Sample preparation method for the analysis of some organophosphorus pesticides residues in tomato by ultrasound-assisted solvent extraction followed by dispersive liquid–liquid microextraction

A very simple and economic method for organophosphorus pesticides (OPPs) residues analysis in tomato by means of gas chromatography–flame photometric detection (GC–FPD) has been developed. The method involves a rapid and small-scale extraction. The sample was homogenised and extraction of the OPPs with acetone was carried out assisted by sonication. No clean-up or evaporation were required after extraction. Pre-concentration of the OPPs from the acetone extract was done by using dispersive liquid–liquid microextraction (DLLME) technique. Chlorobenzene was added in micro-level volume as extraction solvent and triphenylphosphate as internal standard in DLLME procedure. The method showed good linearity over the range assayed (0.5–1000 μg kg⁻¹) and the detection limits for the pesticides studied varied from 0.1 to 0.5 μg kg⁻¹. Repeatability studies resulted a relative standard deviation lower than 10% in all cases. The proposed method was used to determine pesticides levels in tomatoes grown in open field.     

Evaluation of cost-effective methods in the pesticide residue analysis of non-fatty baby foods

Three non-fatty ready-to-eat baby food matrices (fruits: juice, purée and cocktail plus rice flour/starch and sugar) were fortified with 0.01, 0.05, 0.1 and 0.2 mg/kg of dimethoate, chlorpyrifos, methidathion, phosalone and diazinon. Simple methods including extraction by ethyl acetate [EtAc] and acetone partition and determination by gas chromatography with Nitrogen–Phosphorus Detector (GC–NPD) were used. Acceptable pesticides recoveries (70–110%), low detection and quantification limits (0.001 to >0.1 mg/kg and 0.005 to 0.04 mg/kg, respectively) and repeatabilities (%RSDs), in 0.01 mg/kg, within 2.9–13.9% were observed. However, analytes recoveries were affected (p < 0.05) by both the baby food formulation and the extraction method used. Specifically, fruits purée and cocktail EtAc extracts gave excessively over-(dimethoate recoveries of 119.7–153.5%) or underestimation (phosalone and especially diazinon recoveries of 19.3–79.2%) in contrast to fruits juice (e.g., 61.3–87.9%). Also, EtAc extracts showed higher amount of lipophilic compounds and provided lower recoveries for non-polar analytes than those of acetone partition. Consequently, the examined methods may be successfully applied in non-fatty baby foods with the matrix-matched standards determination, following improvements of certain parameters in relation to the clean-up of samples.     

Analysis of pesticide residues in seaweeds using matrix solid-phase dispersion and gas chromatography–mass spectrometry detection

Products containing organophosphates, carbamates and pyrethroids pesticides, employed as chemotherapeutants in aquaculture, can remain as residues in the marine environment. Matrix solid-phase dispersion (MSPD) was developed to extract seventeen pesticides from seaweed samples using Florisil and graphitized carbon black as clean-up adsorbents prior to gas chromatography–mass spectrometry (GC–MS) determination. The extraction has been optimised by a Box–Behnken design. The optimal conditions were 1 g of seaweed sample, 4 g of anhydrous sodium sulphate as dispersant, 3.6 g of Florisil and 0.4 g of GCB and an elution volume of 14 mL of a hexane:ethyl acetate mixture containing 40% ethyl acetate. The recoveries ranged from 81.6% to 113.2% with relative standard deviations (RSDs) ranging from 1.6% to 13.2%. The limits of detection (LOD) ranged from 0.5 to 2.9 ngg⁻¹. Internal quality control was successfully carried out to verify the quality of the data obtained in the analysis of these pesticides in seaweed samples.     

Fast screening of pesticide residues in fruit juice by solid-phase microextraction and gas chromatography–mass spectrometry

A new vanguard–rearguard analytical method for determining 54 pesticide residues in different fruit juices (natural and commercial orange, peach and pineapple juices were tested) is proposed. For that, in a first step, a fast screening (vanguard) method is applied for detecting those samples containing pesticides at concentrations above a pre-established cut-off value. In a second step, those samples are re-analyzed by a conventional pesticide residue (rearguard) method that confirms the presence of the pesticides and quantifies them. The sample process is very simple, fast and semiautomatic and therefore, it reduces significantly the average time required per sample, increases precision and minimizing human mistakes. Only 1 mL of juice sample is required for analysis. Pesticides are quickly extracted with ethyl acetate in a test tube, transferred to a mixture water:acetone 9:1 (v/v), and isolated by solid-phase microextraction (SPME). The SPME screening method only requires 10 min of SPME extraction. The SPME confirming/quantifying method requires 55 min of SPME extraction. The instrumental determination is carried out by gas chromatography–mass spectrometry (GC–MS) using a full scan acquisition mode for the screening method (less than 17 min of chromatographic run) and a tandem mass spectrometry (MS/MS) acquisition mode for the quantifying/confirming method (less than 70 min of chromatographic run). The use of full scan MS and tandem MS for the detection increase significantly the certainty of the results. Also, the combination of a solvent and SPME extractions and GC–MS/MS offers a significant selectivity and sensitivity with a proven reduction of false positive and negative cases. The use of a vanguard–rearguard strategy can reduce the 50% of the total time required for determining routinely juices in a laboratory by a traditional strategy (identification, confirmation and quantitation of the pesticides in the samples by a conventional analytical method).     

Optimization of ethanol extraction and further purification of isoflavones from soybean sprout cotyledon

Isoflavones from cotyledons of soybean sprouts were extracted with aqueous ethanol and further concentrated to obtain a product with a high concentration of isoflavone. The ethanol concentration, extraction time and reaction temperature were optimized by using response surface methodology (RSM). Isoflavones in aqueous ethanol were concentrated by a three-step procedure comprised of solid phase extraction (SPE) with Diaion HP-20 and Amberlite-XAD-2 adsorption columns, acid hydrolysis, and liquid–liquid extraction. The maximum amount of isoflavone in aqueous ethanol extracts (11.6 mg/g solid) was obtained when isoflavones in cotyledons (2.18 mg/ g solid) were extracted with 80–90% (v/v) aqueous ethanol above 90 °C for more than 100 min. The isoflavone extracts, obtained by SPE with a Diaion HP-20 column contained 100 mg/g solid. The liquid–liquid extraction (LLE) with ethyl ether further concentrated the extracts up to 229 mg/g solid, retaining 63% of the initial isoflavones.     

Analysis of pesticide residues in sugarcane juice using QuEChERS sample preparation and gas chromatography with electron capture detection

QuEChERS sample preparation was used for the determination of 7 pesticides residues in 80 samples of sugarcane juice collected from two Brazilian cities, in two different periods. The method involved extraction with acetonitrile, liquid–liquid partition with addition of MgSO₄ and NaCl followed by dispersive SPE cleanup with PSA sorbent and the analyses were carried out with a GC–ECD equipment. The method was validated using sugarcane juice spiked at 0.025, 0.10 and 0.20 mg/L and the average recovery by the method varied from 62.9% to 107.5% with RSDs < 18%. The method showed good linearity and the LODs for the pesticides studied ranged from 0.003 to 0.04 mg/L. No pesticide residue was detected (>LOD) amongst the 80 samples analysed.     

One-Step Synthesis of Zirconia and Magnetite Nanocomposite Immobilized Chitosan for Micro-Solid-Phase Extraction of Organophosphorous Pesticides from Juice and Water Samples Prior to Gas Chromatography/Mass Spectroscopy

In this research, a magnetic sorbent was prepared by immobilizing zirconia and magnetite (Fe₃O₄) nanoparticles in chitosan, which is characterized and used as an effective nanosorbent in magnetic dispersive micro-solid-phase extraction (MDMSPE) of organophosphorous pesticides (OPPs) from juice and water samples prior to gas chromatography-mass detection (GC-MS). The properties and morphology of synthesized sorbent were characterized by scanning electron microscopy (SEM), Fourier transform-infrared spectroscopy (FT-IR), vibrating sample magnetometry (VSM), and differential scanning calorimetric (DSC) analysis. The main experimental parameters including pH level, extraction time, sorbent mass, salt concentration, and desorption conditions were investigated and optimized to maximize extraction efficiency. Under optimized conditions, the calibration curves were obtained in the concentration range of 0.1–500 ng mL^?1 with correlation coefficients between 0.9993 and 0.9999. The limits of detection (signal-to-noise ratio (S/N) = 3) and limits of quantification (S/N = 10) of the method ranged from 0.031 to 0.034 ng mL^?1 and 0.105–0.112 ng mL^?1, respectively. The intra-day and inter-day RSDs were 2.2–5.7 and 2.5–7.5%, respectively. The method was successfully applied to the analysis of OPPs in fruit juices (apple, peach, and cherry) and water (mineral, tap, and river) real samples, with recoveries in the range of 86.0–106.0% for the spiked juice and water samples. The results showed that with combination of high selectivity of zirconia and magnetic property of magnetite as well as immobilizing ability of chitosan, the fabricated sorbent exhibited exceptional extraction ability toward the OPPs.     

A validated matrix solid-phase dispersion method for the extraction of organophosphorus pesticides from bovine samples

A method based on matrix solid-phase dispersion (MSPD) was developed for the quantitative extraction of five organophosphorus (OPPs) pesticides from bovine samples. The determination was carried out by high performance liquid chromatography (HPLC) with diode array spectrophotometric UV detection. The MSPD extraction with octadecylsilyl (C18) sorbent combined with a silica gel clean-up and acetonitrile elution was optimised for chlorpyrifos, chlorfenvinphos, diazinon, fenitrothion, and parathion-methyl. The method was validated, yielding recovery values higher than 94%, except for chlorfenvinphos in liver (55%), and precision values, expressed as relative standard deviations (RSDs), which were less than or equal to 15% in liver and 11.5% in muscle at spiking levels of 0.25, 2.5 and 5 μg g⁻¹. Linearity was studied from 0.5 to 15 μg g⁻¹, and the limits of detection (LODs) were found to be lower than 0.1 μg g⁻¹_. This method was applied to the analysis of real samples with confirmative analyses performed using gas chromatography–mass spectrometry (GC–MS) in selected ion monitoring mode (SIM).     

Multi-residue method for the determination of 450 pesticide residues in honey, fruit juice and wine by double-cartridge solid-phase extraction/gas chromatography-mass spectrometry and liquid chromatography-tandem mass spectrometry

A multi-residue method was developed for the determination of 450 pesticide residues in honey, fruit juice and wine using double-cartridge solid-phase extraction (SPE), gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-tandem mass spectrometry (LC-MS-MS). The method development was based on an appraisal of the characteristics of GC-MS and LC-MS-MS for 654 pesticides as well as the efficiency of extraction and purification from honey, fruit juice and wine. Samples were first diluted with water plus acetone, then extracted with portions of dichloromethane. The extracts were concentrated and cleaned up with graphitized carbon black and aminopropyl cartridges stacked in tandem. Pesticides were eluted with acetonitrile + toluene, and the eluates were concentrated. For 383 pesticides, the eluate was extracted with hexane twice and internal standard solution was added prior to GC-MS determination. For 67 pesticides, extraction was with methanol prior to LC-MS-MS determination. The limit of detection for the method was between 1.0 and 300 ng g^-1 depending on each pesticide analyte. At the three fortification levels of 2.0-3000 ng g^-1, the average recovery rates were between 59 and 123%, among which 413 pesticides (92% of the 450) had recovery rates of 70-120% and 35 pesticides (8% of the 450) had recovery rates of 59-70%. There were 437 pesticides (97% of the 450) with a relative standard deviation below 25%; there were 13 varieties (3% of the 450) between 25.0 and 30.4%.     

Determination of patulin in apple and quince products by GC–MS using C5–7 patulin as internal standard

A reliable gas chromatographic mass spectrometric method has been validated for the determination of trace levels (<10 μgL⁻¹) of patulin in apple products and quince jam. The method was based on extraction of patulin with ethyl acetate-hexane, alkalinisation and silylation with N,O-bis-trimethylsilyltrifluoroacetamide with 1% of trimethylchloro-silane. The accurate determination of patulin was achieved by employing commercial ¹³C_5–7 patulin labelled as an internal standard, which allowed compensating target analyte losses and enhancement or suppression matrix effects. Limits of detection and quantification of method using real samples were 0.4 and 1.6 μgkg⁻¹, respectively. Recoveries of patulin from samples spiked at 8–50 μgkg⁻¹ levels ranged between 71% and 89%. The repeatability of measurements (expressed as relative standard deviation) was lower than 16%. The method was successfully applied to the determination of patulin in apple fruit and apple products including juice, cider and baby food, and also in quince fruit and quince jam. A new PCR system for the detection of Penicillium expansum in samples containing highly degraded DNA was developed which permitted the detection of the mould in 2/3 of the samples containing patulin, including juices and jams.     

Multiresidue method for determination of 88 pesticides in berry fruits using solid-phase extraction and gas chromatography–mass spectrometry: Determination of 88 pesticides in berries using SPE and GC–MS

A method using solid phase extraction (SPE) cleanup followed by gas chromatography–mass spectrometry (GC–MS) has been established for quantitative determination of 88 pesticide residues in berry fruits including raspberry, strawberry, blueberry and grape. Based on an appraisal of the characteristics of GC–MS, validation experiments were conducted for 88 pesticides. In the method, solid-phase extraction was carried out using Envi-Carb cartridge coupled with NH₂-LC cartridge with acetonitrile–toluene (3:1, v/v) as the eluted solvent. In the linear range of each pesticide, the correlation coefficient was R² ? 0.99. At the low, medium and high three fortification levels of 0.05–0.5 mg kg⁻¹, recoveries fell within 63–137%. The relative standard deviation was between 1% and 19% for all 88 pesticides. Low limits of detection (0.006–0.05 mg kg⁻¹) and quantification (0.02–0.15 mg kg⁻¹) were readily achieved with this method for all tested pesticides.     

Multiresidue method for analysis of pesticides in pepper and tomato by gas chromatography with nitrogen–phosphorus detection

An analytical multiresidue method for the simultaneous determination of various classes of pesticides in vegetables (pepper and tomato) was developed. Vegetable samples are extracted with acetone and the pesticides are partitioned into ethyl acetate/cyclohexane. Final determination was made by gas chromatography with nitrogen–phosphorus detection. Confirmation analysis of pesticides was carried out by gas chromatography coupled with mass spectrometry in the selected ion monitoring (SIM) mode. The identification of compounds was based on retention time and on comparison of the primary and secondary ions. Recovery studies were performed at 0.05, 0.1 and 0.02 mg kg⁻¹ fortification levels of each compound and the recoveries obtained ranged from 70.1% to 128.5% with relative standard deviations lower than 7%. The method showed good linearity over the range assayed 50–1500 μg l⁻¹ and the detection and quantification limits for the pesticides studied varied from 0.1 to 4.4 μg kg⁻¹ and 0.4 to 14.5 μg kg⁻¹, respectively. The proposed method was used to determine pesticides levels in peppers and tomatoes grown in experimental greenhouses.     

Assessment of DFG-S19 method for the determination of common endocrine disruptor pesticides in wine samples with an estimation of the uncertainty of the analytical results

A gas chromatographic method for the determination of endocrine disruptor pesticides (Chlorpyrifos, Penconazole, Procymidone, Iprodione, Bromopropylate and Lambda-Cyhalothrin) in wine samples is described. A general DFG-S19 method for residual pesticide determination in all kind of food stuff was investigated to simplify and adopt for wine samples in this work. Alternative sample preparation routes were elucidated and compared according to their recovery values. Four different separation techniques were tested and the method employing florosil column after a LLE procedure was applied for wine samples with satisfactory recovery ratios (72–97%). The pesticides were extracted from the sample by cyclohexane–ethyl acetate mixture (1:1 v/v) and cleaned up by florosil column. The regression coefficients were at least 0.99 and relative standard deviations were no higher than 16%. Detection limits were in the range of 0.6–2.9 ng/mL and the relative expanded measurement uncertainties were calculated in the 7–22% range.     

Degradation behaviour of methamidophos and chlorpyrifos in apple juice treated with pulsed electric fields

Apple juice (13 °Brix) spiked with methamidophos and chlorpyrifos (2–3 mg/l of each compound) was treated by pulsed electric fields (PEF), and pesticide residues were quantified by gas chromatography with flame photometric detection (GC-FPD). Results showed that electric field strength (8–20 kV/cm) and pulse number (6–26 pulses) have significant effects on the degradation of methamidophos and chlorpyrifos. PEF treatment is effective for the degradation of methamidophos and chlorpyrifos residues in apple juice, and chlorpyrifos is much more labile to PEF than methamidophos. An increase in either pulse number or electric field strength could speed the degradation of methamidophos and chlorpyrifos, and the kinetics equations and related parameters quantitatively characterized the degradation behavior of the pesticides. The exponential model better fits the experimental data for all treatments than the linear model.     

Influence of technological processing on apple aroma analysed by high resolution gas chromatography–mass spectrometry and on-line gas chromatography-combustion/pyrolysis-isotope ratio mass spectrometry

Extracts obtained by simultaneous distillation extraction (SDE) from industrial raw materials, namely single strength apple juices, and concentrates and aromas made thereof (each n = 31, from one production line; origin Poland, Germany, Turkey, Romania and China), as well as commercially available juices (n = 27), were analysed by standard controlled capillary gas chromatography–mass spectrometry (HRGC–MS). During the technological processing from juice to the aroma, no qualitative changes in the apple aroma profile were observed. Major constituents of the juices and aromas under study were found to be 1-hexanol (juice, 0.06–5.9 mg/l; aroma, 47–685 mg/l), 1-butanol (juice, 0.1–4.7 mg/l; aroma, 17–370 mg/l); E-2-hexenol (juice, 0.01–3.4 mg/l; aroma, 12–300 mg/l); E-2-hexenal (juice, 0–3.0 mg/l; aroma 0–470 mg/l), and butyl acetate (juice, 0–1.7 mg/l; aroma, 0–165 mg/l). By far the major component of the apple juice concentrates under study was furfural (2.4–56 mg/kg). The observed occurrence of 3-methyl-1-butanol (juice, 0.01–2.1 mg/l; aroma, 1.5–134 mg/l) and, in part, its acetate (juice, 0–0.3 mg/l; aroma, 0–3.3 mg/l), both known not to be genuine apple constituents, was obviously caused by fermentative effects in the course of industrial juice production. In addition, on-line capillary gas chromatography–isotope ratio mass spectrometry was used in the combustion (C) and the pyrolysis (P) modes (HRGC–C/P–IRMS) for the determination of δ¹³C_V-PDB and δ²H_V-SMOW values of selected apple flavour constituents to check potential isotope discrimination during distillative aroma production. As shown by means of the representative examples of E-2-hexenal, 1-hexanol and E-2-hexenol, their δ²H_V-SMOW values were slightly depleted. However, authenticity assessment by stable IRMS will not be influenced by this effect.     

Analysis of volatile compounds of pineapple wine using solid-phase microextraction techniques

An analytical procedure based on headspace solid-phase microextraction (HS-SPME) method combined with GC–MS was developed for the extraction and quantification of volatile compounds from pineapple wine. Different sample preparation (SPME fibre type, addition of sodium chloride, extraction time and temperature) were evaluated to optimise the method. For the final method, 8 ml of pineapple wine were placed in a 15 ml headspace vial with addition of 1 g of NaCl; a polydimethylsiloxane SPME fibre was used for extraction at 30 °C for 30 min with continuous stirring. The volatile compounds have shown a good linearity in the range of concentrations studied with regression coefficients higher than 0.98, and the reproducibility expressed as relative standard deviation ranged from 4.2% (2-phenylethyl acetate) to 7.1% (ethyl benzoate). The values obtained for detection and quantification limits were low enough to permit the determination of volatiles in pineapple wine. Using this method, 18 volatiles were identified, including 13 esters, 4 alcohols and one acid. Ethyl octanoate, ethyl acetate, 3-methyl-1-butanol and ethyl decanoate were the major constituents. A tentative study to estimate the contribution of the identified compounds to the aroma of the wine, on the basis of their odour activity values (OAV), indicated that the compounds potentially most important to pineapple wine included ethyl octanoate, ethyl acetate and ethyl 2-methylpropanoate.     

Supercritical fluid extraction in situ derivatization for simultaneous determination of chloramphenicol,florfenicol and thiamphenicol in shrimp

The applicability of supercritical fluid extraction in situ derivatization was investigated for determination of trace amounts of amphenicols (chloramphenicol, florfenicol and thiamphenicol) in shrimp. Quantification was performed by using electron-capture negative chemical ionisation-gas chromatography/mass spectrometry (NCI–GC/MS). The parameters of supercritical fluid extraction (addition of modifier, temperature, pressure, extraction time and extraction mode) and in situ derivatization (collection solvent and derivatization reagent) were varied with control. The optimum extractions were obtained using 600 μL ethyl acetate as a modifier for supercritical carbon dioxide with static extraction for 5 min, then dynamic extraction for 10 min at 25 MPa and 60 °C. The conditions for in situ derivatization were 200 μL N,O-bis(trimethylsilyl) trifluoroacetamide containing 1% trimethylchlorosilane in 20 mL ethyl acetate as collection solvent. The new method of supercritical fluid extraction in situ derivatization was found to be linear over the concentration range of 20–5000 pg/g, with detection limits ranging from 8.7 to 17.4 pg/g (using the selective ion monitoring mode), with a R.S.D. (relative standard deviation) less than 15.3% (n = 5). Analysis of spiked shrimp samples revealed that matrix had little effect on extraction. The results presented here indicate that supercritical fluid extraction in situ derivatization is for the trace analysis of amphenicol bacteriostats in shrimp samples.     

Identification of phenolics in the fruit of emblica (Phyllanthus emblica L.) and their antioxidant activities

An activity-directed fractionation and purification process was used to identify the antioxidative components of emblica fruit. Dried fruit of emblica was extracted with methanol and then partitioned by ethyl ether, ethyl acetate, butanol and water. The ethyl acetate fraction showed the strongest 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity among four fractions. The ethyl acetate fraction was then subjected to separation and purification using Sephadex LH-20 chromatography and reverse-phase high-performance liquid chromatography (HPLC). Six compounds were identified to be geraniin (1), quercetin 3-β-d-glucopyranoside (2), kaempferol 3-β-d-glucopyranoside (3), isocorilagin (4), quercetin (5), and kaempferol (6), respectively, by spectral methods, ¹H and ¹³C nuclear magnetic resonance (NMR) spectroscopy, ultraviolet–visible (UV–Vis) spectrophotometry and mass spectroscopy (MS), and comparison with literatures. Compounds 2–4 and 6 were identified from emblica fruit for the first time. Furthermore, the antioxidant activities of purified compounds were screened for their antioxidative potential using lipid peroxidation and DPPH systems. All the purified compounds showed strong antioxidant and radical scavenging activities. Amongst, geraniin showed the highest antioxidant activity (4.7 and 65.7 μM of IC₅₀ values for DPPH and lipid peroxidation assay, respectively) than other purified compounds.     

Simultaneous Determination of Organochlorine, Organophosphorus, and Pyrethroid Pesticides in Bee Pollens by Solid-Phase Extraction Cleanup Followed by Gas Chromatography Using Electron-Capture Detector

A method for routine determination of the residues of nine organochlorine pesticides (OCPs), ten organophosphorus pesticides (OPPs), and seven pyrethroid pesticides (PPs) in bee pollens was developed. Bee pollen samples were extracted by petroleum ether followed by solid-phase extraction cleaning and detected by gas chromatography–micro electron capture detection. Range of detection limits are 0.3–3.3 μg/kg for OCPs, 1.0–19.1 μg/kg for PPs and 1.1–19.7 μg/kg for OPPs. Recoveries of OCPs, OPPs, and PPs were in the range of 88.9–122.7 %, 86.8–123.1 %, and 90.8–118.7 %, respectively. The method was applied successfully to analyze real bee pollen samples. The results show a low level of contamination caused by pesticide residues indicating safe supply of bee pollen for consumers.     

Determination of organophosphorus pesticides in pakchoi samples by headspace solid-phase microextraction coupled with gas chromatography using home-made fiber

A home-made sol-gel-derived co-poly (hydroxy-terminated silicone divinylbenzene) (OH-TSO/DVB) coating fiber has firstly been applied for headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography (GC)—nitrogen-phosphorus detector (NPD) to determine five organophosphorus pesticides (OPPs) in pakchoi samples. The following parameters influencing on the extraction efficiency of HS-SPME were optimized statistically: extraction temperature, extraction time, ionic strength, constant agitation, effect of sample matrix, desorption temperature, and desorption time. Compared with commercial available fibers and OH-TSO SPME fiber, this fiber showed statistically better enrichment capability for these pesticides. For the developed HS-SPME-GC method, it was found that the linearity was all two orders of magnitude, with the limits of detection (LOD) ranging from 0.007 to 0.07 ng g⁻¹, and relative standard deviations (RSD) varying between 4.1 and 8.7% (n = 5). Recoveries of spiked pakchoi samples ranged from 80.74 to 101.47% for every pesticide at each investigated concentration. Overall, it indicated that the obtained method is a validated and accurate procedure for determination of OPPs in pakchoi samples.