Preparation of D-histidine modified zeolitic imidazolate framework-90 coated capillary column and its application in open-tube capillary electrochromatography enantioseparation

Metal-organic framework materials are a class of novel crystalline porous materials with regular pore structures formed by covalent bonding between metal centers and organic functional groups. Metal-organic framework materials have attracted great interest in analytical chemistry due to their unique properties such as good stability and permanent porosity. In this work, D-histidine was used to carry out chiral modification of zeolitic imidazolate framework-90 under mild conditions, and the D-histidine modified zeolitic imidazolate framework-90 coated capillary column was prepared. This chiral capillary column was used to separate epinephrine, norepinephrine, terbutaline, and tryptophan enantiomers. Under optimum conditions, baseline separations were achieved. The intra-day, inter-day, and inter-column relative standard deviations (n = 3) of the four pairs of enantiomeric migration times were 0.15%–0.56%, 0.74%–2.40%, and 1.93%–3.18%, respectively. Moreover, the D-histidine modified zeolitic imidazolate framework-90 coated capillary could be reused for at least 150 runs without significant changes in the separation efficiency and migration time.     

Multiresidue method for the determination of 227 pesticides in hot pepper (Capsicum annuum L.) by liquid chromatography with tandem mass spectrometry†

A high‐throughput, rapid, and efficient modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method with a simple cleanup procedure has been developed for simultaneously determining 227 pesticides in pepper samples by liquid chromatography with tandem mass spectrometry (running time: 10 min). Pesticide residues were extracted/partitioned with an acetonitrile/DisQuE QuEChERS pouch, and the resulting samples were cleaned up with different methods: dispersive solid‐phase extraction with primary secondary amines or multiwalled carbon nanotubes and graphitized carbon solid mini cartridge column. The results indicated that multiwalled carbon nanotubes dispersive sorbents achieved the best recoveries and had less matrix interference. The numbers of pesticides with a recovery in the range of 70–120% were 199 at a spiked level of 40 μg/kg. The correlation coefficients (r²) for 227 pesticides were above 0.99, while the limits of quantitation of pesticides in pepper samples ranged from 0.13 to 13.51 μg/kg (S/N = 10), and the limits of detection ranged from 0.04 to 4.05 μg/kg (S/N = 3). The relative standard deviations of approximately 197 pesticides were below 20% at spiked levels of 40 μg/kg. Based on these results, the proposed method was chosen as the most suitable cleanup procedure for the determination of multiresidue pesticides in pepper samples.     

Analytical method for 44 pesticide residues in spinach using multi‐plug‐filtration cleanup based on multiwalled carbon nanotubes with liquid chromatography and tandem mass spectrometry detection

Spinach is one of the most commonly planted vegetables worldwide. A high chlorophyll content makes spinach a complicated matrix in pesticide residue analysis. In this study, a rapid clean‐up method was developed for the analysis of pesticide multi‐residues in spinach followed by liquid chromatography with tandem mass spectrometry. A modified QuEChERS method with multiwalled carbon nanotubes and carbon material was adopted in the multi‐Plug Filtration Cleanup procedure. This method was validated for 44 representative pesticides spiked at two concentration levels of 10 and 100 μg/kg. The pesticides of different physicochemical properties were registered on spinach in China. The recoveries were between 76 and 114% for major pesticides with relative standard deviations of less than 15%, except for quizalofop‐P‐ethyl, pyrimethanil, and carbendazim. Matrix‐matched calibration curves were performed with the coefficients of determination higher than 0.995 for the studied pesticides for concentration levels of 10–500 μg/kg. The limits of quantitation ranged from 2 to 10 μg/kg. The developed method was successfully applied to determine pesticide residues in Chinese market spinach samples.     

Vasodilator Effect of Ethanolic Extract of Mulberry Leaves (Morus alba L.) in Rat and Rabbit

The effects of ethanolic extracts of Mulberry Leaves (Morus alba L.) on nitric oxide (NO) serum level in rat and diameter of blood vessels in rabbit ear were investigated. NO level of ethanolic extract of mulberry leaves at dose of 100 mg/kg bw rats gave significant difference compared to negative control (P<0,05) at minute 30 after extract administration (4,51 ± 4,31 μM). Ethanolic extract of mulberry leaves at dose of 200 mg/kg bw had no significant difference in NO serum level. However, ethanolic extract of mulberry leaves at dose of 400 mg/kg bw rats increased NO serum level significantly compared to negative control (P<0,05) at minute 0, 10, 30, 60, and 90 after extract administration. The maximum serum level of NO of 400 mg/kg bw mulberry extract was 4,62 ± 3,05 μM, and it is the highest among other groups. Therefore this dose was choosen for vasodilatation assay in rabbit. Observation on blood vessels diameter in rabbit ears showed that ethanolic extract of mulberry leaves were able to dilatate the big vessels and small vessels of rabbit ears significantly compared to negative control (P<0,05) at minute 60 after extract administration. In conclusion, ethanolic extract of mulberry leaves at dose of 400 mg/kg bw rats or 202.67 mg/kg bw rabbits has a vasodilator effect, probably due to an increase of NO serum level.     

气相色谱-串联质谱技术分析烟草中49种农药残留

采用改进的QuEChERS(quick, easy, cheap, effective, rugged and safe)前处理法,结合气相色谱-串联质谱(GC-MS/MS)技术建立了检测烟草中49种农药残留的分析方法。样品用含0.1%乙酸的乙腈溶液提取,提取液被氮吹至干后,残渣用乙腈-乙酸乙酯(1:1, v/v)溶液溶解,溶解液经N-丙基乙二胺(PSA)吸附剂、无水MgSO4、C18吸附剂净化后,直接进行GC-MS/MS测定,内标法定量。实验结果表明,49种农药在低质量浓度(0.05 μg/L)的加标水平下的平均加标回收率为60.4%～104.8%,高质量浓度(5 μg/L)的平均加标回收率为70%～115%,相对标准偏差均小于15%;其中16种农药的方法检出限(LOD)分别为0.01～0.03 μg/kg,其余33种农药的LOD均小于0.01 μg/kg;相关系数都大于或等于0.991。该方法样品前处理简单、分析时间短、灵敏度和精密度均符合农药多残留痕量检测技术的要求,适用于烟草中多种农药残留的检测。     

Graphene oxide based molecularly imprinted polymers modified with β‐cyclodextrin for selective extraction of di(2‐ethylhexyl) phthalate in environmental waters

Graphene oxide based molecularly imprinted polymers modified with β‐cyclodextrin were prepared as solid‐phase extraction column sorbents for specific recognition and sensitive detection of di(2‐ethylhexyl) phthalate in water samples. The morphology and composition of synthesized sorbents were characterized by scanning electron microscopy, thermo‐gravimetric analysis, Raman spectroscopy, and Fourier‐transform infrared spectroscopy. The conditions affecting the performance of extraction procedures such as desorption solvent types and volume, sample pH and volume were investigated. The loading capacity (8.2 μg/mg) of the prepared sorbents increased eight times after modification with β‐cyclodextrin. The developed extraction procedures coupled to high‐performance liquid chromatography exhibited good linearity (0.2–500 μg/L), low limit of detection (0.052 μg/L), and good precision (relative standard deviation?5.7%) under optimized conditions. The developed solid‐phase extraction technique with prepared sorbents has been successfully applied in extracting trace di(2‐ethylhexyl) phthalate from real natural waters with high efficiency, good selectivity, and desirable recoveries.     

A covalently cross‐linked microporous polymer based micro‐solid phase extraction for online analysis of trace pesticide residues in citrus fruits

Covalently cross‐linked microporous polymers are a new class of highly cross‐linked porous network materials with large surface area and potential superiority in sample pretreatment. In this work, a covalently cross‐linked microporous polymer was well designed and synthesized by condensation of acylhydrazines in terephthalic dihydrazide with aldehyde groups in 1,3,5‐benzenetricarboxaldehyde. The adsorption mechanism was explored and discussed based on π‐π stacking interaction and steric effect. Then, a covalently cross‐linked microporous polymer was employed as the adsorbent of online micro‐solid‐phase extraction coupled with high‐performance liquid chromatography for the enrichment and analysis of trace pesticide residues in citrus fruits. The method was successfully applied to the online analysis of sugar orange and Huangdigan samples with the detection limits of 0.10–0.30 μg/kg. It was satisfactory that chlorpifos and triazophos in real sugar orange and Huangdigan samples could be actually found and quantified at concentrations of 0.20 and 0.51 mg/kg, respectively. The recoveries of sugar orange and Huangdigan samples were in the range of 70.0–103 and 74.0–119% with relative standard deviations of 0.4–9.7 and 0.5–9.2% (n = 3), respectively. The proposed method was accurate, reliable, and convenient for the online simultaneous analysis of trace pesticide residues in citrus fruits.     

Rapid multiplug filtration cleanup method for the determination of 124 pesticide residues in rice,wheat, and corn

A simple and rapid multiplug filtration cleanup method based on multiwalled carbon nanotubes was developed to determine 124 pesticide residues in rice, wheat, and corn, which could be done in a few seconds without conditioning and elution steps. Various combinations of sorbents were optimized for each matrix with a dispersive solid‐phase extraction procedure to get a satisfactory recovery and clean‐up performance. Good linearity was obtained for all pesticides with calibration curve coefficients larger than 0.9958. Most recoveries for the majority pesticides were between 70 and 120% (n = 5) with relative standard deviations below 20%. The limit of detection was 0.1–1.3 μg/kg, and the limit of quantification was 0.2–4.3 μg/kg for the pesticides in all matrices. The work suggests that the multiplug filtration cleanup method is better than the dispersive solid‐phase extraction method and it could be applied to routinely monitor pesticide residues in market samples.     

QuEChERS-液相色谱-串联质谱法测定棕榈原油中敌草快等6种农药残留

建立了QuEChERS-液相色谱-串联质谱同时测定棕榈原油中敌草快、乐果、倍硫磷、倍硫磷亚砜、倍硫磷砜、氟吡甲禾灵残留量的方法。以回收率及基质效应为考察指标,评估了乙二胺-N-丙基硅烷(PSA)/C18混合物、C18键合锆胶(Z-Sep+)/C18混合物、Z-Sep+、C18 4种分散吸附剂的净化效果,结果表明Z-Sep+/C18的净化效果最佳。样品采用含1%(v/v)乙酸的甲醇溶液提取,Z-Sep+/C18分散固相萃取净化;液相色谱以Atlantis T3色谱柱梯度洗脱分离,质谱分析采用电喷雾正离子电离、多反应监测模式,以基质匹配校准曲线外标法进行定量。6种农药在3个添加水平(10、20、250 μg/kg)下的回收率范围为70.0%~97.9%,相对标准偏差范围为2.6%~10.2%; 6种农药的定量限(S/N≥10)为0.1~2.5 μg/kg。该方法简便、灵敏、准确、环保,适用于棕榈原油中上述6种农药残留的定性、定量分析。     

Rapid analysis of pesticide residues in drinking water samples by dispersive solid‐phase extraction based on multiwalled carbon nanotubes and pulse glow discharge ion source ion mobility spectrometry

An analytical method based on dispersive solid‐phase extraction with a multiwalled carbon nanotubes sorbent coupled with positive pulse glow discharge ion mobility spectrometry was developed for analysis of 30 pesticide residues in drinking water samples. Reduced ion mobilities and the mass–mobility correlation of 30 pesticides were measured. The pesticides were divided into five groups to verify the separation capability of pulse glow discharge in mobility spectrometry. The extraction conditions such as desorption solvent, ionic strength, conditions of adsorption and desorption, the amounts of multiwalled carbon nanotubes, and solution pH were optimized. The enrichment factors of pesticides were 5.4‐ to 48.7‐fold (theoretical enrichment factor was 50‐fold). The detection limits of pesticides were 0.01～0.77 μg/kg. The linear range was 0.005–0.2 mg/L for pesticide standard solutions, with determination coefficients from 0.9616 to 0.9999. The method was applied for the analysis of practical and spiked drinking water samples. All results were confirmed by high‐performance liquid chromatography with tandem mass spectrometry. The proposed method was proven to be a commendably rapid screening qualitative and semiquantitative technique for the analysis of pesticide residues in drinking water samples on site.     

Multi-residue analysis of 206 pesticides in grass forage by the one-step quick,easy, cheap,effective, rugged,and safe method combined with ultrahigh-performance liquid chromatography quadrupole orbitrap mass spectrometry

A novel method for detecting pesticide multi-residue in grass forage (alfalfa and oat) was established based on the one-step automatic extraction and purification technology of quick, easy, cheap, effective, rugged, and safe combined with ultrahigh-performance liquid chromatography quadrupole Orbitrap high-resolution mass spectrometry. The crushed sample was extracted with acetonitrile with 1% acetate, followed by a cleanup step with a primary-secondary amine, octadecylsilane, and graphitized carbon black. The extraction and purification were carried out using the one-step automatic pretreatment equipment. The target pesticides were acquired in positive ion electrospray ionization mode and full scan/data dependent secondary scan mode. The calibration curve shows good linearity over the corresponding concentration range, with the coefficient of determination greater than 0.99. The screening detection limits were 0.5–50 μg/kg, and the limit of quantification for the 206 pesticides was set at 1–50 μg/kg. At the spiking levels of one, two, and 10 times of limit of quantification, more than 95% of pesticides had recovery between 70–120%, with a relative standard deviation ≤20%. The method was proved to be simple, rapid, high-sensitivity, and could be routinely used for the high throughput screening and quantitative analysis of pesticide residues in alfalfa and oat.     

Analysis of residues of 81 pesticides on ginkgo leaves using QuEChERS sample preparation and gas chromatography/mass spectrometry

Pesticide residues on Ginkgo leaves are a safety concern. A fast and reliable method was developed for the analysis of 81 pesticides on Ginkgo leaves, which are pharmaceutically valuable. The method consists of a modified Quick, Easy, Cheap, Effective, Rugged, and Safe sample preparation method and GC/MS detection. Five sorbents (graphitized carbon black, primary secondary amine, amino, alumina, and Florisil) and two solvents (toluene and hexane) were optimized for the cleanup procedure. The LOD and LOQ ranged from 0.05 to 17.6 and 0.16 to 58.8 microg/kg, respectively. A majority of the pesticides (86-94%) gave satisfactory recoveries (70-110%), and 1-6% of the substances gave recoveries higher than 110% of the spiked concentration (n = 5) at 0.02, 0.05, and 0.1 mg/kg. Less than 5% of the substances showed recoveries lower than 70%. The method was proven to be repeatable with RSDs lower than 20%.     

Simultaneous determination of pyrametostrobin and its two metabolites in cucumber and soil using a quick,easy, cheap,effective, rugged,and safe method with HPLC–MS/MS

An easy, effective and sensitive analytical method for the simultaneous determination of a novel fungicide pyrametostrobin and its two metabolites pyrametostrobin‐M1 and pyrametostrobin‐M2 in cucumber and soil was developed using a quick, easy, cheap, effective, rugged, and safe method with high‐performance liquid chromatography and tandem mass spectrometry. The extraction solvent was acetonitrile, and cleanup sorbents were primary secondary amine and graphitized carbon black for cucumber samples and primary secondary amine for soil samples. The three target compounds were successfully separated between 3.2 and 3.9 min using a Waters CORTECS™ C₁₈ column connected to an electrospray ionization source. All the matrix‐matched samples at three fortified levels (10, 100 and 1000  μg/kg) provided satisfactory recoveries in the range of 78.8–93.8% with relative standard deviations below 6.9%. The limits of quantitation for the three compounds were below 0.183 μg/kg. The proposed method was validated by analyzing real samples.     

Application of low-pressure gas chromatography/tandem mass spectrometry to the determination of pesticide residues in tropical fruits

A multiresidue method has been developed for determining pesticide residues in the tropical fruits kiwi, custard apple, and mango. The intended purpose of the method is for regulatory analyses of commodities for pesticides that have established maximum residue limits. A fast and simple extraction method with cyclohexane-ethyl acetate (1 + 1, v/v) and a high-speed homogenizer was optimized. Pressurized liquid extraction was evaluated as an alternative automated extraction technique. The pesticide residues were determined by using low-pressure gas chromatography coupled to tandem mass spectrometry. The proposed methodology was validated for each matrix. Pesticide recoveries ranged from 70 to 110%, with repeatability relative standard deviations of < or = 18% at spiking levels of 12 and 50 microg/kg. The limits of quantitation were in the range of 0.03-6.17 microg/kg, and the limits of detection were between 0.01 and 3.75 microg/kg. Mango can be selected as a representative matrix for calibration on the basis of the results of a potential matrix effect study. The method was successfully applied to the determination of pesticide residues in real samples in Spain.     

基于QuEChERS净化-气相色谱法同时测定蔬菜中6种有机磷类农药残留

建立了QuEChERS（Quick,Easy,Cheap,Effective,Rugged and Safe）法-气相色谱法测定蔬菜中6种有机磷农药残留量的检测方法.样品用1%乙酸乙腈提取,经N-丙基乙二胺（PSA）和无水硫酸镁分散固相萃取净化,气相色谱火焰光度检测器测定.考察了QuEChERS法在两种不同体系（氯化钠盐析和乙酸盐缓冲体系）的提取净化效果.试验结果表明,在乙酸盐缓冲体系中,有机磷农药残留更加稳定,回收率更高.6种有机磷农药残留在0.2~10.0 mg/L之间线性关系良好,相关系数（R²）均大于0.999,检出限在0.003 5~0.015 mg/L之间.低、中、高3个添加水平的回收率在78.5%~106.3%之间,相对标准偏差在1.4%~6.3%之间.方法简单、快捷,准确可靠,适合大批量样品农残检测.     

Rapid determination of pesticide residues in herbs using selective pressurized liquid extraction and fast gas chromatography coupled with mass spectrometry

A selective pressurized liquid extraction and gas chromatography coupled with triple quadrupole mass spectrometer method was developed for simultaneous determination of 52 pesticide residues in medicine and food dual-purpose herbs. The developed extraction method integrated extraction and cleanup processes for sample preparation. The sorbents, 5 g Florisil and 100 mg graphitized carbon black, were placed inside the extraction cell to remove matrix interferences. Optimized conditions of selective pressurized liquid extraction were ethyl acetate as extraction solvent, 120°C of extraction temperature, 6 min of static extraction time, 50% of flush volume extracted for two cycles. An ultra inert capillary GC-MS HP-5 UI column (20 m × 0.18 mm id, 0.18 μm) and column backflush system were used for the analysis. Multiple-reaction monitoring was employed for the quantitative analysis with electron ionization mode. All calibration curves showed good linearity (r(2) > 0.995) within the test ranges. The average recoveries of most pesticides were from 81 to 118%. The validated method was successfully applied for the determination of pesticide residues in four herbs. The results indicate that selective pressurized liquid extraction and GC-MS/MS is a sensitive and reliable analytical method for the simultaneous determination of multiple pesticide residues in herbs.     

Development of GC–MS/MS method for environmental monitoring of 49 pesticide residues in food commodities in Al-Rass,Al-Qassim region,Saudi Arabia

The harmful effects of pesticide residues are a threat to our health. Therefore, the current study aimed to validate a simple method for the determination of pesticide residues in commonly consumed fruits and vegetables from Al-Rass, Al-Qassim region, Saudi Arabia. A total of 1430 samples were collected from a local market and then analyzed for monitoring of 49 pesticide residues. A quick, easy, cheap, effective, rugged, and safe (QuEChERS) multi-residue extraction method followed by gas chromatography equipped with triple-quadrupole mass spectrometry (GC–MS/MS) was successfully implemented. This 17-min-run analytical method detects and quantifies pesticide residues with acceptable validation performance parameters in terms of sensitivity, selectivity, linearity, the limit of quantification, accuracy, and precision. The linear range of the calibration curves ranged from 10 to 300 µg/L, all the pesticide LODs ranged from 0.0005 to 0.0024 mg/kg, and the pesticide LOQs ranged from 0.0011 to 0.0047 mg/kg. The recovery values at the three fortification levels ranged from 78 % to 107 %, and the precision values (expressed as RSD%) were less than 20 % for all of the investigated analytes. The results showed that 138 (9.65 %) of the analyzed samples were contaminated with pesticide residues, 40 (2.80 %) of the analyzed samples exceeded the maximum residue limit (MRL) of the European Commission regulations (EC) for pesticides residues, 98 (6.85 %) of the analyzed samples were contaminated with residues below the MRL, and 1292 (90.35 %) of the analyzed samples were pesticide residue-free. Coriander contained the highest percentage (46.88 %) of pesticide residues, particularly tetradifon that representing 18.75 % noncompliance with the MRL, followed by parsley, with 20.59 % pesticide residues (10.29 % non-compliance). Multiple pesticide residues were observed most frequently in tomatoes and dates which were contaminated with buprofezin and ethion respectively.     

QuEChERS-UPLC-MS/MS法检测苹果中5种农药残留

建立了QuEChERS-超高效液相色谱-串联质谱(QuEChERS-UPLC-MS/MS)检测苹果中5种农药残留的分析方法。样品采用QuEChERS进行前处理,乙腈提取,经PSA、纳米氧化锆(Nano-ZrO₂)和多壁碳纳米管(MWCNTs)组合净化,结合UPLC-MS/MS检测,外标法定量。结果表明,在0.005~0.5 mg/L的浓度范围内5种农药在苹果基质中的线性关系良好,R²≥0.9950;在0.05,0.5和5 mg/kg的添加水平下5种农药的平均回收率在78.1%~117.5%之间,相对标准偏差(RSDs)在1.8%~9.1%之间;定量限(LOQ)为0.1~2μg/kg。该方法适用于苹果中5种农药残留检测。     

Development and Validation of a Modified QuEChERS Method for the Analysis of Bisphenols in Meats by UPLC-MS/MS

A reliable and affordable QuEChERS (quick, easy, cheap, effective, rugged, and safe) methodology in combination with ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC–MS/MS) was successfully developed and validated for the determination of eight bisphenols (BPs) residues containing in meats (chicken, duck, beef, pork, fish, shrimp, and mutton). A novel QuEChERS method optimization was carried out in terms of process efficiency (PE), matrix effect (ME), and extraction recovery (RE). After a simple vortex extraction of the samples with acetonitrile, 1 g sodium acetate was used for salting out (NaAC), and 100 mg primary secondary amine (PSA) purifying reagents were used for purification. The properties of the sorbents were assessed by the obtained parameters, such as matrix effect (ME), linearity, sensitivity, accuracy, and precision. Under the optimal conditions, BPs were well separated on an ACQUITY UPLC BEH ® C₁₈ column in 8 min by gradient elution, and exhibited a good linear relationship (R²?>?0.9988) in the linear range. Moreover, the limits of detection (LODs) and the limits of quantification (LOQs) were located in the range of 0.01– 0.11 μg/kg and 0.03 – 0.37 μg/kg, respectively. The developed method was satisfactory in terms of accuracy (relative recoveries: 76.1% – 113.7%) and precision (relative standard deviations below 10.3%). Finally, the developed method was successfully employed to identify and quantify BPs residues in 28 real meat samples. The proposed QuEChERS-UPLC–MS/MS method is simple, high efficiency, cost-effective, practical, and susceptible to being implemented in routine laboratories to quickly detect the BPs in meats (chicken, duck, beef, pork, fish, shrimp, and mutton). In this sense, the method is useful for obtaining BPs residue data to evaluate the contamination status of BPs in meat food and provide scientific support for scientific supervision.

     

Solid-phase extraction on sorbents of different retention mechanisms followed by determination by gas chromatography-mass spectrometric and gas chromatography-electron capture detection of pesticide residues in crops

Implementation of a mixed-mode solid-phase extraction is discussed as a promising approach for matrix clean-up in multiresidue/multimatrix methods. Sorbents characterized by different mechanisms of sorption such as reversed-phase (graphitized carbon), weak anion exchange (primary-secondary amine) and strong anion exchange (quaternary amine) were studied for their effectiveness in the removal of the matrix co-extractives in grains, fruits and vegetables for trace pesticide residues analysis. The pesticide residues were determined by gas chromatography with electron capture and mass spectrometric detection. Recoveries data of 25 pesticides from different groups at 0.01 mg/kg level ranged between 73 and 117% and with standard deviation below 15%. The limits of quantification were below or at 0.01 mg/kg.