Dispersive Solid-phase Extraction Technique Research Articles

Method validation and monitoring of emamectin benzoate in mature banana fruit with peel and pulp through Liquid chromatography-Mass spectrometry/ Mass spectrometry (LC-MS/MS)

Emamectin benzoate has been frequently used in the banana ecosystem to combat the damage of pseudostem weevil. Therefore, the present study was conducted to validate the method, to assess harvest time residues and monitor emamectin benzoate residues in mature banana peel and pulp samples through LC-MS/MS. The validated method was used to determine emamectin benzoate residue in market banana samples. The study used Waters Alliance LC and Acquity TQD with an electrospray ionization interface in the positive ion mode. An isocratic flow of 0.1% formic acid (HCOOH) in water and 0.1% HCOOH in acetonitrile (CH3CN) was utilised for separation. CH3CN was utilised to extract emamectin benzoate residue from the samples, and a dispersive solid-phase extraction technique was used for subsequent cleanup. Linearity tests were performed with standard solutions containing 0.01 to 0.1 g mL-1, with three replicates for each concentration. For mature banana peel & pulp and mature banana pulp matrices, satisfactory recoveries of 79.85 to 95.09% and 89.20 to 100.94%, respectively and high precision relative standard deviations of 0.56 to 2.34% and 2.33 to 6.88%, respectively were obtained. For mature banana (peel and pulp, pulp alone) fruits, the lower detection and quantification limits were (0.003, 0.008), and (0.002, 0.007). The validated approach was utilised to analyse mature banana fruit samples obtained from emamectin benzoate treated fields and banana samples purchased from the local market.  Results showed satisfactory validation of parameters like linearity, the limit of detection and quantification, and recovery for determining emamectin benzoate residues in banana fruit.

Study on Activated Carbon derived from Cassava Peels as Magnetic Solid of Dispersive Solid Phase Extraction Technique for Determination of Tetracycline

Concern on the existence of antibiotic residues in aqueous environment has been growing in recent years since they are known to impart various severe effects on human health and environment. In general, the concentration of antibiotic residue in environment is in trace level and often below the limit of detection of analytical instruments, implying that sample preparation prior to analysis requires particular strategy. In the present work, activated carbon produced from cassava peel was converted into magnetite activated carbon followed by utilization of magnetite activated carbon produced as adsorbent for tetracycline antibiotic, in order to evaluate its potential as the material for dispersive solid‐phase extraction (DSPE).Characteristics of the adsorbent were investigated using several techniques including Scanning electron microscopy (SEM) and X‐ray diffraction. Several parameters influencing the adsorption by DSPE were optimized. The tetracycline adsorbed by magnetic activated carbon was analyzed using a UV-Vis spectrophotometer at a wavelength of 275 nm. Characterizations revealed that the adsorbent has irregular surface, rough and highly porous structure with magnetic properties. Adsorption experiments indicate that equilibrium reached at pH 6, time 10 minute and adsorbate concentration 1 mg/L. By application of 20 mg adsorbent, the highest percentage of adsorption of 73 was achieved. The study indicates that magnetic activated carbon from cassava peel has promising potential as a low-cost and effective adsorbent for determination of tetracycline residues in aquatic environment.

Vortex assisted dispersive solid phase extraction of thallium followed by electrothermal atomic absorption spectrometry, Adsorption mechanism and soft computing algorithm prediction

ABSTRACT Vortex-assisted dispersive solid-phase extraction technique was used as a rapid and efficient method for preconcentration of ultra-trace levels of total thallium (Tl) followed by electrothermal atomic absorption spectrometry. Graphene oxide-modified polyvinylpyrrolidone nanocomposite was prepared as an adsorbent and characterised by the Fourier transform infrared spectrometry, field emission-scanning electron microscopy, energy-dispersive X-ray spectroscopy , and X-ray diffraction spectroscopy. To find the optimum conditions for extraction of ultra-trace levels of Tl (ӀӀӀ), the response surface methodology based on central composite design was used. Based on the results, pH = 6.6, amounts of adsorbent = 7.7 mg, extraction time = 27 min and desorption time = 5 min provide maximum extraction recovery for Tl (ӀӀӀ). Under the optimum conditions, the calibration curve was linear in the range of 0.08–1.5 µg L−1 Tl (ӀӀӀ) with the R 2 value of 0.9985. The relative standard deviation was 4.0% (n = 7) and the detection limit was 0.019 µg L−1 (n = 8). Also, the enrichment factor which could be calculated from the slope of the calibration curve after preconcentration step to that without preconcentration was 95.8. To understand the adsorption mechanism, two-parameter and three-parameter adsorption isotherms were studied, and the obtained results show that the adsorption of Tl (ӀӀӀ) followed by the Freundlich isotherm and the maximum adsorption capacity was 142.8 mg g−1. Also, the results of adsorption kinetic show that the adsorption of Tl (ӀӀӀ) was followed by the pseudo-first-order kinetic model. Moreover, random tree (RT) and artificial neural network (ANN) are employed for prediction of adsorption performance based on effective parameters. The outcomes of soft computing demonstrated that RT (R 2 = 0.95) and ANN (R 2 = 0.87) have acceptable accuracy for estimation and prediction of extraction recovery of Tl (ӀӀӀ).

A simple, environmental-friendly and reliable d-SPE method using amino-containing metal–organic framework MIL-125-NH2 to determine pesticide residues in pomelo samples from different localities

A simple, environmentally-friendly and reliable method was developed to simultaneously monitor the residue of methyl 1-naphthalene acetate, parathion-methyl, fenitrothion, bromophos and phenthoate in pomelo by using dispersive solid-phase extraction technique (d-SPE). In this method, these target analytes were captured by MIL-125-NH2 and detected by GC–MS/MS. The key parameters of d-SPE were optimized by the single factor experiment. Under the optimized conditions, a good determination coefficient (R2 > 0.9922) and extraction recoveries (64.7–116.8%) are obtained. The limit of detections (0.03–1.07 ng/g) is lower than the MRLs in citrus fruits established by EU (10–15000 ng/g) and China (10–10000 ng/g). The precisions of intra-day and inter-day are 1.3–8.9% and 3.8–14.9%, respectively. In addition, the sorbent MIL-125-NH2 is stable and can be reused at least eight times. These results prove the established method is efficient and reliable to detect the pesticide residues in pomelo.

Determination of three diphenyl ether herbicides in rice by magnetic solid phase extraction using Fe<sub>3</sub>O<sub>4</sub>@MOF-808 coupled with high performance liquid chromatography

利用溶剂热法构筑了Fe3O4@MOF-808吸附剂,将其用于大米中除草醚(NIT)、乙氧氟草醚(OXY)和甲羧除草醚(BIF)3种二苯醚类除草剂的富集,结合高效液相色谱法,建立了大米中该类除草剂的分析方法。研究通过傅里叶变换红外光谱、X射线衍射仪、扫描电子显微镜以及振动样品磁强计对构筑的磁性吸附剂的结构、表面形貌及磁强度进行表征。表征结果显示,球形的Fe3O4纳米颗粒与八面体形貌的MOF-808成功复合,Fe3O4@MOF-808饱和磁化强度可达40.35 emu/g,可以满足磁性固相萃取的需求;对吸附剂用于大米中3种二苯醚类除草剂富集的磁性固相萃取条件(吸附剂用量、吸附时间、洗脱溶剂种类以及洗脱体积)进行了优化。优化结果显示,25 mg吸附剂在6 min内即可达到对目标物的完全吸附,洗脱溶剂采用0.5 mL×2的甲醇。在最优的磁性固相萃取条件下,结合高效液相色谱-紫外检测法,建立了大米中3种二苯醚类除草剂的分析方法。方法在2~300 μg/L范围内线性关系良好(r > 0.998), NIT、OXY、BIF的检出限和定量限依次为0.6、0.6、0.4 μg/kg和2.0、2.0、1.5 μg/kg,在5、10和20 μg/kg 3个加标水平下的回收率为87.3%~96.7%,相对标准偏差不超过10.8%,且富集因子在25~29之间。将所建方法用于大米中NIT、OXY、BIF的分析,各样品均未检出这3种二苯醚类除草剂。该方法具有操作简单、快速、准确的特点,适用于大米样品中除草剂的残留分析。

Use of modified henequen fibers for the analysis of malachite green and leuco-malachite green in fish muscle by d-SPE followed by capillary electrophoresis

A novel and simple procedure for the determination of malachite green (MG) and leuco-malachite green (LMG) in fish muscle was designed and validated. The method involved the use of henequen fibers modified with copper phthalocyanine as an efficient adsorbent in a dispersive-solid phase extraction technique. Following the extraction and pre-concentration process, CE-DAD was employed to quantify MG and LMG. The structural similarity of MG and LMG and the presence of the cationic forms under acidic conditions are the main drawbacks to determine these analytes in capillary electrophoresis. The proposed methodology allowed for the effective extraction and separation of both analytes using d-SPE-CE-DAD. The experimental parameters of the d-SPE technique were evaluated in order to get the highest pre-concentration efficiency. Under optimum conditions, the methodology achieves a limit of detection of 12.5 μg kg−1 for malachite green and 5.0 μg kg−1 for leuco-malachite green. Repeatability and reproducibility (%RSD n = 3) were less than 5.0% RSD in all cases, indicating that the method shows good precision for the analysis of real samples. In order to evaluate the accuracy of the method, the recovery was evaluated in tilapia samples at three concentration levels, recoveries varied from 88.7% to 109.5% for MG and from 65.3% to 88.8% for LMG. The method was validated and successfully applied to determine MG and LMG in fish samples.

Preparation of a magnetic polystyrene nanocomposite for dispersive solid-phase extraction of copper ions in environmental samples

The core shell nanostructure of magnetic polystyrene (PS@Fe3O4) was prepared and its physic-chemical properties were studied FT-IR, SEM, TEM, VSM and BET + BJH. The new adsorbent was applied in the dispersive solid phase extraction technique for measuring copper ions in water, Soil and Oyster samples. Analysis is carried out using a flame atomic absorption spectrometry system. Effective parameters on extraction efficiency, such as pH of extraction solution, sorbent dosage, contact time, concentration and volume of desorption eluent and desorption time were optimized using one at a time method. N2 adsorption-desorption experiment resulted in high BET surface area (32.002 m2 g−1) and large pore volume (0.1794 cm3 g−1) for PS@ Fe3O4 nanocomposite. Under the optimum conditions, a calibration curve within the range of 5–40 ng mL−1 with an appropriate coefficient of determination (R2) of 0.9946 was obtained. Preconcentration factor (PF) and limit of detection (LOD) were found to be 55 and 1.6 ng mL−1, respectively. The repeatability and reproducibility for three replicate measurements at the concentration of 25 ng mL−1 were 2.5%–1.4%, respectively. The Freundlich adsorption isotherm and pseudo-second-order kinetic model were consistent to experimental data in adsorption mechanism study. The maximum adsorption capacity was 19.56 mg g−1 for Cu (II). Finally, the efficiency of the method was investigated for analysis of the copper in environmental samples and good relative recoveries (RR%) were obtained within the range of 99.2% to 101.2%.

Ligandless dispersive solid phase extraction of cobalt ion using magnetic graphene oxide as an adsorbent followed by its determination with electrothermal atomic absorption spectrometry

ABSTRACT Ligandless dispersive solid phase extraction technique was used for preconcentration of cobalt ion (Co2+) followed by its determination using electrothermal atomic absorption spectrometry (ETAAS). Graphene oxide (GO) was synthesised from graphite by the Hummer method and chemically magnetised to synthesise of the magnetic graphene oxide (MGO). The synthesised MGO was characterised by the Fourier transform-infrared spectrophotometry (FT-IR), vibrating sample magnetometer (VSM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) and then used as an adsorbent for solid phase extraction of Co2+. The main parameters affecting the extraction recovery of Co2+ including pH of sample solution, amounts of adsorbent, extraction time and type and concentration of desorption solvent were investigated and optimised. The calibration curve was plotted in the range of 0.08–1.2 µg L−1 Co2+ with a correlation coefficient of 0.9987. The intra-day precision based on six replicate analysis of 0.2 µg L−1 Co2+ was 3.8% and the limit of detection (LOD) was 0.023 µg L−1 Co2+ (n = 5). Also, the adsorption isotherms and adsorption kinetics were investigated and based on the obtained results, the adsorption of Co2+ onto the MGO nanocomposite followed by both Langmuir and Freundlich isotherms with a maximum adsorption capacity of 114.9 mg g−1 Co2+. The results of kinetic models also show that the adsorption of Co2+ followed by the pseudo second order kinetic model. The accuracy of the proposed method was successfully checked by the analysis of two certified reference materials including certified reference material-trace metals in drinking water (CRM-TMDW) and spinach leaves 1570a samples (Student t-test with 95% confidence limit, n = 5). Finally, the proposed rapid and efficient solid phase extraction technique was used for the determination of trace levels of Co2+ in the human saliva, urine and different real samples.

Analysis of imidacloprid and pyrimethanil in shallot (Allium ascalonicum) grown under greenhouse conditions using tandem mass spectrometry: establishment of pre‐harvest residue limits

In this study, the original Quick, Easy, Cheap, Effective, Rugged and Safe method was used for the extraction of imidacloprid and pyrimethanil followed by a rapid clean-up through dispersive solid-phase extraction technique with primary secondary amine sorbent and magnesium sulfate in shallot. Residues were analyzed using LC-tandem mass spectrometry in positive-ion electrospray ionization mode. The limits of detection and quantification were estimated to be 0.006 and 0.02 mg/kg, respectively. The samples were fortified at two different concentration levels (0.2 and 1.0 mg/kg), and the recoveries ranged between 79.7 and 83.9% with relative standard deviation values < 6%. The method was successfully applied for the establishment of the pre-harvest residue limits (PHRL). The rate of disappearance of imidacloprid and pyrimethanil on shallot was described with first-order kinetics (imidacloprid, y(2)  = 0.9670; pyrimethanil, y(2)  = 0.9841), with half-lives of 2.87 and 2.08 days, respectively. Based on the dissipation patterns of the pesticide residues, the PHRL was recommended at 7.86 mg/kg for 14 days (PHRL14 ) and 1.98 mg/kg for 7 days (PHRL7 ) before harvest for imidacloprid, and 21.64 mg/kg for 7 days (PHRL7 ) and 9.28 mg/kg for 4 days (PHRL4 ) before harvest for pyrimethanil in shallot.

A QuEChERS‐based extraction method for the residual analysis of pyraclofos and tebufenpyrad in perilla leaves using gas chromatography: application to dissipation pattern

The objective of this work was to establish a simple extraction method for the residual analysis of pyraclofos and tebufenpyrad in Perilla leaves. A QuEChERS (quick, easy, cheap, effective, rugged and safe) method was used for extraction using ethyl acetate as an extraction solvent, and cleanup was carried out using dispersive solid-phase extraction technique. The samples were analyzed using gas chromatography with nitrogen phosphorous detector and confirmed by gas chromatography-mass spectrometry. The linearity was excellent (r(2) = 1.0) in matrix-matched calibration for both pesticides. The recoveries at two fortification levels were 80.76-95.38% with relative standard deviation lower than 5%. The limits of detection and limits of quantification were 0.01 and 0.033 mg/kg for both pesticides, respectively. The results revealed that the dissipation pattern of pyraclofos and tebufenpyrad followed first-order kinetics. The pyraclofos and tebufenpyrad residues declined to a level below the maximum residue limits within 14 day between the last application and harvesting. We suggest that pyraclofos and tebufenpyrad could be used efficiently on perilla leaves under the recommended dosage conditions.

Determination of (fluoro)quinolones in eggs by liquid chromatography with fluorescence detection and confirmation by liquid chromatography–tandem mass spectrometry

A multiresidue analytical procedure for determination of seven fluoroquinolones (marbofloxacin, norfloxacin as internal standard, ciprofloxacin, danofloxacin, enrofloxacin, sarafloxacin and difloxacin), and three quinolones (oxolinic acid, nalidixic acid and flumequine) in eggs is presented. The procedure is based on dispersive solid-phase extraction technique with acetonitrile as extractant. Norfloxacin and ciprofloxacin - d8 were used as internal standards to quantify the (fluoro)quinolones. Analyses were realised by LC-FLD for screening and LC-MS/MS for confirmatory purposes. The whole procedure was evaluated according to the Commission Decision 2002/657/EC. Specificity, decision limit (CCα), detection capacity (CCβ), recovery (absolute and relative), precision (repeatability and reproducibility) were determined during validation process. Recoveries (relative) for the LC-FLD screening determination ranged from 85% to 93%, repeatability and reproducibility were in the range of 5-9% to 9-16%, respectively. CCα and CCβ were 13-37 and 17-43 μg/kg pending on analite. For the LC-MS/MS confirmatory method, the relative recoveries were satisfactory (92-99%) with repeatability and reproducibility in the range of 4-7% to 6-12%, respectively. CCα and CCβ were 3-7 and 7-11 μg/kg depending on the analite. The results of both prepared methods showed these analytical procedures simple, rapid, sensitive and suitable for routine control of eggs.

Dispersive solid-phase extraction followed by liquid chromatography–tandem mass spectrometry for the multi-residue analysis of pesticides in raw bovine milk

A fast multi-residue method based on dispersive solid-phase extraction (DSPE) followed by liquid chromatography–tandem mass spectrometry was developed for the simultaneous determination of 44 pesticides in raw bovine milk. Raw bovine milk samples did not percolate through SPE cartridges usually applied for pesticide extraction from homogenized pasteurized milk samples. Therefore, a DSPE technique was implemented and validated for the first time in this work. Graphitized non-porous carbon and C18 modified silica materials were tested both in combination with magnesium sulfate and bonded silica with ethylenediamine-N-propyl phase. The efficiency of the DSPE process was studied at several concentration levels obtaining the higher recoveries with C18 material. The method performance was also assessed and the limits of quantification reached the ng g −1 level, complying with the most recent maximum residue levels. The DSPE method was also shown to be suited to both the fatty and skimmed fractions issued from raw milk. Finally, the extraction method was successfully applied to the analysis of raw milk samples collected in 23 farms of dairy cattle from NW Spain (Galicia).