140 results about "Isotope dilution" patented technology

The invention discloses an isotope dilution mass spectrometry method for determining the content of uranium in a uranium niobium alloy. A formula for calculating the content of uranium in the uranium niobium alloy is derived according to an isotope dilution mass spectrometry principle. A decomposition process of the uranium niobium alloy is researched, the sampling quantity and the amount of a diluent are optimized, and the influences of mass spectrum line interference and alloy element interference on a measurement result are discussed. The method comprises the following steps: adding nitric acid and hydrofluoric acid to quantitatively dissolve the uranium niobium alloy, adding a quantitative amount of a uranium isotope diluent to directly prepare a mixed sample solution, determining the mixed solution and the uranium isotope proportion in the uranium niobium alloy sample through mass spectrometry, and calculating the content of uranium in the uranium niobium alloy. Quantitative separation of uranium is not needed by the determined method. An XRF technique, an ICP-AES technique and an element analysis technique are used to measure the content of niobium and the total content of impurity elements in the uranium niobium alloy, and back stepping is carried out to obtain the corresponding uranium content order in order to verify the accuracy of the analytical result, and the obtained result is consistent with a result obtained through the experiment method. When the method disclosed in the invention is used to analyze the uranium niobium alloy sample, the relative standard uncertainty of determination results is 0.2% (6 determinations), and the expanded uncertainty is 0.5% (95% confidence level).

The invention relates to a detection method and application of a carboxy methyl lysine ingredient in food. The detection method comprises the following steps of: carrying out derivatization by a derivating agent after protein acid in a sample is hydrolyzed; obtaining solution to be detected from the derived solution by solid-phase extraction; carrying out qualitative and quantitative analysis on the carboxy methyl lysine ingredient in the food by adopting a tandem mass spectrometry of isotope dilution ultra-performance liquid chromatography, wherein the derivating agent is 9-fluorenylmethyl chloroformate.

The invention discloses a quick measurement method for coumarin and safrole in essence and flavor. The quick measurement method comprises the steps of performing oscillation extraction on an essence and flavor sample by taking ethyl alcohol aqueous solution as a solvent, filtering an extracting solution through an organic filtering film, and measuring the coumarin and the safrole through ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS / MS). The quick measurement method has the characteristics that difficulties in quantified separation and purification of a complicated mixture system are avoided through quantification by an isotope dilution internal standard method; the ethyl alcohol aqueous solution is used as the sample extraction solvent, so that the extraction efficiency is guaranteed, and the amount of organic impurities, which enter a chromatographic column, in small samples is reduced; furthermore, the chromatographic column is effectively protected; compared with the conventional method, the UPLC-MS / MS is high in analysis speed, high in repetitiveness and high in recycling rate, and is suitable for analysis of a large batch of samples.

Provided is a combustion pretreatment-isotope dilution mass spectrometry measuring concentration of a target element for detection contained in a target sample for detection by using an isotope dilution mass spectrometry, including: pretreating the target sample for detection by combustion during an isotope dilution mass spectrometry, to thereby stabilize an isotope and further improve analysis ability, and therefore, the present invention is expected to be utilized as an element analysis method surpassing accuracy of the existing mass spectrometry method.

The invention discloses a method for preparing a pork powder standard substance with clenbuterol. The method comprises the following steps: performing simulated feeding so as to obtain a pork raw material polluted by clenbuterol, crushing a sample, directly mixing with water in a proper ratio, preparing freeze-dried pork by using a freeze-drying method directly without homogenation, and implementing steps of grinding, screening, uniform mixing, radiation and the like, thereby obtaining freeze-dried pork powder in good uniformity. Value confirmation, uniformity inspection and stability monitoring of standard substances are implemented by using a liquid chromatogram isotope dilution mass spectrometry (LC-ID-MS / MS) method for verifying accuracy through international comparison. The pork powder standard substance with clenbuterol, which is prepared by using the method, is good in uniformity and stability, and can be applied to analysis method evaluation for residue detection on clenbuterol in pork, quality control in analysis process and laboratory capability evaluation.

The invention discloses a preparation method of a chloramphenicol-containing fishmeal standard material. The method is characterized in that the raw fishmeal polluted by chloramphenicol is obtained through simulating feeding; a sample is preprocessed and mixed with water by proper ratio; then the mixture is uniformly pulped; the freeze-dried fish is obtained by a freezing drying method; the freeze-dried fish is grinded, screened, uniformly mixed and irradiated to prepare the freeze-dried fishmeal which is high in uniformity; the uniformity is detected, the stability is monitored, and the standard material is assigned by high-accuracy measuring through a liquid chromatography-isotope dilution mass spectrometry. The trace chloramphenicol containing freeze-dried fishmeal is high in uniformity and stability and is applicable to the evaluation of method for analyzing the trace chloramphenicol residue in an aquatic product, the quality control in analyzing, and the assessment of lab ability; the standard material is applicable to calibrating of metering devices and evaluation of measurement methods.

The invention discloses a determination method for bromo-dioxin in an environment sample, particularly relates to determination of the bromo-dioxin in coexistence of polybrominated diphenyl ethers and the bromo-dioxin, and belongs to the field of detection of the bromo-dioxin. The determination method comprises pre-treatment of the sample and instrument analysis. The pre-treatment of the sample comprises Soxhlet extraction-sulfuric acid treatment-purification by multilayered silica gel columns-purification by an active carbon silica gel column-nitrogen blowing concentration; and the determination is as follows: an isotope dilution-high resolution gas chromatography-high resolution mass spectrometry (HRGC-HRMS) is used for determining the test sample. The problems that the polybrominated diphenyl ethers and the bromo-dioxin are difficult to separate when the polybrominated diphenyl ethers and the bromo-dioxin coexist, and the bromo-dioxin is decomposed into the polybrominated diphenyl ethers in the instrument analysis process are solved, so that the method is a high-sensitivity and high-accuracy analysis method for determining the bromo-dioxin in the sample.

A spinning cell device is described for fast and convenient standardization and analysis of constituents and isotopes in solid samples by laser ablation inductively coupled plasma (LA-ICP) spectrometry. The method and apparatus for performing he method require the sample under test and a standard to be spun during ablation allowing the quasi-simultaneous ablation of both materials. The aerosols resulting from the ablation of sample and standard are mixed in the ablation cell allowing quantification of the ablated metals by the method of standard addition or isotope dilution. The relative proportion of standard verses sample ablated can be changed by altering the trajectory of the laser beam. The ablated aerosol is swept into an inductively coupled plasma by a carrier gas and analyzed by mass spectrometry.

The invention discloses a detection method of free and combined carboxy methyl lysine in milk and dairy products. According to the detection method, isotope dilution high performance liquid chromatography- tandem ion trap mass spectrometry is adopted to detect free carboxy methyl lysine and carboxy methyl lysine combined with protein in milk and dairy products. According to the detection method, using of ion-pairing agent is avoided; no derivatization pretreatment is needed; efficiency, accuracy, sensitivity, and reproducibility are high; linearity range is wide; the detection method possesses unique features in analysis of the content of free carboxy methyl lysine and carboxy methyl lysine combined with protein in milk and dairy products, can be used for rapid and accurate qualitative and quantitative analysis on free carboxy methyl lysine and carboxy methyl lysine combined with protein in milk and dairy products, and can be used for detection of free and combined carboxy methyl lysine in milk and dairy products preferably.

The invention discloses a method for detecting serum glycated albumin and a special candidate reference substance thereof. The present invention provides a method using an isotope dilution liquid chromatography tandem mass spectrometry method for the determination of glycated albumin content in a sample to be detected. The method comprises the following steps: 1) preparing a standard solution, and separating and purifying the albumin in a sample to be detected; 2) preparing a working standard solution and a working sample to be detected; 3) respectively detecting the working standard solution and the working sample to be detected by using a liquid chromatography tandem mass spectrometer to obtain the glycated albumin content in the sample to be detected. The experiment of the invention has proved that based on a JSCC recommendation method, a candidate reference method for accurate determination of glycated albumin is established by using the liquid chromatography tandem triple quadrupole. On this basis, a GA candidate reference substance for freezing and mixing human serum matrix is developed, and the invention is expected to be further used for the chamber evaluation and validation of the GA project.

The invention discloses a method for accurately testing the digestion efficiency of proteins in a matrix. The method comprises the following steps: (1) performing specific peptide fragment screening and digestion on target proteins for determining specific digestion peptide fragments; (2) synthesizing the specific peptide fragments; (3) preparing a standard protein mother liquor; (4) performing preliminary measurement on the concentration of the target proteins; (5) performing the digestion and measuring the concentration; (6) adding a diluent, performing the digestion and performing isotopic dilution mass spectrometry measurement on the concentration of the specific peptide fragments; (7) calculating the concentration of the proteins according to the concentration of the specific peptide fragments; (8) calculating the digestion efficiency when the concentration of added target proteins is used in the step (6); (9) repeating the steps (6)-(8), and adding different protein amounts every time to obtain a series of digestion efficiency values; and (10) plotting according to the protein addition amount and the digestion efficiency and extrapolating the digestion efficiency when the added protein amount is zero so as to obtain the accurate digestion efficiency of the proteins. The method has the advantages of high accuracy and good traceability.

The invention discloses a method of quantifying the content of recombinant troponin I by peptide fragment isotope dilution mass-spectrography and relates to a method of accurately quantifying the content of recombinant troponin I. The method comprises the following steps: designing a characteristic peptide fragment; determining mass spectrometry ion pairs of the characteristic peptide fragment; performing an LC-MRM condition research; performing sample analysis pre-treatment which mainly comprises the steps: recombinant protein degeneration, reductive alkylation, enzymolysis, sample purification and concentration of the sample; data analysis: concentration of a cTnI specific peptide fragment and the appearance time of the cTnI protein peptide being 4.20min; and recovery rate and precision: the recovery rate and precision meet the specification, and the mass spectrometer condition on the recombinant cTnI specific peptide fragment liquid phase is researched and modified. The established method is good in accuracy and fast in speed, and the appearance time is 4.20min.

The invention discloses a protein isotope dilution tandem mass spectrometry method based on a chemical labeling technology. The method comprises (1) labeling a sample to be detected by a chemical label A to obtain a labeled sample, (2) labeling an internal standard substance with a chemical label iso-A with an isotope label to obtain a labeled internal standard substance, (3) uniformly mixing the labeled sample and the labeled internal standard substance according to a preset ratio to obtain an initial sample, (4) pretreating the initial sample to obtain a fed sample, and (5) carrying out mass spectrometry on the fed sample. The sample and internal standard substance are respectively labeled, then are mixed, then added into a reaction system and then are treated so that the sample and internal standard substance are subjected to the same matrix effect and have the same operation error in the same system and thus the error can be corrected.

The present invention provides a correction method for determination of trace element in a sample by isotope dilution mass spectrometry, and belongs to the field of isotope dilution mass spectrometry determination. During value determination of the trace element in a to-be-tested sample by isotope dilution mass spectrometry, when isotopic abundance ratios of a to-be-tested element in a standard material solution and a to-be-tested sample solution are not equal due to matrix interference, the isotopic abundance ratio of the to-be-tested element in the standard material solution and the isotopic abundance ratio of the to-be-tested element in the to-be-tested sample solution are respectively measured, and then according to the correction method, correction coefficient K is calculated; and measurement value associated with the to-be-tested sample can be calibrated by use of the K value for finally realizing the accurate determination of the content of the trace element in the to-be-tested sample by isotope dilution mass spectrometry. The method solves the to-be-tested sample matrix interference effect on the value determination accuracy during determination of the content of the trace element in the to-be-tested sample by isotope dilution mass spectrometry.

The invention discloses an LC-MS quantitative detection method for melamine and tricyanic acid in human urine. The method is characterized in that the isotope dilution technology is adopted, and in pre-processing of an urine sample, 13C3, 15N3-melamine or deuterated melamine, 13C3 and 15N3-tricyanic acid are respectively added in interior label solution; melamine and tricyanic acid in human urine are respectively extracted by a liquid-liquid extraction method; an LC-MS / MS method is established to respectively and quantitatively detect the concentration of melamine and tricyanic acid in human urine; a liquid chromatogram takes filled columns such as phenyl, fluorophenyl, silica gel and the like as immobile phase; methanol, acetonitrile, water, formic acid solution or mixed liquid as mobile phase; in chromatographic resolution, isocratic elution or gradient elution is carried out; and in mass spectrometric detection, an ESI Source is used for detecting the content of melamine and tricyanic acid in human urine. The minimum limit of quantification of melamine and tricyanic acid can reach 10ng / ml. The processing of a sample by the method in the invention is economical, simple and convenient, in addition, the detection has strong specificity and high sensitivity, and various methodology indicators can reach related technological requirements of the Chinese Pharmacopoeia.

The invention provides a quantitative plasmid DNA (Deoxyribonucleic Acid) detection kit which has the characteristics of adopting a plasmid DNA standard substance to accurately quantify by using an ultrasonic-isotope dilution mass-spectrography with high accuracy, and making up the defect that a conventional kit cannot quantify the plasmid DNA. The invention further provides a plasmid DNA quantitative detection method which comprises the following steps of: respectively measuring fluorescence signal strengths of the plasmid DNA standard substances of different concentrations; drawing a concentration-fluorescence signal strength standard curve; subsequently measuring the fluorescence signal strength of a plasmid DNA sample to be measured; and accurately calculating the DNA concentration of the sample to be measured according to the drawn standard curve. According to the method and the kit, standard plasmids are adopted to be used as the DNA standard to quantify in a fluorescent dye method for the first time with high sensitivity, and DNA as low as 1pg can be detected; the linear range is wide, and plasmid DNA of 0.25-1000ng / Ml can be detected; and the standard plasmids are quantified by using the ultrasonic-isotope dilution mass-spectrography, and the quantitative value obtained is low in uncertainty and high in accuracy.

The invention relates to an isotope dilution high resolution chromaticness combination method for simultaneously detecting organic chlorine pesticides and polychlorinated biphenyl in a biological sample. The method can realize simultaneous purification of the two targets of the organic chlorine pesticides and the polychlorinated biphenyl in a pre-treatment process, and a detection process can be carried out simultaneously. The sample pretreatment employs a method combining gel permeation chromatography with Florisil silica column (or silica gel column) purification. A gold standard method using an isotope dilution high resolution GC-MS is employed for the detection. Compared with a traditional low resolution mass spectrum and an electron capture detector (ECD) method, the interference and false positive results are reduced, and the indexes such as the method deletion limit and the quantitative result accuracy are greatly improved. The method can save more than 50% of labour amount, time and consumables such as solvents, and filler materials in comparison with a method for respective and step by step measurement of the organic chlorine and the polychlorinated biphenyl, and has important meaning for research and monitor of the organic chlorine pesticides and the polychlorinated biphenyl.

The invention discloses a method for rapidly and sensitively combined-testing Vitamin K1 by isotope dilution ultra-high performance liquid chromatography, wherein the method includes steps of (1), preparing reference substance solution of Vitamin K1 and isotope internal standard solution of Vitamin K1; (2), setup up a standard curve of the Vitamin K1; (3), sampling chromatogram of a sample solution to be tested; (4), determining the concentration of the Vitamin K1 in the sample to be tested. When the method for combined-testing Vitamin K1 by isotope dilution ultra-high performance liquid chromatography is used for test the Vitamin K1 in serum, the method is simple and rapid, high in accuracy, strong in specificity, high in accuracy, and good in sensitivity.

A method of analyzing ethylated thymidine DNA adducts is disclosed. The method comprises the steps of: providing leukocyte DNA; adding at least one isotope-labeled internal standard and a plurality of enzymes to the leukocyte DNA, and hydrolyzing the leukocyte DNA into a plurality of nucleosides; using a solid-phase extraction column to extract the plurality of nucleosides; and using a stable isotope dilution nanoflow liquid chromatography-nanospray ionization tandem mass spectrometry to detect and quantify at least one ethylated thymidine DNA adduct in the plurality of extracted nucleosides.

The present invention discloses a method for determining the serum miR-224 content by using the isotope dilution mass spectrometry. The method comprises the following steps: (1) synthesizing a singlestrand of miR-224 nucleic acid to formulate into a solution, and establishing a standard curve; (2) synthesizing a nucleic acid peptide probe to formulate into the solution for capturing miR-224; (3)synthesizing the isotopically labeled polypeptide to formulate into the solution as an internal standard; (4) extracting the miRNA in a serum sample; (5) biotinylating the extracted miRNA; (6) reacting the miRNA with the streptomycin agarose sphere to form the miRNA-biotin-streptavidin agarose sphere complex; (7) adding the nucleic acid peptide probe to capture the miR-224-biotin-streptavidin agarose sphere complex; (8) after washing the complex, adding trypsin for enzymatic hydrolysis, then performing solid phase extraction on the enzymatic hydrolysate, and drying and re-dissolving the extracted polypeptide; (9)performing mass spectrometry on the dissolved polypeptide and the isotopically labeled polypeptide sample; and (10) calculating the miR-224 content in the serum sample. The methoddisclosed by the present invention has high accuracy and reliable results.

The invention discloses a preparation method for an edible oil standard substance containing a capsicine compound. The capsicine compound is uniformly added into soybean oil through a method of gradual dilution and uniform mixing, so the edible oil matrix standard substance containing trace capsicine residual is obtained. Uniformity examination, stability monitoring and assignment of the standard substance are carried out in virtue of high-accuracy measurement of liquid chromatography-isotope dilution mass spectrometry. The standard substance has good uniformity and stability, can be used for detection of the capsicine compound in edible oil and for preliminary screening and discrimination of drainage oil, and is applicable to calibration of a measuring instrument and evaluation of a measuring method as the standard substance.

The invention discloses a determination method of plutonium age in a trace plutonium sample. The method comprises the following steps of: adding plutonium and the isotopic diluents of daughter uranium thereof, namely, Pu and U, in the sample; adding concentrated nitric acid for heating and price adjustment; and then loading a TEVA resin column, using a chemical separation method to respectively obtain a Pu component and a U component, and using a multi-receiving inductive coupling plasma mass spectrometry to measure the Pu component and the Am component respectively to obtain the values of Pu / Pu and U / U . According to the amount of the added diluents, the value of Pu / U is calculated and substituted into the age-calculating formula to obtain the age of plutonium. The deviation between the age measured by the method and the reference value is within 5%.

The invention belongs to the field of environmental organic pollutant analysis method application and particularly relates to a pretreatment process of using a bimetallic composite oxide nanomaterialwith a special shape and a large specific surface as an accelerated solvent extraction filler for determination of multiple persistent organic pollutants in an atmospheric particulate sample. According to the pretreatment process, an isotope dilution mass spectrometry method is adopted for detection, the standard recovery rate of the multiple persistent organic pollutants in the particulate sampleis within the range of 80.0-120.0%, and relative standard deviations are all within the range of 0.5-7.0%. The pretreatment analysis method is rapid, accurate and effective, meets the requirement forgreen chemistry and can be applied to routine detection of multiple types of organic matter in atmospheric particulates.

The invention discloses a mercapturic acid adduct detection method for evaluating short-term exposure of acrylamide. The method includes the steps that 1, urine to be detected is pretreated; 2, the pretreated urine is subjected to chromatographic detection; 3, a standard curve method is adopted for performing quantitative analysis on the detection result. An isotope dilution ultrahigh performance liquid chromatography-tandem mass spectrometry method (UHPLC-MS / MS) is adopted for quantifying four mercapturic acid adducts of acrylamide, analysis time is greatly shortened, meanwhile, the four mercapturic acid metabolins are well separated, synchronous detection of the four mercapturic acid adducts is achieved, and therefore the internal exposure quantity of acrylamide can be evaluated more comprehensively.

The invention belongs to the field of an application of environmental organic pollutant analysis methods, and particularly relates to an application of integrated accelerated solvent extraction and purification in a pretreatment method for determining polycyclic aromatic hydrocarbon and polychlorinated biphenyl organic pollutants in marine sediments and quality control of interferents. A marine sediment sample can achieve integration of extraction and purification through the method, an extraction solvent is n-hexane: dichloromethane (1: 1, v / v), an extraction temperature is 80-140 DEG C, a cycle index is 3-8, and static extraction time is 5-20 min; a purification adsorbent is 0.5-2g of Florisil, the silica gel, neutral aluminum oxide, alkaline aluminum oxide, acidic aluminum oxide and Mg-Al-LDO; and an isotope dilution gas chromatography-tandem mass spectrometry method is adopted for detection, an adding standard recovery rate of 16 PAHs in a sample is 80%-120%, the adding standard recovery rate of 7 PCBs is 85%-120%, and a relative standard deviation is 0.5%-6.0%. The pretreatment method is a green, simple, convenient and rapid method for detecting the organic pollutants in the marine sediment sample.

The invention discloses a method for fixing the value of a standard substance of a G2 EPSPS protein solution. The method comprises the following steps: accurately testing the content of a pure G2 EPSPS protein product by using an isotope dilution spectrum method and an amino acid analysis method, finally preparing a G2 EPSPS protein solution standard substance by using a gravimetric method-volumetric method, carrying out value measuring verification by using an ELISA (Enzyme Lined Immunosorbent Assay) method, carrying out uniformity and stability inspection, and carrying out preservation stability verification by putting a stabilizer into the standard substance. The G2 EPSPS protein standard substance prepared by using the method is particularly significant for detecting whether the G2 EPSPS protein in a glyphosate tolerant transgenic crop is reasonably expressed or not. The invention provides the method for fixing the value of the standard substance in the G2 EPSPS protein solution, and the method has good reliability, accuracy and traceability.

The invention discloses a measuring method for amino acid in electronic cigarette smoke liquid. The method comprises the steps that a diluted hydrochloric acid solution is used as extraction liquid, an electronic cigarette smoke liquid sample is vibrated and extracted, extraction liquid is filtered through an organic filter film, seventeen kinds of amino acids in the electronic cigarette smoke liquid are measured through a high performance liquid chromatography-tandem mass spectrum combined method, and quantitation is carried out through an internal standard method. By the adoption of isotope dilution internal standard method quantitation, the influences of matrix effects in the analysis process are avoided; direct sampling is adopted, the content of seventeen kinds of amino acids in the electronic cigarette smoke liquid can be rapidly and accurately detected, repeatability and the recovery rate are good, and the measuring method is applicable to rapid analysis of industrial large-batch samples.

The invention discloses a method for quickly determining trace osmium in nickel alloy by inductively coupled plasma mass spectrometry. By adding a reducing agent ascorbic acid into the solution to be tested, the high-valence osmium (+8) is reduced, and the valence of the osmium standard solution is The state is consistent, so that the atomization efficiency in ICP-MS is consistent, and the standard curve method is used to directly measure the amount of osmium in the nickel alloy test solution on the inductively coupled plasma mass spectrometer. Other coexisting elements in the nickel alloy will not be Restored to solid form and precipitated. The sample does not need to be absorbed by distillation to determine the amount of osmium by ICP-MS; it does not depend on the addition of isotope diluent while processing the sample 190 Os, make it fully mixed with the sample or standard solution, exchange to reach equilibrium, keep the same chemical form of osmium, and then use the ICP-MS method to determine the amount of osmium. The method can accurately and quickly measure the trace osmium in the nickel alloy material rich in platinum group metals by using the method. The method is simple, fast and has high accuracy and meets the analysis requirements of the trace osmium in the nickel alloy.

The invention discloses a method for determining eugenol in aquatic products using isotope dilution gas chromatography mass spectrometry, and relates to the technical field of physicochemical detection of drug residues in the aquatic products. A muscle sample is extracted by an organic solution in advance, a C18 solid phase extraction column is adopted to conduct purification, GC-MS / MS MS analysis is adopted to determine the drug residues in the aquatic products, the method comprises the following steps that preparation is conducted, wherein fish body dissection and homogenization are conducted, and low-temperature storage is conducted in a refrigerator at 20 DEG C; isotopes are added for internal standard and mixing is conducted uniformly; the organic solution is adopted for extraction; the C18 solid phase extraction column is adopted to conduct the purification; redissolving is conducted after rotary evaporation and concentration; supernatant is absorbed to be subjected to the GC-MS / MS MS analysis after being filtered by an organic phase filtration membrane of 0.22 micrometer. By the adoption of the method for determining eugenol in the aquatic products using the isotope dilution gas chromatography mass spectrometry, the defects are overcome that an existing external standard quantitative method is strong in substrate interference and poor in quantitative accuracy, and the method has the advantages of being less in interference and high in accuracy and sensitivity.

The invention relates to a stable isotope 13C or 15N-labeled biurea synthesis method. Stable isotope-labeled urea and stable isotope-labeled hydrazine hydrate as raw materials undergo a reaction under the acid catalysis action and the product is purified to form the stable isotope-labeled biurea. Compared with the prior art, the synthesis method has mild reaction conditions and a high isotope utilization rate. Through separation purification, the stable isotope 13C or 15N-labeled biurea has chemical purity of 99% or more, isotopic abundance of 99atom% or more and mass number difference of 3 or more, satisfies requirements on an internal standard reagent in isotope dilution mass spectrometry-based detection of biurea residues in a flour product and has a good practical value and a good economic value.