Metabolite Residues Research Articles

Covalent Triazine Framework Sorbent for Solid Phase Extraction of Fipronil and its Metabolite in Eggs with Ultra-High Performance Liquid Chromatography-Tandem Mass Spectrometry

ABSTRACT A solid-phase extraction (SPE) method was established for fipronil and its metabolite residues (fipronil desulfinyl, fipronil sulphone and fipronil sulphide) in eggs with a covalent triazine framework (CTF) porous material as the adsorbent followed by ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) detection. Multiple probes and quantum chemistry theory calculations were conducted to describe the versatile adsorption property directly and quantifiably. The conjugated structure of CTF and N-containing triazine generated π-π interactions and hydrogen bonds between the CTF and the targets, which led to high extraction efficiency and recoveries. The solid-phase extraction parameters, including amount of the adsorbent, type of eluent, amount of eluent and loading rate were investigated. Under the optimal experimental conditions, the recoveries of the analytes were between 85.5% and 103.2%, and the RSD (n = 5) was between 1.8% and 3.6%. The LODs and LOQs were 0.13–0.2 ng g−1 and 0.5–0.8 ng g−1, respectively. The sorbent can effectively reduce the interference of the matrix and meet the detection requirements of fipronil and its metabolites in eggs. These results imply that the CTF as adsorbents have great potential in the analysis of trace targets in samples with complex matrices.

An Integrated Strategy for Purification by Combining Solid-Phase Extraction with Dispersive-Solid-Phase Extraction for Detecting 22 Pesticides and Metabolite Residues in Fish.

A robust isotope-labeled internal standard method was established for the detection of 22 pesticides and metabolite residues in four kinds of fish; two were from freshwater fish, and two were from marine fish. Pesticides with wide application possibilities in rice in China, strong leaching to water, or high bioconcentration factors (BCF) in fish were selected. The samples were extracted with 1% acetic acid-99% acetonitrile. The extracts were first purified by solid-phase extraction (PEP-plus), cleaned with dispersive-solid-phase extraction (PSA and C18), and finally analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The results showed that good linearities for the target compounds were observed in the range of 0.1-100 ng/mL, and the correlation coefficient (R2) of each compound was greater than 0.99. The recoveries of the method were within 70-120% with RSDs <20% at three different spiked concentration levels (0.5, 5, and 100 ng/g). The quantitative limit of the method was 0.5-5 ng/g. The method is shown to be sensitive and accurate and can meet the demands for the quantitative analysis of pesticides in fish.

Quantitative determination of pyriproxyfen and its metabolite residues in bee products of China using a modified QuEChERS approach with UPLC-MS/MS

Given the key role of bees as indicators for environmental assessment, residues in bees and bee products have attracted great interest. In this regard, an improved, highly sensitive method for quantifying the insecticide pyriproxyfen and its four metabolites (4′-OH-Pyr, DPH-Pyr, 2-OH-PY, 4′-OH-POP) in honeybees, larvae, and bee products (honey, pollen, royal jelly and wax) should be established. For this purpose, we used ultra-performance liquid chromatography coupled with triple-quadrupole mass spectrometry for rapid quantification (≤5 min). Recoveries for various matrices ranged from 73.77% to 114.97%, with satisfactory intra-day and inter-day precision (relative standard deviations of 0.03–8.61% and 0.10–7.25%, respectively). The results demonstrated excellent linearity (R2 > 0.9903) with a limit of quantification of 1 μg/kg for six different matrices. We collected and analyzed 597 samples (honey, bees and wax) from four major beekeeping areas in China. Only 47 of these samples contained residues of pyriproxyfen and two of its metabolites (2-OH-PY, 4′-OH-Pyr), and high levels of contamination were found in bee samples (2–739 μg/kg), with substantive accumulation in wax (levels were 9.49% higher than in other samples). The result demonstrate that the method provides a reliable and convenient means of monitoring pyriproxyfen and its metabolites in bee products for better product quality, human health, and international commercial competition and also lays a foundation for risk assessment of potential pyriproxyfen contamination in China.

Tissue Depletion of Olaquindox and Its Six Metabolites in Pigs and Broilers: Identification of a Suitable Marker Residue.

The depletion profiles of olaquindox and its six major metabolites, including O1 (N1-deoxyolaquindox), O2 (deoxyolaquindox), O3 (2-carboxamide-3-methylquinoxaline-N4-oxide), O4 (2-carboxymethylaminocarbonyl-3-methylquinoxaline-N4-oxide), O5 (2-carboxymethylaminocarbonyl-3-methylquinoxaline), and O6 [3-methyl-quinoxaline-2-carboxylic acid (MQCA)] were studied with a sensitive and accurate HPLC-UV method in pigs and broilers after oral administration of olaquindox at the rate of 50 mg kg−1 feed for 14 consecutive days. Five medicated pigs and six medicated broilers and one control animal for each time point were anesthetized and killed at different time points (6 h and 1, 3, 7, and 14 days for pigs and 6 h and 1, 3, 5, and 7 days for broilers) after ingestion of the medicated feed ceased and samples of muscle, liver, kidney, and fat were collected. The samples were assayed using a liquid chromatographic method. Mean concentrations of O2 (deoxyolaquindox) metabolite residues in all tissues of pigs were higher than other metabolite residues at each time point. MQCA was detected at lower concentrations and eliminated more rapidly than deoxyolaquindox (calculated t1/2 1.78–2.28 days vs. t1/2 2.04–2.46 days). The elimination half-lives of deoxyolaquindox residue in broilers' liver and kidney tissues (t1/2 >4 days) were much longer than those in pigs. Thus, the use of olaquindox in poultry is clearly inappropriate, as significant drug residues will occur without a withdrawal time. The results that deoxyolaquindox occurs at higher concentrations in kidney tissue and is more persistent than other residues in edible tissues of pigs which indicate that deoxyolaquindox is the most relevant marker residue and should be monitored in the routine surveillance of olaquindox-related residues in foods of animal origin.

Simultaneous determination of 11 prohibited and restricted veterinary drugs and their metabolites in animal-derived foods by ultra performance liquid chromatography-tandem mass spectrometry coupled with solid phase extraction

建立了固相萃取-超高效液相色谱-串联质谱(SPE-UPLC-MS/MS)同时检测鸡蛋、液态奶、鸡肉及淡水鱼中4类(氯霉素类、硝基咪唑类、林可酰胺类与大环内酯类)8种禁限兽药与3种代谢物残留的分析方法。对样品前处理及色谱条件进行优化,样品经0.1 mol/L pH 9.0的磷酸盐缓冲液水解分散,乙腈提取,提取液经乙酸乙酯萃取后浓缩至近干,残留物用0.3 mL甲醇溶解,再加入5.7 mL磷酸盐缓冲液,混匀,溶解液经Oasis HLB固相萃取柱净化后上机分析,以甲醇与0.1%甲酸水溶液作为流动相进行梯度洗脱,经ACQUITY UPLC BEH C18色谱柱(100 mm×2.1 mm, 1.7 μm)分离,采用ESI+和ESI-电离,在多反应监测模式下采集,同位素内标法定量。结果表明,11种待测物在色谱柱上完全基线分离,在各自范围内线性关系良好,相关系数(R2)>0.99,方法的检出限(LOD)为0.050~0.50 μg/kg,定量限(LOQ)为0.20~1.5 μg/kg。各待测物的平均回收率为65.3%~108%,相对标准偏差(RSD)为0.40%~21%。将该方法应用于市售样品中上述4类兽药残留的常规监测,其阳性样本的检测结果与标准方法测定结果无显著性差异。该方法灵敏度高,稳定性好,定量准确,适用于动物源性食品中多种禁限兽药及代谢物残留的同时快速测定。

Antibiotics and Non-Targeted Metabolite Residues Detection as a Comprehensive Approach toward Food Safety in Raw Milk.

Antibiotic residues in milk are a serious health and technological problem in dairy processes. This study aims to verify the absence of administered antimicrobials after therapeutic treatments, taking into consideration the withdrawal period, and to evaluate the reliability of screening tests under field conditions after confirmatory HPLC-HRMS (High Performance Liquid Chromatography-High-Resolution Mass Spectrometry) Orbitrap analysis. Moreover, the presence of expected or non-targeted metabolites was investigated using the new Compound Discoverer approach. The presence of antimicrobial drugs was shown in 29% of the samples, and also sometimes their metabolites (for enrofloxacin and lincomycin), despite the fact that samples were collected at the seventh milking. Moreover, in 9% of the samples, undeclared treatments were revealed due to the presence of both parent drugs and metabolites. Lastly, the putative identification of two new enrofloxacin metabolites, ENRO-N-methylacetamide and ENRO-ornithine, was proposed. In the light of this evidence, it must be borne in mind that metabolites, some of which are pharmacologically active, may also pose a risk to consumers and for the entire processing of milk in the cheese industries.

Simultaneous analysis and risk assessment of Quizalofop, Acifluorfen, bentazone and its metabolites residues in peanut and straw under field conditions of China

In this study, we developed and validated a simple and robust method for simultaneous determination of quizalofop-p-ethyl, acifluorfen, bentazone and its two metabolites residues in peanut and straw. All samples were extracted by 0.8% formic acetonitrile (v:v) and pure water. The peanut samples were cleaned up by florisil, while the straw samples were cleansed using florisil and graphitized carbon black (GCB) by adding a desorption procedure at 55 °C. The residues were determined by a high performance liquid chromatography electro-spray ionization tandem mass spectrometry (HPLC-MS/MS). The mean recoveries of five analytes in both matrixes ranged from 77% to 110% with relative standard deviations (RSDs) <12.6%. The limits of quantification (LOQs) were 0.01 mg/kg in peanut and 0.02 mg/kg in straw. And the limits of detection (LODs) ranged from 0.047 to 0.356 μg/L. The established method was successfully applied to determine the terminal residues of the five analytes in peanut and straw samples from supervised field trials. The results showed that the residues of all analytes were less than LOQs in peanut while that was up to 0.031 mg/kg in straw. Based on residues data in peanut, chronic dietary intake risk of three pesticides was evaluated, and the results showed that the risk of all pesticides were negligible for Chinese residents.

Determination of Three Typical Metabolites of Pyrethroid Pesticides in Tea Using a Modified QuEChERS Sample Preparation by Ultra-High Performance Liquid Chromatography Tandem Mass Spectrometry.

Pyrethroid pesticides are widely used on tea plants, and their residues of high frequency and concentration have received great attention. Until recently, the residues of typical metabolites of pyrethroid pesticides in tea were unknown. Herein, a modified “quick, easy, cheap, effective, rugged and safe” (QuEChERS) method for the determination of three typical metabolites of pyrethroid pesticides in tea, using ultra performance liquid chromatography tandem mass spectrometry, was developed. The mixture of florisil, octadecylsilane, and graphite carbon black was employed as modified QuEChERS adsorbents. A Kinetex C18 column achieved good separation and chromatographic peaks of all analytes. The calibration curves of 3-phenoxybenzoic acid (3-PBA) and 4-fluoro-3-phenoxybenzoic acid (4-F-3-PBA) were linear in the range of 0.1–50 ng mL−1 (determination coefficient R2 higher than 0.999), and that of cis-3-(2-chloro-3,3,3-trifluoroprop-1-en-1-yl)-2,2-dimethylcyclopropanecarboxylic acid (TFA) was in the range of 1–100 ng mL−1 (R2 higher than 0.998). The method was validated and recoveries ranged from 83.0% to 117.3%. Intra- and inter-day precisions were lower than or equal to 13.2%. The limits of quantification of 3-PBA, 4-F-3-PBA, and TFA were 5, 2, and 10 μg kg−1, respectively. A total of 22 tea samples were monitored using this method, and 3-PBA and TFA were found in two green tea samples.

Preparation and identification of methylene blue polyclonal antibody

Methylene blue and its metabolites (azure A, azure B and azure C) residues in fishery products were dangerous for human health and it still remains a big challenge in China. However, there are few available assays to detect specifically methylene blue and its metabolites residues in fishery products. In order to establish an enzyme-linked immunosorbent assay (ELISA) method for the detection of methylene blue and its metabolites residues in fishery products, methylene blue metabolite azure C with similar structure as methylene blue was selected as the hapten of methylene blue. The amino group on azure C was coupled with the carboxyl group on protein by glutaraldehyde method to prepare the immunogen azure C-BSA and coating antigen azure C-OVA. Immunogen and coating antigen were identified by ultraviolet scanning (UV) and matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS). BALB/c mice were immunized with azure C-BSA as immunogen at a dose of 0.2 mg for one mouse, and then the titer, sensitivity and specificity of the obtained polyclonal antibody were detected. Results showed that the artificial antigen of azure C-BSA and azure C-OVA was synthesized successfully, with the coupling ratio of the prepared artificial antigen azure C-BSA and azure C-OVA was about 31∶1 and 52∶1, respectively. The titer of polyclonal antibody obtained from mouse was above 16 000, and the NO.2 mice had the highest antibody titer with the half inhibitory concentration (IC₅₀) of 43.9 ng·mL^-1. The antibody cross reacted with the methylene blue metabolites azure A, azure B and azure C, and the cross reaction rates were 127.6%, 84.7% and 138.1%, respectively. There was no cross reaction with other common dyes, indicating that the antibody was of good specificity. This experiment successfully synthesized methylene blue artificial antigen and obtained mouse-derived polyantiserum with good immunological properties, which laid the foundation for the preparation of monoclonal antibody and the development of rapid immunological detection method.

Adsorption of Pharmaceutical Contaminants from Aqueous Solutions Using N,O-Carboxymethyl Chitosan/Polyethylene Oxide (PEO) Electrospun Nanofibers

Residues of pharmaceutical and direct metabolites discharged into the aquatic environment have become a challenge for wastewater treatment facilities due to their increase in concentration and their different physicochemical properties. These emerging contaminants are daily detected in surface water and wastewater discharged by municipalities. To remediate the contaminated water, various methods are currently used including primary, secondary, and tertiary advanced treatments. However, some economic and environmental limitations have forced the scientific community to develop alternative disinfection processes to purify wastewater. As such, the adsorption strategy represents a “green” low-cost and effective solution to remove pollutants from water. In this study, a nanomaterial made of N,O-carboxymethyl chitosan (N,O-CMCS) was prepared using chitosan (CS) and monochloroacetic acid under various conditions. N,O-CMCS electrospun was synthetized with the copolymer polyethylene oxide (PEO) to create nanofiber membranes showing a better specificity toward diversified contaminants depending on the pH of medium. The developed adsorbent was used to remove fluoxetine (FLX) from aqueous solutions. The new nanomaterial was characterised using FTIR, NMR, and SEM techniques. Sorption batch tests were carried out using high-performance liquid chromatography and ultraviolet diode array detector (HPLC-UV DAD) under controlled pH experimental conditions to determine the contaminant removal capacity of the nanomaterial. The promising adsorption results obtained with N,O-CMCS/PEO nanofibers are among the best ones obtained so far in comparison to other commercial and synthetized adsorbents tested for FLX’s adsorption. Kinetic experiments were also performed to investigate effects of contact times on the FLX adsorption. Experimental results were fitted to both common kinetic models pseudo-first and second order. The latter kinetic model described the best the sorption on surface. It revealed a possible chemisorption mechanism with electrostatic bounding for N,O-CMCS/PEO nanofibers.

Distribution of antibiotics in water, sediments and biofilm in an urban river (Córdoba, Argentina, LA).

In this study, we evaluated the distribution of up to forty-three antibiotics and 4 metabolites residues in different environmental compartments of an urban river receiving both diffuse and point sources of pollution. This is the first study to assess the fate of different antibiotic families in water, biofilms and sediments simultaneously under a real urban river scenario. Solid phase extraction, bead-beating disruption and pressurized liquid extraction were applied for sample preparation of water, biofilm and sediment respectively, followed by the quantification of target antibiotics by UPLC-ESI-MS/MS. Twelve antibiotics belonging to eight chemical families were detected in Suquía River samples (67% positive samples). Sites downstream the WWTP discharge were the most polluted ones. Concentrations of positive samples ranged 0.003-0.29 µg L-1 in water (max. cephalexin), 2-652 µg kg-1d.w. in biofilm (max. ciprofloxacin) and 2-34 µg kg-1d.w. in sediment (max. ofloxacin). Fluoroquinolones, macrolides and trimethoprim were the most frequently detected antibiotics in the three compartments. However cephalexin was the prevalent antibiotic in water. Antibiotics exhibited preference for their accumulation from water into biofilms rather than in sediments (bioaccumulation factors > 1,000 L kg-1d.w. in biofilms, while pseudo-partition coefficients in sediments < 1,000 L kg-1d.w.). Downstream the WWTP there was an association of antibiotics levels in biofilms with ash-free dry weight, opposite to chlorophyll-a (indicative of heterotrophic communities). Cephalexin and clarithromycin in river water were found to pose high risk for the aquatic ecosystem, while ciprofloxacin presented high risk for development of antimicrobial resistance. This study contributes to the understanding of the fate and distribution of antibiotic pollution in urban rivers, reveals biofilm accumulation as an important environmental fate, and calls for attention to government authorities to manage identified highly risk antibiotics.

Regulatory groundwater monitoring: Realistic residues of pinoxaden and metabolites at vulnerable locations

A bespoke groundwater monitoring programme was designed to generate a database of pinoxaden and metabolite concentrations in shallow groundwater at agricultural locations across Europe. The data generated from this programme represent a higher tier refinement of modelled exposure estimates and provide realistic information on groundwater quality at vulnerable locations which will aid plant protection product (PPP) assessment in Europe in relation to Regulation (EC) No. 1107/2009.The Regulatory GeoPEARL_3.3.3 model developed by RIVM was used to estimate the vulnerability of cereal growing regions to leaching of two pinoxaden metabolites across the entire EU at a 1 km2 level using 20 years of daily weather data (MARS, EU JRC). Seventy sites located within the upper 50th percentile of leaching vulnerability from this modelling exercise, crop density and shallow groundwater were selected for monitoring groundwater.Retrospective and prospective pinoxaden product applications at candidate sites were recorded and these data used to place sites in the distribution for Europe. The 70 sites all fulfil the site assessment criteria and have no confining layers which may prevent or delay leaching. All sites equipped with groundwater wells had a minimum of two pinoxaden applications in the preceding four years to cereal crops.A total of 1326 samples were analysed from up to 90 down hydraulic gradient wells at 70 locations between June 2015 and July 2018. Results indicate that pinoxaden and pinoxaden metabolites are very unlikely to reach shallow groundwater at concentrations greater than 0.1 μg/L for relevant metabolites, or 10 μg/L for non-relevant metabolites, respectively (Sanco/221/2000-rev.10). Over 38 months of groundwater monitoring the annual average and 90th percentile for pinoxaden or its metabolites never exceeded 0.1 μg/L and it is proposed that these data infer that exposure to these metabolites is minimal.

Neonicotinoid insecticide and their metabolite residues in fruit juices: Implications for dietary intake in China

Neonicotinoid insecticides (NEOs) have become the most widely used insecticides worldwide, and they are ubiquitous in food (i.e., fruit juices). In the present study, occurrence of seven NEOs and four metabolites (m-NEOs) in 400 fruit juice samples were investigated. NEOs and m-NEOs were frequently detected (65%–86%) in fruit juice samples. The median residues of NEOs and m-NEOs were ranged from 0.06 ng/mL to 0.94 ng/mL. Seasonal variations in NEOs and m-NEOs in fruit juices were found, indicating that the target analyte residues during the dry season were remarkably higher than those of residues during wet season. The relative potency factor (RPF) method was used to integrate individual NEOs into a single metric [imidacloprid (IMIRPF)] representing the intakes of IMI equivalent to total NEOs for each fruit juice sample. The estimated daily intake (EDI) of total NEOs for the general Chinese population was obtained. The median IMIRPF for total fruit juices was 13.4 ng/g, and the median EDI of NEOs was 18.2 ng/kg bw/day for the general population. Although the EDIs in this study were considerably lower than the acceptable daily intake (60 μg/kg bw/day, ADI), the dietary exposure risks for total NEOs should not be ignored because of the increasing usage of NEOs and their ubiquitous presence in fruit juices in China. To the best of our knowledge, this report was the first time to document residues of NEO and m-NEO in fruit juice samples collected from China.

Analysis of 81 pesticides and metabolite residues in fruits and vegetables by diatomaceous earth column extraction and LC/MS/MS determination

A multi-residue method for determining 81 pesticides and metabolite residues in vegetables and fruits by liquid chromatography/tandem mass spectrometry (LC/MS/MS) with electrospray ionization was developed. Pesticide residues were extracted from samples with acetone. Macroporous diatomaceous earth column was used instead of the separatory funnel for liquid/liquid extraction. Ethyl acetate was used as eluting solvent for diatomaceous earth column. This sample preparation technique by diatomaceous earth column was easy, fast and environment-friendly. It can reduce the sample preparation time and solvent consumption as well as eliminate the emulsion problem. Eighty-one analytes of different chemical families of insecticides, acaricides, fungicides, herbicides, plant growth regulators and 4 pesticide metabolites were determined in a single 25 min LC/MS/MS run. The pesticides were separated on an Atlantis T3 column using a gradient elution. Data acquisition under MS/MS for every pesticide or metabolite was achieved by applying multiple reaction monitoring (MRM) of two fragment ion transitions to provide high sensitivity and selectivity for both quantification and confirmation. A total of 162 MRM transitions were monitored. The standard addition was employed to compensate for the matrix effects to achieve the maximum accuracy of the LC/MS/MS method. Vegetable (bok choy) and fruit samples (grape or orange) were fortified with pesticides of low (0.05 or 0.1 ppm) and high (0.5 ppm) levels, and the triplicate results showed satisfactory recoveries and repeatability. The recoveries for most pesticides ranged from 70 to 120% and the coefficients of variation of all pesticides were below 25% in all matrices. The developed method, compared with traditional GC or LC method, showed less time-consumption and higher sensitivity. The proposed method is considered satisfactory for routine monitoring of pesticide residues in fruits and vegetables.

A multiresidue method for determining 136 pesticides and metabolites in fruits and vegetables: Application of macroporous diatomaceous earth column

A fast and easy multiresidue method using the macroporous diatomaceous earth (MDE) column for determining 136 pesticide an metabolite residues in fruits and vegetables was developed. The MDE column was used instead of the separation funnel for liquid/liquid partition in sample preparation. Through MDF columns, the preparation of test solution became easier and faster than traditional funnel liquid/liquid partition. The emulsion problem can also be avoided. Fifty one pesticides including acephate were determined by gas chromatography (GC) with a pulsed flame photometric detector (GC/PFPD) and 63 pesticides including aldrin were detected by GC with electron capture detection (GC/ ECD). Twenty carbamate peticides and metabolites including aldicarb were determined by high performance liquid chromatography with a post-column derivaization system and a fluorescence detector (HPLC/FLD) and two benzimidazole pesticides including carbendazim and thiabendazole were detected by HPLC with an ultraviolet detector (HPLC/UV). Recovery studies were performed by spiking pesticides (0.05-2.0 ppm) in fruit and vegetable samples, and the triplicate results showed satisfactory recoveries and repeatability. The detection limits ranged from 0.003 to 0.2 ppm. The developed multireside method can be employed to other pesticides or matrices with an easier and less solvent consumption way to prepare sample solution. It is an environment-friendly and useful method for routine pesticide analysis.

Simultaneous determination of nitrapyrin and its metabolite residues in food crops by derivatization with gas chromatography-triple quadrupole mass spectrometry

A method based on precolumn derivatization along with gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS) was developed for the determination of nitrapyrin and its metabolite, 6-chloropicolinic acid, in crops. The samples were extracted by acid acetonitrile, and subjected to precolumn derivatization using a sulfoacid. The quantification of the analytes was performed by the internal standard method. Good linear relationships between the peak areas and mass concentrations of the analytes were obtained in the range of 0.025-0.2 mg/L with correlation coefficients greater than 0.995 (n=6). The limits of quantification (LOQs) were 0.05 mg/kg. The recoveries of the analytes in crops at three spiked levels (0.05, 0.1, and 0.2 mg/kg) were in the range of 80.4%-98.4%, with relative standard deviations between 1.0% and 10.1% (n=6). This new method satisfies the related regulations for the determination of nitrapyrin and its metabolite in crops.

Rapid screening of amitraz and its metabolite residues in honey using a quick, easy, cheap, effective, rugged, and safe extraction method coupled with UHPLC and Q Exactive.

A method for determining amitraz and 2,4-dimethylaniline in honey was established by using ultra-high-performance liquid chromatoghaphy and Q Exactive after applying quick, easy, cheap, effective, rugged, and safe extractingprocess. A suitable extraction method was designed to extract the amitraz and 2,4-dimethylaniline after a suitable amount of honey samples was dissolved. A Thermo Syncronis C18 column (100 × 2.1mm, 1.7μm) was used for chromatographic separation of the samples. Then the two compounds were quantitatively analyzed via a program of Q Exactive. The linearity of amitraz and 2,4-dimethylaniline was good in the concentration range of 0.5-100μg/L, and the correlation coefficient R2 was >0.99. The average recovery and relative standard deviation of each component were 81.3-90.0% and 5.1-7.2%. The 24- and 48-h test results showed that the sample needed to be tested within 24h. The limit of detection was 0.1μg/kg for amitraz and 2,4-dimethylaniline, whereas for both the limit of quantitation was 0.3μg/kg.

Study and comparison of detection methods for prochloraz and its metabolite residue in garlic bolting

Two analytical methods for the determination of prochloraz and its metabolite residues in garlic bolting were established and compared. In the QuEChERS method, the sample was extracted with acetonitrile and purified in a QuEChERS purification tube, and then, the contents of prochloraz and its metabolite 2,4,6-trichlorophenol were determined by gas chromatography. The hydrolysis method involved extraction of the sample with acetonitrile, hydrolysis by pyridine hydrochloride, purification with sulfuric acid, and determination of the prochloraz content by gas chromatography. The standard curve in the hydrolysis and QuEChERS methods showed a good linear relationship in the concentration range of 0.01-2 mg/L, and the correlation coefficient (r2) was greater than 0.999. The limit of quantitation (LOQ) for prochloraz in the hydrolysis method was 0.005 mg/kg. The LOQ for prochloraz in the QuEChERS method was 0.039 mg/kg, and that for 2,4,6-trichlorophenol was 0.003 mg/kg. At three spiked levels in the sample, the recoveries were 81.5%-105.4%, and the relative standard deviations (RSDs) were between 1.3%-6.8%. In the determination of positive samples, the hydrolysis method can detect the total amount of prochloraz and its main metabolites. QuEChERS method can detect the presence and contents of prochloraz and its main metabolite 2,4,6-trichlorophenol. These two methods can complement each other for the detection and confirmation of prochloraz and its metabolites in garlic bolting.

Degradation of Fenoxaprop-p-Ethyl and Its Metabolite in Soil and Wheat Crops

The dissipation kinetics of fenoxaprop-p-ethyl and its metabolite (fenoxaprop acid) at two application rates under wheat field conditions for two seasons was investigated. Herbicides were extracted by solid liquid extraction, cleaned up, and analyzed by a liquid chromatography-UV detector. Dissipation followed first-order kinetics; in soil, fenoxaprop-p-ethyl dissipated rapidly with an average half-life of 1.45 to 2.30 days, while fenoxaprop acid persisted for more than 30 days. The method was validated in terms of accuracy, linearity, specificity, and precision. Linearity was in the range of 5 to 5,000 ng, with a limit of detection (LOD) of 2 and 1 ng for fenoxaprop-p-ethyl and fenoxaprop acid, respectively. The quantitation limits in soil, grain, and straw were 5, 8, and 10 ng g-1 for fenoxaprop-p-ethyl and 5, 10, and 10 ng g-1 for fenoxaprop acid, respectively. Recovery in soil, grains, and straw ranged from 85.1 to 91.25%, 72.5 to 84.66%, and 77.64 to 82.24% for fenoxaprop-p-ethyl and 80.56 to 86.5%, 78 to 81.88%, and 75.2 to 79.68% for fenoxaprop acid, respectively. At harvest, no detectable residues of fenoxaprop-p-ethyl or acid were observed in soil, wheat grain, and straw samples. Owing to the short persistence under field conditions, fenoxaprop-p-ethyl is safe for use because parent and metabolite residues were below the European Union maximum residue limit and would not pose an adverse effect on the environment and human or animal foods.

Residues of legacy organochlorine pesticides and DDT metabolites in highly consumed fish from the polluted Guanabara Bay, Brazil: distribution and assessment of human health risk

Organochlorine (OCP) pesticides were determined in samples of sardine (Sardinella brasiliensis), whitemouth croaker (Micropogonias furnieri), and mullet (Mugil liza) from Guanabara Bay (state of Rio de Janeiro, Brazil). OCP concentrations and fish consumption were linked with acceptable daily intake values in order to assess the human health risk for the Brazilian population. The total concentrations of OCPs (Σ OCP) was 6.6 ng/g f.w., 7.5 ng/g f.w., and 2.8 ng/g f.w. for sardines, corvina, and mullet, respectively. There was a significant difference (P < 0.05) among the species related to o,p’-DDD and o,p’-DDT concentrations. Both DDT-related compounds were 5 and 76 times more abundant in sardines than in whitemouth croaker and mullet. Newly discovered DDT metabolite, o-Cl-DDMU, was frequently detected in the fish. None of the samples exceeded the maximum limits for acceptable levels of OCP residues. According to the data of average intake of Brazilian population, none of three species exceeded toxicological parameter. The investigated fishes are considered as safe for human consumption in regard to exposure of the studied OCPs. However, fish may be a intake source of OCP metabolites such as o-Cl-DDMU whose toxicity is still unknown.