CN112630320A - Method for detecting content of aromatic hydrocarbon mineral oil in milk powder by using full-two-dimensional gas chromatography-time-of-flight mass spectrometry - Google Patents
Method for detecting content of aromatic hydrocarbon mineral oil in milk powder by using full-two-dimensional gas chromatography-time-of-flight mass spectrometry Download PDFInfo
- Publication number
- CN112630320A CN112630320A CN202011363758.3A CN202011363758A CN112630320A CN 112630320 A CN112630320 A CN 112630320A CN 202011363758 A CN202011363758 A CN 202011363758A CN 112630320 A CN112630320 A CN 112630320A
- Authority
- CN
- China
- Prior art keywords
- column
- dimensional
- temperature
- time
- milk powder
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/62—Detectors specially adapted therefor
- G01N30/72—Mass spectrometers
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/04—Preparation or injection of sample to be analysed
- G01N2030/042—Standards
- G01N2030/045—Standards internal
Landscapes
- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
Abstract
The invention discloses a method for detecting the content of aromatic hydrocarbon mineral oil in milk powder by using a full-two-dimensional gas chromatography-time-of-flight mass spectrometry. The method has the advantages that the milk powder is subjected to proper pretreatment, and then the aromatic hydrocarbon mineral oil content in the milk powder is detected and determined by using the full-two-dimensional gas chromatography-time-of-flight mass spectrometer, the pretreatment is simple, the aromatic hydrocarbon mineral oil content in the milk powder can be effectively separated and detected, the sensitivity is high, the pretreatment is simple, the operation is easy, the detection limit is low, and the content can reach 0.1 ppm.
Description
Technical Field
The invention relates to a method for detecting the content of aromatic hydrocarbon mineral oil in milk powder by using a full-two-dimensional gas chromatography-time-of-flight mass spectrometry, belonging to the technical field of chemical analysis.
Background
Mineral Oil (MOH) is a hydrocarbon mixture obtained by fractionating crude petroleum oil, and generally has 10 to 50 carbon atoms, and mainly includes saturated hydrocarbon Mineral Oil (MOSH) and aromatic hydrocarbon Mineral Oil (MOAH), the former being composed of linear, branched and cyclic alkanes, and the latter being composed of alkylated polyaromatic hydrocarbon compounds. Research shows that MOH is easy to accumulate in human body for a long time after being taken in a diet, is a pollutant with the largest accumulation amount in the human body, and the toxicity of MOSH is mainly reflected in the biological accumulation property, can form granuloma and causes harm to organs; MOAH is mutagenic, and particularly MOAH with 3 or more benzene rings is carcinogenic, so that MOAH remains in food are of more concern. In the national mineral oil regulations issued in 2017 in Germany, the limit value of MOAH (C16-C35) transferred from the food packaging material is 0.5 mg/kg.
At present, the detection method for mineral oil in food mainly comprises a saponification method, an infrared spectrophotometer method, a gas chromatography-hydrogen ion flame method, a liquid chromatography-gas chromatography-hydrogen ion flame ionization method and the like. However, the methods generally have the problems of complicated pretreatment process, easy pollution, inaccurate separation and quantification, high equipment cost, no popularization, false positive and the like.
Disclosure of Invention
The invention overcomes the defects of the prior art and provides a method for detecting the content of aromatic hydrocarbon mineral oil in milk powder by using a full two-dimensional gas chromatography-time-of-flight mass spectrometry. The method has the advantages that the milk powder is subjected to proper pretreatment, and then the aromatic hydrocarbon mineral oil content in the milk powder is detected and determined by using the full-two-dimensional gas chromatography-time-of-flight mass spectrometer, the pretreatment is simple, and the aromatic hydrocarbon mineral oil content in the milk powder can be effectively separated and detected.
A method for detecting the content of aromatic hydrocarbon mineral oil in milk powder by utilizing a full two-dimensional gas chromatography-time-of-flight mass spectrum comprises the following steps:
1) weighing 10-15g of milk powder, adding an internal standard substance and 30-35mL of n-hexane, carrying out ultrasonic treatment for 120-130min, filtering nitrogen, and carrying out blowing concentration until the volume of the liquid is 1-2mL to obtain a concentrated solution;
2) purifying and removing impurities from the concentrated solution obtained in the step 1) through a silver nitrate SPE small column;
3) leaching a silver nitrate SPE small column by using 10-20mL of mixed solution of normal hexane and toluene, blowing leaching liquid nitrogen to be dry, and adding 1-1.5mL of normal hexane to redissolve and load the sample;
4) setting appropriate detection conditions by adopting a full two-dimensional gas chromatography-time-of-flight mass spectrometer, qualitatively analyzing target components by using an NIST (Nist standard library) and retention time, and determining the content of aromatic hydrocarbon mineral oil in a sample by using an internal standard method.
Further, the internal standard substance in the step 1) is a mixture of 1,3, 5-tri-tert-butyl benzene (TBB) and 1-methylnaphthalene (1-MN); the addition amount of the 1,3, 5-tri-tert-butyl benzene (TBB) is 0.05mg added in each kilogram of milk powder, and the addition amount of the 1-methylnaphthalene (1-MN) is 0.05mg added in each kilogram of milk powder.
Further, the silver nitrate SPE cartridge in the step 2) is a 0.3% customized silver nitrate silica gel glass cartridge.
Further, the mixed solution of n-hexane and toluene in the step 3) is a solution obtained by mixing n-hexane and toluene according to a volume ratio of 2: 1.
Further, the chromatographic column of the comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometer in the step 4) adopts a GC x GC column system, the one-dimensional chromatographic column is a nonpolar capillary column, the two-dimensional chromatographic column is a medium-polarity column, and the one-dimensional chromatographic column and the two-dimensional chromatographic column are connected in series through a capillary column joint connector.
Further, the detection conditions in the step 4) include a sample introduction condition, a column oven temperature rise program, a modem condition, and a time-of-flight mass spectrometer condition.
Further, the sample injection conditions are as follows: the sample inlet temperature is 280 ℃, the sample injection volume is 2 mu L, the flow distribution mode is not adopted, helium is carried, and the flow rate is 1.5 mL/min;
the temperature raising procedure of the column incubator is that the initial temperature of the one-dimensional column incubator is 50 ℃, the temperature is kept for 3min, then the temperature is raised to 210 ℃ at the speed of 8 ℃, then the temperature is raised to 300 ℃ at the speed of 10 ℃, the temperature is kept for 22min, the temperature compensation of the two-dimensional chromatographic column relative to the one-dimensional column incubator is 5 ℃, and the temperature compensation of the modulator relative to the two-dimensional column is 15 ℃;
the modem adopts the conditions of a solid-state thermal modulator, a DV modulation column (1.2m multiplied by 0.25mm), a period of 6s and thermal desorption time of 0.8 s;
the time-of-flight mass spectrometer has the conditions of an electron bombardment source, 200 muA of filament emission current, 70eV of electron energy, 250 ℃ of ion source temperature, 280 ℃ of interface temperature, 50-600 amu of collection mass range, 100 spectrum/s of collection speed and 400s of solvent delay.
Has the advantages that:
(1) the detection method has high sensitivity, and can effectively separate the target.
(2) The detection method has simple pretreatment and easy operation.
(3) The detection method has low detection limit which can reach 0.1 ppm.
Drawings
FIG. 1 is a spectrum of MOAH and MOSH standards of the invention;
FIG. 2 is a sample spectrum without the addition of a standard substance according to the present invention;
fig. 3 is a standard operating curve for the present invention.
Detailed Description
In order to make the technical solutions in the present application better understood, the present invention is further illustrated with reference to the following embodiments, which are only a part of the embodiments of the present application, but not all of them, and the present invention is not limited by the following embodiments.
Example 1
Unless otherwise specified, the containers according to the invention are made of glass. The internal standards used were 1,3, 5-tri-tert-butylbenzene (TBB), 1-methylnaphthalene (1-MN). The SPE cartridge was a 0.3% custom silver nitrate silica glass cartridge.
Example 1
(1) Accurately weighing 10g of milk powder sample, placing the milk powder sample in a 250mL conical flask with a plug, sequentially adding 0.05mg/kg of mixed internal standard and 30mL of normal hexane, carrying out ultrasonic treatment for 120min, filtering, taking all clear liquid, and carrying out nitrogen-blown concentration to about 1 mL. Activating a silver nitrate silica gel SPE small column by using n-hexane, purifying a concentrated solution by using the small column, and then purifying by using 12mL of n-hexane: the elution was carried out with a toluene (v: v ═ 2: 1) solution, the flow rate being controlled at 1 drop/s. The eluent is blown to be nearly dry by nitrogen, and then 1mL of n-hexane is added for redissolving and loading.
(2) Full two-dimensional gas chromatography-time-of-flight mass spectrometer: the chromatographic column adopts a GC x GC column system, the one-dimensional chromatographic column is a nonpolar capillary column, the two-dimensional chromatographic column is a medium polarity column, and the one-dimensional chromatographic column and the two-dimensional chromatographic column are connected in series through a capillary column joint connector;
sample introduction conditions are as follows: the sample inlet temperature is 280 ℃, the sample injection volume is 2 mu L, and the mode of no shunt is adopted;
carrying helium gas at a flow rate of 1.5 mL/min;
column oven temperature program: the initial temperature of the one-dimensional column incubator is 50 ℃, the temperature is maintained for 3min, then the temperature is increased to 210 ℃ at the speed of 8 ℃, then the temperature is increased to 300 ℃ at the speed of 10 ℃, the temperature is maintained for 22min, the temperature compensation of the two-dimensional chromatographic column relative to the one-dimensional column incubator is 5 ℃, and the temperature compensation of the modulator relative to the two-dimensional column is 15 ℃.
Modem conditions: a solid thermal modulator, a DV modulation column (1.2 m.times.0.25 mm), a period of 6s, and a thermal resolution time of 0.8s were used.
Time-of-flight mass spectrometer conditions: an electron bombardment source, a filament emission current of 200 muA, electron energy of 70eV, an ion source temperature of 250 ℃, an interface temperature of 280 ℃, an acquisition mass range of 50-600 amu, an acquisition speed of 100 spectrums/s and solvent delay of 400 s.
The spectra of the MOAH and MOSH standards are shown in figure 1, indicating the location of the two major types of mineral oils. Determining a target area according to an aromatic hydrocarbon mineral oil standard, then carrying out area summation, and calculating the content of the target by using a matrix standard curve and internal standard correction, wherein TBB is usually used as a positioning marker for marking the separation condition of MOAH in mineral oil, and 1-MN is a quantitative internal standard for calculating the content of the mineral oil by correction.
(3) Matrix standard curve: preparing polycyclic aromatic hydrocarbon standard substance solutions with different concentrations (1ppm, 5ppm and 20ppm) by using a matrix solution of a milk powder sampleAnd analyzing by an instrument to obtain the area sum of the target object so as to obtain a response value corresponding to the concentration, and drawing a matrix standard curve of the aromatic mineral oil by taking the response value as a vertical coordinate and the corresponding concentration as a horizontal coordinate. As shown in FIG. 3, the measured peak area value and the concentration of aromatic hydrocarbon mineral oil were determined as a matrix calibration curve of y-294244471 x-195330151, R2＝0.999。
(4) And (2) after the sample is pretreated in the step (1), a full-two-dimensional gas chromatography-time-of-flight mass spectrometer is used for sampling to obtain the peak area sum of the target object, the sum is brought into a matrix standard curve to obtain the sample injection concentration of the target object in the sample, and the actual concentration of the target object in the sample is obtained through internal standard correction.
Example 2
The recovery rate of the added standard is used for quality control of the detection method. By using the method of the invention, the recovery rate of the added standard is measured.
The same sample was taken in two portions, one portion was added with a quantitative aromatic mineral oil standard substance, and both portions were analyzed according to the method of example 1, and the measured value of the spiked sample and the measured value of the sample (without adding the standard substance) were measured, respectively, and fig. 2 shows the analytical spectrum of the sample, and the spiked recovery was obtained by using the following calculation formula.
The recovery rate in standard addition is (measured value of standard addition sample-measured value of sample)/standard addition amount x 100%
The experimental result shows that the recovery rate of the added standard obtained by the method is 93-107%.
Methods and devices not described in detail in the present invention are all the prior art and are not described in detail.
The principles and embodiments of the present invention are explained in detail by using specific embodiments, and the above description of the embodiments is only used to help understanding the method and the core idea of the present invention. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.
Claims (7)
1. A method for detecting the content of aromatic hydrocarbon mineral oil in milk powder by utilizing a full two-dimensional gas chromatography-time-of-flight mass spectrum is characterized by comprising the following steps:
1) weighing 10-15g of milk powder, adding an internal standard substance and 30-35mL of n-hexane, carrying out ultrasonic treatment for 120-130min, filtering nitrogen, and carrying out blowing concentration until the volume of the liquid is 1-2mL to obtain a concentrated solution;
2) purifying and removing impurities from the concentrated solution obtained in the step 1) through a silver nitrate SPE small column;
3) leaching a silver nitrate SPE small column by using 10-20mL of mixed solution of normal hexane and toluene, blowing leaching liquid nitrogen to be dry, and adding 1-1.5mL of normal hexane to redissolve and load the sample;
4) setting appropriate detection conditions by adopting a full two-dimensional gas chromatography-time-of-flight mass spectrometer, qualitatively analyzing target components by using an NIST (Nist standard library) and retention time, and determining the content of aromatic hydrocarbon mineral oil in a sample by using an internal standard method.
2. The method of claim 1, wherein the internal standard in step 1) is a mixture of 1,3, 5-tri-tert-butylbenzene and 1-methylnaphthalene; the addition amount of the 1,3, 5-tri-tert-butylbenzene is 0.05mg added in each kilogram of milk powder, and the addition amount of the 1-methylnaphthalene is 0.05mg added in each kilogram of milk powder.
3. The method of claim 1, wherein the silver nitrate SPE cartridge in step 2) is a 0.3% custom silver nitrate silica glass cartridge.
4. The method according to claim 1, wherein the mixed solution of n-hexane and toluene in the step 3) is a solution obtained by mixing n-hexane and toluene at a volume ratio of 2: 1.
5. The method as claimed in claim 1, wherein the chromatography column of the comprehensive two-dimensional gas chromatography-time of flight mass spectrometer in step 4) adopts a GC x GC column system, the one-dimensional chromatography column is a non-polar capillary column, the two-dimensional chromatography column is a medium-polar column, and the one-dimensional chromatography column and the two-dimensional chromatography column are connected in series by a capillary column joint connector.
6. The method of claim 1, wherein the detection conditions of step 4) comprise sample introduction conditions, column oven temperature program, modem conditions, time-of-flight mass spectrometer conditions.
7. The method of claim 6, wherein the sample introduction conditions are as follows: the sample inlet temperature is 280 ℃, the sample injection volume is 2 mu L, the flow distribution mode is not adopted, helium is carried, and the flow rate is 1.5 mL/min;
the temperature raising program of the column incubator is that the initial temperature of the one-dimensional column incubator is 50 ℃, the temperature is kept for 3min, then the temperature is raised to 210 ℃ at the speed of 8 ℃, then the temperature is raised to 300 ℃ at the speed of 10 ℃, the temperature is kept for 22min, the temperature compensation of the two-dimensional chromatographic column relative to the one-dimensional column incubator is 5 ℃, and the temperature compensation of the modulator relative to the two-dimensional column is 15 ℃;
the modem adopts a solid-state thermal modulator, a DV modulation column is 1.2m multiplied by 0.25mm, the period is 6s, and the thermal desorption time is 0.8 s;
the time-of-flight mass spectrometer is characterized in that the conditions of an electron bombardment source, filament emission current of 200 muA, electron energy of 70eV, ion source temperature of 250 ℃, interface temperature of 280 ℃, collection mass range of 50-600 amu, collection speed of 100 spectrums/s and solvent delay of 400s are adopted.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011363758.3A CN112630320A (en) | 2020-11-27 | 2020-11-27 | Method for detecting content of aromatic hydrocarbon mineral oil in milk powder by using full-two-dimensional gas chromatography-time-of-flight mass spectrometry |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011363758.3A CN112630320A (en) | 2020-11-27 | 2020-11-27 | Method for detecting content of aromatic hydrocarbon mineral oil in milk powder by using full-two-dimensional gas chromatography-time-of-flight mass spectrometry |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN112630320A true CN112630320A (en) | 2021-04-09 |
Family
ID=75306478
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202011363758.3A Pending CN112630320A (en) | 2020-11-27 | 2020-11-27 | Method for detecting content of aromatic hydrocarbon mineral oil in milk powder by using full-two-dimensional gas chromatography-time-of-flight mass spectrometry |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN112630320A (en) |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101680862A (en) * | 2006-10-25 | 2010-03-24 | 普拉德研究及开发股份有限公司 | High-precision Contaminant Estimation of Hydrocarbon Samples Using GC×GC |
| CN107456780A (en) * | 2017-08-07 | 2017-12-12 | 中国食品发酵工业研究院 | It is a kind of to be used for solid-phase extraction column of saturation mineral hydrocarbon oil measure and its preparation method and application in food |
| CN108107137A (en) * | 2017-12-15 | 2018-06-01 | 中国食品发酵工业研究院 | A kind of method of saturated hydrocarbons mineral oil and aromatic hydrocarbon mineral oil in separation determination vegetable oil |
-
2020
- 2020-11-27 CN CN202011363758.3A patent/CN112630320A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101680862A (en) * | 2006-10-25 | 2010-03-24 | 普拉德研究及开发股份有限公司 | High-precision Contaminant Estimation of Hydrocarbon Samples Using GC×GC |
| CN107456780A (en) * | 2017-08-07 | 2017-12-12 | 中国食品发酵工业研究院 | It is a kind of to be used for solid-phase extraction column of saturation mineral hydrocarbon oil measure and its preparation method and application in food |
| CN108107137A (en) * | 2017-12-15 | 2018-06-01 | 中国食品发酵工业研究院 | A kind of method of saturated hydrocarbons mineral oil and aromatic hydrocarbon mineral oil in separation determination vegetable oil |
Non-Patent Citations (4)
| Title |
|---|
| KATELL FISELIER等: "Development of a manual method for the determination of mineral oil in foods and paperboard", 《JOURNAL OF CHROMATOGRAPHY A》 * |
| MICHAEL KOCH等: "Separation of the mineral oil aromatic hydrocarbons of three and more aromatic rings from those of one or two aromatic rings", 《JOURNAL OF SEPARATION SCIENCE》 * |
| 孙姗姗等: "气相色谱串联质谱法快速筛查乳粉及巧克力中矿物油指标成分", 《食品安全质量检测学报》 * |
| 陈燕芬等: "全二维气相色谱-飞行时间质谱测定婴幼儿配方奶粉中的矿物油", 《食品安全质量检测学报》 * |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Gallagher et al. | Rapid determination of the neurotoxin lolitrem B in perennial ryegrass by high-performance liquid chromatography with fluorescence detection | |
| Snell et al. | Performance improvements in the determination of mercury species in natural gas condensate using an on-line amalgamation trap or solid-phase micro-extraction with capillary gas chromatography–microwave-induced plasma atomic emission spectrometry | |
| Chakraborti et al. | Determination of ionic alkyllead compounds in water by gas chromatography/atomic absorption spectrometry | |
| CN107219313B (en) | Method for detecting 24 polycyclic aromatic hydrocarbons in edible oil based on molecular imprinting solid phase extraction-gas/mass spectrometry combined technology | |
| CN105784894B (en) | Pesticide residue detection method for traditional Chinese medicine | |
| CN107884493A (en) | The method of short chain chlorinated paraffin in comprehensive two dimensional gas chromatography flying time mass spectrum analysis environmental sample | |
| CN102213700A (en) | Method for measuring content of pyrethroid pesticides in mainstream smoke of cigarettes | |
| CN102998382B (en) | Method for measuring contents of methanol, sec-butyl alcohol, sesamol and musk xylene in additive for cigarette | |
| CN112229929A (en) | Method for on-line GPC-GC-MS/MS non-target rapid screening of pesticide residues in tea | |
| Munyeza et al. | Development and optimization of a plunger assisted solvent extraction method for polycyclic aromatic hydrocarbons sampled onto multi-channel silicone rubber traps | |
| CN114384168B (en) | Determination method for residual quantity of dazomet and metabolite methyl isothiocyanate in plant-derived food | |
| CN102735786A (en) | Online trapping and analyzing method for benzo[a]pyrene in thermal cracking products, and apparatus thereof | |
| Liu et al. | Fast and effective low‐temperature freezing extraction technique to determine organotin compounds in edible vegetable oil | |
| CN112630320A (en) | Method for detecting content of aromatic hydrocarbon mineral oil in milk powder by using full-two-dimensional gas chromatography-time-of-flight mass spectrometry | |
| Jiang et al. | Development of a more specific and accurate multiple reaction monitoring method based on GC–EI/MS/MS for simultaneously monitoring and determining 34 kinds of pesticides in Qianjinzhidai pills | |
| Serra et al. | Organotin speciation in environmental matrices by automated on-line hydride generation-programmed temperature vaporization-capillary gas chromatography–mass spectrometry detection | |
| CN108344831B (en) | Method for measuring polycyclic aromatic hydrocarbon in tobacco, main stream smoke or heated non-burning cigarette | |
| CN110596276A (en) | Method for measuring dithiocarbamate residues in tea leaves by headspace-gas chromatography-mass spectrometry | |
| CN113866336B (en) | Integrated detection method for safrole and dihydrosafrole in ginger and ginger powder | |
| Ahmed et al. | Development of dry-herb vaporizer-assisted solid-phase microextraction for the analysis of volatile organic compounds | |
| Vinas et al. | Liquid chromatography-hydride generation-atomic absorption spectrometry for the speciation of tin in seafoods | |
| Thurman et al. | Injection port derivatization for GC/MS–MS: analysis of hormones in water | |
| CN112255323B (en) | Novel chlorine-enhanced ionization reagent for liquid chromatography-mass spectrometry detection and application thereof | |
| De Waele et al. | Laser microprobe mass analysis of plastic-contaminated asbestos fiber surfaces | |
| Nishikawa et al. | Liquid chromatographic determination of low molecular weight alkylthiols in air via derivatization with 7-chloro-4-nitro-2, 1, 3-benzoxadiazole |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| RJ01 | Rejection of invention patent application after publication | ||
| RJ01 | Rejection of invention patent application after publication |
Application publication date: 20210409 |