMPP content in a compound fertilizer, which comprises the following steps of S1, preparing a standard working solution, S2, preprocessing a sample, S3, detecting by chromatography-mass spectrometry, and S4, quantitatively analyzing. Aiming at the quantitative error caused by matrix effect, the invention provides a gradient standard working solution prepared by using a blank fertilizer matrix extracting solution, and the physical and chemical property difference between a sample and a standard product is eliminated through matrix matching, so that the accuracy of a calibration curve is improved. Secondly, in order to strengthen the purification effect of complex matrix samples, a C18 solid phase extraction column is introduced to combine with methanol-water system elution, and the activation and re-dissolution conditions are optimized, so that nonpolar interferents such as lipid, pigment and the like are effectively removed, the complex matrix samples are compatible with NY/T3423-2019 water extraction systems, the sensitivity and the anti-interference capability are obviously better than those of HPLC-UV by adopting an ESI + /MRM mode, and the complex matrix samples are suitable for research and development/internal control/confirmation, and if the complex matrix samples are used for supervision and sampling/arbitration, the method verification and approval are required to be completed.

Inventors

  • WEI ZHANBO
  • LIU ZHIGUANG
  • WANG LINGLI
  • DONG JINGJING

Assignees

  • 中国科学院沈阳应用生态研究所

Dates

Publication Date
20260512
Application Date
20260323

Claims (9)

  1. 1. The method for measuring the DMPP content in the compound fertilizer is characterized by comprising the following steps of: s1, preparing a standard working solution, namely preparing a matrix matching standard working solution with DMPP concentration gradients of 0.01, 0.05, 0.1, 0.5 and 1.0mg/L by taking a blank fertilizer matrix extracting solution as a solvent; S2, sample pretreatment: Weighing 2 parts by mass of a sample of the solid fertilizer, adding 20 parts by mass of primary water, extracting for 30 minutes at 25+/-2 ℃ in an oscillating way, centrifuging for 10 minutes at 10000r/min, and taking supernatant; Taking 2 parts by mass of a sample of the liquid fertilizer, adding 18 parts by mass of primary water for dilution, oscillating for 10 minutes, and centrifuging to obtain a supernatant; The method comprises the steps of (1) carrying out complex matrix sample, passing supernatant through an activated C18 solid phase extraction column, eluting with 5 parts by mass of methanol and 5 parts by mass of primary water in sequence, collecting methanol eluting liquid nitrogen, blowing to be nearly dry, and carrying out primary water re-dissolution with 1 part by mass, wherein the nitrogen blowing re-dissolution step adopts a constant temperature of 45+/-2 ℃, the nitrogen flow rate is 2.5-3.0L/min, and evaporating until the residual liquid is less than or equal to 0.05 part by mass; S3, chromatography-mass spectrometry detection: chromatographic conditions, mobile phase A, aqueous solution containing 0.1 part by mass of formic acid, mobile phase B and acetonitrile; gradient elution procedure, 20% phase 0-2minB, 5min up to 80%, hold to 7min,7.1min back to 20% and equilibrate to 10min; chromatographic column, C18 reverse phase column 2.1mm×100mm, particle size 1.8-2.6 μm, flow rate 0.3mL/min, and sample injection amount 5 μl; The mass spectrum condition, ion source, electrospray positive ion mode ESI + , monitoring mode, multi-reaction monitoring MRM, parent ion m/z186.1, quantitative ion m/z139.0, collision energy 18eV, and qualitative ion m/z122.0 collision energy 15eV; S4, quantitatively analyzing, namely establishing a matrix matching standard curve R 2 which is more than or equal to 0.995 by using the gradient concentration standard working solution, and calculating the DMPP content in the sample by using an external standard method, wherein the detection limit of the method is less than or equal to 0.005mg/kg, and the quantitative limit is less than or equal to 0.015mg/kg.
  2. 2. The method for measuring the DMPP content in the compound fertilizer according to claim 1, wherein the qualitative sub-ions comprise m/z 122.0+/-0.1 and m/z 93.0+/-0.1, the collision energy is 15+/-1 eV and 25+/-1 eV respectively, the abundance of the m/z93.0 sub-ions is more than or equal to 30% of the abundance of the m/z122.0 sub-ions, otherwise, the false positive is judged.
  3. 3. The method for determining the content of DMPP in a compound fertilizer according to claim 1, wherein in the gradient elution procedure, the formic acid content of the mobile phase A is 0.099-0.101 parts by mass per 100 parts of the aqueous solution, and the purity of the mobile phase B is not less than 99.9% of acetonitrile.
  4. 4. The method for measuring the content of DMPP in a compound fertilizer according to claim 1, wherein the complex matrix sample SPE purified eluent complex solution is a primary aqueous solution containing 0.24-0.26 parts by mass of methanol.
  5. 5. The method for measuring the content of DMPP in a compound fertilizer according to claim 1, wherein in the step of oscillating extraction, 0.05-0.1 part by mass of sodium dodecyl sulfate, SDS and C 12 H 25 SO 4 Na are added into a solid sample; after the centrifugation step, the supernatant was prefiltered with a 0.45 μm filter membrane, which was previously soaked with 5 parts by mass of methanol and 10 parts by mass of primary water.
  6. 6. The method for measuring the content of DMPP in the compound fertilizer according to claim 1, wherein deuterated DMPP internal standard d 3 -DMPP,[ 2 H 3 ]C 5 H 8 N 2 + is added to the solution to be measured before mass spectrum detection, and the concentration is 0.05 parts by mass per 1000 parts of the solution.
  7. 7. The method for determining the content of DMPP in a compound fertilizer according to claim 1, wherein the mass spectrum source temperature is 148-152 ℃, the desolventizing gas temperature is 345-355 ℃ and the gas flow is 785-815L/h.
  8. 8. The method for measuring the DMPP content in the compound fertilizer according to claim 1, wherein the nitrogen blowing and re-dissolving step is carried out at a constant temperature of 45+/-2 ℃ at a nitrogen flow rate of 2.5-3.0L/min, and the nitrogen blowing and re-dissolving step is carried out until the residual liquid is less than or equal to 0.05 mass parts.
  9. 9. The method for measuring the content of DMPP in a compound fertilizer according to claim 1, wherein 0.01 parts by mass of monopotassium phosphate KH 2 PO 4 is added to every 100 parts of solution when the matrix is prepared to match the standard working solution.

Description

Method for measuring DMPP content in compound fertilizer Technical Field The invention belongs to the technical field of chemical detection, and particularly relates to a method for measuring DMPP content in a compound fertilizer. Background DMPP (dimethyl pyrazole phosphate) is used as a high-efficiency nitrification inhibitor, is widely applied to compound fertilizer production, and delays the conversion of ammonium nitrogen to nitrate nitrogen by inhibiting the activity of nitrifying bacteria in soil, so that the fertilizer utilization rate is improved and the nitrogen loss is reduced. However, DMPP is typically added to compound fertilizers in relatively low amounts (typically 0.5-1.5% w/w) and the fertilizer matrix composition is complex and may contain pigments, organic solvent residues or other interfering substances, resulting in challenges for accurate quantitative analysis. At present, high Performance Liquid Chromatography (HPLC) or liquid chromatography-mass spectrometry (LC-MS/MS) technology is mostly adopted for the detection method of DMPP, but the traditional method has the following limitations that firstly, the influence of matrix effect is not fully considered, quantitative deviation can be caused by directly using a pure solvent standard curve, secondly, the pretreatment step is simple, interference components in a complex matrix are difficult to effectively remove, particularly ion inhibition or chromatographic peak tailing is easy to be caused for a liquid fertilizer or a sample containing a surfactant, thirdly, mass spectrum parameter optimization is insufficient, and false positive results can occur due to single qualitative basis, so that the method for measuring the DMPP content in the compound fertilizer is provided. Disclosure of Invention The invention aims to provide a method for measuring DMPP content in a compound fertilizer, aiming at quantitative errors caused by matrix effects, the method is characterized in that a blank fertilizer matrix extracting solution is adopted to prepare a gradient standard working solution, physical and chemical property differences between a sample and a standard product are eliminated through matrix matching, and the accuracy of a calibration curve is improved. Secondly, in order to strengthen the purifying effect of the complex matrix sample, a C18 solid phase extraction column is introduced to combine with the methanol-water system for elution, and the activating and redissolving conditions are optimized, so that nonpolar interferents such as lipid, pigment and the like are effectively removed. In order to achieve the above purpose, the invention adopts the following technical scheme: A method for measuring the content of DMPP in a compound fertilizer comprises the following steps: s1, preparing a standard working solution, namely preparing a matrix matching standard working solution with DMPP concentration gradients of 0.01, 0.05, 0.1, 0.5 and 1.0mg/L by taking a blank fertilizer matrix extracting solution as a solvent; S2, sample pretreatment: Weighing 2 parts by mass of a sample of the solid fertilizer, adding 20 parts by mass of primary water, extracting for 30 minutes at 25+/-2 ℃ in an oscillating way, centrifuging for 10 minutes at 10000r/min, and taking supernatant; Taking 2 parts by mass of a sample of the liquid fertilizer, adding 18 parts by mass of primary water for dilution, oscillating for 10 minutes, and centrifuging to obtain a supernatant; The complex matrix sample is prepared by passing the supernatant through an activated C18 solid phase extraction column under the activation conditions of sequentially eluting with 5 parts by mass of methanol and 5 parts by mass of primary water, collecting methanol eluting liquid nitrogen, blowing to be nearly dry, and re-dissolving with 1 part by mass of primary water; S3, chromatography-mass spectrometry detection: chromatographic conditions, mobile phase A, aqueous solution containing 0.1 part by mass of formic acid, mobile phase B and acetonitrile; gradient elution procedure, 20% phase 0-2minB, 5min up to 80%, hold to 7min,7.1min back to 20% and equilibrate to 10min; chromatographic column, C18 reverse phase column 2.1mm×100mm, particle size 1.8-2.6 μm, flow rate 0.3mL/min, and sample injection amount 5 μl; The mass spectrum condition, ion source, electrospray positive ion mode ESI +, monitoring mode, multi-reaction monitoring MRM, parent ion m/z186.1, quantitative ion m/z139.0, collision energy 18eV, and qualitative ion m/z122.0 collision energy 15eV; S4, quantitatively analyzing, namely establishing a matrix matching standard curve R 2 which is more than or equal to 0.995 by using the gradient concentration standard working solution, and calculating the DMPP content in the sample by using an external standard method, wherein the detection limit of the method is less than or equal to 0.005mg/kg, and the quantitative limit is less than or equal to 0.015mg/kg. Preferably, the qualitative