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Gas Chromatography Triple Quadrupole Mass Spectrometry TSQ Quantum XLS for the Analysis of 9 Organochlorine Pesticides and Pyrethroid Pesticides
Zhu Manjie, Thermo Fisher Scientific
Key words
TSQ Quantum XLS; organochlorine pesticides; pyrethroid pesticides.
1 Introduction
Organochlorine pesticides are the most powerful synthetic pesticides discovered for the first time in human history. They have long been the protagonists of pest control in the world's agricultural production. Studies have shown that organochlorine pesticides, although less toxic, have a longer residual period in the environment and are more difficult to degrade. The large amount of application not only causes direct pollution to crops, but also remains in soil and water, and is enriched by food chain. Enter the human body and endanger human health (1-2). Pyrethroid is an important class of synthetic insecticides. Compared with traditional organochlorine pesticides, it has high efficiency, broad spectrum, relatively low toxicity and biodegradability. It is a widely used pesticide in recent years. These pesticides are still toxic and have certain accumulation. Some varieties are also carcinogenic, teratogenic and mutagenic. They are the main test subjects in recent years (3-4).
In this experiment, TSQ Quantum XLS was combined with a highly inert and weakly polar column to analyze organochlorine pesticides and pyrethroid pesticides, and excellent results were obtained. The minimum detection limit of the matrix sample is between 0.05-0.5 ppb, and the linearity is good in the range of 1 ppb-500 ppb, and the RSD% of the continuous 5-needle injection in the matrix spiked sample is 1.52%-3.30%.
2 Experimental part
2.1 Instruments and columns
TSQ Quantum XLS Triple Quadrupole Gas Chromatography Mass Spectrometer (Thermo Fisher Scientific, USA), TG-5MS (30mX0.25mmX0.25um), highly inert, weakly polar column.
GC method:
Transmission line temperature: 280oC;
Inlet: 250oC, no split pressure injection, no split time 1min, pressurization pressure 150kPa, pressurization time 1min;
Carrier gas: constant current, 1.2ml/min;
Column oven: stand at 50oC for 1min, increase to 240oC at 30oC/min, hold for 1min, then increase to 300oC at 8oC/min for 2min.
Injection volume: 2ul
Mass spectrometry method:
Ion source temperature: 250 oC, filament current is 25uA, collision gas is 1.0mTorr, using T-SRM method, no time period is required, the ion pairs of each compound are shown in the following table:
3. Experimental result
3.1 Standard curve
A gradient concentration of the mixed solution was prepared at concentrations of 1 ppb, 5 ppb, 10 ppb, 50 ppb, 100 ppb and 500 ppb. The standard curve of each compound is shown in the figure below, and R2 is above 0.995:
Figure 1: Standard curve of nine chlorine-containing pesticides
3.2 Sensitivity
The sensitivity of the TSQ Quantum XLS was measured by a stepwise dilution method, and the minimum detection limit of each compound was finally determined as shown in Fig. 2. The minimum detection limit for all organochlorine pesticides is between 0.05 and 0.5 ppb. Due to the 5MS column, o,p'-DDT and p,p'-DDD are not completely separated, but from the results, the peak intensity at the lowest detection limit is not affected. If further experiments are required, a 1701 class of moderately polar columns can be used, and the two compounds can be completely separated.
Figure 2: Sensitivity of nine chlorine-containing pesticides
3.3 Reproducibility
The reproducibility index of the 10 ppb standard for 5 consecutive injections showed that the RSD of each compound was between 2.14% and 3.36%, and the RSD of each compound in the celery matrix was between 1.52% and 3.30%, indicating that the TSQ Quantum XLS has Good stability.
Table 1: Reproducibility results for 10 ppb standards
4. in conclusion
TSQ Quantum XLS is Thermo Fisher Scientific's new generation of triple quadrupole gas chromatography mass spectrometers with extremely high performance, including high sensitivity, stability and good resistance to contamination. The minimum detection limits of the nine common chlorinated pesticides tested in this experiment ranged from 0.05 to 0.5 ppb, indicating that the TSQ Quantum XLS is extremely sensitive and meets routine or deeper inspection requirements. Moreover, in terms of reproducibility, continuous five-needle injection, RSD is 1.52% - 3.30%, indicating that TSQ Quantum XLS has good stability.
references:
(1). Yang Lili, Ma Yingfeng, Hu Enyu, Wang Liyuan. Determination of Organochlorine Pesticides in Water by Solid Phase Extraction-GC/MS Method[J].Environmental Monitoring Management and Technology,2008,20(1):25-28.
(2). Zhu Jie, Yang Xin, Feng Jinfang et al. Study on HS-SPME-GC-MS analysis method for organochlorine pesticides and pyrethroid pesticide residues in milk[J]. 2007,04:289- 293
(3). Li Yongjun, Huang Zhiqiang, Dai Hua et al. Determination of Pyrethroid Pesticide Residues in Tea by Gas Chromatography-Mass Spectrometry[J]. Chinese Journal of Analytical Chemistry, 2002, 30(7): 865-868.
(4). Yang Lei, Wang Baoxing, Hou Ying et al. Rapid Determination of Pyrethroid Pesticide Residues in Tea by SBSE-TDS-GC-MS[J]. FOOD SCIENCE, 2007, 28(11): 435-439.