TSQ 8000 Evo detects 11 nitrosamines in rubber and elastomeric materials

Li Chunli Peng Xing
Thermo Fisher Scientific (China) Co., Ltd.
Foreword
N-nitroso compounds are a strong class of chemical carcinogens, including nitrosamines and nitrosamines, commonly referred to as nitrosamines. More than 300 N-nitroso compounds have been shown to be carcinogenic in one or more animals [1], and more than 40 animals, including primates, are susceptible to N-nitroso compounds and cause cancer. Moreover, the tumors induced by such carcinogens in experimental animals are similar in morphology and biochemical characteristics to the tumors found in the corresponding human organs [2]. The US Environmental Protection Agency (USEPA) believes that N-nitrosodimethylamine (NDMA) is carcinogenic at very low concentrations (0.7 ng/L) and has been listed as a priority control contaminant [3]. Many countries and international organizations have established strict standards for the detection of N-nitrosamines in their products [4][5][6]. For example, China issued the GB28482-2012 Safety Requirements for Infants and Young Pacifiers; In the "New Toy Safety Directive" (2009/48/EC), there are extremely strict regulations on the content of N-nitrosamine and the amount of migration. At the same time, the EU harmonized standard EN71-12, which is compatible with the directive, requires the detection of at least 13 N-nitrosamines, including aliphatic nitrosamines, alicyclic nitrosamines and aromatic nitrosamines.
Therefore, the development of a rapid, sensitive and accurate method for the determination of N-nitrosamine compounds is urgently needed for the research of hygienic detection, reduction and control of nitrosamine content. The use of GC-MS/MS for the detection of N-nitrosamines has been used to some extent [7][8]. Thermo Fisher Scientific's tandem GC/MS combined with the TSQ 8000 Evo features high sensitivity, low background interference and high stability. This paper uses the TSQ 8000 Evo as a platform to establish 11 N-nitrosamine GC-MS/MS detection methods in rubber and elastomer materials, combined with Thermo Fisher Scientific's unique TraceFinder software system for data acquisition, data analysis and The report output enables fast data collection and intelligent processing of data results. It provides strong technical support for the trace detection of N-nitrosamine.
1. Experimental part
1.1 Instruments and reagents
Mass Spectrometer: TSQ 8000 Evo Mass Spectrometer (Thermo Fisher Scientific, USA);
Gas Chromatograph: Trace 1310 Gas Chromatography with AI 1310 Autosampler (race
Mercury Technology, USA);
Column: TR-5MS (30 m × 0.25 mm × 0.25 μm) capillary column;
Reagents: n-hexane, acetone, methanol; all chromatographic grade
1.2 Experimental methods
1.2.1 Gas phase method
Program temperature: programmed temperature: 35 ° C (maintained for 3 min), 10 ° C / min to
100 ° C (maintained for 1 min), 25 ° C / min to 250 ° C (dimensional
Hold 3 min)
Inlet temperature: SSL split without split (220 ° C) with Splitless splitless mode
Carrier gas flow rate: 1.0 mL/min (constant current)
Transmission line temperature: 250 ° C
Injection volume: 1.0 μL
1.2.2 Mass Spectrometry
Mass spectrometry run time: 19 min
Scanning method: Timed-SRM
Collision gas pressure: 1.0 m Torr argon
The SRM conditions are as follows:
Mass spectrometry information of 11 N-nitrosamine compounds and 1 internal standard substance
1.3 sample preparation
The sample was prepared to a size of 2 mm × 2 mm × 2 mm (even sampling).
1.4 sample preparation
1.4.1 Sample extraction
Accurately weigh 5.00 g (accurate to 0.01 g) in a 40 mL brown glass bottle, add 30 mL of methanol, ultrasonically extract at room temperature for 30 min, filter the transfer solution into a 250 mL flat-bottomed flask; add 20 mL of methanol to the sample. Solvent, repeat the sonication and transfer steps, and wash the brown bottle 2-3 times with a small amount of methanol, combine the two ultrasonic and wash solutions; rotary evaporation of the solution (35 ° C, 150 mbar) to about 4 mL, on a vortex mixer Shake well for 1 min and transfer the sample solution to a 10 mL stoppered centrifuge tube. Another 1 mL of methanol was used to wash the flat-bottomed flask wall 2-3 times, and the mixture was vortexed for 1 min on a vortex mixer, and the washing solution was combined in a 10 mL stoppered centrifuge tube.
1.4.2 Purification
Place the C18 solid phase extraction cartridge on a solid phase extraction unit and pre-rinse the C18 cartridge with 5 mL of methanol. The sample solution is injected into the small column, and the effluent is collected in the centrifuge tube. When the liquid level of the sample liquid drops to the upper layer of the small column packing, 5 mL of methanol is added for elution, and all the effluent is collected and collected in the centrifuge tube.
1.4.3 Concentration
The sample solution was placed in a 250 mL flat-bottomed flask, and the wall of the centrifuge tube was rinsed 2-3 times with a small amount of methanol. The washing solution was combined in a flat-bottomed flask, and the solution was rotary evaporated (35 ° C, 150 mbar) to about 4 mL to remove the flat bottom. The flask was shaken well for 1 min on a vortex mixer, then the solution in the flat-bottomed flask was transferred to a 5 mL brown volumetric flask. The flat-bottomed flask was rinsed with a small amount of methanol for 2 to 3 times, and thoroughly shaken on a vortex mixer for 1 min. The washing solution was combined in a brown volumetric flask and made up to the mark with methanol. After filtering through a 0.45 μm filter, the analysis was carried out.
2. Experimental results
2.1 Simplify analysis steps using TraceFinder software
Using TraceFinder, a software platform unique to the TSQ 8000 series, not only enables fast, batch, automated acquisition and processing of data, but also automates the generation of common data reports in the lab. The Database database, Master method, Instrument method and AutoSRM MS conditional automatic optimization software combines software. The workflow is shown in Figure 1.
Figure 1. TraceFinder workflow
Information about most common compound methods is included in the TraceFinder built-in database. The mass spectrometry method information for detecting the compounds involved can be queried, edited, extracted, and directly imported into the instrument method using TraceFinder. These compounds include compounds of common interest such as pesticides, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, polybrominated biphenyls, polybrominated diphenyl ethers, and phthalates.
2.2 Automatic optimization of compound information using AutoSRM software
For the 11 N-nitroso compounds and 1 internal standard substance, the chromatographic mass spectrometry conditions are unknown at the initial stage of the method, and the corresponding chromatographic and mass spectrometric methods need to be optimized. The AutoSRM software, which is unique to the TSQ 8000 series, can also be used for automatic optimization, enabling automatic generation of instrument methods after optimization.
The AutoSRM program automatically performs the following three steps: 1. Full scan analysis. Usually the strongest ions will be used as parent ions. 2. Perform a full sweep of the daughter ion on the parent ion. The strongest ion of the signal. 3. Optimize the collision energy for the selected parent/child pair. The workflow is shown in Figure 2.
Figure 2 AutoSRM workflow
2.3 qualitative results
The TR-5MS column used in the experiment has a good separation effect on N-nitrosamine compounds. Twelve compounds (including one internal standard substance) have good chromatograms in the separation time of 19 min. The results are shown in Fig. 3. Shown.
Figure 3. Chromatogram of 12 compounds
2.3 method recovery rate and instrument stability
Four substances (NDPA, NDEA, NDBA, NMphA) were selected to be mixed standards, and the accuracy and recovery rate of the pretreatment method were investigated. According to the EU guidelines on pesticide residues, the recovery rate needs to be between 70-120%. The experiment was carried out at a concentration level of 100 μg/kg, and two parallel samples were determined. The results are shown in Table 1. The results show that the recovery rate is between 70-120%, and the method is accurate.
At the same time, the stability of the instrument was investigated. The four compounds were configured as 5.0 μg/kg standard samples and injected continuously for 6 times to obtain the corresponding relative standard deviation (RSD) of each target compound. The stability of the test instrument was obtained. Sex, as shown in Table 1. The RSD of all four compounds was less than 5.0%. The results show that the instrument has good stability when it is continuously injected at low concentration level (≤ 5 μg/kg), which meets the requirements of trace detection.
Table 1 Recovery rate experiment results
2.4 Method sensitivity , detection limit and actual sample determination
The TraceFinder software enables simultaneous data acquisition and data processing. It quickly and automatically processes the detection results of compounds based on pre-set qualitative and quantitative ions, while achieving qualitative and quantitative functions. Figure 4 shows the NDPA spectrum information.
The experimental samples were processed according to the above pretreatment methods, and a matrix standard curve of 0.05, 0.1, 0.2, 0.5, 1, 2, 20, 50 μg/kg was prepared from the blank sample matrix, and subjected to the determined chromatographic and mass spectrometric conditions. The measurement is performed, and the measurement results are analyzed to determine the sensitivity and detection limit of the method. At the same time, two commercially available products (baby pacifiers and toy balloons) were selected, and 11 kinds of N-nitrosamine compounds were determined.
The TSQ 8000 Evo has high sensitivity and strong anti-interference ability. The 11 compounds tested have good detection results at lower concentration levels, which fully meet the regulatory requirements, as shown in Table 2. At the same time, a small amount of NDBA residue was detected in both actual samples. The results are shown in Table 3.
2.4 Conclusion
The experimental results show that TSQ 8000 Evo has high selectivity, high sensitivity, high stability and high throughput when detecting samples containing trace nitrosamines, and has excellent performance in detecting harmful compounds. At the same time, the powerful TraceFinder software integrates data acquisition, processing, and method development. Automation of data processing is achieved while simplifying the experimental steps. TraceFinder's own AutoSRM software provides reliable support for the optimal development of mass spectrometry conditions for unknown information compounds.
Figure 4. NDPA mass spectral information (2 μg/kg)
Table 2. Safety requirements set in EN 71-12:2013
Table 3. Sensitivity, detection limits, and actual sample measurements
3. References
[1] R. Preussmann. Carcinogenic N-nitroso compounds and their environmental significance. [M]
[2] Bogovski P. Bogovski S. Animal species in which N-nitroso compounds induce cancer [J]. International Journal of Cancer, 1981, 24: 471-474.
[3] US Environmental Protection Agency. N-Nitrosodimethylamine (CASRN 62-75-9). http://
[4] GB 28482-2012 "Children's pacifier safety requirements"
[5] EU New Toy Safety Directive (2009/48/EC)
[6] EN 71-12:2013 Nitrosamines and nitrosamines
[7] Tong Yugui, Lin Wei, Lin Zhong. Determination of N-nitrosamine content in footwear rubber materials by gas chromatography-mass spectrometry[J]. Leather Science and Engineering. 2011, 5 (21): 56-60.
[8] Li Wei, Bai Hua, Li Haiyu et al. Determination of the migration of 15 N-nitrosamines and their precursors in latex children's products by solid phase extraction-gas chromatography-tandem mass spectrometry[J]. Chromatography. 2014,1 (32): 81-88.

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