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Application Note Food Testing and Agriculture

Analysis of Organophosphorus and Organochlorine Pesticides in Fruit and Vegetables Using an Agilent 8890 GC with Four Detectors

Author Abstract Youjuan Zhang Agilent Technologies This Application Note describes an effective and reliable analytical method for (Shanghai) Co. Ltd, the determination of organophosphorus and organochlorine pesticide residues in 1 Shanghai 200131 P.R. China fruit and vegetables following the China Standard NY/T 761-2008. An unpurged two-way capillary flow technology (CFT) device was used to split the sample 1:1 onto two columns then to two detectors. Compared with the traditional pretreatment procedure described in NY/T 761-2008, a simplified Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) method was used in this application, and provided sufficient sample matrix cleanup while preserving low-level analyte detection. Area repeatability, linearity, and recovery were evaluated for both organophosphorus and organochlorine pesticides using an Agilent 8890 GC system with four detectors. Introduction spectrometry methods have obvious instrument to provide greater flexibility advantages in qualitative analysis, and compared to other lab GCs. For both The use of pesticides has played an can determine dozens or even hundreds organophosphorus and organochlorine important role in the prevention and of pesticide residues simultaneously with pesticides analysis, labs do not need control of pests and the resulting high efficiency. Consequently, the price to change hardware; the only thing improvement of agricultural yields. of the instrument is relatively expensive. they need to do is to reinstall different Two common pesticide classes Although gas chromatography has columns onto different detectors. used in agricultural treatments have less qualitative ability than MS, it is still Sample pretreatment is important organophosphorus and organochlorine welcomed by many labs because of its for the analysis of multipesticide chemical structures. selective detectors and low detection residues, which directly affects the work For the determination of cost. ECD has excellent selectivity for efficiency and sensitivity. The NY/T 761 organophosphorus and organochlorine chlorine, and is a good choice for the method uses traditional, labor-intensive pesticide residues in fruit and analysis of organochlorine pesticides. extraction and cleanup procedures vegetables, gas chromatography (GC), FPD has high selectivity for sulfur and for sample pretreatment. The cleanup gas chromatography/mass phosphorus, and it is a good choice procedure of organochlorine pesticides spectrometry (GC/MSD), and gas for the analysis of organophosphorus and organophosphorus pesticides is chromatography/tandem mass pesticides. In the NY/T 761 method, different. That means two different spectrometry (GC/QQQ) methods are a primary column and confirmation pretreatments are needed for the same widely used. Correspondingly, China column are used in tandem to achieve sample when organophosphorus and has issued a series of standards for accurate qualitative analysis and prevent organochlorine pesticides both need the determination of those pesticides. false-positive results. This dual-column to be tested. The popular sample NY/T 761-2008 describes a GC method approach also provides quantitative pretreatment method of QuEChERS is with an electron capture detector results for both organophosphorus the optimal method for high-throughput (ECD) and flame photometric detector and organochlorine pesticides when sample analysis. Most importantly, the (FPD). GB/T 19648-20062 describes a used with two FPDs and two ECDs. same sample pretreatment process can GC/MSD method for 500 pesticides, Normally, labs need two GC systems be used both for organophosphorus and and GB 23200.113-20183 is a GC/QQQ to follow the NY/T 761 method strictly. organochlorine pesticides, which greatly method for 208 pesticides. Mass However, the 8890 GC can have two improves the analysis efficiency. FPDs and two ECDs installed on one

2 Experimental A FPD1 B ECD1 FPD2 ECD2 HP-50+ DB-5 Instrumentation HP-1 DB-17 Inlet Inlet An 8890 GC with an SSL inlet equipped with two ECDs and two FPDs was Splitter Splitter used for this series of experiments. An Retention Retention gap gap unpurged two-way CFT device was used to split the sample 1:1 onto two columns Figure 1. Agilent capillary flow technology two-way splitter without makeup gas (p/n G3181B) and diagram of instrument setup of simultaneous confirmation from a single injection onto both the primary and for detection on two detectors. For confirmation columns. (A) FPDs for phosphorus detection, (B) ECDs for chlorine detection. organophosphorus pesticides analysis, the primary column and confirmation column were Agilent HP-50+ and Table 1. Chromatographic conditions.

Agilent HP-1. A dual-column, dual-ECD Organophosphorus method system with an Agilent DB-5 primary GC Agilent 8890 GC equipped with two FPDs analysis column and an Agilent DB‑17 confirmatory column was used to Split/splitless Inlet Temperature: 220 °C separate the organochlorine pesticides. Splitless mode, purge flow 60 mL/min at 0.75 min. The analysis on organophosphorus pesticides and organochlorine pesticides Liner Agilent Ultra Inert, splitless, single taper, glass wool (p/n 5190-2293) analysis cannot be run simultaneously Injection 2 µL because of their different temperature Retention Gap 0.5 m × 0.53 mm id deactivated fused silica tubing (p/n 160-2535-5) programs. Compared with the Column1: Agilent HP-50+ 30 m × 0.53 mm, 1 µm (p/n 19095L-023) Column Agilent 7890 GC, which can only install Column2: Agilent HP-1 30 m × 0.53 mm, 1.5 µm (p/n 19095Z-323) three detectors at most, the 8890 GC Carrier Nitrogen, 10 mL/min, constant flow (the column flow is the same for column 1 and 2) is more flexible, and can install four Oven 150 °C (2 minutes), 8 °C/min to 250 °C (12 minutes) detectors at the same time. Therefore, Temperature: 250 °C Emission block: 150 °C labs do not need to change the hardware; FPD Plus 1 and 2 Hydrogen: 60 mL/min they must only reinstall the appropriate Air: 60 mL/min Make-up gas (N2): 60 mL/min columns to the right detectors. Figure 1 shows the schematics for the instrument Organochlorine method setup. Table 1 lists the chromatographic GC Agilent 8890 GC equipped with two ECDs conditions used for these analyses. Split/splitless Inlet Temperature: 200 °C Reagents and chemicals Split mode, split ratio: 10:1

All reagents and solvents were HPLC Liner Agilent Ultra Inert, split, low pressure drop, glass wool (p/n 5190-2295) grade. Acetonitrile (ACN) and hexane Injection 2 µL were purchased from J&K Scientific Retention Gap 0.5 m × 0.53 mm id deactivated fused silica tubing (p/n 160-2535-5) LTD. Acetone was purchased from Column1: Agilent DB-5 30 m × 0.25 mm, 0.25 µm (p/n 122-5032) Column ANPEL Laboratory Technologies Column2: Agilent DB-17 30 m × 0.25 mm, 0.25 µm (p/n 122-1732) (Shanghai) Inc. All organophosphorus Carrier Nitrogen, 1 mL/min, constant flow (the column flow is the same for column 1 and 2) 150 °C (2 minutes), 6 °C/min to 270 °C and organochlorine single standards Oven (12 minutes, hold 23 minutes for analysis) were purchased from J&K Scientific LTD Temperature: 320 °C and ANPEL Laboratory Technologies ECD 1 and 2 Make-up gas (N2): 25 mL/min (Shanghai) Inc.

3 Solutions and standards Table 2. Data results for organophosphorus pesticides analysis on an Agilent HP-50+ column. Table 2 shows 54 organophosphorus Linearity % RSD (n = 8) pesticides divided into four groups. Range MDL No. Name (mg/kg) R2 Low Middle High (mg/kg) % Recovery Group According to the response values of 1 0.05–0.5 0.9982 2.8 1.5 1.5 0.004 108.9 1 each pesticide on the instrument, a 2 0.05–0.5 0.9989 4.6 3.1 1.6 0.007 97.7 1 certain volume of single pesticide 3 0.05–0.5 0.997 4.3 2.3 1.6 0.007 105.3 1 standard solution of the same group was accurately added and diluted with 4 0.05–0.5 0.9984 3.1 2.7 2.1 0.006 118.2 1 acetone. The same method was used to 5 0.05–0.5 0.9981 0.6 1.6 1.3 0.002 111.4 1 prepare four groups of stock solutions 6 -methyl 0.05–0.5 0.9984 1.6 2.1 1.6 0.003 116 1 of organophosphorus pesticide mixture. 7 0.05–0.5 0.9982 2.7 1.7 1.3 0.003 115.1 1 Calibration standards were diluted by 8 Pirimiphos-ethyl 0.05–0.5 0.9985 2.6 1.4 1.4 0.003 111.8 1 matrix blank (see Sample preparation). 9 0.05–0.5 0.999 3 2.4 1.6 0.005 111 1 10 0.2–2.0 0.9922 4.4 2.8 3.6 0.05 110.9 1 11 Ditalimfos 0.05–0.5 0.9994 2.6 1.6 1.1 0.004 70.4 1 12 Triazophos 0.05–0.5 0.9992 3.6 2 2.4 0.007 104.5 1 13 0.2–2.0 0.9998 2.2 2.2 1.6 0.009 102 1 14 Trichlorfon 0.2–2.0 0.999 3 3.5 2.2 0.05 115.4 2 15 0.05–0.5 0.9987 1.2 1.5 1.9 0.004 98.5 2 16 0.05–0.5 0.9988 2 1.2 1.9 0.004 97.4 2 17 0.05–0.5 0.9982 4.5 3.7 1.8 0.008 102.5 2 18 0.05–0.5 0.998 2.5 1.5 1.9 0.006 95 2 19 0.05–0.5 0.9968 3.5 2.3 2.2 0.003 87.4 2 20 Chlorpyrifos-methyl 0.05–0.5 0.9986 2.4 1.2 1.7 0.004 92.1 2 21 0.05–0.5 0.9991 3.5 2 1.1 0.007 97.2 2 22 0.05–0.5 0.9992 2.9 2.8 1.4 0.005 97.4 2 23 Bromophos 0.05–0.5 0.9986 3.6 3.1 1.1 0.009 100.2 2 24 Bromophos-ethyl 0.05–0.5 0.999 2.2 1.6 0.9 0.007 101 2 25 0.05–0.5 0.9995 3.4 2.7 0.8 0.008 104.7 2 26 0.05–0.5 0.9995 1.6 1.7 0.8 0.004 111.6 2 27 Pyrazophos 0.2–2.0 0.9998 2.4 3.1 2.4 0.02 108.6 2 28 0.2–2.0 0.9997 4.2 2.6 2.6 0.02 107.1 2 29 0.05–0.5 0.9999 3.5 3.2 2.9 0.004 107.7 3 30 0.05–0.5 0.9999 2.1 1.2 1.7 0.001 94.1 3 31 0.05–0.5 0.9999 2.2 2.1 2.2 0.003 94 3 32 0.05–0.5 0.9995 3.2 0.8 1.6 0.004 93.4 3 33 Dichlofenthion 0.05–0.5 0.9999 3.4 1.7 1.4 0.003 93.2 3 34 Fenchlorphos 0.05–0.5 0.9999 2.2 1.4 1.5 0.003 94.7 3 35 Pirimiphos-methyl 0.05–0.5 0.9999 2.8 2 1.5 0.004 94.2 3 36 Parathion 0.05–0.5 0.9997 3.2 1.5 1.3 0.003 93.9 3 37 Isofenphos 0.05–0.5 0.9999 3.9 3 2.1 0.005 93.5 3 38 0.05–0.5 0.9998 2.7 1.7 1.3 0.004 93.6 3 39 Phosfolan-methyl 0.05–0.5 0.998 2.3 2.9 1.7 0.01 102 3 40 Famphur 0.05–0.5 0.9999 2.7 2.6 3.2 0.02 102 3 41 0.2–2.0 0.9993 2.9 3.1 2.3 0.008 102 3 42 Azinphos-ethyl 0.2–2.0 0.9996 2.8 2.3 1.7 0.02 116.5 3 43 0.1–1.0 0.9999 2.6 3.3 1.9 0.02 95.5 4 44 0.05–0.5 0.9998 3.9 2.6 1.3 0.005 118.1 4 45 Propetamphos 0.05–0.5 0.9995 4 2.8 1.4 0.007 101.5 4

4 Table 3 shows 41 organochlorine Table 2. Data results for organophosphorus pesticides analysis on an Agilent HP-50+ column (continued). pesticides divided into three groups. Linearity % RSD (n = 8) A certain volume of single pesticide Range MDL % 2 standard solution of the same group No. Name (mg/kg) R Low Middle High (mg/kg) Recovery Group 46-1 -1 4 was accurately added and diluted with 0.1–1.0 0.9999 3.6 1.9 0.9 0.02 100.7 hexane. The same method was used to 46-2 Phosphamidon-2 4 prepare three groups of stock solutions 47 0.05–0.5 0.9999 2.3 2.7 1.1 0.004 97.5 4 of organochlorine pesticide mixture. 48 0.05–0.5 0.9999 1.9 1.9 1 0.005 98.1 4 Calibration standards were diluted by 49 Isocarbophos 0.05–0.5 0.9999 2.6 1.8 1 0.004 96.9 4 matrix blank (see Sample preparation). 50 0.05–0.5 0.9999 2.8 1.6 1 0.004 97 4 51 0.05–0.5 0.9998 2.1 2.4 0.8 0.007 97.9 4 52 Phosfolan 0.05–0.5 0.9999 2.7 3.3 2.5 0.02 97.2 4 53 EPN 0.05–0.5 0.9993 2.8 3.8 1.8 0.009 100.4 4 54 Azinphos-methyl 0.2–2.0 0.9995 2 3.7 1.5 0.02 91.3 4

Table 3. Data results for organochlorine pesticides analysis on an Agilent DB-5 column.

% RSD (n = 8) Linearity Range 0.05 0.1 0.5 MDL % No. Name (mg/kg) R2 mg/kg mg/kg mg/kg (mg/kg) Recovery Group 1 α-BHC 0.05–0.5 0.9996 1.1 1.2 1 0.00003 98.6 1 2 Simazine 0.05–0.5 0.9931 0.8 1.3 1 0.002 88.1 1 3 Atrazine 0.05–0.5 0.9912 2.1 0.9 1 0.002 78.3 1 4 δ-BHC 0.05–0.5 0.9991 0.6 1.3 1 0.00003 93.7 1 5 0.05–0.5 0.9996 0.8 1.1 0.8 0.00003 118.6 1 6 0.05–0.5 0.9997 0.6 1.2 0.8 0.00004 108.5 1 7 o,p’-DDE 0.05–0.5 0.9997 1.1 1.2 0.7 0.00004 101.7 1 8 p,p’-DDE 0.05–0.5 0.9998 0.7 1.1 0.9 0.00005 106.6 1 9 o,p’-DDD 0.05–0.5 0.9996 1.2 1.1 0.8 0.00004 77.3 1 10 p,p’-DDT 0.05–0.5 0.9997 0.9 0.5 0.5 0.00006 111 1 11 Iprodione 0.05–0.5 0.9974 1 1.3 1.7 0.0007 113.5 1 12 0.05–0.5 0.9998 1 1.7 0.8 0.0002 116 1 13 cis- 0.05–0.5 0.9999 1.6 2.2 0.8 0.0004 114 1 14-1 -1 1

14-2 Cyfluthrin-2 0.05–0.5 0.9982 2.8 1.8 1.1 0.0005 1 114.8 14-3 Cyfluthrin-3 1 14-4 Cyfluthrin-4 1 15-1 tau-Fluvalinate-1 1 0.05–0.5 0.999 2.8 1.4 0.7 0.0005 105 15-2 tau-Fluvalinate-2 1 16 β-BHC 0.05–0.5 0.9998 1 0.2 0.8 0.00007 89.2 2 17 γ-BHC 0.05–0.5 0.9999 1.4 0.3 0.9 0.00003 94.7 2 18 Pentachloronitrobenzene 0.05–0.5 0.9999 1.2 0.2 0.9 0.00003 91.6 2 19 Propanil 0.05–0.5 0.9999 4 1.1 1 0.0002 98.7 2 20 Vinclozolin 0.05–0.5 0.9999 1.9 1.3 0.8 0.00009 89.4 2 21-1 -1 2 0.05–0.5 0.9984 2.1 0.5 0.8 0.00008 94.8 21-2 Endosulfan-2 2 22 p,p’- DDD 0.05–0.5 0.9995 3.8 2 1 0.00006 96.4 2 23 0.05–0.5 0.9982 2 2.8 3.3 0.0006 95.6 2 24 Lambda- 0.05–0.5 0.9991 2.1 0.4 0.9 0.0001 94.1 2 25 Permethrin 0.05–0.5 0.9987 2.3 1.3 2.2 0.0005 107.5 2

5 Table 3. Data results for organochlorine pesticides analysis on an Agilent DB-5 column (continued).

% RSD (n = 8) Linearity Range 0.05 0.1 0.5 MDL % No. Name (mg/kg) R2 mg/kg mg/kg mg/kg (mg/kg) Recovery Group 26-1 Flucythrinate-1 2 0.05–0.5 0.991 1.3 0.4 1 0.0005 92 26-2 Flucythrinate-2 2 27 Dicloran 0.05–0.5 0.9998 1.2 1.7 1.7 0.00006 80.1 3 28 Hexachlorobenzene 0.05–0.5 0.9997 0.9 1.8 0.5 0.00004 85.2 3 29 Chlorothalonil 0.05–0.5 0.9996 1 0.3 0.4 0.00006 82.7 3 30 Triadimefon 0.05–0.5 0.9997 0.9 1.1 0.6 0.00007 87.4 3 31 Procymidone 0.05–0.5 0.9995 0.6 0.5 0.6 0.0001 99.5 3 32 Butachlor 0.05–0.5 0.9997 0.7 0.5 0.5 0.0003 89.3 3 33 0.05–0.5 0.9997 0.7 0.7 0.6 0.00004 85.7 3 34 0.05–0.5 0.9996 0.8 0.7 0.5 0.00004 84.6 3 35 Chlorobenzilate 0.05–0.5 0.9983 2.3 1.6 0.3 0.0003 89.5 3 36 o,p’- DDT 0.05–0.5 0.9998 1.1 0.8 0.5 0.00007 94.1 3 37-1 -1 3 0.05–0.5 0.997 2.2 1.1 2.4 0.0003 85.7 37-2 Tetramethrin-2 3 38 0.05–0.5 0.9999 0.9 1.1 0.6 0.0002 90.72 3 39-1 -1 3

39-2 Cypermethrin-2 1.9 0.8 1.1 0.0003 81.7 3 0.05–0.5 0.997 39-3 Cypermethrin-3 3 39-4 Cypermethrin-4 3 40-1 -1 3 0.05–0.5 0.998 1.2 0.6 0.6 0.0003 93.9 40-2 Fenvalerate-2 3 41 Deltamethrin 0.05–0.5 0.9994 1.4 0.6 0.6 0.0002 86.6 3

6 Sample preparation QuEChERS sample preparation workflow An apple sample was purchased from Weigh a 10 g sample (±0.01 g) into a 50 mL centrifuge tube. a local grocery store. Ten grams of homogenized apple sample were weighed into a 50 mL centrifuge tube, Add spike solution, and vortex for one minute.* and two ceramic homogenizers were added to the sample. QC samples were Add ACN (10 mL) and two ceramic homogenizers (p/n 5982-9313). spiked with appropriate amounts of spiking solution to yield QC samples with a quantitative concentration of Add a QuEChERS extraction salt packet (p/n 5982-5650), and vortex for one minute approximately 0.1 mg/kg. Ten milliliters of acetonitrile were added to the tube. An Agilent QuEChERS extraction salt packet Centrifuge for five minutes at 5,000 rpm at 10 °C. (part number 5982‑5650) containing 4 g of MgSO , 1 g of sodium chloride, 4 Transfer 6 mL of the upper layer to a dispersive tube (p/n 5982-5056). 1 g of Na-citrate, and 0.5 g of disodium citrate sesquihydrate was added to each centrifuge tube for extraction. An Vortex for one minute, and centrifuge for five minutes at 5,000 rpm at 10 °C. Agilent QuEChERS general fruit and vegetables dispersive SPE 15 mL tube (part number 5982-5056) was used for Transfer 1 mL of the upper layer to a tube, then dry the final supernatant under nitrogen. cleanup. For fruits and vegetables with high pigments and fats, other types Use 1 mL of appropriate solvents** to reconstitute, vortex for one minute, of QuEChERS packets are needed for and centrifuge for five minutes at 5,000 rpm at 10 °C. extraction and cleanup. The details of the sample preparation procedure are shown in Figure 2. Transfer the extract to an autosampler vial. Matrix blanks were prepared in the same * This is for the recovery test. For matrix blanks, skip this step. ** Using acetone for organophosphorus pesticides, while using hexane for organochlorine pesticides. manner as the samples, except there was no addition of spike solution. Figure 2. Flowchart of the QuEChERS extraction procedure for apple samples.

7 Dimethoate Results and discussion A Acetone Parathion-methyl Matrix Ditalimfos Disulfoton Chlorpyrifos

Organophosphorus Acephate Pirimiphos-ethyl pesticides analysis Fenthion The sample matrix has a great influence on the results of pesticide Dicrotophos analysis. Figure 3 shows a comparison Phoxim of pesticide chromatograms in an apple matrix blank and acetone. Blue represents a standard prepared in acetone, while red represents a standard prepared in the apple matrix blank. It B shows that for some compounds, using Methamidophos Acetone a matrix blank to dilute the working Matrix solution can improve the sensitivity, especially for some compounds that are difficult to analyze, such as acephate and methamidophos. Organophosphorus pesticides, particularly polar pesticides such as acephate and methamidophos, tend to have broad peaks or tailing. The Figure 3. Comparison of chromatograms in apple matrix and acetone (approximately 0.1 mg/ kg) using an peak shapes were also improved in the Agilent HP-50+ 30 m × 0.53 mm, 1 µm capillary GC column. matrix blank. Group 1 220 A Simultaneous primary and confirmation HP-50+ 13 200 analysis from a single injection was 5 180 2 6 accomplished using a dual-FPD GC 160 4 11 system. An Agilent CFT 2-way splitter 140 8 1 7 without make-up device was used in 120 9 100 12 this system. The 54 organophosphorus 150 pA 3 10 pesticides were divided into four groups 80 60 for easy and accurate retention time 40 determination. Figures 4 to 7 illustrate 20 the analyses of groups 1, 2, 3, and 4 0 organophosphorus pesticide mixtures on 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Time (min) 220 B HP-1 the HP-50+ and HP-1 columns. 200 13 180 160 2 140 120 5 6 100

150 pA 4 11 1 7 8 12 80 9 3 60 40 10 20 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Time (min)

Figure 4. Chromatograms of group 1 organophosphorus pesticide standard solution (approximately 0.1 mg/kg) on a dual-column system using Agilent HP-50+ and HP-1 capillary GC columns.

8 Matrix-matched calibration standards 220 Group 2 A HP-50+ and spiked QC samples were prepared 200 14 27 by spiking appropriate standard solutions 180 160 into the matrix blank. For 44 compounds 19 26 140 analyzed, the linearity range was in the 15 20 22 120 16 28 range of 0.05 to 0.5 mg/kg. For other 100 18 24 150 pA 17 21 25 compounds such as phoxim, phosmet, 80 23 trichlorfon, pyrazophos, and so on, which 60 have low response factor, the linearity 40 20 range was 0.2 to 2 mg/kg. Table 2 shows 0 the details. Linearity across the range 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 studied gave R2 values of 0.992 for 220 Time (min) B HP-1 all the organophosphorus pesticides. 200 14 Most of them have R2 values greater 180 160 than 0.999. Table 2 lists the correlation 27 140 coefficient for each of the pesticides on 120 21 an HP‑50+ column. 100 19 26 28 150 pA 15 22 24 Repeatability assessments at three 80 17 16 20 60 18 25 levels: low, middle, and high were 23 40 obtained for all compounds in apple 20 matrix. For most compounds, the low 0 level was 0.05 mg/kg, the middle level 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Time (min) was 0.1 mg/kg, and the high level was 0.5 mg/kg. For low response value Figure 5. Chromatograms of group 2 organophosphorus pesticide standard solution (about 0.1 mg/kg) on compounds, the low, middle, and high a dual-column system using HP-50+ and HP-1 capillary GC columns. levels were 0.2, 0.4, and 2 mg/kg except Group 3 30 naled and phosphamidon. Table 2 shows 260 A HP-50+ 240 that the area RSDs were less than 5% for 220 all the compounds, which demonstrated 200 180 29 41 the accurate, precise, and stable 36 39 160 31 42 140 34 38 performance of this system. 32 33 120 35

150 pA 37 Signal-to-noise ratio (S/N) was used for 100 method detection limit (MDL) calculation. 80 60 40 A concentration of the lowest calibration 40 level was used to test the MDL, and the 20 0 values for all compounds are listed in 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Time (min) Table 2. B 260 HP-1 39 36 33 34 240 35 220 200 180 29 30 42 160 41 140 35 120 34 150 pA 100 31 32 39 36 38 80 33 37 60 40 40 20 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Time (min)

Figure 6. Chromatograms of group 3 organophosphorus pesticide standard solution (about 0.1 mg/kg) on a dual-column system using HP-50+ and HP-1 capillary GC columns.

9 A As described in the Sample preparation 170 HP-50+ Group 4 160 section, QC samples were spiked with 150 appropriate amounts of spiking solution 140 130 49 54 46-2 to yield QC samples with quantitative 120 50 110 44 47 concentration of 0.1 mg/kg (for low 100 48 response value compounds such as 90 80 43 45 51 phoxim, acquired at the 0.4 mg/kg 150 pA 70 52 53 60 46-1 level). Recoveries were determined on 50 40 an HP-50+ column, and the results for 30 20 all organophosphorus pesticides were 10 between 70.4 and 118.2%. Table 2 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 lists the recoveries for the individual Time (min) B HP-1 pesticide. Most of the compounds, 200 49 50 even the polar compounds such as 180 48 52 47 160 51 acephate and methamidophos, have 54 good recovery data due to the excellent 140 extraction and cleanup process of 120 52 100 47

150 pA 49 QuEChERS, as shown in Figure 8. 44 50 80 46-1 46-2 48 53 60 45 43 51 40 20 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Time (min)

Figure 7. Chromatograms of group 4 organophosphorus pesticide standard solution (approximately 0.1 mg/kg) on a dual-column system using Agilent HP-50+ and HP-1 capillary GC columns.

% Recovery for organophosphorus pesticides 140 120 100 80 60

% Recovery 40 20 0 l l l l l r s s s s s s s s s s e e e e n n n n n at EP N thio n nofo Naled Ethion mphu ra ra zophos Phoxim Phor Fo Sulfote p Diazinon Fenthion ichlorfo Fa Phosme t Terbufo iazophos Pa Acephate Pa Malathio Phosfola n Ditalimfos Disulfoto Dichlorvo Phosalon Tr Mevinpho Tr Omethoat Profenofos ichloronat Isofenphos Quinalphos Dimethoate Bromopho Py ra Fenitrothio Coumapho Chlorpyrifo Dicrotophos thion-methyl Ethopropho Methidathion Tr Fenchlorpho s Isocarbophos achlorvinpho ra Dichlofenthio Azinphos-ethy Propetamphos Phosphamidon Monocrotopho Pirimiphos-ethy Methamidopho s Azinphos-methy Pa Bromophos-ethy Phosfolan-methyl Tetr Pirimiphos-methy l Chlorpyrifos-methy

Figure 8. Recovery data of organophosphorus pesticides.

10 Organochlorine pesticides analysis Group 1 A Similar to the analysis of 4,500 DB-5 4 5 1 organophosphorus pesticides, 4,000 6 simultaneous primary and confirmation 3,500 13 14 analysis from a single injection was 3,000 7 8 11 2,500 9 accomplished using a dual-ECD GC Hz 10 system for organochlorine pesticides 2,000 analysis. A CFT two-way splitter without 1,500 11 make-up device was used in this system. 1,000 12 2 14 15 500 13 Forty-one organochlorine pesticides were 3 divided into three groups. Figures 9 to 11 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 illustrate the analysis of groups 1, 2, and Time (min) 4,500 3 organochlorine pesticide mixtures on B DB-17 DB-5 and DB-17 columns. 4,000 3,500 4 1 5 3,000 6 8 2,500 7 9 Hz 2,000 10 1,500

1,000 13 3 12 15 500 14 2 11

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 Time (min)

Figure 9. Chromatograms of group 1 organochlorine pesticide standard solution (0.1 mg/kg) on a dual-column system using DB-5 and DB-17 capillary GC columns.

Group 2 5,500 17 A DB-5 17 5,000 18 18 4,500 4,000 16 3,500 3,000 Hz 2,500 22 2,000 21-2 16 20 1,500 24 1,000 19 21-1 26 500 23 25

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 Time (min) 5,000 B DB-17 4,500 17 18 4,000 3,500 3,000 Hz 2,500 2,000 16 22 1,500 20 21 23,24 1,000 19 26 500 25

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 Time (min)

Figure 10. Chromatograms of group 2 organochlorine pesticide standard solution (0.1 mg/kg) on a dual‑column system using DB-5 and DB-17 capillary GC columns.

11 Group 3 For the analysis of organochlorine 3,000 A DB-5 28 33 38 pesticides, some compounds such 2,800 34 2,600 39 as cyfluthrin and cypermethrin have 2,400 2,200 37 isomers. The retention times of those 2,000 27 isomers were close, and it was difficult 1,800 35 37 1,600 29 to achieve baseline separation, as shown Hz 1,400 30 36 in Figure 12. For these compounds, the 1,200 1,000 31 41 setting of integration parameters was 800 38 40 39 600 32 particularly important. Because the 400 37 standards purchased from the vendor 200 were also isomer mixtures, and no 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 Time (min) other compounds eluted between the 3,000 B DB-17 33 isomers, those isomers were integrated 2,800 34 2,600 28 as one peak for quantitative analysis. 2,400 36 Figure 13 shows that, in OpenLab CDS 2,200 33 2,000 34 2.3 software, the Area Sum function can 1,800 27 1,600 35 help integrate the isomers. Hz 29 1,400 36 1,200 30 1,000 800 31 38 40 600 32 39 400 35 37 41 200 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 Time (min)

Figure 11. Chromatograms of group 3 organochlorine pesticide standard solution (0.1 mg/kg) on a dual‑column system using Agilent DB-5 and DB-17 capillary GC columns.

2,000 Cyfluthrin 1,900 1,800 1,700 1,600 1,500 1,400 1,300 1,200 1,100 Hz 1,000 900 800 700 600 500 400 300 200

24.2 24.3 24.4 24.5 24.6 24.7 24.8 24.9 25.0 25.1 25.2 25.3 Time (min)

Figure 12. Chromatogram of cyfluthrin isomers using the Area Sum function for integration.

12 Matrix-matched calibration standards and spiked QC samples were prepared by spiking appropriate standard solutions into the matrix blank. The spiking concentration for calibration standards were between 0.05 and 0.5 mg/kg in apple matrix. The data were processed with OpenLab CDS 2.3 software. Table 3 shows the results on a DB-5 column, the R2 values >0.991 for all organochlorine pesticides. The area RSD values for eight replicates at three levels were below 4%, with the typical RSD below 2%. Compared to the NY/T 761 method, the optimized extraction and cleanup procedure was validated by running spiked samples at 0.1 mg/kg level. Acceptable recoveries were achieved Figure 13. Integration table for cyfluthrin isomers. for most of the analytes. Recoveries were between 77.3 and 118.6%. Table 3 also shows the MDL results for the 41 compounds. S/N was used for MDL calculation. The results were better than the NY/T 761 method reference results.

% Recovery for organochlorine pesticides 140 120 100 80 60

% Recovery 40 20 0 e e e e e e n n n C C C an at zine -DDE -DDE -DDT -DDT -DDD -DDD Aldrin ra γ-BH Endrin α-BHC δ-BH β-BH Dicofol Dieldri p,p' p,p' o,p' o,p' Diclor At Propanil p,p' o,p' amethrin Simazin e Iprodion Butachlo r Cyfluthrin Bifenthrin iadimefo n Vinclozolin Heptachlor Permethri n Endosulfan -Fluvalinat Fenvaler Tr u Deltamethri Tetr Flucythrinate Procymidon Cypermethri n Chlorothalonil Fenpropathri ci s -Permethri n ta Chlorobenzilate Lambda-cyhalothri n Hexachlorobenzen Pentachloronitrobenzen

Figure 14. Recovery data of organochlorine pesticides.

13 Conclusion References

An Agilent 8890 GC configured with four 1. China National Standard NY/T detectors (two FPDs and two ECDs) 761-2008, Determination of was used to screen organophosphorus Organophosphorus, Organochlorine, and organochlorine pesticides in fruit and Residues and vegetables. Splitting the samples in Vegetables and Fruits. into two different columns then to 2. China National Standard GB/T two detectors facilitated selectivity, 19648-2006, Determination of identification, and confirmation of 500 Pesticides and Metabolites organophosphorus pesticides and Residues in Vegetables and Fruits, organochlorine pesticides from single Gas Chromatography/Mass injections of each extract, increasing Spectrometry Method. laboratory productivity. 3. China National Food Safety Standard This Application Note demonstrates GB 23200.113-2018, Determination excellent sensitivity, area repeatability, of 208 Pesticides and Metabolites peak shape, and resolution for both Residues in Foods of Plant Origin, organophosphorus and organochlorine Gas Chromatography-Tandem Mass pesticides, which shows that this Spectrometry Method. four‑detector system is an ideal platform for the NY/T 761-2008 method.

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