Validation of QuEChERS-based UPLC-MS/MS method for determination of quinoid niclosamide (LDS) residue in water,soil and rice samples

A sensitive, rapid and easy analytical method was validated for the determination of quinoid niclosamide (LDS) molluscicide in water, rice and soil using a QuEChERS extraction procedure and ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) detection. The LDS was extracted by using acetonitrile and then cleaned up by using dispersive solid-phase extraction with florisil and C18 sorbents. The determination of the target compound was achieved in less than 3 min using an electrospray ionisation source in negative mode. The overall average recoveries for this method in water, rice and soil matrix at three fortified levels ranged from 82.54 to 99.9%, with relative standard deviations in the range of 1.51 to 4.86% (n = 5). The calculated limits of detection were lower than 0.1 µg kg^?1 and quantification was 5 µg kg^?1; these values were much lower than the maximum residue levels established by the Australian standard (0.01 mg kg^?1). The results of the method validation confirmed that this proposed method is convenient and reliable for the determination of LDS molluscicide in water, rice and soil samples.     

Analysis of triallate residue and degradation rate in wheat and soil by liquid chromatography coupled to tandem mass spectroscopy detection with multi-walled carbon nanotubes

A modified quick, easy, cheap, effective, rugged and safe (QuEChERS) method for the analysis of triallate residue in wheat and soil was developed and validated. Multi-walled carbon nanotubes were used as clean-up sorbent. The residual levels and dissipation rates of triallate in wheat and soil were determined by liquid chromatography–tandem mass spectrometry. The limit of quantification was established as 0.01, 0.02 and 0.05 mg kg^?1 for soil, wheat and wheat plant samples, respectively. The average recoveries of triallate ranged from 77% to 108% at fortified levels of 0.01–0.5 mg kg^?1 with relative standard deviations of 3.0–8.4% (n = 5). From residue trials at three geographical experimental plots in China, the results showed that the half-lives of triallate in soils were 1.13–1.63 days. For trials applied according to the label recommendation, the final residues of triallate in wheat at harvest time were all below 0.05 mg kg^?1 (the maximum residue levels of China, Japan, Korea and the US).     

Residue analysis of fosthiazate in cucumber and soil by QuEChERS and GC-MS

A convenient method was developed for the determination and validation of fosthiazate in cucumber and soil. The procedure is based on liquid partitioning with acetonitrile followed by dispersive solid phase extraction as the clean-up step, after which samples were analysed by gas chromatography-mass spectrometry (GC-MS). The average recoveries ranged from 91.2 % to 99.0 % with relative standard deviations (RSDs) of less than 6.05 %, at three fortification levels (0.02 mg kg^?1, 0.1 mg kg^?1, 0.5 mg kg^?1) in cucumber and soil, and the limits of quantification (LOQs) for fosthiazate were all established at 0.02 mg kg^?1. The proposed method was applied successfully to analyses of the dissipation and residue of fosthiazate in field trials. The dissipation rate of fosthiazate was described using pseudo-first-order kinetics with a half-life of 4.33 days and 4.08 days in soil in Beijing and Shandong, respectively. In the terminal residue experiment, fosthiazate residues in cucumber and soil were clearly below the maximum residue level (MRL, 0.2 mg kg^?1) set in China.     

Residues and dissipation of guadipyr in rice ecological system

A modified QuEChERs method with liquid chromatography-tandem mass spectrometry for analysis of guadipyr residue and dissipation in rice matrices, paddy soil and paddy water was developed and validated. Mean recoveries and relative standard deviations in paddy soil, paddy water, rice plant, rice straw, rice hull and husked rice matrices at three spiking levels were 83.1–116.5% and 1.6–9.5%, respectively. The half-life of guadipyr was determined in 2 years at three different field sites in China via a dissipation experiment. The half-lives of guadipyr in paddy water were 0.22–0.37 days, 0.24–3.33 days in paddy soil and 0.44–1.90 days in rice plant. The terminal residues of guadipyr ranged from ND (concentrations of guadipyr were below limit of detection) to 50 μg kg^?1 in paddy soil, 10–470 μg kg^?1 in rice hull, ND70 μg kg^?1 in husked rice and ND to 110 μg kg^?1 in rice straw. The results would be helpful in fixing maximum residue limit of guadipyr, a new insecticide, in rice.     

MSPD–GC–MS–MS Determination of Residues of 15 Organic Nitrogen-Containing Pesticides in Vegetables

A novel and simple method for determination of 15 organic nitrogen-containing pesticides in vegetables using matrix solid-phase dispersion (MSPD) coupled with gas chromatography tandem mass spectrometry (GC–MS–MS) has been developed. The efficiencies of different sorbents (florisil, silicone, neutral alumina) for the MSPD were compared. Mean recoveries of the method using neutral alumina varied from 73.26 to 111.83% with relative standard deviations of 0.79–15.33% in the concentration range of 0.01, 0.02 and 0.05 mg kg^?1. The limits of detection were typically in the 0.0007–0.0320 mg kg^?1 range, which were 10–100 times lower than the maximum residue levels established by the European Union. This method was applied to residue detection in vegetables, in which organic nitrogen-containing compounds were detected at low concentrations.     

Analysis of residue dynamics of clofentezine in tangerine and field soil by QuEChERS and HPLC-UV methods

A field experiment was conducted to evaluate clofentezine residue levels and dissipation trend in tangerine and soil for the safe application of clofentezine. A modified QuEChERS-HPLC-UVD method was developed to analyse clofentezine in tangerine and soil. Tangerine samples were homogenised and extracted by acetonitrile and then cleaned up with dispersive solid phase extraction (dSPE) by primary and secondary amine (PSA) and C₁₈. Clofentezine residue was determined by high-performance liquid chromatography (HPLC) with a UV detector (UVD) at the wavelength of 268 nm. The presented method achieved the good linear relationship within the range from 0.05 to 5.0 mg kg^?1 for clofentezine (R² > 0.998). At the fortification levels of 0.05, 0.50 and 1.00 mg kg^?1 in tangerine pulp, tangerine peel and soil, recoveries ranged from 75.9% to 117.7% with relative standard deviations (RSD) less than 8.2%. In the supervised field trials, the half-lives of clofentezine in tangerine and soil were approximately 11.3 and 8.6 days, respectively. At pre-harvest interval of 21 days, the residue of clofentezine in tangerine was below the maximum residue limits (MRL) (0.5 mg kg^?1). Clofentezine (Water Dispersible Granule, 80%) was recommended to be sprayed twice and the recommended dosage ranged from 250 to 375 mg kg^?1.     

MSPD Procedure for Determination of Carbofuran, Pyrimethanil and Tetraconazole Residues in Banana by GC–MS

An extraction method based on matrix solid-phase dispersion was developed to determine carbofuran, pyrimethanil and tetraconazole in banana using gas chromatography–mass spectrometry. The best results were obtained using 2.0 g of banana, 1.0 g of silica as dispersant sorbent and n-hexane:ethyl acetate (1:4, v/v) as eluting solvent. The method was validated using banana samples fortified with pesticides at different concentration levels (0.05–2.0 mg kg^?1). Average recoveries (four replicates) ranged from 68 to 111%, with relative standard deviations between 6.6 and 20.5%. Detection and quantification limits for banana ranged from 0.02 to 0.05 and 0.05 to 0.10 mg kg^?1, respectively.     

Simultaneous Analysis of Hexaconazole, Myclobutanil, and Tebuconazole Residues in Apples and Soil by SPE Clean-Up and GC with Nitrogen–Phosphorus Detection

A facile and sensitive method utilizing capillary gas chromatography with nitrogen phosphorus detection (GC–NPD) has been developed and validated for simultaneous analysis of hexaconazole, myclobutanil, and tebuconazole, three broad-spectrum systemic fungicides, in apples and soil. Two samples were fortified with the three pesticides and subjected to ultrasonic extraction, followed by solid-phase extraction (SPE) to remove coextractives, before analysis by GC–NPD. SPE procedures were performed on PSA cartridges (500 mg, 3 mL), the analytes being eluted with n-hexane–acetone (9:1 v/v, 2 mL). Recovery of three pesticides from the fortified apple and soil samples ranged from 94.5 to 107.3% with relative standard deviations less than 9.7% at the three spike levels (0.01, 0.1, and 0.5 mg kg^?1). Limits of quantification of the method for apple and soil were 0.01 mg kg^?1, sufficiently below the maximum residue limits. Direct confirmation of the analytes in samples was achieved by gas chromatography–mass spectrometry (GC–MS).     

Residues and risk assessment of bifenthrin and chlorfenapyr in eggplant and soil under open ecosystem conditions

Dissipation and residue levels of bifenthrin and chlorfenapyr in eggplant and soil under field conditions were investigated using gas chromatography coupled with an electron capture detector (GC-ECD). The mean recoveries of bifenthrin and chlorfenapyr were 85.2–104.9%, with relative standard deviations (RSDs) of 0.5–9.1%. The limit of quantification (LOQ) was 0.01 mg kg^?1. Bifenthrin exhibited half-lives of 3.3 to 4.1 days in eggplant and 17.8 to 25.7 days in soil; the half-lives of chlorfenapyr were 3.5 to 3.8 days in eggplant and 21.7 to 27.7 days in soil. During harvest, the terminal residues of bifenthrin and chlorfenapyr were below 0.031 and 0.083 mg kg^?1, respectively. Risk assessment for different groups of people in China was evaluated. The risk quotients (RQs) of bifenthrin and chlorfenapyr were ranged from 0.0068 to 0.0148 and from 0.0033 to 0.0072, respectively. These results may provide guidance on reasonable use of pesticides and serve as a basis for establishing maximum residue limits (MRLs) in China.     

Determination of carbamates at trace levels in water and cucumber by capillary liquid chromatography

A sensitive and reliable method using capillary HPLC with UV-diode array detection (DAD) has been developed and validated for trace determination of carbamate pesticides in cucumber and environmental water samples. The analytes, including carbofuran, carbaryl, methiocarb, promecarb, benthiocarb and fenoxycarb, present legal residue levels regulated by the EU Council Directive 98/83/EC on drinking water and by the Regulation (EC) No. 396/2005 on vegetables. A previous off-line solid-phase extraction (SPE) procedure was required for preconcentration and sample clean-up. The separation was achieved using a C₁₈ column (150?mm?×?0.5?mm I.D, 5?µm particle size) and a mobile phase consisting of ACN?:?water using gradient mode, with a flow rate of 10?µl min^?1. Taking advantages of the characteristics of capillary HPLC, low volume of sample and solvents were required, achieving limits of detection for the studied compounds ranged from 10.0–29.6?ng l^?1 for water samples and 1.8–5.6?µg kg^?1 for cucumber, using UV-detection. Recoveries studies for fortified samples, at three different concentration levels, were carried out obtaining recoveries ranging from 70.0 to 111.1% and relative standard deviations (RSDs) lower than 10.6%.     

Residue and dissipation of zinc thiazole in tobacco field ecosystem

A high-performance liquid chromatography with ultraviolet (HPLC-UV) detection method after derivatisation was developed for the first time for the novel fungicide zinc thiazole residue in tobacco samples. Field trials in two different locations were conducted to investigate the dissipation and residue of zinc thiazole in tobacco leaves and soil. The average recoveries of zinc thiazole were in the range of 82.5%–93.9% with relative standard deviations (RSDs) of 1.2%–9.1%. The zinc thiazole showed a rapid dissipation rate in fresh tobacco leaves with the half-lives of 1.1–1.6 days. The terminal residues of zinc thiazole in cured tobacco leaves and soil were 2.8–28.0 mg kg^?1and <0.05 mg kg^?1, respectively. The results could be used to establish the maximum residue limits (MRLs) and provide guidance for the scientific use of zinc thiazole in agriculture.     

Dissipation dynamics of fenamidone and propamocarb hydrochloride in pepper,soil and residue analysis in vegetables by ultra-performance liquid chromatography coupled with tandem mass spectrometry

In this study, a rapid and sensitive method was developed for determining fenamidone and propamocarb hydrochloride residues in vegetables and soil by ultra-performance liquid chromatography-tandem mass spectrometry. The dissipation dynamics of fenamidone and propamocarb hydrochloride in pepper and soil was investigated in Beijing, Henan and Shandong provinces. The target compounds were extracted with methanol and cleaned with dispersive solid phase extraction using primary secondary amine. Two pairs of precursor product ion transitions for fenamidone and propamocarb hydrochloride were measured and evaluated. Average recoveries of fenamidone in potato, tomato, cabbage, pepper and soil at three levels (10, 100 and 1000 μg kg^?1) ranged from 76.91% to 107.31% with relative standard deviations (RSDs) from 2.74% to 10.87% (n = 15). The average recoveries of propamocarb hydrochloride ranged from 74.84% to 97.96% with RSDs from 2.43% to 16.16% (n = 15). The limits of detection (LODs) for fenamidone in each matrix were 0.131–0.291 μg kg^?1, and the limits of quantification (LOQs) were 0.436–0.970 μg kg^?1. The LODs for propamocarb hydrochloride were 0.125–0.633 μg kg^?1, and the LOQs were 0.417–2.11 μg kg^?1. The results also showed that the dissipation of fenamidone and propamocarb hydrochloride in pepper and soil followed first-order kinetics model more than that of bi-exponential models. The half-lives of propamocarb hydrochloride were 6.90–15.78 days in pepper and 13.56–23.02 days in soil. The half-lives of fenamidone were 7.48–11.29 days in pepper and 35.18–42.78 days in soil.     

Determination of Organophosphorus Pesticides in Soybean Oil, Peanut Oil and Sesame Oil by Low-Temperature Extraction and GC-FPD

A low-temperature clean-up method for residue determination was developed and validated for 14 organophosphorus pesticides in soybean oil, peanut oil and sesame oil by gas chromatography with flame photometric detector (GC-FPD). A different matrix influenced the response and retention time of pesticides. Hence matrix-matched calibration standards were used to counteract the matrix effect. The pesticide responses in blank samples of soybean oil, peanut oil and sesame oil were within the linear range of 0.02–1 mg kg⁻¹ and the correlation coefficients were higher than 0.9989. Average recoveries obtained from different oil samples at three fortified levels were higher than 50% with relative standard deviations (RSDs) of less than 15%. The limit of detections (LODs) of studied pesticides ranged from 2 to 5 μg kg⁻¹. Thirty-nine commercial samples were analyzed, and the results were confirmed by gas chromatography–mass spectrometry (GC–MS) in selective ion monitoring (SIM) mode.     

Buprofezin dissipation and safety assessment in open field cabbage and cauliflower using GC/ITMS employing an analyte protectant

An analytical method for the determination of buprofezin residues in cabbage and cauliflower was developed and validated using gas chromatography with ion trap mass spectrometry. The analyte protectant d ‐sorbitol was used at a concentration level of 0.5 mg mL^?1 in acetonitrile instead of in matrix for constructing the calibration curves of the buprofezin standard. The average recoveries ranged from 91.3 to 96.8%, with an RSD of ≤2.7%. The limits of detection and quantitation of the method in cabbage and cauliflower were 1.3, 1.7 and 4.3, 6.2 μg kg^?1, respectively. The residual levels and dissipation kinetics of buprofezin 25% wettabe powder in cabbage and cauliflower cultivated under open field conditions was investigated at the single (T1) and double (T2) recommended rates of application. Half‐life periods were found to be 1.73 and 2.1 days in cabbage, whereas in cauliflower, these values were 1.85 and 2.36 days at T1 and T2, respectively. Based on the dissipation study, and the maximum residue limit value of 0.05 mg kg^?1, the proposed pre‐harvest interval of buprofezin in cabbage was 3–6 days and that in cauliflower was 4–10 days. The results showed that buprofezin is safe for application at both recommended application rates.     

Dissipation rates of saisentong residues in fresh tobacco,tobacco powder and soil determined by high-performance liquid chromatography coupled with diode array detection

Two independent field trials were performed in Guizhou and Hunan, China in 2013 to investigate the dissipation and residue levels of saisentong in tobacco and soil. A novel and accurate method using high-performance liquid chromatography with diode array detection was developed and validated to determine saisentong levels in tobacco and soil. The average recovery of saisentong at fortification levels of 0.5, 2.5, 5.0 and 50.0 mg kg^?1 in fresh tobacco ranged from 75.92 to 107.40% with a relative standard deviation (RSD) of 0.94 to 7.55%, that at fortification levels of 0.5, 2.0 and 5.0 mg kg^?1 in tobacco powder ranged from 74.96 to 94.43% with a relative standard deviation (RSD) of 4.38 to 8.14%, and that at fortification levels of 0.1, 0.5 and 5.0 mg kg^?1 in soil ranged from 86.90 to 100.0% with an RSD of 1.38 to 4.62%. The limit of detection (LOD) of saisentong was 0.15 mg?kg^?1 in tobacco and 0.03 mg kg^?1 in soil, and the limit of quantification (LOQ) was 0.5 mg kg^?1 in tobacco and 0.1 mg kg^?1 in soil, respectively. For field experiments, the half-lives of saisentong in tobacco from Guizhou and Hunan were 5.9 and 1.6 days, respectively; those in soil were 14.7 and 12.0 days, respectively. The results suggest that the saisentong dissipation curves followed the first-order kinetic. The terminal residues of saisengtong in tobacco ranged from 0.5 to 9.39 mg kg^?1 at pre-harvest intervals (PHI) of 7, 14 and 21 days.     

Residue analysis of four diacylhydrazine insecticides in fruits and vegetables by Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) method using ultra-performance liquid chromatography coupled to tandem mass spectrometry

The new analytical method using Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) procedure for simultaneous determination of diacylhydrazine insecticide residues in fruits and vegetables was developed using ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS). The four insecticides (tebufenozide, methoxfenozide, chromafenozide, and halofenozide) were extracted from six fruit and vegetable matrices using acetonitrile and subsequently cleaned up using primary secondary amine (PSA) or octadecylsilane (C18) as sorbent prior to UPLC-MS/MS analysis. The determination of the target compounds was achieved in less than 3.0 min using an electrospray ionization source in positive mode (ESI+) for tebufenozide, methoxfenozide, and halofenozide and in negative mode (ESI−) for chromafenozide. The limits of detection were below 0.6 μg kg⁻¹, while the limit of quantification did not exceed 2 μg kg⁻¹ in different matrices. The QuEChERS procedure by using two sorbents (PSA and C18) and the matrix-matched standards gave satisfactory recoveries and relative standard deviation (RSD) values in different matrices at four spiked levels (0.01, 0.05, 0.1, and 1 mg kg⁻¹). The overall average recoveries for this method in apple, grape, cucumber, tomato, cabbage, and spinach at four levels ranged from 74.2% to 112.5% with RSDs in the range of 1.4–13.8% (n = 5) for all analytes. This study provides a theoretical basis for China to draw up maximum residue limits and analytical method for diacylhydrazine insecticide in vegetables and fruits.     

Determination of Chlorantraniliprole Residues in Corn and Soil by UPLC�CESI�CMS/MS and Its Application to a Pharmacokinetic Study

A rapid, highly sensitive, and selective method was developed for the determination of the insecticide chlorantraniliprole (CAP) in corn and soil using ultra-performance liquid chromatography?Ctandem mass spectrometry (UPLC?CMS/MS). Samples were extracted with acetonitrile, and aliquots were cleaned with solid-phase extraction cartridges. Two precursor-product ion transitions for CAP were measured and evaluated to provide maximum confidence in the results. Average recovery for soil, corn grain, and corn straw at different levels (5 or 10, 40, and 100 ??g kg^?1) ranged from 74.9 to 97.5%, with intra-day relative standard deviation (RSD) values of 1.9?C11.3% and inter-day RSD values of 4.7?C10.4%. Coefficients of determination (R ²) of 0.9988 or higher were achieved for CAP in soil, corn grain, and corn straw matrix calibration curves, from 5 to 1,000 ??g L^?1. The CAP limits of quantitation in soil, corn grain, and straw were determined to be 5, 10, and 10 ??g kg^?1, respectively, which were much lower than the maximum residue levels established by the Environmental Protection Agency of United States. UPLC?CMS/MS was used to determine the CAP residues in real corn and soil for studies on their dissipation. The trial results showed that the half-lives of CAP changed from 12.6 to 23.1 days in soils and ranged from 4.9 to 5.4 days in corn straws in the districts of Henan and Shandong, and the average levels of CAP residues in corn grains were all <0.01 mg kg^?1 with a harvest withholding period of 180 days.     

Determination of selected polychlorinated biphenyls in soil by miniaturised ultrasonic solvent extraction and gas chromatography-mass-selective detection

Miniaturised ultrasonic solvent extraction procedure was developed for the determination of selected polychlorinated biphenyls (PCBs) in soil samples by gas chromatography-mass-selective detection by using 2³ factorial experimental design. Recoveries of PCBs from fortified soil samples are over 90% for three different fortification levels between 40 and 120 μg kg⁻¹, and relative standard deviations of the recoveries are below 7%. The limits of detection (LODs) ranged from 0.003 to 0.006 μg kg⁻¹. The performance of the proposed method was compared to traditional shake flask extraction method on the spiked real soil sample and extraction methods showed comparable efficiencies. Proposed miniaturised ultrasonic solvent extraction offers several advantages, i.e., reducing sample requirement for measurement of target compound, less solvent consumption and reducing the costs associated with solvent purchase and waste disposal.     

Persistence and dissipation of fluopicolide and propamocarb on cabbage and soil under semi-arid climatic conditions

Persistence and dissipation of fluopicolide and propamocarb were studied on cabbage and soil as per good agricultural practices over a period of 2 years. A modified QuEChERS analytical method in conjunction with gas chromatography (GC) and GC–mass spectrometry was used for analysis of fluopicolide and its metabolite, 2,6-dichlorobenzamide, and propamocarb in cabbage and soil. The results of the method validation were satisfactory with recoveries within 74.5–100.81% and relative standard deviations 4.8–13.9% (n = 6). The limit of detection (LOD) and limit of quantification (LOQ) of both fluopicolide and 2,6-dichlorobenzamide were 0.003 µg mL^?1 and 0.01 mg kg^?1, respectively. The LOD and LOQ of propamocarb were 0.03 µg mL^?1 and 0.1 mg kg^?1, respectively. During 2013, the initial residue deposits of fluopicolide on cabbage were 0.60 and 1.48 mg kg^?1 from treatments at the standard and double doses of 100 and 200 g a.i. ha^?1 which dissipated with the half-life of 3.4 and 3.7 days. During 2014, the residues were 0.49 and 1.13 mg kg^?1 which dissipated with the half-life of 4.2 and 5.1 days. Propamocarb residues on cabbage were 5.36 and 12.58 mg kg^?1 in the first study (2013) and 4.85 and 10.26 mg kg^?1 in the second study (2014) from treatments at the standard and double doses of 1000 and 2000 g a.i. ha^?1, respectively. The residues dissipated with the half-life of 4–5.5 days. The preharvest interval, the time required for fluopicolide + propamocarb residues to dissipate below the maximum residue limits (notified by EU) at the standard dose, was 11.8 and 14 days during 2013 and 2014. Residue of 2,6-dichlorobenzamide was always <LOQ in cabbage. Residues of fluopicolide, 2,6-dichlorobenzamide and propamocarb were <LOQ in field soil at harvest.     

Dissipation dynamics and final residues of flutriafol in tobacco and soil using ultrasound-assisted extraction before liquid chromatography/tandem mass spectrometry

The dissipation dynamics and final residues of flutriafol on tobacco plant and soil were studied under field conditions. The residues of flutriafol in soil, green tobacco leaves and cured tobacco leaves were extracted by ultrasound-assisted extraction, cleaned up by dispersive solid-phase extraction and detected by liquid chromatography with tandem mass spectrometry. The limits of detection of flutriafol in soil, green tobacco leaves and cured tobacco leaves were 0.006, 0.033 and 0.033 mg·kg^?1, respectively. The limits of quantification of flutriafol in soil, green tobacco leaves and cured tobacco leaves were 0.02, 0.1 and 0.1 mg·kg^?1, respectively. Recoveries were 72.9–102% with relative standard deviations of less than 12% in soil and tobacco matrix. For field experiments, the half-lives of flutriafol in soil and green tobacco leaves were 9.2–11.5 and 9.5–11.1 days, respectively. At harvest, the final residue levels of flutriafol in cured tobacco leaves collected 21 days after one application at the recommended dosage were below 2.0 mg/kg. The maximum residue limit maximum residue limit (MRL) for flutriafol in tobacco has not yet been established in any countries. The data could help the Chinese Government to establish the MRL of flutriafol in tobacco and provide guidance on the proper use of flutriafol.