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Rapid screening of 122 pesticide residues in tobacco using TSQ 8000 Evo triple quadrupole temper
Key words
TSQ 8000 Evo; tobacco matrix; pesticide residues; rapid screening; method package
1. Foreword
On January 15, 2014, China National Tobacco Corporation issued the industry standard YQ/T 47.1-2014 for the determination of various pesticide residues in tobacco and tobacco products. The first part is the method of serially detecting phenolic pesticide residues. The standard was officially implemented on February 10, 2014. Thermo Fisher Scientific developed this industry standard
A method for detecting multiple pesticide residues in tobacco.
In this experiment, TSQ 8000 Evo was combined with Thermo Fisher Scientific Residue Analysis Column (TR-pesticide II 30 m*0.25 mm*0.25 μm) to analyze 122 pesticide residues in tobacco, and excellent results were obtained. The minimum detection limit for various pesticides is between 0.004ppb and 0.75ppb, with good linearity in the range of 5 ppb–200 ppb, and continuous injection of 5 ppb samples for 5 consecutive shots, resulting in an RSD between 1.01%–9.69%. , indicating that this method has good reproducibility.
2. Experimental part
2.1 Instruments and columns
TSQ 8000 Evo Triple Quadrupole Gas Chromatography Mass Spectrometer (Thermo ScientificTM USA), TR-pesticide II Pesticide Residue Column (30 m*0.25 mm*0.25 μm with 5m precolumn)
2.2 Instrument method
GC method:
Transmission line temperature: 300oC.
PTV inlet: starting temperature is 70oC, injection time is 0.05 min; then it is raised to 280oC at 4.5oC/min for 1 min, all compounds are transferred to the column by temperature-programmed injection; then at 14.5oC /min rises to 320oC for 5 min, setting the cleaning mode of the inlet. No split injection, no split time 1.5min.
Carrier gas: constant current, 1.2 mL/min;
Column oven: 40oC for 1.5 min, raised to 90° at 25oC/min for 1.5 min; then raised to 180oC at 25oC/min; then raised to 280oC at 5oC/min; finally at 10oC/ The rate of min rises to 300oC for 5 min. The entire temperature program was 35 min.
Injection volume: 2 μl
Mass spectrometry method:
Ion source temperature: 300 oC, filament current 25 μA, T-SRM method, no time period required. Some methods are shown in Figure 1 (total 402 pairs of SRM ion pairs):
2.3 pre-processing methods
extract
Weigh 2 g of the sample into a 50 mL capped centrifuge tube to the nearest 0.01 g, add 10 mL of water (4.1), shake with a hand-held centrifuge tube until the sample is thoroughly mixed with water, and let stand for 10 min. Pipette 10 mL of acetonitrile (4.2) and 0.1 mL of mixed internal standard working solution (4.11.4) into the centrifuge tube and place on a vortex mixing shaker (5.2) for 2 min at 2000 r/min. The tube was frozen and stored at (-18 ° C ~ -20 ° C) for 10 min and then taken out. Add 5 mL of toluene (4.3), 4 g of anhydrous magnesium sulfate (4.4), 1 g of sodium chloride (4.5), 1 g of sodium citrate (4.6), and 0.5 g of disodium hydrogen citrate (4.7). Immediately, the centrifuge tube was shaken vigorously to prevent agglomeration, and then placed on a vortex mixing shaker (5.2) for 2 min at 2000 r/min, and then centrifuged at 4000 r/min for 5 min. Collect the supernatant to spare.
Purification
Pipette 1.5 mL of the sample extract supernatant (7.1) into a 2 mL centrifuge tube and add 150 mg of anhydrous magnesium sulfate (4.4) and 50 mg of N-propyl ethylenediamine to bond the solid phase adsorbent (4.8). The mixture was shaken at 2000 r/min for 2 min on a vortex mixing oscillator (5.2), centrifuged at 4000 r/min for 5 min, and the supernatant was collected for analysis.
3. Experimental results
3.1 Auto SRM optimizes ion pair information for some compounds
The entire experimental flow of the TSQ 8000 Evo can be seen in Figure 2. The TraceFinder software that comes with the TSQ 8000 Evo has a database of more than 1000 compound ion pair information, such as pesticides, environmental pollutants, etc., analyzed by conventional triple quadrupole temperament analysis. Therefore, when we need to complete the method of establishing the compound on hand, we can first refer to the ion pair information in the database. Compound ion pair information not found in the database can be automated using the TSQ 8000 Evo's proprietary AutoSRM software.
AutoSRM, as its name implies, is a software that automatically optimizes the compound SRM ion pair. The software optimizes the method by selecting the parent ion, selecting the daughter ion, and automatically optimizing the collision energy. This greatly simplifies the conventional tandem temperament.
The steps of establishing a compound detection method save time. Thermo Fisher Scientific's new generation of triple quadrupole gas chromatography mass spectrometer TSQ 8000 Evo's exclusive AutoSRM function automatically optimizes ion pair information and collision energy, and is intelligent when the number of compounds optimized at one time is high. Adjust the number of injections in order to get the optimal method in the least amount of time, making the whole method building part more simple and convenient. The steps for the entire AutoSRM are shown in Figure 1: 1) Select the parent ion
2) Selecting child ions
3) Optimize collision energy
3.2 standard curve
5 ppb, 10 ppb, 20 ppb, 50 ppb, 100 ppb, 200 ppb mixed solution were prepared and quantified by internal standard method. The internal standard was atrazine or triphenyl phosphate (determined by retention time) The substances were internal standards. The compounds with retention time of 20 min before this experiment were treated with atrazine as internal standard and after 20 min with triphenyl phosphate as internal standard). The table below lists the standard curve equations and linear correlation coefficients for all 122 compounds. It can be seen that using the TSQ 8000 Evo fast scan to detect these 122 compounds gives a good linearity and is useful for quantitative accuracy.
Table 1: Linear equations and correlation coefficients for 122 compounds (* indicates IS)
3.3 Reproducibility and minimum detection limit
Repeat the injection of 5 needles with a 10 ppb sample to demonstrate the reproducibility of the method. The reproducible results obtained are shown in the figure below, and the reproducibility of all compounds is between 1.01% and 9.69% (as shown in Table 2). Samples of 100 ppt, 200 ppt, 500 ppt, 1 ppb, and 2 ppb were separately prepared, and the minimum detection limit and the minimum limit of quantification of the compound were estimated according to S/N of 3 and S/N of 10. The LOD and LOQ of each compound are shown in Table 2.
Table 2: Minimum detection limits and reproducibility of 122 compounds (* indicates IS)
Select a chromatogram of some compounds at 100 ppt:
Figure 4: Chromatogram of a part of the compound 100 ppt
3.4 Methodology for detection of pesticide residues in tobacco
The method package is a simple instrumental application process for the customer's needs by the application department of Thermo Fisher Scientific and Mass Spectrometry. The compounds involved in the method package are common compounds that can be detected on GC/MS, such as pesticide residues. Cycloaliphatic hydrocarbons, polychlorinated biphenyls, polybrominated biphenyls, polybrominated diphenyl ethers, phthalates, and the like. The function of the method package is to enable customers to use the instrument faster and easier, and get started as soon as possible. The method package includes injection method, data processing method (TraceFinder method folder), related application articles, related standards, column information, pre-processing methods, data files, etc. The customer can directly call the injection method and data processing method to complete the compound. Qualitative and quantitative analysis. Since the TSQ 8000 Evo uses the T-SRM injection method instead of the time-sharing method, the original injection method can be called directly, even if there is a slight deviation in retention time, it will not affect the final result. In addition, the database that comes with TraceFinder software can directly edit the data processing method. The database includes the name of the compound, ion pair, collision energy, quantitative ion, qualitative ion, CAS number and other information. At the same time, TraceFinder software can automatically correlate the method files that generate TSQ 8000 Evo according to the data processing method. This way, TraceFinder can be used to directly generate data processing methods and partial injection methods. The entire process is automated, requiring little operator input of any operational information.
To quickly create a method, copy the folder in the method package directly to C:\ TraceFinderData\32\Methods. The method can be opened in the TraceFinder software. This method includes data processing methods and injection methods.
Figure 5: Open Method Package
4. Conclusion :
The Thermo ScientificTM Triple Quadrupole Tandem GC/MS TSQ 8000 Evo provides fast analysis of pesticide residues in tobacco. The methodological validation showed that the linearity, detection limit and RSD value of the method met the requirements of YQ/T 47.1-2014 for the determination of various pesticide residues in tobacco and tobacco products and the maximum residue limit for YQ 50-2014 tobacco leaf pesticides. Using the Thermo Fisher method package, you can quickly establish injection methods and data processing methods, and use them without the need to integrate information creation methods from the database. Instead, you can use a ready-made method to save a lot of time and improve analysis efficiency. First- and second-level high-resolution mass spectrometry data ensure the reliability of qualitative and quantitative results; comparable to the sensitivity and wide linear range of high-end triple quadrupoles, it is easy to quantify trace impurities in drugs. Compared with triple quadrupole mass spectrometry, Q Exactive Focus uses primary mass spectrometry to quantify the need to optimize the parent ion and daughter ion parameters.
Accurate quantification can be achieved with the precise molecular mass of the target compound, which is more convenient and faster. By using two-stage high-resolution mass spectrometry, the full scan information of the daughter ions can be recorded, and the more specialized daughter ions can be flexibly selected for quantification in the data post-processing, and the matrix interference can be effectively eliminated, the selectivity is better, and the sensitivity is higher.