Use of graphitic carbon black and primary secondary amine for determination of 17 organophosphorus pesticide residues in spinach

Simultaneous Determination of 147 Pesticide Residues in Traditional Chinese Medicines by GC-MS/MS

Determination of pesticide residues remains a challenge in traditional Chinese medicines in which complex compounds may interfere with analysis signals. This study reports the development of a simple, effective, and high-throughput method combining gas chromatography-tandem mass spectrometry (GC-MS/MS) with either QuEChERS or solid phase extraction (SPE) to determine 147 pesticide residues in traditional Chinese medicines simultaneously. In SPE, the mixture of n-hexane and ethyl acetate (1:1, v/v) was selected to extract 147 pesticides in honeysuckle, and the extracted pesticides were determined by GC-MS/MS. The limits of detection for all pesticides were within 0.01-0.05 mg/kg. The recoveries were within 70-120% and the relative standard deviations were below 20% for over 90% pesticides. The coefficients of determination were up to 0.999 for the linearity between MS signals and different concentrations of pesticides (20-200 ng/mL). The analytical performance was confirmed in determining pesticide residues in dried tangerine peel. SPE achieved comparable recoveries for all pesticides compared to the QuEChERS method.

Determination of Synthetic Pyrethroids and Hexaconazole Residues in curry leaves and decontamination through household techniques

A multiresidue method was developed and validated for the simultaneous determination of eight synthetic pyrethroids and hexaconazole fungicide residues in curry leaves. The method involves extraction of leaf sample with ethyl acetate, purified by dispersive SPE with primary secondary amine and graphitized carbon black. The gas chromatography-electron capture detector (GC-ECD) used for residue estimation and confirmed using gas chromatography-mass spectrometry (GC-MS) with the LOQ of 0.03 μg/g. The recoveries of all pesticides were in the range of 75 to 110% with a relative standard deviation of less than 7%. The matrix effect was within the acceptable limit of less than 20% as prescribed by SANTE guidelines. The decontamination was carried out to reduce the concentration of residues in curry leaves by different household techniques and lemon juice (2%) solution was found to be more effective (35.71-56.52%) followed by 2% tamarind (23.48 to 42.94%), hot water (18.44 to 46.74%), 2% salt water (10.98 to 42.71%) and least in tap water (3.57 to 27.84%). The method was successfully applied for routine monitoring of pesticide residues in curry leaves.

Fe3O4 nanoparticles as matrix solid-phase dispersion extraction adsorbents for the analysis of thirty pesticides in vegetables by ultrahigh-performance liquid chromatography-tandem mass spectrometry

Herein we report the first example of Fe₃O₄ nanoparticles (FNPs) being used as single-matrix solid-phase dispersion (MSPD) adsorbents for the extraction of 30 representative pesticides from vegetables. This study was aimed at analyzing the extracted samples using ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Various condition parameters, such as the eluent, volume of the eluent, and amount of FNPs were optimized to achieve good sensitivity and precision for the elution and extraction of the analytes. The developed method was validated using matrices consisting of eight vegetables (lettuce, cucumber, carrot, tomato, pepper, shallot, Chinese flowering cabbage, and cabbage) spiked with 30 pesticides at concentrations of 0.01, 0.1, and 1.0 mg/kg. The recoveries of the 30 pesticides (organophosphorus, triazole, carbamate, nicotine, amide, and other different structures of pesticides) were in the range 71.0-110.8% (n = 5) (except those of prothioconazole and dinotefuran), with relative standard deviations lower than 13.5% in all the matrices under optimal conditions. The matrix effects were observed by comparing the slope of the matrix-matched standard calibration curve with that of the solvent. However, the matrix effects of the eight vegetables did not show evident regularities. For pepper, tomato, and shallot, a sizable number of pesticides (24, 21, and 21, respectively) showed suppressive matrix effects. On the other hand, for cucumber, Chinese flowering cabbage, and cabbage, a good number of pesticides (19, 18, and 15, respectively) showed negligible matrix effects. Furthermore, for carrot matrices, 21 pesticides showed a matrix enhancement effect. Excellent linearity was achieved at pesticide concentrations of 0.01-1.0 mg/L, and the limits of quantification (LOQ) for the developed method reached 0.01 mg/kg (except that for dinotefuran, which was 0.1 mg/kg), based on the spiked test. The developed method was successfully employed in the analysis of real samples in Nanning, China, and three pesticide residues (halosulfuron methyl, tebuconazole, and azoxystrobin) were commonly detected in vegetable samples. In the present study, a reliable method-validation performance and excellent cleanup effects were observed by using the modified MSPD method consisting of the FNPs in the cleanup step.

Optimized residue analysis method for broflanilide and its metabolites in agricultural produce using the QuEChERS method and LC-MS/MS

Since broflanilide is a newly developed pesticide, analytical methods are required to determine the corresponding pesticide residues in diverse crops and foods. In this study, a pesticide residue analysis method was optimized for the detection and quantification of broflanilide and its two metabolites, DM-8007 and S(PFH-OH)-8007, in brown rice, soybean, apple, green pepper, mandarin, and kimchi cabbage. Residue samples were extracted from the produce using QuEChERS acetate and citrate buffering methods and were purified by dispersive solid-phase extraction (d-SPE) using six different adsorbent compositions with varying amounts of primary secondary amine (PSA), C18, and graphitized carbon black. All the sample preparation methods gave low-to-medium matrix effects, as confirmed by liquid chromatography-tandem mass spectrometry using standard solutions and matrix-matched standards. In particular, the use of the citrate buffering method, in combination with purification by d-SPE using 25 mg of PSA and a mixture of other adsorbents, consistently gave low matrix effects that in the range from -18.3 to 18.8%. Pesticide recoveries within the valid recovery range 70-120% were obtained both with and without d-SPE purification using 25 mg of PSA and other adsorbents. Thus, the developed residue analysis method is viable for the determination of broflanilide and its metabolites in various crops.

Determination of hexabromocyclododecane enantiomers in chicken whole blood by a modified quick, easy, cheap, effective, rugged, and safe method with liquid chromatography and tandem mass spectrometry

A rapid and simple analytical method has been developed for the determination of hexabromocyclododecane enantiomers in chicken whole blood, based on a modified quick, easy, cheap, effective, rugged, and safe approach before liquid chromatography coupled with tandem mass spectrometry. The factors influencing performance of method were investigated by single factor experiment, and further optimized by the response surface methodology based on Box-Behnken design. The matrix effects were also evaluated by the isotopic dilution method. Under the optimal conditions, the proposed method showed good linearity within the range of 1-500 μg/L and good repeatability with relative standard deviation less than 9.5% (n = 5). The limits of detection (S/N = 3) were 0.03-0.19 μg/L. The developed method was successfully applied for the analysis of hexabromocyclododecane enantiomers in real chicken blood samples. The satisfactory recoveries ranging of 83.6-115.0% were obtained (at spiked levels of 5, 20, and 100 μg/L). The results demonstrated that the proposed method would be a practical value method for the determination of hexabromocyclododecane enantiomers in animal blood. It would be further developed with confidence to analyze other lipophilic organic pollutants in blood sample.

Dissipation kinetics and residue of LH-2010A in cucumber and soil under greenhouse condition

LH-2010A is a newly developed fungicide with novel mode of action in the treatment of cucurbit downy mildew. Dissipation kinetics and residue levels of LH-2010A in cucumber were investigated using a QuEChERS method with GC-ECD. Field trials were constructed at three different sites in China in 2013 and 2014. The average recoveries of LH-2010A in fortified samples were between 94.0 and 106.2% for cucumber and between 84.4% and 98.7% for soil, with relative standard deviations within 3%. The dissipation rate of LH-2010A residue was evaluated assuming a pseudo first-order kinetics. The half-lives of LH-2010A were 2.8-4.2 days and 6.3-9.4 days in cucumber and soil samples, respectively. The terminal residues in cucumber were 0.077-0.207 mg/kg and 0.109-0.307 mg/kg on the first day after spray at the recommended dosage and 1.5 times of the recommended dosage, respectively. Using this rapid and sensitive method, we determined the dissipation kinetics and residue level of HL-2010A in cucumber. The suggested MRL value of HL-2010A in cucumber is 0.5 mg/kg. The research would provide guidance for proper and safe use of this newly developed fungicide in cucumber in greenhouse ecosystems.

Multifamily determination of pesticide residues in soya-based nutraceutical products by GC/MS-MS

An analytical method based on a modified QuEChERS extraction coupled with gas chromatography-tandem mass spectrometry (GC-MS/MS) was evaluated for the determination of 177 pesticides in soya-based nutraceutical products. The QuEChERS method was optimised and different extraction solvents and clean-up approaches were tested, obtaining the most efficient conditions with a mixture of sorbents (PSA, C18, GBC and Zr-Sep(+)). Recoveries were evaluated at 10, 50 and 100 μg/kg and ranged between 70% and 120%. Precision was expressed as relative standard deviation (RSD), and it was evaluated for more than 160 pesticides as intra and inter-day precision, with values always below 20% and 25%, respectively. Limits of detection (LODs) ranged from 0.1 to 10 μg/kg, whereas limits of quantification (LOQs) from 0.5 to 20 μg/kg. The applicability of the method was proved by analysing soya-based nutraceuticals. Two pesticides were found in these samples, malathion and pyriproxyfen, at 11.1 and 1.5 μg/kg respectively.

Dissipation kinetics and residues of florasulam and tribenuron-methyl in wheat ecosystem

The dissipation kinetics and residual levels of florasulam and tribenuron-methyl in wheat field ecosystem were determined using a quick, easy, cheap, efficient, rugged and safe method (QuEChERS) with rapid resolution liquid chromatography tandem mass spectrometry (RRLC-MS/MS). The average recoveries of florasulam and tribenuron-methyl at three spiking levels in wheat plant, soil, wheat straw and wheat grain ranged from 72.8% to 99.2% with relative standard deviations (RSDs) were less than 10.1% and 82.5% to 103.8% with RSDs were less than 9.4%, respectively. The limits of quantification (LOQs) of florasulam and tribenuron-methyl for wheat plant, wheat straw, wheat grain and soil were 0.01, 0.01, 0.005, 0.005 mg kg(-1), respectively. The field trials results showed that the half-lives of florasulam were 2.76-10.83 d. Half-lives for tribenuron-methyl were found to be 1.27-5.37 d. The terminal residues in wheat grain were much lower than maximum residue limits (MRLs) set by China (0.01 mg kg(-1) for florasulam and 0.05 mg kg(-1) for tribenuron-methyl), which considered to be safe for human beings. These results will contribute to establishing the scientific basis of the dosage of florasulam and tribenuron-methyl for use in wheat field ecosystems.

Convenient analytical method for quantitative determination of 23 pesticide residues in herbs by gas chromatography-mass spectrometry

A convenient analytical method for quantitative characterization of 23 pesticides in three herbs has been developed. Pesticides tested included organochlorine, organophosphorus and pyrethroids. Primary secondary amine and graphitized carbon black as dispersive-SPE sorbent were applied to clean up the sample. Analytical method was established by using the technique of gas chromatography coupled with electron impact mass spectrometry in the selected ion monitoring mode (GC-MS-SIM). The recoveries of all pesticides were in the range of 78.4%-119.2% at three spiked levels of 5, 20 and 50 μg/kg, and the relative standard deviations were below 9.5%. The limits of detections of all pesticides were less than 3.0 μg/kg. This analytical method could be applied to the analysis of commonly used pesticides in commercial herbs.

Simultaneous determination of organophosphorus pesticides in Chinese herbal medicines by microwave-assisted extraction coupled with dispersive-solid phase extraction and gas chromatography

A reliable, rapid and nontoxic analytical method was proposed for the simultaneous determination of 16 organophosphorus pesticides in Chinese herbal medicines. The pesticides were extracted by ethanol and the experimental variables, such as temperature, extraction time and volume of ethanol, were optimized through orthogonal array experimental design. Cleanup of extracts was performed with dispersive-solid phase extraction using primary secondary amine as the sorbent. The determination of pesticides in the final extracts was carried out by gas chromatography-flame photometric detection. Under optimized conditions the obtained recoveries, except for isocarbophos, were in the range 73.8-123%, with relative standard deviations equal to or lower than 15.2% and limits of detection ranging from 0.001 to 0.009 mg/kg.

Method development for the determination of 52 pesticides in tobacco by liquid chromatography-tandem mass spectrometry

A method using reversed phase liquid chromatography-electrospray ionization-tandem mass spectrometry was developed for the determination of 52 pesticides in tobacco. The influence of mobile phase additives was investigated to improve sensitivity and accuracy of the method and to reduce matrix effects. The tobacco extracts were purified via a Chem Elut partition cartridge by consecutive elution with pentane followed by dichloromethane. The two fractions were further purified by Florisil solid-phase extraction with acetone or diethyl ether elution. An additional dispersive solid-phase extraction step with primary-secondary amine led to decreased recoveries of several pesticides due to degradation or binding to the sorbent. The method was validated for the tobacco types Burley, Oriental and Virginia. The recovery rates of almost all pesticides ranged between 70 and 120%. The limits of quantification were below or near the 10 ng/g level. Few but significant differences between the tobacco types could be found regarding recovery and sensitivity.